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lOOM/l-77 


MANUAL 


Plant  Diseases 


BY 


PROF.  DR.  PAUL  SORAUER 


Third  Edition—  Prof .  Dr.  Sorauer 

In  Collaboration  with 

Prof.  Dr.  G,  Lindau     And      Dr.  L.  Reh 

Private  Docent  at  the  University  Assistant  in  the  Museum  of  Natural 

of  Berlin  History  in  Hamburg 


TRANSLATED  BY  FRANCES  DORRANCE 


EDGAR  T. 


MANUAL 


OF 


Plant  Diseases 


PROF.  DR.  PAUL  SORAUER 


Third  Edition — Prof.  Dr.  Sorauer 


In  Collaboration  with 


Prof.  Dr.  G.  Lindau      And      Dr.  L.  Reh 

Private  Decent  at  the  University  Assistant  in  the  Museum  of  Natural 

of  Berlin  History  in  Hamburg 


TRANSLATED  BY  FRANCES  DORRANCE 

Volume  I 
NON-PARASITIC  DISEASES 

BY 

PROF.  DR.  PAUL  SORAUER 

BERLIN 


WITH  208  ILLUSTRATIONS  IN  THE  TEXT 


Copyrighted,  1922 

By 

FRANCES  DORRANCE 


ERRATA. 


Contents, 
Page  8, 
"  23, 
"  53- 
"  93» 
"  99. 
"  167, 
"   204. 

"    265, 


293. 
338, 
339. 
420- 

430. 
442, 
461, 
498: 
548, 
696, 
723. 
765, 
802 

855: 


37. 

5- 
21, 
19. 

6, 


page  X,  line  23,  for  Leguminaceae,  read  Legvuninosae. 
line  27,.  for  stems,  read  shoots. 
"     16,    "     preventive,  read  preventative. 
"       5,    "     Prunualus,  read  Prunulus. 
Fig.    4,  caption,  for  Schomiinzach,  read  Schonmiinzach. 
line  34,  for  Miicor  spinosa,  read  Miicor  spinosus. 
Arahanose,  read  Arabinose. 
Fiisiarium,  read  Fusarivmi. 
Leguminoseae.  read  Leguniinosae. 
Dioscora,  read  Dioscorea. 
Zolites,  read  Zeolites. 
B.   suhstilis,   read  B.  subtilis. 
7-8,    "     Clostridium  gelatinosa,read  Clostridiuiiv  gelatinosum. 
18,  after  Mold  fungi,  insert  (Miicor  stolonifcra  and  Asper- 

g  ill  is  nigcr). 
20,  for  honiogany,  read  homogamy. 
30,    "     fruit  spears,  read  fruit  spurs. 
II,    "     Fruchtuchen,  rcflrf  Fruchtkuchen. 
22  "     Leguminaceae,  read  Leguminosae. 

line  II,  after  inner  growth,  insert  (internal  intumescences). 
Fig.  80,  caption,  for  Acacia  pendulata,  read  Acacia  pendula. 
line  24,  after  rough  places,  insert  (scurvy  spots). 
I,  for  Chapter  XL,  read  Chapter  XL 
24,    "     psycho-clinic,  read  psychro-clinic. 
22,    "     Bacillus  pseudarabinus,  read  Bad.  pscudarahinum. 
38,    "     Grapholithia,  read  Grapholitha. 
36,    "     Boulle  celeste,  read  Bouillie  celeste. 
Fig.  186,  caption,  for  formaton,  read  formation. 
line  II.  for  Trula,  read  Torula. 
"     II,    "     vernatis,  read  vernalis. 


TABLE  OF  CONTENTS. 


Page 
PREFACE  to  the  German  edition 3 

IXTRODUCTIOX. 

Section  i.    THE  NATURE  OF  DISEASE. 

1.  Limitation  of  the  conception  of  disease   5 

2.  Production  of  the  disease   8 

3.  Relation  of  the  plant  to  its  environment   lO 

4.  Parasitic  diseases    13 

5.  Epidemics    19 

6.  Artificial  immunization  and  internal  therapy    23 

7.  Predisposition     25 

8.  Predisposition  and   immunity    27 

9.  Inheritance  of  disease  and  of  predisposition    31 

ID.     Degeneration     34 

Section  2.     HISTORICAL  SURVEY. 
Historical   Survey    41-70 

APPENDIX    70 

DETAILED  EXPOSITION. 

Section  i.     DISEASES  DUE  TO  UNFAVORABLE  SOIL  CONDITIONS. 
Chapter  I.     The  location  of  the  soil 72 

1.  Elevation  above  sea  level  72 

a.  General  changes  in  habitat. 

In  relation  to  herbaceous  plants 72 

Development  of  the  aerial  axis  of  woody  plants 76 

Adjustment  of  the  root  body  of  woody  plants 78 

b.  Special  cases  of  disease   81 

Retrogression  in  the  cultivation  of  the  larch   81 

Lack  of  success  with  tropical  plantations  84 

2.  Slope  of  the  surface  of  the  soil 86 

a.  Too    steep    slopes    89 

b.  Growth  of  stilts,  elevation  of  the  roots  of  trees  92 

c.  Too   deep  planting 98 

Too  deep  planting  of  trees   98 

Too  deep  sowing  of  seed  : 106 

Roots  from  the  tips  of  grain  seeds  ' 116 

3.  Greater  horizontal   differences    120 

Glassy  grain  kernels 129 

4.  Continental  and  marine  climates   131 

5.  Influence  of  forests   134 

Chapter  II.     Unfavorable  physical  constitution  of  the  soil   138 

1.  Limited   soil   mass 138 

Root   curvature    138 

Dwarf  growth    (Nanism)    142 

Too  thick  seeding 147 

2.  Unsuitable   soil  structure    148 

a.  Light    soils    148 

Disadvantage  of  sandy  soils    148 

Lowering  of  the  ground  water  level  i5o 

The  dying  of  alders   i5.^ 

Street   planting    I53 

Effect  of  drought  on  field  products   I55 

Effect   of  drought  on   germination    157 

Treatment  of  tree  seeds    IS8 

Blasting  in  grains  and  legumes 160 


VIU 

Page 

Thread  formation  in  the  potato  ( I-ilositas)    i6i 

Diaphysis  (Growiuff  out)  of  the  potato 163 

Formation  of  tubers  witliout  foliage  164 

Aerial   potato  tubers   165 

Premature   ripening  of    fruits    165 

Rusty    plums    166 

l-'urther  |)henomena  of  premature  ripening   166 

Mealiness  of  fruit    166 

Bitter  pit  in  the  apple  168 

Stoniness  of  pears  and   lithiasis    170 

X'arieties  of   fruit   suitable   for  dry  soils 1.74 

Stunting  of  plants  175 

Pilosis    177 

Lignification  of  roots   179 

Ball  dryness  of  the  Ericaceae  181 

Means  of  overcoming  lack  of  moisture  in  the  soil   182 

Irrigation    182 

Cultivation  of  the  soil   183 

Mulching  of  the  soil   184 

Soils  with  a  plant  cover   185 

l'"orest    litter    186 

Forests     187 

Fallow  land    188 

b.  Loamy  soils    189 

General    characteristics    189 

Covering  of  the  soil  with  silt   191 

Improvement  of  soils  which  are  becoming  compact  194 

Inundations    195 

Conversion  of  lands  into  swamps  196 

Burning  of  plants  in  moist  soils   199 

r)cla_\  cd   seeding   200 

Souring  of  seed    20i 

Souring  of  potted  plants   203 

Injudicious    watering    206 

Use  of  saucers  under  pots   208 

Running  out  of  potatoes  208 

Sensitiveness  of   the   sweet  cherry    200 

Tan  disease    209 

Girdling  of  the  red  beech  219 

Root  disease  of  the  true  chestnut  (Mai  nero)   219 

Rootblight  of  sugar  and  fodder  beets. 220 

Tropical   plants    227 

Root-rot  of  sugar  cane   227 

'    '  "Diseases   of   cotton    228 

Castor  bean  cultures  229 

Tobacco  229 

CofTec    230 

Cocoa  and  tea  231 

Other  tropical   plants    231 

Means  for  overcomiug  the  disadvantages  of  heavy  soils 232 

'  Harrowing    236 

Use  of  lime,  marl,  and  plaster  22,'j 

3.  Disadvantages  of  moor  soil   240 

Acids  in  the  soil    240 

Raw  humus   241 

Meadow   ore    243 

Poisoning  of  the  soil  by  metallic  sulfur  250 

Susceptibility  to  frost  of  moor  vegetation   251 

The  usefulness  of  the  spruce   253 

Changes  in  moor  soil  through  cultivation   256 

Rotten  bark    258 

Horticultural   moor  plants    260 

Specking  of  orchids   261 

Chapter  HI.     Unfavorable  chemical  soil  constitution   264 

I.  Relation  of  the  food  stuffs  to  the  soil  structure  264 

A.  Soil  absorption  resulting  from  chemico-physical  processes    264 

B.  Work  of  the  soil  organisms  268 


IX 

Page 
2.  Relation  of  the  nutritive  substances  to  the  plants   274 

A.  Lack  of  moisture  and  nutritive  substances   275 

a.  Lack  of  moisture   275 

Influence  of  the  various  plant  coverings   275 

Wilting    276 

Change  in  production  due  to  lack  of  moisture 278 

Discoloration  of  woody  plants   279 

Red  coloration  in  grain   281 

"Reds"  of  hops    282 

"Leaf  scorch"  of  grapes,  "Parching"  of  vines.  "Red  scorch" 283 

Yellowing  due  to  the  grafting  stock    284 

Premature   drying  of   the   foliage    284 

Burning  out  of  grass 285 

Silver  leaf    285 

Water  core  of  apples  286 

b.  Changes  in  production  due  to  a  lack  of  nitrogen   287 

Starvation  conditions  in   Cryptogams 287 

Production  of  sterile  blossoms    (Sterility) 289 

Seedless    fruits     292 

Behavior  of  weak  seeds  295 

Dropping  of  the  fruit  296 

Drying  of  the  inflorescences  on  decorative  plants   296 

Formation  of  thorns   297 

c.  Changes  in  production  due  to  a  lack  of  potassimn   298 

d.  Changes  in  production  due  to  a  lack  of  calcium   301 

e.  Changes  due  to  a  lack  of  magnesium   305 

f .  Changes  due  to  a  lack  of  chlorin 306 

g.  Lack  of  iron  and  "jaundice"  (Icterus )    307 

h.  Changes  due  to  a  lack  of  phosphorus  and  sulphur 312 

i.    Changes  due  to  a  lack  of  oxygen   313 

General    phenomena    313 

Brusone  disease  of  rice   315 

Diseases  of  gladioli 316 

k.  Changes  due  to  a  lack  of  carbon-dioxid 316 

B.  Excess  of  water  and  nutritive  substances  319 

a.  Excess  of  water   319 

Moisture    319 

Clogging  of  drain   tiles    319 

Sprouted  grain    320 

Rupturing  of  fleshy  parts  of  plants   321 

Woolly  streaks  in  apple  cores  324 

Ring  disease  of  hyacinth  bulbs 326 

Springing  of  the  bark   2)2- 

Shedding  of   the  bark    328 

Water    sprouts    331 

Union  of  parts   333 

Compulsory  twisting  (Spiralismus  Mor. )    334 

Dropsy    (Oedema )     335 

a.  In   small    fruits    335 

b.  In  stone  fruits   338 

Swellings  on  the  St.  John's  Bread  tree   339 

Retrogressive  metamorphosis   (Phyllody)    340 

Barrenness  of  the  hop   342 

Forked  growth  of  grape  vines   345 

Falling  of  the  leaves   346 

Leaf   casting   diseases    349 

Leaf-fall  in  house  plants    35^ 

Dropping  of  the  flowering  organs   Z^bT^ 

Shelling  of  the  grape  blossom    354 

Shedding  of  the  young  flower  clusters  of  hyacintlis 356 

Twig  abscission    y^~ 

b.  Increase  of  food  concentration 360 

Changes   in   meadows    362 

Sewage  disposal   fields    364 

Scurvy   disease    367 

Progressive   metamorphosis Z~~ 

Pressure  of  the  buds   (Blastomania   A.  Br.) 17^ 


X 

Page 
Goitre  gnarl  of  trees   378 

c.  Effect  of  ail  excess  of  nitrogen 387 

Over-fertilized   seed    387 

Over-fertilized  beets   38Q 

Over-fertilized    potatoes    390 

Chile  saltpetre  with  woody  plants  391 

Over-fertilization  of  vegetables  and  other  field  crops 392 

Excessive  nitrogen  fertilization  for  decorative  plants  393 

Leaf  curl  of  the  potato   395 

d.  Excess  of  calcium  and  magnesium  399 

Excess  of  calcium   with   grapes    402 

e.  Excess    of    potassium    403 

f.  Excess  of  phosphoric  acid  405 

g.  Excess  of   carbon-dioxid    406 

Section  2.    INJURIOUS  ATMOSPHERIC  IXFLUEXXES. 

Chapter  IV.     Too  dry  air    408 

Injury  to  buds    408 

Defoliation  due  to  heat    .411 

Honey   dew    412 

Heart  rot  and  dry  rot  of  fodder  and  sugar  beets  415 

Faulty  development  of  the  blossoms  416 

House  plants   419 

Hard  seeds  in   the   Leguminaceae 420 

Chapter  V.     Excessive  humidity    423 

Mode  of  growth  with  continued  atmospheric  humidity 423 

Influence  of  moist  air  on  plants  injured  by  drought  425 

Cork  outgrowths    426 

Cork  disease  of  the  cacti   428 

Bitten  or  perforated  leaves   430 

Formation  of  cork  on  fruits   432 

Yellow  spots   (Aurigo)    434 

Intumescences    435 

Tubercle  disease  of  the  rubber  plant  449 

Skin  diseases  of  hyacinths   451 

Glassy  condition  of  cacti   453 

Chapter  VI.     Fog   458 

Chapter  VII.     Rainstorms    461 

Chapter  VIII.    Hail   463 

Chapter  IX.     Wind    471 

Chapter    X.     Electrical    discharges    480 

Flashes  of  lightning  480 

Blight  of  conifer  tops   487 

Differences  between  lightning  and  frnst  w(ninds  in  conifers 489 

Injuries  to  trees  in  cities  and  towns  493 

Effect  of  spray  lightning  on  grapevines  493 

Spray  lightning  on  fields  and  meadows  495 

Disadvantages  in  electro-culture    496 

Chapter  XI.     Lack  of  heat    498 

A.  General  survey   498 

Life  phenomena  at  low  temperatures  498 

Autumn   coloration    500 

Frosting  and   freezing  to  death    504 

Theories  as  to  the  nature  of  frost  action  507 

Disturbances  due  to  chilling   513 

B.  Special  instances  of  frost  action  514 

Turning  sweet  of  potatoes  514 

Running  to  seed  of  beets   516 

Frosty  taste  in  grapes   518 

Changes  in  the  blossom  organs 518 

Rust  rings  in  fruits  523 


XI 

Page 

Behavior  of  older  foliage  with  acute  frost  action    524 

Deficient  greening  of  younger  leaves  526 

Defoliation   due   to    frost    527 

Behavior  of  beet  and  cabbage  plants  in  frost 531 


Frost    blisters 


532 


Comb-like  splitting  of  the  leaves   53, _ 

Heaving  of  seeds  536 

Internal  injuries  in  young  grain   537 

Internal  injuries  in  the  grain  stalk   539 

Lodging  of  the  stalk  542 

Condition   of    sterile   heads    542 

Phenomena  of  movement  due  to  frost  547 

Freezing  back  of  older  branch  tips   553 

Dying  of  the  cherry  trees  along  the  Rhine  555 

Branch  blight  in  forest  trees   558 

Freezing  of  the  spring  growth  559 

Freezing  of   roots    562 

Frost  clefts    566 

Frost   blisters    569 

Frost   wrinkles    574 

Bark  tatters  and   cork  holes    575 

Phenomena  of  discoloration  in  trunks  and  branches   576 

Frost    line    579 

Internal  splitting  of  the  trunk  and  branches 581 

Open   frost   tears    583 

Canker    (Carcinoma)     586 

a.  Canker  of  the  apple  tree  586 

b.  Crotch  canker  in  fruit  and  forest  trees  593 

c.  Canker  on  cherry  trees   594 

d.  Canker   (Scab)    of  the  grapevine   596 

e.  Canker  on   Spiraea   598 

f .  Canker  of  the  rose   602 

g.  Canker  of  the  blackberry    606 

Corresponding  features  in  canker  swellings    607 

Blight   (Sphacelus)    608 

Aggregations  of   parenchyma   wood    613 

False  annual  rings,  double  rings,  etc 615 

Experimental  production  of  parenchyma  wood  by  frost  action 617 

Theory  of  the  mechanical  action  of  frost   620 

Rupture  of  the  cuticle   623 

Protective  measures  against   frost   624 

a.  Snow    covering    624 

b.  Use  of  water   626 

c.  Effect  of  wind   627 

d.  Smudge     628 

Frost  prediction    ^ 630 

Hardy  fruit  varieties 631 

Snow  pressure,  ice  coating  and  icicles 634 

Chapter  XII.     Excess  of  heat 638 

Death   from   heat 638 

Poor  development  of  our  vegetables  in  the  tropics  639 

Postponement  of  the  usual  seed  time  in  our  latitudes 639 

Sunburn   of   leaves  in   nature    641 

Sunburn   spots   in   conservatories    643 

Defoliation     644 

Sunburn  in  blossoms  and  fruits   645 

Injury  to  grapes  from  sunburn   646 

Sun  cracks    .' 647 

Influence  of  too  great  soil  heat 648 

Failure   of   the   pineapple    650 

Classiness    of    orchids    651 

Failure  in  forcing  blossom  bulbs   651 

Seed  which  has  suffered  from  self -heating   .652 

Chapter  XIII.     Lack  of  light   654 

Etiolation    654 

Shading     657 


XM 

Page 

Lodging  of  grain  662 

Lack  of  light  as  predisposition  to  disease  666 

Chapter  XIV.     Excess  of  light    671 

Section  3.     EXZVMATIC  DISEASES. 

Chapter  XV.     Displacement  of  enzymatic  functions  675 

General  discussion   675 

Albinism    (Variegation)    677 

Mosaic  disease  of  tobacco  684 

Pox  of  tobacco  689 

White  rust  of  tobacco   690 

Disease  of  tlie  peanut  in  German  East  Africa 690 

Shrivelling  disease  of  the  mulberry   690 

Sereh  disease  of  the  sugar  cane   692 

Cobb's  disease  of  the  sugar  cane ^96 

Peach  yellows    697 

Gummosis  of  the  cherry   699 

Exudation  of  gum  in  other  plants   707 

Exudation  of  gum  in  the  Acacia  707 

Gummy  exudation  of  the  bitter  orange   708 

Black-leg  of  the  edible  chestnut   709 

Gummosis  of  the  fig  tree  710 

Exudation  of  manna    ~ii 

Resinosis   ....  7  r  i 

Formation  of  resin  in  dicotyledonous  plants 716 

Section  4.    EFFECT  OF  IN'JURIOUS  GASES  AXD  LIQUIDS. 

Chapter  XVI.     Gases  in  smoke   718 

Sulphurous    acids    718 

Hydrochloric  acid  and  chlorin    724 

Hydrofluoric   acid    729 

Nitric    acid 730 

.\mmonia     730 

Tar  and  asphalt  fumes   '/I2 

Bromine     735 

Chapter   XVII.     Solid    substances   given    off   by   chinmeys   and    the   distillates   they 

contain .737 

Hydrogen    sulfid    742 

Soda    dust    743 

Control    plants    744 

Illuminating  gas  and   acetylene    744 

Chapter   XVIII.     Waste    water    748 

Waste  water  containing  sodium  chlorid    748 

Waste  water  containing  calcium  chlorid  and  magnesium  chlorid 751 

Waste  water  containing  barium  chlorid    752 

Waste   water   containing   zinc   sulfate    752 

Waste  water  containing  iron  sulfate    753 

Waste  water  containing  copper  sulfate  and  copper  nitrate  754 

Chapter  XIX.     Injurious  effects  of  cultural  methods .756 

Coating  substances    756 

.Anaesthetica     765 

Injuries  due  to   fertilizers    "jd-j 

Section  5.     WOUXDS. 

Chapter  XX.    Wounds  to  the  axial  organs   772 

General  discussion    772 

Scarification    wounds    776 

Inscriptions    781 

Injury  due  to  wild  animals   781 

Overgrowth  of  cross  wounds  in  many-year-old  trees   783 

Overgrowth  processes  in  year-old  branches    785 

Girdling    callus    787 


XIU 

Page 

Injuries  to  the  bark   797 

Historical    survey    797 

Personal    observations    805 

Bending  of  the  branches    810 

Twisting  of  the  branches   815 

Effect  of  constricting  the  axis   817 

Branch   cuttings    821 

Utilization  of   various  axial  organs   for   cuttings    825 

Grafting    829 

Oculation,    or    budding    833 

Copulation  and  grafting 838 

Longevity  of  grafted  or  budded  individuals   839 

Mutual   influence   of   scion   and   stock 841 

Natural   processes  of   coalescence    847 

Wound    protection     850 

Wound   gum    851 

Slimy  exudation  of  trees    854 

Root    injuries    856 

Gnarly  overgrowth  edges    859 

Bark  tubers   861 

Leaf  injuries   871 

Leaf  cuttings  873 

Injury  to  the  foliage 879 

Supplement    881 


LIST  OF  ILLUSTRATIONS. 


Fig.  Page 

I,  2.     Roots  of  Quercus  Pedunculata  grown  between  rocks  79 

3.  Spruce  root  with  fleshy  compensatory  root 81 

4.  Stihed  spruce  near  Schonmiuizach   93 

5, 6.     Stilted  pine  from  Grunewald   95 

7, 8.     Resin  galls  on  stilt-like  roots  of  the  pine  96 

9.     Rye  seedling  with  too  deep  sowing   112 

10.  Cross  section  through  the  lowest  node  of  young  rye  plant   1 14 

11.  Wheat  grains  with  roots  from  testa  at  tip  of  seed  grain  116 

12,  13,  14.     Microscopical  enlargements  of  Fig.  11 117,  119 

15.  Dwarf  s])ecinK'n  of  Thuja  ob'usa  i J3 

16.  Cutting  from  potato  tuber  with  the  filament  disease   162 

17.  Prolilicatcd    potato    •  •  .  163 

18.  Parenchyma  cell  from  ripe  apple  after  treatment  with  undiluted  glycerin 169 

19.  Pear  diseased  with  Lithiasis  171 

20.  Cross-section  of  stone  cell  from  pear  shown  in  Fig.  19 173 

21,  22.     Corresponding  sections  through  a  cultivated  and  a  wild  carrot 181 

23.  Apple  root  with  ruptured  tan  spots  210 

24.  Cross-section  through  a  tan  spot  in  an  apple  root  211 

25.  Bark  of  apple  tree  trunk  with  tan  spots  212 

26.  Cross-section  through  tan  spot  on  trunk  of  apple  tree  213 

27.  Cherry  branch  with  tan  cushions 214 

28.  New  wood  on  a  bark  wound  of  a  cherry  trunk 216 

29    A  "meadow  ore  pine"   246 

30.  Roots  of  an  oak  in  meadow  ore   247 

31.  Moor  pine  with  flatly  extended  roots   248 

32.  Canker-like,  wounded  place  on  the  moor  pine   249 

33.  Spruce  family  produced  by  natural  layering 254 

34.  Oak  with  a  formation  of  sinkers   255 

35.  IMouldy  bark  scale  of  a  moor  pine  259 

36.  Seedless  pear   : 294 

27.     Cross-section  through  branch  of  Rhamnus  cathartica    298 

38.  Cross-section  through  thorn  of  Rhamnus  cathartica   299 

39.  Leaf  injuries  from  a  lack  of  potassium   302 

40.  Buckwheat  plant  grown  in  a  normal  nutrient  solution  307 

41.  Buckwlieat  plant  grown   in   a  solution   free   from  chlorin 308 

42.  Bean  plant  split  as  the  result  of  excess  of  water  322 

43.  Apple  core  with  woolly  streaks  324 

44.  Rupture  of  carpel  of  apple  due  to  a  woolly  streak  325 

45.  Elm  bark  with  protruding  tissue  islands   328 

46.  Elm  bark  with  bark  excrescence  (cross-section)    329 

47,  48.     Fasciated  branch  of  Picca  cxcclsa   332 

49.  Fasciation  of  AInus  glutinosa   233 

50.  Dropsy  in   Ribes  aurcuiii    336 

51.  Transitional  stages  between  normal  and  leafy  hop  catkins   343 

52.  Carrot  diseased  with  deep  scurvy  367 

53.  Lentical  formation  on  the  potato  skin  369 

54.  Cone  disease  in  the  Scotch  pine   ^^73 

55.  Sprouting  pears    374 

56.  Larch  cone  with  growth  of  the  axis  continued  375 

57.  Rosette  shoot  of  a  Scotch  pine  377 

58.  Peeled,  gnarled  growth  of  the  maple   379 

5Q.     Gnarl   formation  on  branches   of  .\Ialus  sinensis   380 

60.  Cross-section  through  a  gnarl  cushion   380 

61.  Longitudinal  section  through  the  spikes  of  a  gnarl  381 

62.  Gnarl  formation  in  the  black  currant  382 

63.  Cross-section   through   twig  covered   with   gnarls 383 

64.  Cross-section  through  bark  of  the  black  currant   383 

65.  Medullary  ray  in  the  first  stages  of  gnarl  formation  384 

66.  Diagrammatic  representation  of  mutual  relations  of  fertilizers   400 

^7,  68.     Cross-sections  through  the  bud  coverings  of  Quercus  and  of  Pinus 409 


XV 

Fig.  Page 

69.     Cross-section  through  the  apical  region  of  a  closed  blossom  of  Hifpeastruin 

robustum     418 

70,  71.     Cork  excrescences  in  Phyllocactus 428,  429 

72.     Perforated  potato  leaf,  due  to  cork  formation  431 

~3.     Grapes  with  cork  warts  on  fruit  stems   432 

74.  Cross-section  through  the  warty  fruit  stem  of  a  grape 433 

75.  Leaf  intumescences  in  Cassia  loinentosa  436 

76.  Intumescence  in  Myrmecodia  echinafa 437 

77.  Intumescence  on  the  stem  of  a  grape  ' 439 

78.  Intumescence  on  the  lower  node  of  an  oat  plant  441 

79.  Intumescence  on  stem  of  Lavetera  truncsiris   442 

80,  81.     Intumescence  on  branch  of  Acacia  pcndiila ■  .442 

82.  Cross-section  through  intumescence  of  Acacia  pendula 443 

83.  Intumescence  on  blossom  of  Cymbidium  Lowi 444 

84.  Cross-section  through  intumescence  on  perianth  of  Cyiiibidtiiiv.  Loivi  445 

8s,  86.     Intumescence  on  pea-pods   446,  447 

87.     Cross-section  through  leaf  tubercle  of  the  rubber  tree  450 

88,  89.     Hyacinth  bulb  with  pustules  of  the  skin  disease  451,  452 

90.  Glassy  place  in  Cere  us  nycticaliis 456 

91.  Effect  of  hail  on  a  blade  of  rye_ 464 

92,  93.     Head  of  wheat  broken  by  hail 465,  466 

94.  Cross-section  through  tomato  wall,  injured  by  hail ...467 

95.  Wind  bent  and  broken  spruces 473 

96.  Craspedodromous  and  Camptodromous  venation 478 

97.  Oak,  struck  by  lightning 482 

98.  Cross-section  through  spruce  with  overgrown  lightning  wounds 484 

99.  Cross-section   through    annual    ring   of    a    spruce,    in    year   it   was    struck   by 

lightning    _. 485 

100.  Cross-section  through  a  blighted  spruce  tip  487 

101.  Pine,  artificially  frosted 490 

ro2.     Spruce,  showing  traces  of  artificial  lightning 492 

103.  Cross-section  through  petal  of  apple,  injured  by  artificial  frost  S20 

104.  Cross-section  through  young  receptacle  of  apple  injured  by  frost  521 

105.  Primordia  of  apple  flower  bud,  injured  by  frost 522 

106.  Autumnal  abscission  layer  of  a  horse  chestnut  leaf   528 

T07.     Cross-section  through  a  frost  boil  in  an  apple  leaf -533 

108.     Horse  chestnut  leaf,  injured  by  frost  and  torn  during  unfolding  535 

log.     Young  rye  leaf,  injured  by  frost 538 

1 10.     Natural  cavities  in  the  rye  leaf 539 

Tii.     Leaf  node  from  a  rye  plant,  injured  by  frost 540 

T12,  113.     Membrane  swellings  on  leaf  sheaths  of  a  rye  blade,  injured  by  frost 540 

1 14.  Different  forms  of  sterility   543 

115.  Cross-section  through  internode  of  a  sterile  rye  blade   544 

it6.     Cross-section  through  the  node  of  the  sterile  stalk 545 

117.  Cross-section  through  a  spruce  branch,  showing  red  wood  formation ■••551 

118,  119.     Red  wood  and  strain  wood  in  the  spruce  552 

120.  Cherry  sapling  infected  with   Falsa  leucostoma   557 

121.  Buds  of  the  cherry,  injured  by  artificial  frost  560 

!22.     Frost  ridge  on  the  trunk  of  Acer  caiiipestre   567 

123.  Oak  stem,  cleft  by  Polyponis  snlfureus  569 

124.  Starch    structures    formed    in    the    willow    branch    by    chloriodid    of    zinc 

treatment    572 

125.  126.     Frost  boil  on  a  sweet  cherry  branch 573,  574 

127.  Torn  cork  lamellae  on  branch  injured  by  frost 576 

128.  Splitting  of  a  pear  branch  by  artificial  frost 578 

129.  Swelling  of  cell  walls  after  artificial  frost 580 

T30.     Internal  splitting  of  cherry  branch  from  artificial  frost 582 

131.     Bud  cushion  of  a  larch  branch,  injured  by  artificial  frost 584 

T32.     Overgrowing  frost  split  in  apple  branch,  produced  by  artificial  frost 586 

133,  134,  135.     Apple  canker   587,  588 

136.  Juvenile  condition  of  apple  canker 590 

137.  Injurv  to  base  of  branch  by  frost 59i 

T38.     Crotch    canker 593 

T39.     Cherry   canker    595 

140.  Canker  excrescences  in  the  grapevine  596 

141.  Canker  on  Spiraea  599 

142.  143.     Rose  canker   602,  604  ■ 


XVI 

Fig.  Page 

144.  Canker  of  the  wild  blackberry   606 

145.  Frost   spots  on   pear   bark 608 

146.  147.     Blight  spots  on  pear  trunk 610,  611 

148*,  149.     Internal  frost  wounds  on  an  oak  branch   618,  621 

150.'     Curve   for   tinding   night   frosts 631 

i':;!.     Cross-section  through  sunburn  spot  in  leaf  of   Clivia  itobilis 643 

152,  153,  154-     Light  and  shade  leaves  of  the  beech 660 

155!    Twig  of  cherry  with  gum  cavity 701 

156.  Nuclei  of  gum-forming  tissue 704 

157.  Tracheidal   parenchyma  of   Piiius  Strobus  with   resiniferous   layer 713 

158.  159,   if>o,  161.     Resin  centers  in  amber   714-716 

162!     bat  leaf  killed  by  chlorin   fumes 726 

163.  Beech  leaf   affected   by   sulfurous   acid 727 

164.  Birch  leaves  injured  by  sulfurous  acid 728 

165.  Rose  leaf  injured  by  chlorin  fumes 728 

166.  Beech  leaves  injured  by  chlorin   fumes 728 

167.  Birch  leaves  injured  by  chlorin   fumes 729 

168.  Virginia  creeper,  strawberry  and  rose  leaves  injured  by  tar  fumes 733 

169.  170,  171.     Apples  injured  by  spraying  with  Bordeaux  mixture 763,  764 

172.  Apple  leaf  with  dead  spots  and  holes  after  spraying  with  Bordeaux  mixture.  .765 

173.  174.  173-     Scaritication  wounds 777,  778 

176.  Hollow  pine  trunk 779 

177.  Section  of  trunk  of  Picca  ruUiaris  with  overgrowth  of  the  resin  channels 780 

178.  Overgrowth  of  the  cut  surface  of  a  branch 783 

179.  180,  181.     Cross-section  of  a  year-old  cherry  branch 786 

182,  183,  184,   185.     Ringing  wound  on  a  grapevine 789-795 

186.  Callus  formation  from  young  bark  cells  in  ^  barked  trunk 802 

187,  188,  189.     New  tissue  formation  on  a  barked  cherry  trunk 805-808 

190,  191,  192,  193,  194.     Xew  tissue  formation  at  bend  in  an  apple  twig 811-813 

195.  Injury  to  a  branch  due  to  twisting 815 

196.  Constriction  in  branch  due  to  a  wire  ring 819 

197.  Inichsia   cutting    . 822 

198.  Rose    cutting    823 

199.  Budded   rose 832 

200.  Bark  graft  of  .'\esculus,  with  adventitious  buds 837 

201.  Pine  with  natural  in-arching  of  a  second  trunk 848 

202.  Stoppage  of  ducts  in  a  grapevine,  due  to  wound  decay 853 

203.  Alder  root,  barked  by  the  tread  of  feet 856 

204.  Gnarlly  overgrowth  cap  of  the  stump  of  an  oak  branch 860 

205.  Bark  tubers  from  an  apple  trunk   866 

206.  Isolated  wood  centers  in  the  bark  of  a  year-old  pear  branch 869 

207.  Callus  formation  in  a  leaf  of  Leucojum  vcnimn 872 

208.  Leaf  cutting  of  a  begonia 875 


PART  I. 


MANUAL 


OF 


Plant  Diseases 

BY 

PROF.  DR.  PAUL  SORAUER 


Third  Edition-Prof.  Dr.  Sorauer 

In  Collaboration  with 

Prof.  Dr.  G.  Lindau       And       Dr.  L.  Reh 

Private  Decent  at  the  University  Assistant  in  the  Museum  of  Natural  History 

oi  Berlin  in  Hamburg 


TRANSLATED  BY  FRANCES  DORRANGE 


Volume  I 
NON-PARASITIC  DISEASES 

BY 

PROF.  DR.  PAUL  SORAUER 

BERLIN 


WITH  208  ILLUSTRATIONS  IN  THE  TEXT 


MANUAL 


OF 


Plant  Diseases 


BY 


PROF.  DR.  PAUL  SORAUER 


Third  Edition—Prof.  Dr.  Sorauer 

In  Collaboration  with 

Prof.  Dr.  G.  Lindau        And       Dr.  L.  Reh 

Private  Decent  at  the  University  Assistant  in  the  Museum  of  Natural  History 

of  Berlin  in  Hamburg 


TRANSLATED  BY  FRANCES  DORRANGE 


Volume  I 
NON-PARASITIC  DISEASES 

BY 

PROF.  DR.  PAUL  SORAUER 

BERLIN 


WITH  208  ILLUSTRATIONS  IN  THE  TEXT 


Copyrighted,  1914 

By 
FRANCES  DORRANCE 


THE  RECORD  PRESS 
Wilkes-Barre,  Pa. 


PREFACE  TO  THE  GERMAN  EDITION. 


For  the  third  edition  of  my  manual  I  have  requested  the  assistance  of 
Professor  Dr.  Lindau  and  Dr.  Reh.  In  the  second  volume  of  the  work,  the 
former  has  treated  of  vegetable  parasites  and  in  the  third  volume  the  latter, 
the  animal  enemies  of  plants. 

Such  help  seemed  necessary  because,  since  the  appearance  of  the  second 
edition,  the  published  results  of  investigations  have  been  so  numerous  that 
too  long  a  time  would  have  been  required  for  mastering  the  material.  Other- 
wise when  the  last  sheets  appeared  the  first  would  have  become  obsolete. 
Even  with  this  division  of  the  work,  this  unfortunate  condition  has  not  been 
entirely  overcome  and  an  attempt  has  been  made  to  obviate  the  difficulty  by 
listing  some  of  the  more  important  recent  material  in  a  supplementary  biblio- 
graphy. If  the  absence  of  some  works,  especially  of  the  earlier  literature,  is 
noted  the  explanation  lies  in  the  fact  that  we  have  emphasized  especially 
those  studies  necessary  for  the  support  of  our  presentation  of  the  subject. 
A  more  detailed  bibliography  would  be  possible  only  if  the  individual  diseases 
were  treated  in  monographs. 

I  kept  for  my  own  work  the  revision  of  the  first  volume,  comprising  the 
non-parasitic  diseases.  The  fact  that  this  volume  is  the  most  extensive  is  ex- 
plained by  my  standpoint,  already  sufficiently  characterized  in  the  preface  to 
the  second  edition,— because  I  lay  the  chief  weight  on  a  knowledge  of  the 
diseases  produced  by  atmospheric,  soil  and  cultural  conditions.  The  distur- 
bances caused  by  these  factors  are  not  only  the  most  abimdant  and  perma- 
nent but  also  often  form  the  starting  point  for  parasitic  diseases. 

On  this  account,  supported  by  my  own  studies  and  the  observations  of 
other  investigators,  I  was  especially  anxious  to  show  how  the  same  plant 
species  could  be  changed  structurally  and  in  habits  of  growth  according  to 
position  and  the  constitution  of  the  soil.  Individuals  are  sometimes  more 
disposed  to  a  definite  form  of  disease  or  are  more  resistant  to  it,  according 
to  the  difference  in  their  constitutions. 

This  holds  good  also  for  their  behavior  towards  parasitic  organisms.  It 
is  thus  evident  that  not  only  must  the  latter  be  combatted  by  directly  destruc- 
tive methods  but  also  the  chief  emphasis  should  be  laid  on  the  possible  con- 
stitutional change  of  the  host  plant.  Therefore,  we  will  find  the  most  essen- 
tial task  to  be  the  breeding  of  resistant  varieties.  At  the  time  the  first 
edition  of  this  work  was  published,  the  undersigned  stood  alone  as  represen- 
tative of  this  theory  of  predisposition  to  parasitic  attack,  but  now  many  of 
the  most  prominent  investigators  are  counted  among  its  supporters. 

And  thus  I  hope  that  the  idea  for  which  I  have  fought  since  the  be- 
ginning of  my  scientific  activity,  that  is,  the  formation  of  a  rational  plant 


hygiene,  will  finally  come  to  full  recognition.  Primarily,  we  must  learn  to 
protect  the  organism  from  disease,  and  then,  through  force  of  necessity,  may 
take  steps  to  heal  an  organism  which  is  already  diseased. 

In  the  first  volume,  the  first  section  of  the  introduction  treats  of  the  na- 
ture of  disease,  while  the  second  takes  up  the  history  of  its  investigation.  It 
should  be  understood  by  the  term  "historical"  that  I  did  not  wish  to  write  a 
history  of  phytopathology,  which  would  have  taken  much  more  thorough  pre- 
liminary study,  but  did  consider  it  desirable  to  attempt  to  sketch  the  process 
of  the  development  of  this  branch  of  knowledge,  in  order  to  show  how  the 
present  point  of  view  had  developed  in  the  course  of  time. 

In  looking  through  the  specialized  part,  the  reader  may  also  find  that 
even  in  the  present  edition  conclusions  once  based  on  a  considerable  number 
of  my  own  investigations  have  been  abandoned.  The  aid  of  illustrations,  so 
absolutely  necessary  in  phytopathology,  has  been  made  use  of  to  an  appreci- 
ably larger  extent  in  describing  diseases.  In  accordance  with  the  character  of 
the  book,  new  anatomical  drawings  especially  have  been  added.  In  the  vol- 
ume on  parasitic  diseases  many  tables  have  been  gathered  together  for  the 
sake  of  comparison,  in  order  to  make  clear  to  the  reader  the  different  genera 
of  one  family  in  their  distinctive  characteristics. 

The  new  drawings  were  made  by  Fraulein  H.  Detmann  and  Friiulcin  E. 
Lutke,  whom  I  thank  very  much  for  their  work. 

Most  of  all,  however,  I  wish  to  thank  my  collaborators.  With  me,  they 
had  to  solve  the  difficult  problem  of  presenting  the  material  in  a  space  deter- 
mined by  contract  before  the  revision.  During  the  revision,  we  found  our- 
selves confronted  by  the  question  either  of  giving  to  the  whole  subject  a 
briefer  form  than  was  originally  intended,  or  of  working  up  some  chapters 
in  detail  while  summarizing  others.  We  chose  the  latter  course  and  treated 
the  seemingly  most  important  sections  thoroughly  and  the  groups,  which  had 
been  sufficiently  worked  over  in  other  books,  in  a  correspondingly  limited 
way. 

Schoneberg,  October,  1908. 

PAUL  SORAUER. 


INTRODUCTION. 


Section  I. 
THE  NATURE  OF  DISEASE. 


I.     Limitation  of  the  Conception  of  Disease. 

Our  first  task  is  evidently  the  necessity  for  defining  the  province  of 
which  we  will  treat  and  for  expounding  what  we  understand  by  the  term 
"Disease." 

If  we  call  "sick"  only  those  cases  in  which  the  organism  undergoes  such 
a  disturbance  in  its  functions  that  its  existence  seems  threatened,  we  will  be 
in  a  dilemma  when  we  consider  the  changing  developmental  forms  of  our 
cultivated  plants,  for  we  will  then  discover  that  the  above  explanation  is  in- 
sufficient. We  know,  for  example,  that  our  species  of  cabbage,  kohlrabi  and 
cauliflower  are  descended  from  a  plant  similar  to  bank-cress  which,  in  its 
natural  development  as  a  wild  plant,  shows  no  tendency  toward  the  forma- 
tion of  large  leaf-buds  such  as  cabbage  heads,  nor  of  root-like  swellings  of 
the  stem,  as  kohlrabi.  These  vegetables  have  been  produced  by  selection  and 
cultivation  and  are  characterized  by  a  condition  which  we  term  parenchy- 
matosis,  because  the  woody  elements  have  been  replaced  by  a  tender 
parenchyma,  due  to  the  high  degree  of  nitrogen  continuously  supplied  from 
generation  to  generation.  In  dry,  hot  summers  young  plants  grown  on  soils 
poor  in  food  materials  begin  to  show  a  marked  ripening  and,  in  connection 
with  this,  a  reddish  blue  tone  in  their  leaves.  In  case  kohlrabi,  under  such  con- 
ditions, makes  any  development  worth  mentioning,  it  becomes  "stringy," 
that  is,  its  flesh  is  traversed  by  tough,  hard  fibres,  making  it  "woody."  Investi- 
gation shows  that  the  kohlrabi  plant  by  the  curtailment  of  the  supply  of  water 
and  food  materials  is  well  on  the  way  toward  again  developing  a  wood-ring 
with  prosenchymatic  elements,  as  found  constantly  in  the  wild  plant.  Very 
similar  conditions  are  found  in  carrots  in  which  our  normal  uncultivated 
plant  possesses  a  solid  woody  root,  rich  in  starch.  Our  cultivated  varieties, 
on  the  contrary,  have  become  thick,  fleshy  structures;  the  best  containing  no 
starch  at  all  but  the  greatest  possible  amount  of  sugar.  Only  in  the  so-called 
fodder  varieties,  aS;  for  example,  the  white  giant  carrot,  is  still  shown  an 
abundance  of  starch.  Hofllmann-Giessen  has  experimentally  developed  our 
cultivated  carrot  back  to  the  wild  form. 

Now,  is  the  cultivated  form  a  diseased  condition  since  it  actually  suc- 
cumbs more  easily  to  certain  disturbing  influences,  or  is  the  reversion  of  the 


6 

cultivated  plant  to  the  norma!  wild  one  to  be  considered  a  disease?  In  any 
case  this  reversion  is  a  condition  which  must  be  combattcd  as  it  is  evidently 
unfitted  for  our  cultural  efforts. 

In  considering  such  examples  we  see  that,  in  treating  questions  of  dis- 
ease, we  shall  have  to  follow  two  lines  of  work.  We  must  naturally  first 
keep  the  organism's  aim  in  sight.  And  this  aim,  which  the  organism  derives 
from  its  very  origin,  is  to  live,  and  in  fact  to  live  as  long  as  possible.  Every- 
thing which  has  once  been  originated  persists  as  the  eflfect  of  the  causes 
leading  to  its  production,  until  a  stronger  factor  arises  which  disturbs  the 
fixed  order  and  brings  about  other  groupings  of  material,  form  and  function 
(an  inseparable  trinity).  Kut,  up  to  the  time  of  interference  of  such  a  factor, 
the  developed  individual,  with  the  sum  total  of  the  forces  inherent  in  its 
substance,  maintains  its  then  existing  order,  that  is,  its  individuality,  to  which 
a  generally  definable  age  limit  is  set.  This  necessary  mechanical  defense  of 
its  individuality  against  the  constant  attacks  of  exiernal  factors  may  be 
termed  the  "force  of  self-preservation."  In  following  the  second  line,  the 
aim  of  cultivation,  developed  from  the  relation  of  the  plants  to  human  needs, 
is  an  added  important  factor.  These  conditions  of  the  vegetable  organism 
opposing  our  cultural  endeavors  will  be  combatted  as  inexpedient.  But  such 
conditions  need  in  no  way  threaten  the  existence  of  the  individual  and  there- 
fore, according  to  the  above  explanation,  are  not  diseases.  Yet  they  belong  to 
the  province  of  the  pathologist  as  disturbances  which  must  be  considered 
and  overcome. 

In  limiting  the  conception  of  disease,  we  meet  with  similar  difficulties  in 
double  blossoms,  in  as  much  as  this  doubleness  is  due  to  the  fact  that  the 
stamens  have  been  changed  into  petals  and  in  doing  this  have  deformed  the 
pistil.  This  leads  to  sterility.  The  length  of  life  of  the  individual  plant  is  not 
injured  in  any  way  by  this  sterility,  but,  on  the  contrary,  is  actually  length- 
ened as,  for  example,  in  double  petunias.  But  the  aim  of  the  species  is 
affected  since  such  double  blossoms  are  no  longer  able  'o  produce  seeds.  If 
this  kind  of  doubling  becomes  general,  such  species  must  die  out  in  case  all 
vegetative  reproductive  organs  are  missing.  This  variation  in  structural 
development,  threatening  the  existence  of  the  species,  however,  is 
directly  sought  for  in  cultivation  and  any  reversion  to  the  normal,  seedbear- 
ing  form  is  selected  out.  Here  indeed  the  aim  of  cultivation  contradicts  the 
natural  aim  and  pathology  tries  hard  to  overcome  the  natural  trend  opposed 
to  the  momentary  direction  of  the  cultivation,  although  in  doing  this,  it  di- 
rectly threatens  the  existence  of  the  species. 

Such  antagonisms  are  very  numerous.  In  the  list  of  cases  in  which 
only  individual  organs  become  diseased,  one  such  local  disturbance  can  in- 
fluence injuriously  the  organism  as  a  whole,  but  can  yet  be  useful  to  the 
mdividual.  We  would  call  attention  here  to  the  dropping  of  young  fruit  due  to 
drought.  The  cultural  aim  is  naturally  interfered  with  but  the  economy 
of  the  tree  reaps  the  benefit  in  as  much  as  it  saves  the  reserve  materials, 
which  would  have  been  used  in  maturing  the  fruit.    As  a  result  of  this,  the 


tree  is  not  only  in  a  position  to  develop  the  next  set  of  leaves,  but  also  to  set 
numerous  fruit  buds,  which  would  have  remained  suppressed  had  a  full  crop 
exhausted  the  store.  When  late  frosts  injure  the  blossoms  and  young  fruit, 
the  individual  organs  are  certainly  severely  sickened  and  fall  off  later ;  but 
the  tree  itself  has  the  advantage  of  saving  a  quantity  of  food  material.  As 
often  happens,  the  cultural  purpose  can  also  profit  in  this  case,  because  the 
blossoms  developing  after  the  action  of  the  frost  yield  more  perfect  fruit 
and  thus  an  increased  revenue. 

This  defines  clearly  the  difference  between  pure  and  applied  science. 
Pure  science  studies  the  process  of  disease  in  itself  and  can  be  only  cellular 
pathology,  while  applied  science  takes  into  consideration  the  effect  on  the 
diseased  individual  and  its  agricultural  significance.  We  must  unite  both 
forms  of  science  since  we  take  the  purely  scientific  studies  as  the  basis  of 
our  consideration  and  explanation  of  the  economic  effects  of  the  attack  of 
sickness. 

The  consideration  of  the  cultural  needs  forces  us  to  the  following 
division  of  our  subject;  first  of  all,  we  will  have  to  consider  all  cases  which 
threaten  the  individual  aim  of  the  organism,  i.  e.  its  longest  possible  life ; — 
these  are  absolute  diseases.  Then  we  must  discuss  the  disturbances  which 
the  momentary  cultural  aim  experiences  and  which  we  term  relative  diseases. 
I'hese  relative  diseases  may  vary  since  what  cultivation  considers  worth  striv- 
ing for  to-day  may  be  neglected  to-morrow.  For  example,  with  savoy,  every 
reversion  of  the  plant  to  Brussels  sprouts  is  a  disturbance  of  the  cultural 
aim  to  be  avoided  by  changing  the  seed.  If  we  intend  growing  Brussels 
sprouts,  however,  each  variation  of  these  plants  toward  the  savoy  form  is  a 
deterioration,  undesirable  in  cultivation.  Finally,  malformations  are  usually 
unimportant  agriculturally  but  must  be  considered.  Such  malformations 
may  be  a  maturing  of  organs  in  a  manner  differing  from  the  usual  process 
of  development.  These  natural  occurrences,  which,  we  believe,  may  often 
be  traced  back  to  changes  in  pressure  conditions  and  other  mechanical  in- 
fluences due  to  the  formation  of  the  organs,  constitute  a  special  branch  of 
knowledge, — Teratology.  This  is,  however,  to  be  considered  as  one  branch 
of  pathology  and  we  will  have  to  draw  into  our  discussion  these  phenomena 
so  far  as  their  causes  are  known  or  may  be  surmised  with  some  certainty. 

The  method  of  treating  the  material  which  falls  under  the  province  of 
the  study  of  plant  diseases  or  Phytopathology,  will  have  to  be  according  to 
the  following  scheme:— 

I.  Pathography  or  symptomatics,  i.  e.,  the  description  of  the 
disease  according  to  its  individual  signs  or  symptoms. 

II.  Pathogeny  or  etiology,  namely,  investigation  as  to  the  cause 
of  the  disease.  Only  after  the  causes  are  known  is  it  possible  to 
bring  into  use 

III.  Therapy  or  the  study  of  healing  methods  and  to  draw 
into  the  discussion 

IV.  Prophylaxis  or  some  method  of  prevention. 


2.     The  Production  or  the  DISE.\^■.E. 

If  we  have  said  that  we  must  begin  with  the  individual  cells  when  judg- 
ing a  disease,  we  must  know  first  of  all  how  complicated  an  organism  the  cell 
is  and  how  its  structure  and  function  depend  on  the  constitution,  position 
and  action  of  the  micellae  composing  it. 

Let  us,  for  example,  examine  some  effects  of  "swelling."  The  cell  wall 
at  a  given  time  is  saturated  to  a  definite  degree  with  water  of  imbibition,  that 
is,  the  cellulose  micellae  held  together  by  cohesion  are  provided  with  a  water 
sheath  with  a  certain  amount  of  distention.  The  micellae  will  be  separated 
further  from  one  another  or  will  approach  one  another  more  closely  as  the 
water  supply  varies;  that  is,  the  walls  will  sometimes  become  more  dense, 
sometimes  more  flaccid.  Such  fluctuations  are  brought  about  in  the  protoplasm 
of  the  cell  by  the  action  of  substances  which  withdraw  water  osmotically. 
Similar  processes  are  observed  in  chloroplastids,  for  example,  in  grain  leaves 
if  acted  upon  by  weak  chlorin  fumes  or  by  sulfuretted  hydrogen.  The  chlo- 
roplasts  are  seen  to  shrivel  with  the  use  of  chlorine  while  the  chlorophyll 
(jrains  become  pale  green,  doughy,  almost  gelatinous  bodies  with  sulfuretted 
hydrogen. 

In  the  cell  wall,  marked  phenomena  of  flaccidity  may  often  be  restricted 
to  single  spots.  The  so-called  "bead-cells"  in  winter  grain  may  be  taken  as 
examples  of  this.  Individual  cell  groups  near  the  larger  vascular  bundles 
show  bead-like  convex  centres  of  flaccidity  on  the  inner  side  of  their  walls, 
which  later  lose  their  cellulose  character.  If  young,  vigorously  growing 
potato  stems  are  exposed  to  frost,  difl^erent  groups  of  leaf  parenchyma  cells 
will  be  found  later  whose  walls  seem  swollen  in  lines  to  four  times  their 
normal  thickness.  In  this  may  be  observed  the  browning  and  decay  of  the 
niore  dense  wall  lamellae  into  stripes  which  lie  imbedded  in  a  homogeneous, 
lighter  parenchyma. 

In  the  case  of  very  flaccid  membranes,  however,  molecules  will  be  able 
to  penetrate  the  greatly  enlarged  micellar  interstices,  which  cannot  force  an 
entrance  through  the  smaller  ones,  because  of  their  size.  If  changes  in  the 
constitution  of  the  protoplasm  have  been  caused  by  frost,  we  find  substances 
passing  in  and  out  which  could  not  have  been  transferred  before  by  the 
plasma  body.  The  red  coloring  matter  and  the  sugar  in  frosted  red  sugar 
beets  (Beta)  pass  easily  from  the  parenchyma  of  the  beet  into  the  surround- 
ing water.  This  would  be  impossible  in  the  cut  beet,  if  it  had  not  been 
frosted  previously.  The  loosening  of  the  structure  of  the  organic  substance 
is  a  very  normal  process  the  intensity  of  which  depends  on  the  action  of  ex- 
ternal factors,  such  as  water  supply,  light,  warmth,  etc.  If  these  normal 
processes  exceed  a  certain  limit,  they  lead  to  disturbances  which  so  alter  the 
structure  and  function  of  the  cells  that  they  become  unable  to  maintain  life. 
Every  other  process  of  cell  life  may  be  similarly  affected.  Under  the  influ- 
ence of  different  factors  of  growth,  the  process  may  be  hastened  or  retarded. 
We  know  that  each  life  function  oscillates  between  wide  limits,  according  to 


the  action  of  each  individual  vegetative  factor.  We  call  these  limits  the 
minimum  and  maximum  and  the  degree  of  functioning  at  which  a  life  pro- 
cess most  favors  the  development  of  the  organism  the  optimum. 

The  field  of  oscillation  of  the  functions  about  the  optimum,  within  the 
limits  promoting  development  may  be  called  the  "latitude  of  health."  This 
should  not  be  confused  with  "the  latitude  of  life"  for  the  organism  can  still 
live  outside  the  latitude  of  health,  but  its  functions  are  so  weakened  that  its 
development  undergoes  arrest  or  retrogression  and  this  condition  is  disease. 
If  this  cessation  of  the  function  is  temporary,  the  condition  falls  under  the 
conception  of  "check"  and  we  speak  of  check  from  cold  or  from  darkness, 
etc.  But  we  must  guard  against  the  belief  that  the  appearance  of  sickness 
or  a  condition  of  check  or  of  death  in  any  species  is  connected  with  any  pre- 
cise numerical  values  for  the  separate  factors  of  growth.  If,  for  example, 
we  take  two  cuttings  from  the  same  plant  and  cultivate  them  for  some  time  in 
sand  sterilized  by  heat  with  the  same  quantity  of  food  materials  but  keep  one 
cutting  in  a  hot  house  and  the  other  out  of  doors,  in  the  end  the  two  will 
show  a  very  different  susceptibility  to  frost  and  other  atmospheric  factors. 
The  specimen  grown  in  the  hot  house  freezes  more  easily;  that  is,  its  mini- 
mum for  the  maintaining  of  life  is  raised.  Temperatures,  at  which  the  speci- 
men grown  in  the  open  air  remains  within  the  latitude  of  health,  arrest  the 
life  processes  of  the  hot  house  specimen.  Experiments  to  determine- the 
maximum  and  minimum  of  other  factors  of  growth  show  very  similar 
variations  so  that  we  may  arrive  at  the  conclusion  that  for  each  habitat  each 
plant  has  its  ozvn  scale  of  needs,  its  oivn  optimum,  maximum  and  minimum 
and  therefore  possesses  its  ozvn  specific  latitude  of  health. 

Further,  the  circumstance  that  the  different  functions  are  lost  at  dilTer- 
ent  times  should  be  considered.  If,  for  example,  potato  tubers  are  left  for 
some  time  at  a  temperature  of  about  — i°C.,  it  will  be  found  that  respiration 
ceases  sooner  than  the  conversion  of  starch  into  sugar.  This  results  in  an 
accumulation  of  sugar  in  the  tuber  which  is  called  "turning  sweet  of  the 
potato."  If  the  temperature  is  raised  more  slowly  to  possibly  -\-io°C.  the 
stored  sugar  disappears  through  the  increased  activity  of  Ihe  protoplasm  and 
respiration.  If  cucumbers,  tobacco  and  other  heat  loving  plants  have  to 
withstand  a  temperature  of  -i-5°  to  8°C.  for  some  time,  they  show  a  yellow- 
leaf  condition,  which  disappears  with  continued  increase  of  heat.  The 
plants  do  not  die,  but  assimilation  and  growth  are  so  suppressed  that  proces- 
ses, such  as  the  formation  of  gums,  may  be  introduced,  leading  to  the  prema- 
ture death  of  the  individual.  As  in  the  preceding  case  of  deficient  heat, 
deficiency  in  food  materials  or  light, — in  short,  every  decrease  of  any  vege- 
tative function, — so  retards  the  normal  direction  of  the  functions  that  the  in- 
teraction of  these  for  the  purpose  of  a  beneficial  metabolism  is  misdirected. 
Other  combinations  and  functional  directions  (for  example,  fermentations) 
are  now  produced,  which  initiate  the  ending  of  life  prematurely.  The  same 
effect  will  necessarily  appear  every  time  the  maximum  of  any  vegetative 
factor  is  exceeded,  or  even  approximated. 


In  very  many  cases  a  sickness  which  has  already  set  in  is  indicated  by 
chlorosis,  beginning  inconspicuously  and  progressing  slowly.  Even  if  it  is 
possible  to  observe  the  very  beginning  of  chlorosis,  the  beginning  of  the  sick- 
ness itself  has  in  no  way  been  discovered  since  the  first  molecular  changes, 
which  have  led  to  the  yellowing  of  the  chloroplast,  still  remain  unknown  to 
us.  The  boundary  line  where  any  single  factor  of  growth  ceases  to  be  bene- 
ficial and  becomes  a  retarding  factor  may  indeed  be  determined  experiment- 
ally but  in  this  we  see  only  the  final  result  and  not  the  course  of  development ; 
i.  e.,  the  processes  initiating  this  final  result.  So  far  as  our  powers  of  obser- 
vation are  able  to  discover,  health  and  disease  represent  conditions  which 
imperceptibly  pass  over  into  one  another. 

3.     The  Relation  of  the  Plant  to  its  Environment. 

In  the  attempt,  undertaken  in  the  previous  section,  to  demonstrate  how 
health  and  disease  present  interdependent  conditions  like  the  links  of  a  chain, 
we  kept  in  view  first  of  all  the  so-called  constitutional  diseases.  By  this  are 
understood  the  disturbances  in  nutrition  which  influence  the  whole  organism 
sympathetically  and  are  the  results  of  deficiency  or  excess  of  one  of  the 
necessary  vegetative  factors.  Local  diseases  due  to  accidental  interference 
must  be  opposed  to  these  general  diseases.  In  them  the  organism  as  a  whole 
in  its  full  reactionary  capacity  is  exposed  primarily  to  a  disturbance  affect- 
ing only  one  individual  organ.  While  the  action  of  the  necessary  inorganic 
factors  of  growth  come  under  consideration  in  constimtiona!  diseases,  in 
local  diseases  the  important  influences  arc  those  mutually  exerted  on  one 
.another  by  the  organisms. 

There  are  insects  which  seek  out  the  plants  iii  order  to  satisfy  their 
needs  for  nutrition  or  for  habitation,  or  the  planis  themselves  mutually  in- 
'  fiuencc  one  another.  We  find  as  the  most  pertinent  example  the  influence  of 
street  trees  on  the  plants  growing  on  the  other  side  of  the  hedge  row.  We 
notice  especially  in  times  of  drought  that  the  grain  and  potato  plants  found 
within  reach  of  the  tree's  shadow  are  not  only  weaker  in  development  but 
wilt  sooner  and  to  a  greater  degree  than  the  other  plants  in  the  same  field. 
This  disadvantage  is  due  chiefly  to  the  tree  which  keeps  of?  the  rain  and  its 
roots  which  withdraw  the  soil  water.  In  the  field  itself  we  frequently  find 
different  places  in  which  the  seed  has  grown  very  poorly  because  the  wind 
grass  has  choked  the  grain.  The  seed  was  not  sown  too  thin  but  the  germi- 
nation and  first  development  were  choked  by  cold  and  deficiency  in  oxygen 
because  of  impervious  spots  in  the  field.  In  spring  the  soil  does  not  dry  so 
quickly  in  these  places  and  the  moisture  is  retained  longer;  the  soil  conse- 
quently warms  up  less  easily  and  suffers  for  need  of  oxygen.  The  wind 
grass  (Apera  spica  venti)  which  occurs  everywhere  in  grain  fields  is  less 
sensitive  and  under  such  conditions  develops  more  quickly  than  grain. 
Because  of  its  greater  size,  it  chokes  out  the  seedling  grain.  Similar  con- 
ditions arise  in  connection  with  other  weeds,  which,  developing  more  rapidly, 
not  only  take  food  materials  out  of  the  soil  and  away  from  the  cultivated 


II 

plants,  but  also  injure  them  by  shading.  Actually,  however,  this  struggle  for 
room  is  the  factor  first  manifested  in  each  plant  community  and  makes  itself 
felt  in  all  field  and  forest  plantations.  In  the  grain  field  and  in  every  forest 
tract,  the  individual  first  growing  most  strongly  chokes  out  its  weaker  neigh- 
bors. It  is  the  universal  question  of  the  strong  driving  hack  the  weak  which 
must  find  expression  in  all  community  life. 

The  kind  of  community  life  just  described  in  its  relation  to  spacial  sep- 
aration can  be  termed  neighborhood  in  distinction  from  the  mutual  influenc- 
ing of  organisms  when  united  in  space.  A  relationship  of  this  latter  kind 
(symbiosis)  must  be  the  more  intimate  since  one  organism  lives  with  the 
other.  De  Bary  (1866)  distinguished  a  mutualislic  symbiosis  from  an 
antagonistic,  according  to  whether  the  influence  is  mutually  beneficial  or 
detrimental.  The  terms  chosen  by  Vuillemin  (1889)  for  this  relationship 
"symbiosis"  and  "antibiosis'"  seem  less  fortunate  to  us.  We  find  examples 
of  a  mutualistic  community  also  termed  commensalism  by  van  Beneden  in 
1878,  as  companionship  at  table,  in  the  little  bunches  of  roots  of  the  sago 
palm  (Cycadeae)  which  occur  on  the  surface  of  the  soil,  rigidly  branching 
like  witches'  brooms  and  which  harbor  numerous  chains  of  Nostoc  in  the 
large  holes  in  their  bark.  The  genus  Gunnera  shows  similar  conditions. 
Further,  the  case  is  often  mentioned  in  literature,  in  which  a  water  plant, 
Asolla  caroliniana,  resembling  our  Salvinia  natans,  in  the  axillary  hollows  of 
the  leaves,  gives  shelter  to  another  Nostoc  with  longish  members  (Ana- 
baena).  The  most  accessible  example  of  mutualism  is  ofi'ered  by  the  struc- 
ture of  the  lichen  body,  in  v/hich  fungus  and  alga  remain  connected  per- 
manently, to  their  mutual  benefit, — Lichenism. 

In  the  same  way  may  be  explained  the  symbiosis  of  certain  mycelia  and 
the  roots  of  Fagus,  Corylus,  Castanea  and  some  conifers,  the  so-called  root 
fungus  or  mycorrhisa  w^hich  is  usually  considered  a  necessary  and  universal 
arrangement.  In  connection  with  the  mycorrhiza  should  be  mentioned  the 
protective  device  called  Bacteriorhiza  by  Hiltner^  and  Stormer  (in 
Beta  and  Pisum).  Bacteria  penetrate  from  the  soil  into  the  outer  cell  layers 
of  the  roots,  actually  causing  a  browning  of  these  layers,  but  otherwise  not 
especially  disturbing  the  health  of  the  plant.  According  to  Hiltner,  however, 
these  bacteria  prevent  the  penetration  of  other  injurious  organisms  (Phoma, 
etc.). 

Finally  we  will  consider  the  arrangement  of  root  tubercles,  which  may 
be  found  in  different  forms  and  grouping  on  the  roots  of  the  Lcguminoseae 
and  form  those  well-known  grape-like  bodies  in  aiders,  which  not  infre- 
quently may  be  observed  as  spherical  nests  of  short  branched  roots  as  large 
as  one's  fist.  The  organisms  in  the  tubercles  making  the  nitrogen  of  the  air 
available  for  the  plant  and  described  by  the  students  of  legumes  as  Rhic- 
obium  Leguminosarum  Frank,  or  Bacillus  radicicola  Beijerinck,  are  bacteria 


1  Hiltner  and  Peters,  Untersuchungen  iiber  die  Keimlingskrankheiten  der 
Zucker-  und  Runkelriiben.  Arbeiten  d.  Biolog-.  Abt.  am  Kais.  Ge.sundheitsamte. 
Vol.  IV.     Part  3.  1904. 


just  as  the  producers  of  the  silver  white  tubercles  in  Isopyniin  bitcrnatum 
which,  according  to  MacDougaP  develop  extensively  in  soils  free 
from  nitrates.  On  the  other  hand,  the  recent  investigations  of  Bjorkenheim- 
seem  to  prove  that  a  fungus  is  concerned  in  alders. 

In  antagonistic  symbiosis,  dc  Bary  has  used  the  expression  saprophytism 
and  Johow  in  1889  defined  the  idea  more  closely  by  distinguishing  holo- 
saprophytcs  (those  lacking  chlorophyll)  from  hcuiisoprophytcs  (those  con- 
taining chlorophyll). 

P>ischoff  has  contrasted  with  this  the  conception  of  parasitism.  Ac- 
cording to  Sarauw^  the  expression  "parasite"  was  brought  into  use  in  1729 
by  Micheli  for  the  Balanophoreae*.  In  agreement  with  the  classification  of 
the  saprophytes,  Sarauw  has  distinguished  holo parasites  (those  without 
chlorophyll)  from  hcmiparasifes  (those  provided  with  chlorophyll). 

Saprophytism  is  the  ability  of  an  organism  to  take  its  nourishment  from 
decomposing  organic  substances,  while  the  parasite  drav/s  nourishment  from 
the  living  organism.  If  we  test  this  classification,  based  on  the  forms  of 
nutrition,  we  find  that  here,  as  in  all  branches  of  science,  a  sharp  systematic 
subdivision  is  assumed  only  by  representatives  of  a  young  school,  while  those 
of  the  older  and  more  experienced  school  are  convinced  that  transition  forms 
exist  between  the  dififerent  groups. 

If  relative  adjacency  be  compared  with  iiulriciit  association  (symbiosis) 
each  forest  and  each  grain  field  shows  how  constantly  one  organism  influences 
the  other,  according  to  whether  the  one  leaves  any  food  materials,  water  and 
light,  for  the  other.  Just  as  spacial  separation  sets  no  fixed  limitation  to  the 
form  of  nutrition,  the  sub-division  of  the  organisms  into  those  with  purely 
mineral  nutrition  and  those  dependent  on  organic  substances  should  be 
abolished. 

Although  plants  suited  for  independent  self-nourishment  can  draw  their 
nutrient  material  from  purely  mineral  substrata,  yet  the  process  actually 
present  consists  in  their  taking  humus  substances  which  furnish  the  food 
materials  in  an  easily  absorbable  form  because  of  the  activity  of  a  rich  bac- 
terial flora  in  the  soil.  The  advantages  of  supplying  our  fields  with  animal 
manures  should  be  thought  of  in  this  connection. 

Modern  views  have  strongly  modified  this  distinction  between  sapro- 
phytism and  parasitism,  since  they  have  brought  forward  numerous  exam- 
ples showing  that  the  organisms  called  obligate  parasites  may  become  de- 
pendent on  saprophytic  nutrition  in  definite  developmental  phases  and  con- 
versely that  saprophytes  in  many  instances  can  assume  the  parasitic  mode  of 
feeding.      Miyoshi's^   investigations  give   us  a   clear  insight  into  the   way 


1  Minnesota  Botanical  Studies  1894. 

2  Bjorkenheim,  Beitrlige  zur  Kenntnis  des  Pilzes  in  den  Wurzelanschwellungen 
von  AInus  incana.     Zeitschr.  f.  Pflkr.    1904.    p.  129. 

:■>  Sarauw,  G.  F.  L.,  Rodsymbiose  eg  Mykorrlizer  saerlig  hos  Skovtraerne.  Botan- 
isk  Tidsskrift  1893.     Parts  3  and  4. 

■i  But  Tournefort  in  Mem.  Ac.  Paris  1705,  p.  332,  speaks  of  plants  which  grow  on 
other  plants. 

5  Miyoshi,  Manaba,  Ueber  Chemotropismus  der  Pilze.  Bot.  Zeit.  LII,  1894,  pp. 
1-27. 


13 

in  which  such  a  change  takes  place  in  nutrition.  The  experiments  under- 
taken at  Pfeffer's  Institute  in  Leipsic  show  that  fungus  hyphae  are  irritable 
chemically  and  that  the  direction  of  their  growth  may  be  influenced  either 
towards  the  stimulating  substance,  (positive  chcmotropism)  or  away  from 
it  (negative  cJiemotropism).  Indeed  their  mode  of  growth  also  can  be 
changed  since,  for  example,  a  tendency  towards  sprout  formation  sets  in  with 
a  higher  concentration  of  the  solution.  The  commonest  mold  species,  which 
occasionally  become  parasitic  (Mucor,  Penicillium,  Aspergillus)  show  an  irri- 
tability with  substances  which  almost  always  can  be  presupposed  to  be  char- 
acteristic of  phanerogamic  plants.  Besides  dextrin  and  the  neutral  phosphoric 
acid  salts,  sugar  especially  attracts  fungi,  in  case  the  concentration  is  not 
too  high.  Thus,  for  example,  grape  sugar  in  a  50  per  cent,  solution  acts  repel- 
lently  for  Mucor  stolonifer,  the  active  agent  of  decay  of  fruits.  .A.cids,  on  the 
contrary,  and  alkalis  from  the  beginning  act  repellingly.  The  germination 
tubes  of  the  summer  spores  of  Uredo  linearis,  a  grain  rust,  are  attracted  by  a 
decoction  of  plum  and  wheat  leaves.  Especially  interesting  are  the  cultural 
results  with  Penicillinni  glaucum,  whose  hyphae  bore  through  the  cell  walls 
of  a  leaf  impregnated  with  a  2  per  cent,  cane  sugar  solution.  In  the  same  way 
they  penetrated  artificial  cellulose  membranes  and  the  epidermis  of  bulb  scales 
which  lay  on  a  nutrient  gelatine. 

These  are  especially  important  clues  capable  of  explaining  the  numerous 
case  of  sickness  from  Penicillium.  It  is  well  known  that  this  mold,  the 
most  abundant  agent  of  decay  in  stone  fruits,  first  begins  to  spread  when  the 
ripening  process  has  converted  the  starch  into  sugar. 

In  connection  with  the  penetration  of  Penicillium  into  the  scales  of 
bulbs,  we  find  abundant  examples  in  the  cases  of  decay  in  the  tulip,  hyacinth 
and  lily  bulbs  which  occasionally  lead  to  lawsuits.  This  decay  occurs  especially 
extensively  when  wet  years  prevent  the  maturing  of  the  bulbs  or  if  the  bulbs 
are  stored  when  containing  an  unusual  amount  of  sugar  and  then  used  pre- 
maturely for  forcing. 

Thus  zve  see  hozv  the  cell  contents  and  the  cell  ivalls  of  the  host  plant 
can  determine  the  penetration  of  hyphae  and  the  transition  of  the  saprophyte 
into  a  parasite. 


4.     Parasitic  Diseases. 

Supported  by  various  carefully  studied  cases  of  parasitism,  many  ob- 
servers so  generalized  the  conception  of  parasitic  diseases  that  they  assumed 
them  to  be  present  wherever  organisms  are  found  gathered  together.  In 
many  cases  this  is  supported  by  experiments  in  which  the  parasitically  living 
organisms  were  injected  into  the  host  and  were  able  to  produce  a  local  dis- 
ease in  the  tissue. 

With  this  method  the  apparent  proofs  of  parasitic  disease  were  accumu- 
lated in  such  a  way  that  one  was  forced  to  the  assumption  that  there  could 
be  scarcely  any  disease  which  was  not  caused  parasitically-     Infection  ex- 


14 

periments  in  the  laboratory  led  gradually  to  the  knowledge  that  in  many 
cases  of  disease  no  specific  parasites  were  present  but  universally  distributed 
fungous  and  bacterial  forms.  The  further  the  studies  advanced,  the  more 
cases  were  listed  in  which  inoculation  with  spores  of  the  most  common 
molds,  as  Botrytis,  Penicillium,  Cladosporium  etc.,  also  the  most  widely  dis- 
tributed soil  bacteria.  Bacillus  subtilis  and  B.  vulgatiis,  develop  disease  in 
healthy  tissue.  And  finally  was  recognized  the  importance  of  the  question 
how  organisms  universally  present  could  at  times  be  parasitic  in  their  mode 
of  life  and,  at  other  times,  saprophytic.  Corollary  to  this  question  is  one 
which  was  deduced  from  rapidly  increasing  discoveries  in  many  experiments 
with  the  same  methods  of  infection ;  certain  varieties  or  even  individuals 
were  resistant  while  others  succuml)cd  easily  to  the  parasitic  attack.  \Miat 
is  the  cause  of  such  differences? 

Some  of  the  investigators  brought  forward  the  theory  of  virulence  as 
an  explanation  of  such  cases.  It  was  emphasized  that  in  each  separate  case 
parasitism  as  a  struggle  between  tw^o  organisms  had  depended  necessarily 
upon  which  was  the  stronger.  If  the  weapon  of  attack  of  the  parasite,  for 
instance,  be  an  enzyme,  able  to  dissolve  the  cell  walls  of  the  host,  then  it 
would  be  explicable  that  this  process  would  take  place  more  quickly  in  pro- 
portion to  the  increase  of  solvent  ferment  formed  in  any  given  unit  of  time. 
Since  it  was  now  possible  to  prove  experimentally  that  the  strength  of  the 
attack  varied  in  cultures  of  different  nutritive  substances,  it  could  be  said 
that,  w^here  it  became  the  active  agent  of  disease  and  its  production  of  enzy- 
mes especially  abundant,  it  must  have  been  especially  virulent.  Bacterial 
cultures  furnished  the  greatest  number  of  examples  of  change  in  virulence. 
Yet  such  cases  w^ere  also  determined  with  fungi.  De  Bary's  statement  con- 
cerning the  frequently  encountered  mold,  Balryiis  cinerca,  is  well-known. 
He  states  that  the  mycelium  must  develop  by  the  customary  saprophytic 
form  of  nutrition  up  to  a  certain  strength  before  it  becomes  parasitic  and 
successfully  attacks  the  living  parts  of  the  plants.  I  succeeded  in  getting 
like  results  with  the  conidia  of  this  fungus.  Masses  of  spores  were  strewn 
on  delicate  Begonia  leaves  and  kept  very  damp.  After  several  days  it  was 
possible  to  observe  that,  where  these  spores  had  lain  in  thick  masses,  the  leaf 
had  become  diseased,  showing  a  browning  of  the  tissue.  Where  the  spores 
had  lain  isolated,  however,  no  attack  could  be  discerned.  The  action  of  the 
({uantity  of  ferment  excreted  by  the  individual  spores  therefore  proved  in- 
sufficient, while  the  excretion  from  a  mass  of  spores  brought  about  infection. 
It  can  thus  easily  be  understood  that  parasites,  like  every  other  organism,  de- 
velop most  strongly  when  the  nutritive  conditions  are  most  favorable  and 
that  the  stronger  and  the  more  abundant  the  formation  of  their  vegetative 
organs,  the  greater  the  excretion  of  the  enzyme  and  accordingly  the  increase 
in  strength  of  their  attack.    Therefore  their  virulence  is  raised. 

But  these  processes  are  not  sufficient  to  explain  the  fact  that  in  one  field 
when  a  number  of  varieties  are  grow^n  in  a  single  plantation,  certa-n  ones 
may  be  completely  destroyed  while  others  standing  next  are  but  little  injured. 


15 

or  perhaps  absolutely  unattacked.  Since  in  such  cases  the  parasite  is  t[uickly 
and  extensively  distributed  on  one  variety  and  not  on  the  other,  although  the 
atmospheric  conditions  and  other  factors  of  vegetation  are  equally  favorable, 
the  specific  constitution  of  the  host  plant,  in  these  two  cases  must  have  deter- 
mined whether  it  would  become  diseased.  Thus  we  arrive  at  the  conclusion 
that  for  the  production  of  a  parasitic  disease  the  presence  of  the  parasite 
alone  is  not  determinative  but  the  constitution  of  the  host  organism  is  also 
a  determining  factor. 

The  many  infection  experiments  have  led  to  a  classification  of  the  living 
creatures  infesting  other  organisms  and  capable  of  attacking  the  tissue,  in 
which  one  group  is  described  as  obligate  parasites  when  able  tc  attack  the 
host  plant  in  all  stages  of  its  normal  development.  Of  this  group  there  have 
been  separated  as  zuound  parasites  all  such  organisms  as  cannot  attack  the 
organism  possessing  .normal  protective  devices  but  need  the  changes  in  tissue 
ofifefed  by  the  surface  of  a  wound.  In  a  great  many  instances,  however,  we 
have  recognized  the  fact  that  the  parasite  only  finds  the  environment  re- 
quired for  its  development  when  the  host  has  been  affected  and  its  functions 
weakened.  Such  conditions  will  appear  here  as  were  also  decisive  in  the 
experiments  carried  on  by  Miyoshi  (see  preceding  section).  This  group 
bears  the  name  "parasites  of  weakness." 

To  this  last  group  especially  belong  the  numerous  species  which  during 
many  generations  live  on  dead  organic  substances.  They  therefore  must  be 
spoken  of  as  saprophytes  which  occasionally  become  parasitic, — facultative 
parasites.  Therefore  the  boundary  between  parasitism  and  saprophytism  is 
lost  here  and  even  in  those  species  which  are  always  parasites  (obligates), 
such  as  the  varieties  of  smut,  we  find  developmental  phases  with  a  sapro- 
phytic mode  of  nutrition. 

If  we  now,  however,  study  more  closely  the  families  of  our  closest  para- 
sites among  the  fungi,  namely,  the  smuts  and  rusts,  we  will  find  one  fact 
brought  into  prominence  by  the  most  recent  investigations  and  repeatedly 
substantiated;  namely,  that  the  energy  of  grozvth  of  the  parasite  depends  on 
the  host  plant.  We  have  examples  proving  that  the  same  fungus  occurs  in 
different  species  of  the  same  host  genus  in  the  same  habitat,  sometimes  grow- 
ing luxuriantly  in  many  large  centres,  sometimes  sparsely  in  small  forms, 
according  to  whether  the  one  species  has  fleshy  leaves  and  the  other  thin 
ones.  Indeed,  the  rusts  are  so  dependent  upon  their  host  plants  that  biologic 
races  are  formed  which,  agreeing  formally,  nevertheless  show  differences  in 
adjusting  themselves  to  definite  host  plants  and  either  cannot  develop  at  all, 
even  when  carefully  injected  upon  a  related  host  plant,  or  develop  only 
slightly.  Thus  we  have  a  special  form  of  the  common  black  rust  of  grains 
on  rye,  another  on  wheat,  another  on  oats  etc.  Mycologists  cherish  the  con- 
viction that  this  development  into  individual  races  through  the  accommoda- 
tion to  a  special  host  plant  is  a  widespread  phenomenon  constantly  increas- 
ing. What  else  can  such  a  race  formation  indicate  than  that  parasites  in 
their  demands  have  been  and  still  will  be  most  closely  connected  ivith  the 


i6 

constitution  of  their  substratum?  If,  however,  as  previously  shown,  the 
closest  parasite  is  thus  very  dependent  upon  its  host  plant,  it  only  goes  to 
show  how  completely  it  agrees  with  non-parasitic  plants  in  its  demands  for 
zrry  definite  nutritive  conditions,  and  that  with  a  change  in  these  the  para- 
site changes  its  character  and  either  adjusts  itself  or  disappears.  Stahl's 
observations^  on  myxomycete  plasmodia  show  that  we  must  take 
these  phenomena  of  adjustment  into  consideration.  If  the  water  in  the  cul- 
ture glass  was  replaced  by  a  3-2  per  cent,  grape  sugar  solution,  the  plasmodia 
either  died  from  this  sudden  change  or  shunned  the  sugar  solution.  Grad- 
ually, however,  they  accepted  it,  having  accustomed  themselves  to  a  more 
concentrated  solution  (perhaps  by  a  certain  loss  in  water)  and  indeed  in 
such  a  way,  that,  replaced  in  pure  water,  they  showed  considerable  injury. 

In  regard  to  the  formation  of  races,  Pfefifer-  expresses  himself 
thus ;  "Present  discoveries  .  .  .  make  it  clear  that  the  tropistic  reaction 
of  the  same  species  of  bacteria,  flagellates  etc.  gradually  changes  in  accord 
with  the  existing  cultural  conditions.  Thus  it  should  be  understood  that  in 
the  same  species  in  nature  and  in  artificial  cultures  there  is  found  at  times 
a  very  appreciable  ability  to  respond  to  reactions  and  changes,  varying  to  a 
disappearing  point,  according  to  a  definite  stimulus.  Indeed  after  wide  ex- 
perience it  seems  possible  to  breed  races  in  which  a  definite  reaction  to 
tropism  has  been  partially  or  entirely  lost." 

Parasitism  is  nothing  extraordinary.  Possibly  it  is  not  a  factor  which 
has  newly  appeared  since  plant  cultivation  was  begun.  It  should  be  con- 
sidered as  a  nutritive  form  which  arose  gradually  with  the  development  of 
organic  Ufe  and  a  necessary  one,  to  be  looked  upon  as  the  last  link  in  the 
chain  formed  by  the  mutual  interaction  of  organisms.  This  last  link  begins 
with  those  organisms  which  have  the  ability  of  forming  organic  substances 
from  inorganic  material  through  the  action  of  light.  Joined  to  these  are  the 
plants  with  the  lesser  need  of  light,  such  as  are  found  among  the  bacteria 
living  in  humus  where  an  addition  of  quickly  decomposible  organic  sub- 
stances presents  essential  aid  to  the  nutritive  process.  As  the  struggle  for 
light  gains  in  importance  with  an  increasing  numl)cr  of  organisms,  the  more 
pertinent  becomes  the  development  of  groups  of  organisms  requiring  but 
little  light  and  an  ever  greater  need  of  a  method  of  nutrition  by  which  the 
raw  material  is  ofifered  in  the  form  of  organic,  easily  re-worked  substances. 
Such  conditions  are  found  at  present  in  saprophytism. 

With  the  struggle  for  light  in  the  case  of  a  constantly  increasing  num- 
ber of  individuals  comes  also  the  struggle  for  space.  In  the  course  of  time 
the  lack  of  space  will  lead  finally  to  those  forms  of  adjustment  in  the  plant 
world  which  require  soil  for  their  habitat  only  in  the  beginning,  if  at  all,  and 
have  chosen  some  other  organism  as  a  centre  of  colonization.  The  mutual 
interrelations  forming  under  such  conditions  are  partly  friendly,  partly  hos- 
tile, just  as  they  occur  in  mutualistic  and  in  antagonistic  symbiosis. 


Stahl  in  Bot.  Z.  1884,  pp.  163-66. 

PfefEer,  Pflanzenphysiologie,  2  Edition.     Vol.  II,  p.  763.     Leipzig  1904. 


17 

Among  the  species  of  plants  using  some  other  organism  as  a  habitat,  we 
find  the  formation  of  very  different  devices  for  the  means  of  nutrition.  Be- 
ginning with  lichens,  the  assistance  given  by  thalli  acquires  greater  and 
greater  significance,  up  to  the  formation  of  a  mycelium.  The  mycelium  is 
satisfied  with  dead  bark,  or  rather  that  attacked  when  dying,  or  with  the 
leaf  substance  of  its  host,  or  it  can  only  eke  out  its  existence  when,  with  the 
help  of  the  enzyme  which  it  excretes,  it  attacks  the  living  organic  substance 
and  then  calls  parasitism  into  existence. 

But  in  all  these  relations  the  one  fundamental  law  becomes  evident  that 
each  organism  is  associated  with  the  definite  constitution  of  its  substratum. 
This  substratum  must  have  the  exact  requirements  for  satisfying  all  the  de- 
mands of  the  organism,  otherwise  it  cannot  thrive.  Therefore  all  the  organ- 
isms which  we  call  parasites  make  very  definite  demands  on  some  host.  How 
narrowly  limited  these  demands  may  often  be  is  shown  di recti}'  by  the  bac- 
teria, for  which  at  times  slight  fluctuations  in  the  amount  of  heat,  the  acidity 
of  the  nutritive  mixture  etc.,  lead  to  the  replacing  of  certain  species  by  others 
better  adjusted. 

In  order  to  cite  only  a  few  new  examples  we  will  mention  the  investiga- 
tions of  Thomas  Milburn^  who  cultivated  fungi  as  well  as  bacteria. 
Of  the  former  he  found  in  the  case  of  Hypocrea  rufa  that  an  increase  of 
osmotic  pressure  first  suppresses  the  formation  of  pigment  in  the  conidia 
and  finally  inhibits  the  formation  of  conidia.  In  this  fungus  the  color  of  the 
conidia  changes  with  the  reaction  of  the  medium.  If  the  reaction  is  acid, 
green  spores  are  formed;  if  alkaline,  yellow  spores.  A  well  nourished 
mycelium  forms  no  fruit  in  the  dark  but  does  develop  conidia  when  poorly 
nourished.  The  yellow  color  of  the  mycelium  of  Aspergillus  niger  is  very 
sensitive  to  light  and  when  exposed  to  it  turns  black  within  a  few  hours.  The 
F^acillus  ruber  balticus  found  on  potatoes,  the  so-called  "Kieler  bacillus"^ 
which,  according  to  Laurent,  forms  acids  on  certain  nutritive  soils  and  al- 
kalis on  others,  is  so  influenced  in  its  production  of  coloring  matter  by  the 
nutritive  substratum  that  it  develops  a  violet  color  on  an  acid  substratum  and 
orange  red  on  an  alkaline  substratum. 

Lepeschkin"^  observed  that  the  strictly  aerobic  bacteria  from  the 
sputum  in  pneumonia.  Bacillus  Berestnezvi,  can  develop  a  branching  growth 
on  strongly  alkaline  and  on  strongly  acid  substrata,  but  gradually  acidifies 
the  alkaline  substratum.  In  the  presence  of  sugar  (dextrose)  a  pinkish  color 
appears  together  with  the  disintegration  of  the  little  rods  into  oidia.  In 
the  presence  of  larger  amounts  of  nitrogen  compounds  (aspargin,  lecithin, 
peptone)  the  whole  mass  of  bacteria  turns  yellow.  The  optimum  for  growth 
l-es  probably  at  25°C.  Even  at  35°C.  the  bacterium  grows  very  slowly  and 
at  38°C.  is  no  longer  able  to  grow.     It  is  killed  at  55°C. 


1  Thomas   Milburn,   Ueber  Aenderungen   der  Farben   bei  Pilzen  und  Bakterien. 
Centralbl.  f  .Bakteriologie  usw.    II.  Division  1904.     Vol.  XIII.     Nos.  9-11. 

2  See  Breunig-,  Untersuchungen  des  Trinkwassers  der  Stadt  Kiel,   1888. 

3  L,epeschkin.  Zur  Kenntnis  der  Erblichkeit  bei  den  einzelnen  Organismen  usw. 
Centrabl.  f.  Bakteriolog-ie  usw.     II.  Division.     1904.     Vol.  XII.     Nos.  22-24. 


//  dependence  on  the  constitution  of  the  nutritive  substrata  may  be 
proved  for  parasites,  naturally  the  strongest  agent  in  combatting  them  is  the 
removal  of  the  favorable  nutritive  substratum  and  its  alteration  into  one  un- 
favorable for  the  special  parasite. 

Since  cultivated  plants,  by  the  fact  of  their  division  into  susceptible  and 
resistent  varieties,  demonstrate  that  there  is  a  possibility  of  altering  the  nutri- 
tive substratum  i)roduccd  by  living  plants,  the  production  of  such  resistent 
individuals  through  cultivation  is  the  first  aim  of  our  work,  in  regard  to 
overcoming  parasitic  diseases.  It  is  more  eflfective  than  the  present  method 
of  fighting  parasites  locally  or  preventing  their  attacks,  a  method  which  was 
deduced  from  a  narrow  point  of  view.  At  most  this  may  be  carried  through 
cflfectively  for  small  centres  of  disease  but  for  mechanical  reasons  is  im- 
practicable for  general  use.  From  this  point  of  view  parasitism  is  not  such 
a  great  menace  as  it  has  been  represented  to  be. 

If  parasitism  is  a  definite  nutritive  form  of  certain  groups  of  organisms 
which  has  become  necessary  in  the  natural  development  of  the  living  being, 
it  must  have  its  stage  of  equilibrium  in  the  sphere  of  nature.  Arrangements 
must  exist  which  counterbalance  parasitism.  It  must  be  possible  to  hinder 
its  efifcctiveness  by  factors  simultaneously  effective,  for  otherwise  the  nutri- 
tive organisms  could  no  longer  exist.  This  counterbalance  is  found  in 
the  very  definite,  often  narrowly  restricted  environment  which  determines 
the  existence  of  the  parasite.  That  condition  of  a  living  creature  which  we 
are  accustomed  to  term  "healthy,"  without  being  able  as  yet  to  define  it,  is 
one  such  restricting  limit  which  the  parasite  under  normal  conditions  is  not 
able  to  overcome.  For,  since  the  defenders  of  the  extreme  theory  have 
represented  such  parasitic  micro-organisms  as  dangerous  which  are  con- 
stantly present  everywhere  saprophytically  and  as  yet  have  not  killed  the  host 
plants  as  a  whole,  these  plants  must  thus  possess  some  protective  devices  in 
their  normal  development,  which  are  repeated  in  the  same  sense  from  gene- 
ration to  generation.  We  constantly  find  occurring  as  such,  unbroken  de- 
posits of  wax  and  cork,  definite  acidity  of  the  cell  content  etc. 

That  we  now  find  more  and  more  adherents  to  our  theory  is  proved  by 
the  statements  of  one  of  our  most  important  students  of  parasitism,  Met- 
schnikoff^  of  the  Pasteur  Institute.  After  giving  a  number  of  examples 
to  show  that  the  production  of  the  parasitic  disease  is  conditioned  by 
tzvo  causes,  first,  the  parasite  and  secondly,  susceptibility  of  the  organisms, 
he  says,  (page  7)  "if  these  internal  conditions  are  powerless  to  arrest  the 
development  of  the  excitor  of  a  disease,  the  disease  is  produced.  If,  how- 
ever, the  organism  firmly  resists  the  development  of  the  bacteria,  it  is  pro- 
tected and  thus  proves  itself  immune."  (Page  6)  "One  can  no  longer  be  of 
the  opinion  that,  every  time  an  excitor  of  disease  penetrates  a  susceptible 
organism,  the  presence  of  the  same  inevitably  calls  forth  this  specific  dis- 
eased condition.  Loffler's  discovery  of  the  diphtheria  Bacillus  in  the  pharynx 

1  Immunittit  bei  Infektionskrankheiten  by  Elias  Metschnikoff,  Professor  of  the 
Pasteur  Institute  in  Paris.  Authorized  Translation  by  Pr.  Julius  Meyer.  Jena, 
Gustav  Fischer,  1902. 


19 

of  healthy  children  has  been  repeatedly  substantiated  since  that  time  and  yet 
it  is  impossible  to  doubt  the  etiological  significance  of  this  bacillus  for  diph- 
theria. On  the  other  hand  it  has  been  proved  that  Koch's  Vibrio,  although 
the  real  incitor  of  Asiatic  cholera,  nevertheless,  occurs  in  the  digestive  system 
of  healthy  people." 

The  healthy  organism  thus  possesses  a  natural  immunity  and  any  distur- 
bance of  this  aids  the  possible  parasitic  attack. 

5.*   Epidemics. 

If  we  can  define  endemics  as  a  local  malady,  whose  production  is  con- 
nected with  definite  conditions,  narrowly  limited  locally,  then  epidemic  may 
be  called  a  community  malady.  The  expression  "malady"  indicates  the  mul- 
tiplicity of  the  diseased  individuals  in  contrast  to  isolated  cases  of  disease. 
Epidemic  thus  describes  that  condition  in  which  numerous  individuals  suc- 
cumb to  a  given  form  of  disease,  developing  over  large  territories. 

If  an  epidemic  breaks  out,  conditions  must  be  present  which  disturb  the 
functions  of  the  organism  in  numerous  individuals  so  strongly  that  .their 
lives  are  either  threatened  with  a  premature  end  or  are  finally  brought  to 
this  end.  This  disturbance  arises  from  external  causes.  If  these  causes  are 
parasitic  organisms,  their  existence,  as  was  shown  in  the  preceding  chapter, 
is  dependent  on  the  factors  of  growth  favorable  to  their  extensive  increase. 
Among  these  factors  belongs  the  breaking  down  of  the  immunity  of  the 
nutritive  organism. 

Even  with  the  assumption  that  a  parasite  not  indigenous  to  the  countries 
which  suffer  from  the  disease  might  have  caused  the  epidemic  by  its  incur- 
sion, this  circumstance  in  no  way  changes  the  fact  that  the  factors  of  growth 
already  existing  are  determinative  for  the  production  of  the  epidemic.  For. 
whatever  may  wander  into  the  country,  be  it  animal,  fungus  or  bacterium, 
this  incursion  would  not  produce  an  epidemic,  if  the  newcomer  found  no 
opportunity  for  great  increase  and  wide  distribution.  For  example,  who 
does  not  remember  very  effective  representations  of  the  importation  of  the 
Colorado  beetle  as  the  destroyer  of  our  potato  crop,  or  the  extensive  intro- 
duction of  the  San  Jose  scale  as  the  destroyer  of  our  fruit  trees?  Initiated 
persons  know  how  often  embargo  regulations  and  compulsory  disinfection 
have  advanced  protection  against  the  importation  of  parasitic  fungi  ("White 
Rot  of  the  Grape"  etc.)  and  they  have  partially  succeeded  in  getting  it. 

Experience  has  taught  that  no  theoretically  imagined  but  practically  im- 
possible complete  destruction  or  quarantine  of  such  parasites  has  possibly 
protected  us  from  epidemics  but  the  circumstance  that  they  did  not  find  the 
necessary  climate  and  soil  for  their  increase.  Conversely,  the  Phylloxera 
plague  should  be  remembered  which,  despite  all  human  endeavor  and  the 
spending  of  many  millions,  became  more  and  more  widespread.  The 
Phylloxera  finds,  even  in  Europe,  sufficiently  favorable  conditions  for  exis- 
tence and  on  this  account  defies  such  means  for  fighting  it  as  embargo,  dis- 
infection, processes  of  extermination  etc.     Upon  consideration,  it  becomes 


gradually  clearer  that  small  living  creatures,  in  fact,  the  smallest  which  are 
intHKluced  by  means  of  articles  of  commerce  or  can  be  easily  distributed  by 
dust  and  wind,  may  be  kept  out  of  small  enclosed  places  but  not  away  from 
extensive  open  localities,  and  that  one  proceeds  better  by  presupposing  the 
possibilities  of  a  widespread  distribution  of  such  organisms  although  real 
danger  is  to  be  recognized  only  if  an  easy  capacity  for  its  increase  has  been 
proved.  If  now  in  all  parasitic  incursions,  not  the  presence  of  the  parasite 
but  the  conditions  favoring  its  spread  are  proved  decisive  for  the  production 
of  the  epidemic,  then  a  change  in  these  conditions  is  the  best  means  for  com- 
batting them. 

In  regard  to  measures  for  its  suppression  and  prevention,  however,  the 
epidemic  furnishes  special  pointers  in  that,  when  it  occurs  over  extensive 
areas,  it  excludes  as  causes  all  the  factors  which  vary  from  one  another  in 
the  difYerent  diseased  districts.  For,  since  the  malady  attacks  large  plan- 
tations despite  the  variation?  in  such  factors  as,  for  instance,  situation,  com- 
position of  the  soil,  agricultural  methods  etc.,  these  factors  cannot  be  the 
cause.  Rather  the  cause  should  be  sought  in  those  influences  which  are  the 
same  throughout  the  whole  country.  Actually,  this  can  only  be  the  climate. 
On  the  other  hand,  in  endemic  diseases,  conditions  of  the  soil  usually  act  de- 
cisively. They  are  to  be  considered  either  direct  causes  of  disease  since, 
through  unfavorable  chemical  or  physical  pculiarities  they  permanently  dis- 
turb the  functions  of  the  plants,  or  they  act  indirectly,  favoring  the  increase 
of  the  parasites  and  the  strength  of  their  attacks.  In  this,  as  a  rule,  they 
.suppress  at  the  same  time  the  growth  energy  of  the  host  plant.  Soil  damp- 
ness is  the  condition  most  favoring  this.  When  the  capacity  of  thick,  heavy 
soils  for  retaining  water  is  very  great  on  the  level  or  in  hollows,  an  accumu- 
lation usually  occurs  which  finds  no  outlet  and  produces  a  deficiency  of  oxy- 
gen, with  an  excess  of  carbon  dioxid.  The  plants  indicate  this  functional 
disturbance  by  a  change  in  the  chlorophyll  apparatus.  The  leaves,  gradually 
turning  yellow,  form  a  suitable  growing  medium  for  certain  groups  of  fungi. 

In  all  endemics  and  epidemics  a  simultaneous  sickening  of  a  great  num- 
ber of  individuals  indicates  a  considcvahlc  period  of  prcpamtioii  Jcadiii;/  up 
to  the  actual  outbreak  of  the  mahidy. 

For,  according  to  our  conception  of  all  the  phenomena  of  life  as  dynamic 
processes,  each  case  of  disease  may  be  characterized  as  the  immediate  or  in- 
direct result  of  mechanical  disturbances  exercised  by  the  separate  factors  of 
growth  on  the  composition  and  function  of  the  substance.  The  life  of  a  cell 
is  a  constant  struggle  between  the  oscillatory  forms  momentarily  present  in 
the  unstable  organic  compounds  and  the  disturbances  constantly  exercised 
upon  them  ])y  the  factors  of  growth. 

A  change  in  the  substance  and  with  it  one  in  its  function  appear  at 
once  if  the  disturbance  in  one  factor  of  growth  is  so  strong  that  it  is  able  to 
change  the  form  of  oscillation  existing  up  to  that  time.  So  long  as  the  dis- 
turbances as  a  whole  have  the  effect  of  contributing  to  the  development  of 
the  organism  as  a  whole,  that  is,  the  vegetable  individual,  the  plant  remains 


within  the  latitude  of  health.  Disease  follows  if  the  cell  or  the  cell  complex 
is  so  changed  that  ultimately  the  whole  structure  suffers. 

Now,  however,  the  fact,  always  confirmable  by  examples,  that  certain 
cultivated  varieties  show  a  tendency  to  disease  not  shown  by  others  under 
similar  conditions  of  growth,  furnishes  us  proof  that  in  the  different  individ- 
uals the  organic  substance  may  oppose  a  dififering  amount  of  resistance  to 
the  same  attacks.  This  would  mean  that  more  attacks  are  necessary  for  one 
individual  than  for  another  in  order  to  carry  it  out  of  the  latitude  of  health. 
If,  in  an  epidemic,  only  large  numbers  of  individuals  always  suddenly  become 
sick,  besides  the  especially  susceptible  ones  there  must  also  be  others  among 
them  for  which  a  greater  number  of  attacks  and  therefore  a  longer  period 
of  action  is  necessary,  in  order  that  they  may  become  sick.  Therefore  a 
longer  period  of  the  influences  producing  the  disease  must  have  led  up  to 
the  outbreak  of  the  epidemic  and  these  irfluences  are  to  be  seen  in  the  atmosr 
pheric  factors. 

Therefore,  according  to  our  tlieor}-,  each  epidemic  is,  so  to  speak,  the 
explosion  of  a  charge  which  had  been  slowly  accumulating  for  some  time. 
Its  cause  therefore  is  not  to  be  sought,  at  least  exclusively,  in  the  existing 
factors  of  growth  present  at  the  moment  but  in  the  accumulation  of  attacks 
which  for  some  time  previously  have  been  effective  in  the  same  way.  In 
parasitic  epidemics  the  extensive  occurrence  of  the  micro-organism  in  no 
way  represents  the  first  stage  of  the  phenomenon  but  is  a  final  effect  of  long 
preparation.  This  preparation  consists  on  the  one  hand  in  the  gradual  pro- 
duction of  life  conditions  favorable  for  the  enormous  increase  of  the  micro- 
organisms, on  the  other  hand,  in  the  gradual  weakening  of  some  functions 
of  the  host  which  we  believe  are  always  connected  with  this  and  a  correlative 
increase  of  other  functions. 

If,  for  example,  we  study  the  best  known  fungous  epidemic,  potato 
blight,  observation  shows  that  a  period  of  warm,  dull,  sultry  days  usually 
precedes  the  outbreak.  The  fungus  Phytophthora  infcstans  is  always 
present.  Its  astonishingly  rapid  increase,  however,  takes  place  out  of  doors 
only  if  abundant  atmospheric  precipitation  and  a  warm  motionless  air  con- 
tinuously favor  the  production  and  the  scattering  of  the  swarm  spores.  Dur- 
ing weather  of  this  kind  the  potato  plant  develops  a  greater  amount  of  sugar, 
a  more  rapid  stem  growth  and  a  great  number  of  young  leaves;  that  is,  it 
produces  an  especially  susceptible  environment  for  the  development  of  the 
fungus  which  scorns  organs  that  have  become  old.  In  this  way  we  find  that 
whole  fields  may  become  diseased  in  a  few  days. 

On  the  other  hand  we  do  not  find  the  Pytophthora  epidemic  if  the  same 
amount  of  precipitation  occurs  in  the  same  space  of  time  but  in  cold  weather. 
The  epidemic  cannot  develop  if,  with  increased  warmth  and  a  clouded  sky. 
l^ersistent  strong  winds  keep  blowing.  A  similar  relation  is  shown  in  rust 
epidemics  of  grains.  Like  the  majority  of  fungi  the  grain  rusts  love  con- 
tinuous moisture.  Yet  by  no  means  do  we  always  have  rust  epidemics  in  wet 
years,  although  there  might  be  scarcely  one  grain  field  in  which  the  rusts 


22 

would  not  be  present  every  year.  The  epidemic  develops  at  the  time  when 
the  leaves  are  young  and  only  during  periods  of  warm  days  with  frequent 
even  if  almost  unappreciahle  showers  which  make  possible  a  longer  retention 
of  moisture  among  the  plants.  Cold,  wet  summers  generally  prevent  the 
development  of  rust  epidemics.  Similar  conditions  may  be  observed  in 
bacterial  epidemics. 

Therefore,  epidemics  arc  forms  of  disease  which  mature  only  because  of 
far  reaching  factors.  Only  certain  weather  combinations  of  longer  duration 
may  be  considered  as  the  initial  cause.  Naturally  the  intensity  of  the  epi- 
demic will  vary  locally  because  local  factors  will  produce  special  favorable 
conditions.  In  this  way  is  explained  the  occurrence  of  centres  in  which  the 
malady  appears  first  and  disappears  last,  in  case  not  all  the  individuals  are 
killed  in  a  short  time.  In  this  way  is  explained  further  the  retrogression  of 
epidemics  into  endemics ;  that  is,  into  narrowly  confined  centres  of  disease. 
Among  the  epidemics  produced  by  animal  parasites,  those  caused  by  grain 
flies  are  the  most  abundant  with  us.  They  usually  take  place  during  periods 
of  continued  warm,  dry  weather  after  the  winter  conditions  have  been  favor- 
able for  the  individual  grain  flies  which  in  some  regions  are  always  present. 
So  far  as  statistics  now  go,  preferred  centres  and  points  of  departure  may 
often  be  determined  for  this  plague-like  distribution.  Thus,  for  example, 
the  province  Posen  is  proved  to  be  especially  favorable  soil  for  grain  flies. 
From  Posen  as  a  centre  an  epidemic  usually  radiates  towards  Brandenburg, 
Pomerania  and  West  Prussia.  The  whole  Eastern  part  of  Germany  suffers 
more  from  injuries  due  to  flies  than  does  the  Western  p^^rt.  North  Western 
Europe  is  usually  visited  more  frequently  and  intensely  than  South  \\^estern 
and  South  Eastern  Europe. 

According  to  the  point  of  view  here  developed  any  treatment  of  the 
epidemics  by  fighting  the  symptoms  as  they  appear  must  ofifer  the  least  pros- 
pect of  success,  because  these  are  only  the  result  of  initial  stages  which 
existed  long  before.  If  the  parasites  arc  present  in  enormous  quantities  the 
desire  to  kill  the  micro-organisms  is  seen  to  be  a  vain  one  since  no  insecticide 
of  fungicide  can  even  approximately  reach  the  main  mass  and  still  less  cause 
its  death.  Thus  as  the  pestilences  are  induced  by  general  factors  acting  uni- 
versally, they  must  be  combatted  by  broad  means  wdiich  undo  the  life  con- 
ditions of  the  parasite  and  change  the  constitution  of  the  host,  that  is,  the 
functional  direction.  If,  for  example,  long  wet  periods  permit  the  bacterial 
rot  of  potato,  which  we  call  "ivet  rot,"  to  appear  in  epidemic  proportions, 
any  other  means  than  increased  ventilation  of  the  soil  can  scarcely  be  used 
successfully.  So  far  as  specific  anaerobic  bacteria  are  concerned,  the  factor 
favorable  to  growth  (lack  of  oxygen  with  excess  of  carbon  dioxid)  is  re- 
moved by  an  increase  of  oxygen  and  also  by  the  decrease  for  them,  as  well 
as  for  other  bacteria,  of  the  condition  fundamental  to  their  abundant  in- 
crease, an  abundance  of  water.  Nature  generally  works  in  this  way.  If, 
after  the  rainy  periods,  dry,  windy  weather  continues  for  some  time  so  that 
the  soil  dries  and  the  air  circulates  freely,  the  progress  of  the  disease  comes 


23 

naturally  to  a  standstill.  The  recommendation  of  every  regulation  for  the 
prevention  of  infection  by  the  removal  of  infected  potatoes  from  the  field,  or 
by  deep  subsoil  cultivation,  or  the  burning  of  diseased  straw  in  grain  epi- 
demics, we  consider  to  be  a  work  with  insignificant  results  as  contrasted  with 
the  effect  of  changed  life  conditions  for  the  parasite.  The  amount  of  in- 
fected material  in  extensive  districts  does  not  come  under  consideration  at 
all.  At  times  in  the  case  of  damp  rot,  soil  bacteria  co-operate  and  form  a 
dense  condition  of  the  soil.  If  atmospheric  influences  make  themselves  so 
felt  in  certain  soils  that  certain  bacterial  groups  are  able  to  attack  potatoes 
or  other  fruits  of  the  field,  the  number  of  the  causative  agents  of  the  disease 
originally  present  is  almost  of  no  significance. 

The  last  named  examples  of  parasitic  epidemics  due  to  such  micro- 
organisms as  may  be  assumed  to  be  constantly  present  in  the  soil  or  the  air, 
make  clear  to  us,  however,  how  little  prospect  of  success  is  offered  for  com- 
batting an  epidemic  once  it  has  broken  out.  A  greater  protection  for  our 
cultivated  plants  lies  in  preventive  methods.  Such  a  preventive  process  in 
epidemics,  aside  from  the  formation  of  an  universal  plant  hygiene,  can,  how- 
ever, be  induced  by  the  drawing  up  of  a  chart  of  pestilences;  that  is,  a  sum- 
mary of  plague  centres  for  each  individual  epidemic.  In  the  correspondence 
of  certain  characteristics  for  a  number  of  plague  centres,  single  factors  are 
especially  distinguished  as  fundamental  for  the  production  of  an  epidemic ; 
for  example,  dryness  in  light  soils  is  shown  to  be  favorable  for  fly  epi- 
demics of  grain  or  for  the  heart-rot  of  sugar  beets  etc.  Having  thus  deter- 
mined weather  and  soil  combinations  dangerous  for  each  individual  epidemic 
one  can  make  one's  attack  prophylactically  by  means  of  cultural  regulations 
as  soon  as  the  threatening  combination  of  conditions  continues  for  some  time. 
Direct  means  which  kill  the  parasites,  such  as  sprinkling  with  copper  sulfate 
or  dusting  with  sulfur,  will  then  act  only  as  hinderanccs  to  the  epidemics  if 
used  preventively. 


6.     Artificial  Immunization  and  Internal  Therapy. 

It  is  quite  natural  that  in  phytopathology  the  same  course  of  ideas  has 
developed  as  in  animal  pathology  and  accordingly  it  is  not  strange  that  there 
has  gradually  become  evident  a  theory  of  immunizing  plants  artificially ;  i.  e., 
of  so  changing  their  bodily  composition  that  the  parasites  will  no  longer  find 
the  nutritive  soil  necessary  for  colonization,  for  their  wider  distribution. 

There  already  exist  several  works  along  this  line  in  which,  following  in 
part  serum  therapy,  use  is  made  of  immunifying  substances  obtained  from 
the  parasite  itself,  and  again  where  mineral  salts  are  used.  Along  the  former 
line  belong  Beauverie's^  investigations  with  Botrytu  cinerea  and  those 
of    Ray-    with    very    different    kinds    of    parasites.     The     latter     obtained 


1  Beauverie,  J.,  Essai  d'immuni.sation  des  vegetaux  centre  les  maladies  crypto- 
gamiques.  Compt.  rend.  Paris  1901.    11,  p.  107. 

2  Ray,  J.,   Cultures  et  formes   attenuees   des  maladies  cryptogamiques.   Compt. 
rend.  Paris  1901.  II,  p.  307. 


the  result  that  parasitic  organisms  may  be  influenced  in  artificial  cultures 
by  the  nutritive  medium  used.  In  this  their  virulence  is  proved  always  to 
be  less  than  it  is  under  natural  conditions.  By  leeching  the  cultures,  fluids 
may  be  obtained  which  may  be  used  for  the  immunization  of  the  host  plants 
against  the  organism  concerned.  The  author  concludes  further  that  the  in- 
fected plants  are  actually  cultures  of  the  parasites  concerned.  In  this 
maceration  and  extraction  of  the  diseased  plant  jjarts  must  furnish  fluids 
which  would  exercise  an  effect  similar  to  that  of  the  |)arasite  itself.  \\'hon 
modified  by  increased  temperature,  these  fluids  can  1)C  used  for  immunization. 

E.  MarchaP  should  be  especially  mentioned  as  a  representatixe 
of  the  other  line  of  immunization  experiments.  He  worked  with  mineral 
substances,  some  of  which  were  nutritive,  while  others  should  be  considered 
poisonous.  He  sowed  lettuce  in  Sachs'  nutrient  solution  with  the  addition 
of  substances  which  kill  fungi.  The  young  seedlings,  after  the  development 
of  the  first  two  or  three  leaves,  were  infected  with  the  zoo-conidia  of  Brcmia 
Lactucac  and  then  kept  in  a  moist  atmosphere.  The  plants,  not  rendered 
immune  by  the  substances  in  the  nutrient  solution  whicli  would  kill  fungi, 
were  at  once  attacked.  Of  the  salts  used,  the  addition  of  irom  three  to  four 
ten-thousandths  copper  sulfate  to  the  nutrient  solution  was  clearly  proved  to 
increase  the  resistance.  The  addition  of  i-ioooo  copper  sulfate  no  longer 
showed  any  immunizing  effect  whatever.  ^Manganese  sulfate  acted  less  com- 
pletely;  ferrous  sulfate  had  no  effect  at  all.  Calcium  salts  also  (up  to  2-100) 
could  increase  the  resistance  while  nitrates  and  also,  curiously  enough,  phos- 
phates lessened  it. 

The  idea  of  increasing  each  individual's  susceptibility  to  vegetable  para- 
sites by  changing  the  cell  sap  through  the  addition  of  foreign  substances  was 
also  taken  up  by  zoologists  who  proceded  in  accordance  with  the  discovery 
that  parasitic  animals,  for  instance,  scale,  seek  out  weakened  plants  especially. 

Now,  however,  was  associated  with  this  the  though i  that  universal  con- 
ditions of  weakness  in  cases  of  constitutional  disease  as  well  as  conditions  of 
susceptibility  to  parasitic  attack  could  be  healed  by  supplying  salts  of  some 
definite  kind  to  the  plant  body  extra-radically.  This  taking  up  of  substances 
otherwise  than  through  the  roots  was  called  "Internal  Therapy'  and  was 
developed  methodically. 

In  1894,  I.  Schewyrjov-  published  an  article  on  "the  impregna- 
tion of  the  wood  in  living  trees  with  solutions  of  coloring  matter"  (Ueber  die 
Durchtrankung  des  Holzes  lebender  Baume  mit  Farbstofflosungen").  In 
ii  he  describes  the  apparatus  which  he  constructed  for  this  purpose  which  we 
will  call  nutrition  tube  and  nutrition  basin.  The  tube  is  of  steel,  pointed  at 
one  end,  which  is  driven  into  the  bark,  while  the  other  end  is  closed  by  a 
cork,  through  which  passes  a  gimlet.  The  tube  is  filled  with  the  experimental 
liquid,  through  special  openings,  by  means  of  a  rubber  tube.    Then  the  gimlet 


1  Marchal,  E.  De  rimmunisation  de  la  laituc  centre  le  meunier.     Compt.  rend. 

1902.  CXXXV,  p.  1067. 

-'  Schewyrjov  Iwan,    Berichtigung-    usw.    Zeitschrift    ftir    T^flanzenkrankhciten. 

1904.  p.  70. 


25 

is  bored  slowly  down  into  the  wood  to  the  desired  deptli  so  that  the  liquid 
but  no  air  can  penetrate  into  the  canal  thus  formed  by  the  gimlet.  The 
author  who  had  constructed  other  apparatus  also  mentioned  Hartig's  ex- 
periments which  had  the  disadvantage  of  letting  air  penetrate  into  the 
wound.  He  then  began  experiments  on  the  healing  of  chlorosis  which  were 
carried  out  in  1895-6  and  in  1901,  by  garden  owners  in  the  Crimea. 

Later  Mokrzecki^  published  a  number  of  successful  experiments 
on  the  healing  of  chlorosis  in  fruit  trees  carried  out  according  to  the  above 
method,  in  which  he  also  pointed  out  that  the  scale  had  disappeared  from  the 
healed  branches.  He,  as  well  as  Schewyrjov,  built  great  hope  on  this  pro-, 
cess,  not  only  for  the  prevention  of  constitutional  disturbances  in  nutrition 
but  also  especially  for  the  expulsion  of  parasitic  organisms. 

■  My  personal  attitude  toward  this  question  is  much  cooler  and  I  think 
that  the  effectiveness  of  the  methods  will  be  very  limited.  According  to  my 
experiments  on  the  introduction  of  poisonous  solutions  into  the  trunk,  the 
effect  usually  remains  local  but  in  the  most  successful  cases  radiates  grad- 
ually from  the  point  of  introduction  to  a  number  of  branches  and  to  a  con- 
siderable distance  into  the  trurik.  The  constitution  of  the  plant,  conditioned 
by  root  nutrition,  was  not  changed  by  this.  I  found  in  my  experiments  with 
oxalic  acid  that  gum  was  produced  on  a  number  of  cherry  tree  branches 
which  later  partially  died.  However,  the  production  of  gum  did  not  progress 
further  the  following  year  and  the  trees,  moreover,  made  a  healthy  growth. 
Like  this  poisonous  solution,  each  nutritive  mixture  or  healing  serum  remains 
limited  within  narrow  boundaries  and,  as  in  the  most  favorable  case,  only 
temporarily  exercises  any  beneficial  influence.  The  physiological  direction 
of  the  work  of  the  whole  plant  will  not  be  changed  permanently. 


7.     Predisposition. 

We  term  "predisposition"  that  condition  of  certain  individuals  which 
renders  them  more  easily  and  c[uickly  susceptible  to  any  cause  of  disease  than 
are  other  individuals  of  the  same  kind. 

That  such  cases  exist  is  proved  by  daily  discoveries  as  to  the  quantitative 
growth  of  cultivated  plants.  These  discoveries  have  already  found  expression 
in  the  common  use  of  the  terms  tender  and  hardy  varieties  and  individuals 
which  have  been  made  less  resistant.  Observations  show  that  not  only  differ- 
ent cultural  varieties  of  the  same  species  but  even  single  individuals  of  the 
same  variety  possess  a  varying  power  of  resistance  to  weather  extremes,  as, 
for  example,  cold  and  heat,  or  to  parasitic  attack.  In  the  latter  connection, 
it  suffices  to  mention  that  practical  workers  as  well  as  scientific  investigators 
have  now  set  themselves  the  task  of  breeding  more  resistant  varieties. 

At  present  we  are  only  in  a  position  to  indicate  the  direction  in  which  a 
greater  individual  inclination  to  succumb  to  any  parasitic  attack  rnay  be  pro- 


1  Mokrzecki,  S.  A.  Ueber  die  innere  Therapie  der  Pttunzen.     Zeitschr.  f. 
zenkrankheiten.    1903.    p.   257. 


26 

duced.  In  the  previous  divisions  we  have  considered  investigations  showing 
that  different  groups  of  substances  produced  in  the  plant  cells,  as,  for  in- 
stance, sugar,  act  attractively  for  certain  fungi  in  definite  concentrations  and 
repellantly  in  others.  The  number  of  these  groups  of  substances  is  deter- 
mined by  very  different  factors,  as  will  be  shown  more  thoroughly  in  the  next 
chapter.  This  metabolism  will  be  found  favorable  for  the  nutrition  of  the 
parasite  or  unsuitable  for  it,  according  to  the  quantity  produced. 

In  order  to  cite  at  least  one  example  in  this  connection,  we  will  refer  to 
the  investigation  of  Viala  and  Pacott^  on  the  black  rot  of  the  grape. 
The  cultures,  undertaken  with  the  fungus  Gu'ignardia  Bidzvcllii  which  pro- 
duces the  disease,  determined  that  the  development  of  the  fungus  is  depen- 
dent primarily  on  the  sugar  content  of  the  nutrient  substratum  and  its  organic 
salts.  Only  young  leaves  were  affected.  They  contained  1.75  per  cent,  tar- 
taric acid  and  4.3  per  cent,  glucose,  while  the  old  leaves  showed  only  traces 
of  these  substances.  The  berries  were  susceptible  from  the  time  they  began 
to  swell  and  this  susceptibility  continued  up  to  the  beginning  of  the  ripening 
stage.  During  this  time  they  contained  32  to  24  per  cent,  of  acid  and  11  to 
56  per  cent,  of  sugar.  During  ripening  the  acid  content  falls  from  9  to  2  per 
cent.,  but  the  sugar  content  increases  so  greatly  that  the  fungus  can  no  longer 
attack  the  berries.  The  conditions  for  the  white  rot  fungus,  however,  are 
exactly  reversed.  By  this  relation  is  explained  the  strikingly  different  resis- 
tant capacity  of  different  kinds  of  grapes.  In  the  same  way  is  explained  the 
circumstance  that  black  rot  epidemics  generally  occur  in  summer  after 
periods  of  cold  weather  with  subsequent  light  rainfall.  At  this  time  the  acid 
content  is  especially  large  and  the  formation  of  sugar  scanty.  Similar  fluct- 
uations in  the  concentration  of  the  cell  sap  combined  with  the  phenomena  of 
perforation  of  the  membrane,  the  varying  processes  of  tension  in  rhe  tissues 
and  other  mechanical  changes  also  in  the  plants  cause  a  state  of  greater  sus- 
ceptibility to  weather  extremes.  The  more  recent  investigation  is  endeavor- 
ing to  find  more  macroscopic  and  microscopic  characteristics  also  demarking 
the  stages  of  susceptibility  to  injurious  parasitic  attacks. 

The  conditions  pictured  in  the  preceding  example  of  ihc  increased  tend- 
ency of  the  grape  to  become  susceptible  to  the  black  rot  fungi  are  entirely 
normal  developmental  phases  which  are  influenced  by  the  weather.  On  this 
account  we  may  speak  of  such  states  as  normal  predisposition.  In  contrast 
with  these  we  should  distinguish  as  abnormal  predisposition  the  case  in  which 
the  plant  or  one  of  its  organs  has  fallen  into  a  condition  of  weakness  or  of 
disease  from  other  influences  and  in  this  conception  of  one  cause  of  disease 
is  first  given  the  desired  point  of  attack.  As  an  example,  w^e  will  call  attention 
to  the  infection  of  leaves  affected  with  honey  dew  by  the  black  fungi,  to  the 
attacks  of  the  so-called  parasites  of  weakness  and  the  migration  of  wood- 
destroying  fungi  from  wounded  surfaces. 


1  Viala,  P.,  et  Paeottet,   Sur  la  culture  du  black  rot.     Compt.  rend.  Paris  1904. 
Vol.  CXXXVIII,  p.  306. 


27 

8.     Predisposition  and  Immunity. 

In  an  earlier  part  we  have  pointed  out  that  our  theory  as  to  the  produc- 
tion of  parasitic  diseases  has  obtained  support  from  the  most  renowned  in- 
vestigators. Metschnikoff^  who,  as  professor  in  the  Pasteur  Institute 
for  infectious  diseases,  may  be  incontestibly  considered  as  an  exact  con- 
noisseur of  pathogenic  micro-organisms,  expresses  himself  as  follows, 
"Exact  bacterialogical  mvestigations  have  led  to  the  knowledge  that,  in  the 
abundant  bacterial  flora  harbored  by  the  healthy  human  body,  representa- 
tives of  pathogenic  bacterial  species  may  also  be  found.  Aside  from  the 
Bacillus  of  diphtheria  and  the  Vibrio  of  cholera  which  so  often  have  been 
proved  to  be  fully  virulent  in  perfectly  healthy  human  beings,  it  has  been 
shown  that  certain  pathogenic  micro-organisms,  the  Pneumococci,  the  Sta- 
phylococci, Streptococci  and  Colibacilli,  are  present  regularly  or  almost  con- 
stantly in  the  microbe  flora  of  healthy  persons. 

This  discovery  has  of  necessity  led  to  the  conclusion  that  besides  the 
excitor  of  the  disease,  still  a  seeond  cause  of  infectious  diseases  must  exist, 
namely,  a  predisposition  or  a  lack  of  immunity.  An  individual  which  harbors 
one  of  the  species  of  pathogenic  bacteria  above-named  would  be  resistant 
either  permanently  or  for  the  time  being.  But  as  soon  as  this  immunity  dis- 
appears, the  excitor  of  the  disease  becomes  uppermost  and  produces  the 
specific  disease." 

In  regard  to  the  immunity  of  plants,  Metschnikoff  calls  attention  to  the 
investigations  of  de  Bary^  on  Botrytis,  which  we  have  already  men- 
tioned. The  mycelium  of  this  fungus  penetrates  the  cell  walls  by  giving  oft' 
a  fluid  "which  contains  a  digestive  ferment  and  the  oxalic  acid  necessary  for 
this  ferment.  De  Bary  could  prove  the  presence  of  this  kind  of  toxin  by  the 
maceration  of  the  mycelium  of  Sclerotinia  ....  If  the  resulting  fluid 
is  heated  to  52°C.  it  can  no  longer  digest  the  cellulose  membrane  but  is  still 
able  to  cause  plasmolysis  ....  The  results  of  de  Bary's  investigations 
have  been  confirmed  and  in  part  completed  by  Laurent.'"'^ 

We  have  repeated  JNTetschnikoff's  words  in  order  to  characterize  his 
way  of  considering  the  matter.  The  chief  factor  under  consideration  here, 
viz.,  the  eft'ectiveness  of  the  ferment  on  young  membranes  and  its  ineft'ective- 
ness  on  older  ones,  gives  the  author  reason  for  comparing  the  Botrytis  dis- 
eases with  the  infantile  diseases  in  human  beings  (measles,  scarlet  fever). 
In  other  cases  the  different  processes  of  cork  production,  or  suberization, 
found,  for  example,  in  wounds,  act  in  a  way  similar  to  the  membrane  changes 
in  the  ageing  of  the  cells.  In  regard  to  these,  Metschnikoff,  supported  by  the 
investigations  of  Massart^  points  out  that  the  organs  respond  differ- 
ently to  the  traumatic  stimulus  according  to  their  age.  Young  leaves  of 
Clivia,  for  example,  re-act  by  forming  callus,  older  ones  simply  close  the 


1  MetsclinikofE,  Immunitat  bei   Infectionskrankheiten.     Jena,   190' 

2  De  Bary  Bot.  Zeit.  1866. 

a  Laurent,  Annal.  de  I'Institut  Pasteur.     Vol.  Xlll,  p.  44. 
•i  Massart,  La  Cicatrisation  chez  les  plantes.     Brussel  1897. 


28 

wound  by  means  of  a  deposition  of  cork.  Further  protective  means  are  oils, 
resin,  balsams,  milky  juices  and  gums  exuding  from  injuries. 

Metschnikoff  thoroughly  treats  of  Laurent's^  studies  which  are 
mentioned  in  connection  with  other  bacteria  in  the  second  volume  of  this, 
work.  At  this  point,  however,  we  will  emphasize  especially  the  immunity 
I)recautions  against  bacterial  attacks.  The  species  of  the  Colibacillus,  with 
which  Laurent  worked,  secretes  a  ferment  dissolving  the  cellulose  of  the 
j.otato  tuber  and  produces  also  sap  with  alkaline  reaction,  the  presence  of 
which  is  necessary  for  the  process  of  assimilation  on  the  part  of  the  bacteria. 
Xow,  to  be  sure,  Bacillus  Coli  communis  is  naturally  not  a  plant  parasite  but 
it  can  be  changed  into  one.  This  happens  when  it  is  first  cultivated  on  po- 
tatoes whose  resistance  has  been  weakened  by  having  been  dipped  into  alka- 
hne  solutions  As  a  result  of  such  cultivation  the  bacillus  can  act  as  a  plant 
parasite  when  carried  over  to  the  same  species  of  potato.  The  struggle  be- 
tween the  Colibacillus  and  the  potato  depends  therefore  really  on  the  chemi- 
cal action  of  the  alkaline  secretion  of  the  bacillus  on  the  acid  cell  sap  of  the 
potato.  After  fertilization  with  potassium  salts  and  phosphates,  carrots  and 
potatoes  resist  the  bacillus.  On  the  other  hand,  a  phosphate  fertilization 
showed  in  (Topinambur)  that  this  plant  then  became  more  susceptible  to  the 
Jjotrytis  form  of  Sclerotinia  Lihertinia. 

Just  as  clearly  by  strong  nitrogen  fertilization  potatoes  are  made  less  re- 
sistant to  wet  rot.  According  to  our  observations  abundant  fertilizing  with 
nitrates,  ammonia  salts  or  stable  manure,  causes  even  the  most  resistant 
species  to  succumb  to  the  potato  rot.  Laurent  explains  the  difference  in  the 
action  of  parasites  under  the  same  method  of  fertilizing  by  the  fact  that  with 
bacteria  the  secreted  ferment  can  attack  the  cell  membrane  only  in  alkaline 
juices  or  weakly  acid  ones.  An  increased  acidity  of  the  cell  sap,  incited  by 
the  formation  of  acid  salts  resulting  from  phosphate  fertilization,  renders 
the  plants  immune  to  this  fission  fungus.  I  obtained  the  same  results  for 
phosphoric  acid  by  fertilization  experiments  on  sugar  beets,  in  which  the 
Bacillus  betae  was  widely  disseminated  and  had  produced  the  bacterial  for- 
mation of  gum  or  tail  rot.  The  rapid  increase  of  bacteriosis  with  the  abun- 
dant use  of  fertilizers  which  contain  nitrogen  might  be  explained  in  this 
way : — that  the  acid  of  the  cell  sap  is  thereby  decreased.  According  to  de 
lUiry,  the  conditions  for  Sclerotinia  are  exactly  reversed.  Their  ferment 
dissolves  the  cell  wall  only  in  an  acid  fluid.  Most  mycelial  fungi  act 
similarly. 

If,  by  a  change  of  constitution  of  the  cell  sap,  sometimes  a  factor  of  im- 
munity presents  itself  and,  at  other  times,  a  condition  predisposing  to  para- 
sitic disease,  we  are  referred  by  Metschnikoff  (1.  c.  p.  39)  to  a  further  pro- 
cess. He  cites  the  investigations  of  van  Rysselberghe-  who  found, 
especially  in  the  epidermal  cells  of  Tradescantia  that   if  these  cells   were 


1  I^aurent,  Recherohe.s  exptTimentalo.s  sur  les  maladies  des  plantes.  Anna!, 
de  rinst.  Pasteur.     Cit.  Zeitscher.  f.  J'Hanzenkr.  1900,  p.  29. 

-  Osmotische  Reaktion  der  I'fianzenzellen.  Memoires  couronnes  de  I'Academie 
r.  d.  Belgique.  Briissel  1899. 


29 

hrought  into  a  niore  conccntrrited  solution  tb.an  was  normal  to  them,  they 
showed  an  increase  of  intra-cellular  pressure.  If  the  experiment  was  re- 
versed, the  pressure  decreased.  These  changes  in  osmotic  pressure  are 
caused  by  the  difference  in  concentration  of  the  cell  sap  which  may  again  be 
considered  as  a  result  of  chemical  changes.  If  the  cell  comes  in  contact  with 
a  solution  too  highly  concentrated,  it  forms  oxalic  acid  which  acts  strongly 
Gsmotically.  With  Tradescantia,  van  Rysselberghe  proved  the  presence  of 
malic  acid  in  the  normal  sap  and  only  in  rare  cases  any  traces  of  oxalic  acid. 
After  the  plant  had  been  kept  some  days  in  strongly  concentrated  cane  sugar 
solution,  oxalic  acid  was  found  in  clearly  appreciable  amounts.  The  plant 
gradually  adjusts  itself  to  the  higher  concentration  of  this  medium,  produc- 
ing oxalic  acid  in  order  to  increase  the  pressure  of  the  cell  sap.  The  acid  is 
supposed  to  be  formed  at  the  expense  of  grape  sugar.  The  increased  acid 
content  will  act  as  a  protective  means  against  bacterial  attacks.  It  is  also 
suggested  by  some  investigators  as  a  protective  weapon  against  the  attacks 
of  snails  and  leaf  lice. 

Experiments  with  Tradescantia  made  in  the  opposite  direction  seem  to 
me  to  be  very  significant.  If  tissues  from  this  plant  were  taken  from  the 
highly  concentrated  solution  and  put  into  some  strongly  diluted  solution, 
precipitates  of  calcium  oxid  crystals  were  observed  in  the  cell  sap,  thereby 
initiating  a  decrease  of  osmotic  pressure.  When  the  plant  was  put  back  into 
a  stronger  solution  the  oxalic  crystals  were  seen  to  re-dissolve  and  result  in 
a  new  formation  of  acid.  I  found  that  part  of  the  calcium  oxalate  crystals 
disappeared  during  the  sprouting  of  potato  tul^ers  which  also  may  well  be 
ascribed  to  the  increased  formation  of  acid. 

Pfeffer^  also  takes  up  this  automatic  regulation  of  the  acid  con- 
tent since  he  calls  attention  to  the  frec[uent  production  of  turgidity  through 
the  organic  acids  combined  with  bases.  Since  this  remains  constant  during 
and  after  growth,  the  formation  of  acid  must  be  hastened  quantitatively  in 
correspondence  with  the  volume  increase  of  the  cell  and  the  dilution  of  the 
cell  sap  thereby  produced.  Each  unusual  increase  of  turgor,  as,  for  example 
in  the  effort  to  overcome  an  opposing  higher  concentration,  will  be  connected 
with  a  corresponding  increase  in  the  acid  production.  Conversely,  for  exam- 
ple in  the  Crassulaceae,  the  decrease  of  the  acid  content  has  been  proved 
with  an  increase  in  temperature  and  by  illumination.  In  this  sams  sense  the 
experiments  made  by  Charabot  and  Hebert-  have  succeeded.  In  the  shade, 
the  quantity  of  combined  organic  acid  increases  very  considerably. 
The  free  volatile  acids  also  increase.  These  are  found  in  greater  amounts  in 
etiolated  plants  than  in  others.  The  suppression  of  the  inflorescences  in- 
creases in  the  leaves  at  the  expense  of  the  other  organs. 

In  considering  predisposition  and  immunity,  we  have  brought  forward 
the  sugar  content  in  addition  to  the  examples  of  acid  content.     To  what 


1  Pflanzenphysiologie,    II   Edition,    Vol.   I,   p.   4S7. 

2  Charabot,   Eug.,  et  Hebert,   Recherches  sur  1'   aeidite  vegetale.     Compt.   rend, 
hebd.  1904.     CXXXVIII,  1714. 


30 

fluctuation  this  is  exposed  by  changes  in  temperature  is  best  seen  in  Fischer's' 
investigations  cited  by  Pfefifer-.  In  the  so-called  starch  trees,  like  the  linden 
and  birch,  it  is  found  that  starch  is  formed  in  the  bark  within  a  few 
hours  after  the  branches  have  been  brought  into  a  warm  room  from  a 
winter  temperature.  In  the  cold,  sugar  is  again  produced  from  this  starch. 
This  conversion  may  be  repeatedly  produced  and  this  kind  of  sugar  forma- 
tion seems  to  appear  in  many  plants  with  a  lowering  of  the  temper- 
ature. If  now,  for  any  reason  whatever,  the  sugar  formed  from  the 
starch  is  conducted  aw^ay  from  the  organ  the  whole  tissue  may  be  im- 
poverished. Pfefifer  furnishes  proof  of  this  by  the  experiments  carried 
out  in  his  institution  by  Hansteen"  and  Puriewitsch^.  By  a  con- 
tinued removal  of  the  sugar  by  diosmosis,  it  was  possible  to  cause  an  ejection 
of  starch  from  the  isolated  endosperm  of  grasses  as  well  as  the  cotyledons 
of  Phascolus  which  had  been  cut  off  from  the  plant  and  a  giving  ofif  of  the 
glucose  from  the  separate  scales  of  the  bulbs  of  Allium  Ccpa.  If  only  a 
little  water  was  present  into  which  the  sugar  could  pass  from  the  organs  the 
ejection  came  to  a  standstill  because  a  two  to  three  per  cent,  sugar  solution 
inhibits  the  conversion  of  the  starch.  Therefore,  either  a  good  deal  of  water 
must  be  present  or  some  other  means  for  the  removal  of  the  starch  if  the 
ejection  should  be  completed.  Conversely,  a  refilling  of  the  organs  with 
starch  could  be  determined  if  a  still  more  concentrated  solution  wcm'c  used. 

These  examples  may  sufifice  to  show  how  in  the  plant  body  all  the  me- 
tabolic processes  and  all  the  resulting  constructive  piocesses  succumb  under 
constant  quantitative  changes  which  radiate  in  all  directions  from  the  first 
form  of  attack  of  the  factor  causing  the  change.  Each  change  occurring 
locally  is  a  disturbance  in  the  condition  of  equilibrium  existing  up  to  that 
time  in  the  molecular  organization.  If  the  disturbance  is  completed  in  one 
cell  it  must,  so  far  as  dififusible  substances  are  concerned,  be  continued  in  the 
neighboring  ones  as  are  all  dynamic  processes. 

Each  place  in  w^hich  a  new  structure  is  formed  becomes  a  centre  of 
consumption.  The  supply  of  food  to  this  new  structure  leads  to  a  reduction 
in  other  parts.  Each  local  increase  in  photosj'nthesis  exerts  its  influence  on 
the  immediate  surroundings  not  concerned  in  this  process.  The  different 
factors  of  growth  now  act  uninterruptedly  on  the  plant  body  and  disturb  the 
momentary  equilibrium,  first  in  this  direction,  then  in  that.  \\&  have  there- 
fore a  continued  fluctuation  in  all  life  processes  which  is  increased  still  more 
by  the  capacity  for  reaction  peculiar  to  the  individual,  for  we  dare  not  forget 
that  in  restoring  the  disturbed  equilibrium  the  organism  must  endeavor  to 
increase  its  production  of  dififercnt  substances.  If.  for  example,  there  sets 
in  an  increase  of  the  basic  compounds  conditioned  by  nutrition,  an  increased 
acid  content  will  have  to  be  brought  about  and  conversely.  And  within  the 
constant  fluctuations  which  are  a  necessarv  result  lies  the  condition  which 


1  Fi.scher,  A..  Jahrb.  f.  wiss.  Bot.  1891.    Vol.  22. 

-   Physiology  I,   p.   514. 

3  Hansteen,  Flora,  1894.     Supplement. 

*  Puriewitsch,   Ber.  d.  Deutsch.  bot.  Ges.   1896.  p.   207. 


31 

we  term  normal  predisposition.  Thus  the  same  condition  which  represents 
a  state  of  predisposition  toward  a  definite  cause  of  disease  can  act  as  a  state 
of  immunity  to  some  other  cause  of  disease.  Proofs  of  this  are  offered  by 
the  examples  above  cited  of  the  hyperacidity  of  the  cell  sap  which  has  been 
shown  to  give  immunity  to  certain  bacterial  attacks  and  predisposition  to 
those  of  fungi.  In  the  increased  sugar  content,  which  is  connected  with  the 
influence  of  the  acid  in  increasing  the  turgidity,  we  recognize  a  condition 
predisposing  to  injuries  arising  from  frost  and,  on  the  other  hand,  a  pre- 
cautionary means  against  the  disturbing  action  of  drought. 

In  the  very  natural  development  of  the  organism,  therefore,  we  con- 
stantly face  conditions  of  predisposition  and  immunity.  These  are  present  in 
varying  degrees  in  each  individual  since  each  organism  has  special  nutritive 
relations  and  utilizes  differently  the  same  factors  of  growth.  This  explains 
the  phenomenon  that  dift'erent  individuals  in  the  midst  of  a  community  of  the 
same  species  become  sick  or  conversely,  in  the  midst  of  a  centre  of  disease, 
remain  healthy \ 


9.     Inheritance  of  Diseases  and  of  Predisposition. 

In  the  last  four  decades  further  experiments  have  been  made  by  many 
important  investigators  to  explain  theoretically  the  nature  of  heredity.  In 
this,  special  consideration  was  given  to  the  most  juvenile  condition — the 
embryonic  plasma — as  a  transmitter  of  .the  capacity  for  inheritance  and  the 
substance  which  might  be  indicated  as  the  chief  transmitter  of  inheritance 
was  sought  in  part  in  the  cell  nucleus. 

The  above-mentioned  hypotheses  of  biologists  were  drawn  up  to  explain 
especially  the  repetition  of  the  formative  processes  in  the  successive  genera- 
tions of  the  organism.  We  will  call  attention  only  to  Darwin's  "gemmules," 
Haeckel's  "plastidules,"  Weismann's  "germ  plasm"  as  an  '"'heredity  plasm," 
Nageli's  "idio-plasm,"  de  Vries'  "pangene,"  etc. 


1  The  parasitic  theory  as  generally  accepted  at  present  either  still  needs 
an  explanation  of  these  facts  or  is  restricted  to  the  theory  of  resistance.  The 
different  capacity  for  resistance  to  atmospheric  extremes  and  other  non-parasitic 
influences  has  remained  unconsidered.  Thus  Alfred  Fischer*  observes  "Individual 
variations  indeed  occur  often  enough  even  in  man;  a  personal  immunity  of  an 
inexplicable  kind  seems  to  exist  which  in  part  falls  under  the  conception  of  predis- 
position. Even  with  age  natural  immunity  varies  as  shown  by  infantile  diseases. 
The  question  may  be  left  undiscussed  as  to  whether  even  these  may  not  be  con- 
sidered as  immunizing  diseases  which  are  said  to  prepare  the  youthful  mortal  for 
an  existence   surrounded  by  bacteria  and  to  fortify  him." 

On  the  other  hand,  Alfred  Wolff**  explains  "In  all  essentials  the  natural  power 
of  resistance  to  toxins  advances  in  proportion  to  the  organ's  capacity  to  hold  the 
molecules  of  the  poison  and  to  prevent  their  action  on  the  brain.  Thus  only  quali- 
tative and  no  quantitative  differences  exist  between  apparently  so  diametrically 
opposed  phenomena  of  an  innate  non-susceptibility  and  a  high  grade  of  susceptibil- 
ity in  individual  animal  bodies.  These  differences  lie  only  in  the  different  capacity 
of  the  organs  in  different  animal  species  for  the  formation  of  toxin  and  an  eventual 
neutralization." 

♦Fischer,  A.,  Vorlesungen  iiber  Bakterien.  2.  Ed.  p.  347,  Jena,  Gustav  Fischer, 
1903. 

**Alfred  Wolff,  Ueber  Grundgesetze  der  Immunitat,  Centralbl.  f.  Bakteriologie, 
Parasitenkunde  usw.  Sec.  I.  Original.     Vol.  XXXVII.     Part  3,  p.  701,  1904. 


3^ 

According  to  our  theory  there  is  needed  for  the  explanation  of  the  pro- 
cesses of  inheritance,  neither  any  special  locality  such  as  the  embryonic  cells, 
nor  any  special  cell  or  plasm  germ  or  inheritance  mass  or  any  ancestral  plasm, 
for  inheritance  is  a  "mechanical  must"  a  necessary  nnhcrsally  present  me- 
chanical result  of  the  structure  of  the  organic  substance.  As  soon  as  the 
organic  substance,  like  the  inorganic,  is  considered  as  an  atomic  union  which 
retains  its  character  and  therefore  its  specific  peculiarities,  since  the  atoms 
in  the  molecules  exist  in  definite  arrangements  and  fluctuation,  then  this  sub- 
stance presents  the  stage  of  ec|uilibrium  of  definite  forms  of  motion.  If  one 
cannot  define  the  countless  combinations  of  molecular  fluctuations  and  can- 
not construct  the  distention  and  other  mechanical  results  arising  from  the 
dififerent  arrangement,  one  may  yet  characterize  each  organic  structure  as 
the  result  of  a  sum  of  very  definite  combinations  of  molecular  motions  which 
are  conditioned  by  each  other.  Accordingly  the  cytoplasm  of  the  pear  is  a 
plasma  whose  dififerent  micellae  show  in  general  the  molecular  fluctuation 
forms  of  the  plasmatic  substances  but  still  possess  specific  relations  of  fluct- 
uation and  arrangement  which  distinguish  them  from  similarly  located 
micellae  of  the  apple  cytoplasm.  Therefore,  m  each  smallest  particle  in  each 
biogen  of  any  organic  individual  whatever,  an  individual  character  may  be 
found  which  must  remain  constant  as  an  expression  of  the  sum  of  definite 
forms  of  motion  resulting  from  the  law  of  inertia. 

This  constancy  is  a  mechanical  necessity; — for  every  motion  continues 
in  its  existing  form  as  long  as  it  is  not  modified  by  another  demonstration  of 
force  and  each  substance  which  is  the  expression  and  bearer  of  the  motion 
retains  this  form  and  character  until  other  reactions  cause  molecular 
changes^  If,  for  example,  we  speak  of  protoplasm,  we  must  be 
conscious  that  we  do  not  designate  thereby  a  homogeneous  substance  with  a 
fixed  chemical  nature,  but  a  large  group  of  substances  containing  many 
forms.    The  same  is  true  for  cellulose,  sugar,  tannic  acid  etc. 

The  assumption  of  the  existence  of  as  many  variations  of  substances  as 
there  are  individuals  loses  its  strangeness  as  soon  as  we  remember  that  we 
see  about  us  daily  an  equal  number  of  variations  of  figures, — for,  as  a  fact, 
no  one  individual  resembles  another  absolutely.  If,  however,  each  biogen  is 
a  specific  unit,  it  retains  its  character  with  the  provision  that  no  substance 
coming  from  without  may  change  its  molecular  grouping,  no  matter  where 
it  is  located  in  the  plant  body,  nor  whether  it  occurs  in  the  form  of  cellulose 
or  as  somatic  or  embryonic  tissue.  For  all  these  substances  are  indeed  only 
groupings  proceeding  from  one  another.  The  biogens  which  arc  utilized  in 
the  formation  of  the  embryo,  that  is,  at  the  beginning  of  the  new  generation, 
find  an  expression  in  the  new  individual  as  in  the  old  for  the  form  of  fluctu- 
ation which  they  represent.    This  retention  of  the  molecular  form  of  motion 


1  This  viow  of  the  .si)ocnfifity  of  each  biogen  in  every  organism  has  ah-eady 
been  expressed  by  Noll,  since  he  states  that  the  egg  cell  of  a  linden  in  its 
totality  is  alread>-  a  linden  and  cannot  be  anything  else  nor  become  anything  else. 
Noll,  Beobachtiingen  und  Betrachtungen  liber  embryonale  Substanz.  Sond.  "Biolog. 
Centralblatt."     Vol.  XXIII,  l^eipzig  1003,  p.  325. 


33 

in  the  new  generation  is  heredity.  We  are  not  in  the  least  astonished  to  find 
carrot  substance  reproduced  from  carrot  seed.  We  are  also  not  astonished 
to  find  a  table  carrot  produced  from  a  carrot  which  is  rich  in  sugar  and  not 
a  cattle  carrot  rich  in  starch.  Thus  the  same  combinations  of  substances  are 
transmitted  which  represent  the  characteristic  peculiarities  of  our  cultural 
varieties.  If  in  practical  agriculture  we  should  plant  side  by  side  both  of  the 
above-named  varieties  of  carrots  we  would  have  opportunity  to  observe  that 
with  the  appearance  of  a  certain  degree  of  frost,  the  table  carrots  would 
freeze  while  the  cattle  carrots  would  remain  uninjured. 

The  susceptibility  to  cold  of  the  substance  of  different  varieties  of  the 
same  species  is  the  most  easily  observed  example  of  the  inheritance  of  such 
peculiarities  as  represent  predisposition  to  disease.  Each  fruit  grower  can 
name  varieties  of  fruit  which  are  injured  by  frost  in  his  orchards  while 
other  varieties  standing  nearby  are  not  afifected  or  injured.  The  same  rela- 
tions are  found  among  Bowers  and  with  grain  it  is  a  universal  experience 
tliat,  among  the  different  varieties  of  wheat,  for  example,  the  square-heads 
winter-kill  most  easily.  The  same  variation  in  the  resistance  of  dififer- 
cnt  cultural  varieties  is  found  also  in  relation  to  other  cnuses  of  disease,  as, 
for  example,  overheating  and  drought,  excess  of  water  etc.  A  great  deal 
remains  to  be  learned  of  the  cultural  varieties  and  their  study  deserves 
greater  attention  than  has  been  given  to  it  up  to  the  present. 

Thus  cultivation  has  furnished  us  with  an  ornamental  plant,  coxcomb 
(Cclosla  ei'istafa),  which  has  a  stem  with  a  broad,  much  curled  vegetative 
tip.  This  broad,  band-like  transformation  of  the  original  cylindrical  stem 
(fasciafion)  has  become  constant  in  the  seed.  Double  blossoms  are  retained 
from  one  generation  to  another.  Weak  or  one-sided  formation  of  the  sex- 
ual organs  can  become  an  hereditary  peculiarity,  as,  for  example,  in  the 
black  currant  or  in  the  strawberry  culture  in  Alten  Lande  near  Hamburg. 

From  such  examples  one  sees  v/hat  far  reaching  differences  from  the 
usual  mode  of  development  are  transmissible  through  the  seed.  Each  vari- 
ation indicates  a  direct  thrust  against  a  previously  existing  peculiarity  which 
is  so  strong  that  it  is  able  to  shatter  this  peculiarity  permanently.  The 
peculiarities  of  the  organism  possess  a  varying  degree  of  stability,  i.  e.  the 
form  of  motion  which  they  represent  is  often  disturbed  by  a  weak  thrust, 
while  in  other  cases  it  can  not  be  changed  by  the  strongest  attacks  of  the 
surrounding  factors  of  growth.  Among  the  least  fixed  peculiarities  belong 
the  colors  of  the  blossoms,  the  water  and  sugar  content  and  the  size  pro- 
portions of  the  organs  which  can  vary  even  in  the  natural  habitat.  Hardest 
to  alter  or  cause  to  vary  are  the  relative' positions  of  the  organs  and  the  com- 
position of  the  biogens,  viz.,  the  type  of  substance  forming  cabbage  head  or 
of  a  pear  tree  as  such,  and  distinguishable  from  that  of  other  plants.  No 
peculiarity  of  an  organism  may  be  considered  as  indestructible  but  a  num- 
ber of  peculiarities  will  be  retained  from  generation  to  generation  in  their 
present  form  because  no  thrust  has  existed  up  to  that  time  of  sufficient 
strength    to    shake    them.     These    peculiarities,    however,    which     are     ac- 


34 

cessible  for  factors  existing  at  the  time  may  succumb  to  the  thrust  according 
to  the  strength  of  the  attack  and  thus  be  changed.  These  changes,  because 
indicative  of  molecular  transpositions,  are  constant  as  forms  of  fluctuation, 
due  to  the  law  of  inertia  until  new  thrusts  give  a  new  direction  to  the  motion. 
They  are  retained  also  in  the  organs  which  we  call  seeds  and  must  accord- 
ingly be  continued  in  the  new  individual  and  therefore  must  be  hereditary. 
At  times  also,  conditions  contrary  to  The  purpose  of  the  individual,  and  which 
therefore  initiate  the  shortening  of  the  life  period  of  the  individual,  such  as 
a  lesser  firmness  of  the  substance,  will  be  hereditary.  In  this  sense  we  will 
have  to  reckon  with  an  inheritance  of  diseases  and  of  conditions  which  make 
them  especially  inclined  to  predisposition  to  a  disease. 

Besides  the  transference  of  such  physiological  peculiarities  which  pro- 
mote disease  in  the  host  organism  from  one  generation  to  the  other,  the  pos- 
Fibility  of  an  inheritance  of  parasites  through  the  seeds^ofjthe  host  plant 
has  recently  been  disputed.  ErikJEson^,  one  of  the  most  prominent 
investigators  of  rust  diseases,  describes  a  number  of  instances  in  rust  of 
grain  leaves  which  have  led  him  to  believe  that  with  rust  fungi  embryonic 
developmental  stages  exist  in  which  the  fungi  as  naked  plasma,  Mycoplasm, 
appear  united  with  the  plasma  of  the  host  cell.  Such  symbiotic  conditions 
can  be  present  during  the  maturing  of  the  seed  and  can  exist  as  a  dormant 
germ  of  the  rust  disease  in  the  succeeding  generation.  With  weather  con- 
ditions favoring  fungous  development,  the  rust  disease  becomes  apparent  by 
the  mycoplasmated  spots  transmitted  by  inheritance  in  the  form  then  known. 
The  extraordinary  difficulty  of  the  question  as  to  the  existence  of  parasites 
in  a  mycoplasmatic  stage  has  precluded  as  yet  any  fixed  decision  concern- 
ing Eriksson's  point  of  view.  If  the  possibility  of  mycoplasmatic  conditions 
must  be  admitted,  we  still  think,  however,  that  Eriksson's  assuredly  correct 
observations  may  have  this  significance  since  the  forms  described  have  as 
yet  been  found  only  near  mature  spore  centres. 


Degeneration. 


From  time  to  time,  especially  in  practical  work,  it  is  asserted  generally 
tliat  our  cultivated  plants  tend  to  degenerate,  i.  e.  the  quantity  and  quality 
of  their  crops  diminish,  and  that  certain  varieties  run  out.  The  degeneration 
of  such  favorite  cultivated  forms,  said  to  take  place  simultaneously  in  dififer- 
crent  localities,  is  often  traced  to  senility  since  it  is  asserted  that  even  those 
groups  of  forms,  which  we  are  accustomed  to  call  sorts  or  varieties,  like  in- 
dividuals, are  not  able  to  live  beyond  a  definite  age.  This  point  of  view  is 
supported  especially  by  observations  on  our  fruit  trees,  the  varieties  of 
which  are  known  to  be  constantly  propagated  asexually  by  grafting  or 
budding.    Such  varieties  as  a  rule  originate  from  one  individual  plant  grown 

1  See   Literature   in   "Zeitschr.   f.   Pflanzenkrankh."     Annual   nun;bers   for   1903 
and  1904. 


35 

in  a  definite  region,  the  branches  of  which  are  at  once  distributed  as  scions. 
It  is  now  thought  that  all  individuals  produced  by  asexual  propagation  act- 
ually represent  only  the  continuation  of  the  tree  first  developed  from  the 
seed.  Now,  since  each  individual  has  its  own  life  period,  this  many-headed 
individual  which  we  call  a  "variety"  must  fall  victim  to  death  after  a  definite 
length  of  time.  In  this  way  is  explained  the  universally  simultaneous  sick- 
ening and  dying  out  of  many  a  variety.  As  examples  of  this  kind  are  given 
Golden  Pippin  and  Borsdorfer,  two  varieties  of  apple,  on  the  degeneration 
of  which  there  developed  an  extensive  literature  in  the  seventies  of 
the  last  century^. 

Other  old  fruit  varieties  (especially  apple)  are  said  to  sufifer  simultane- 
ously from  sterility  wherever  grown,  become  cankered  and  die.  Potato  var- 
ieties, formerly  widely  acknowledged  to  be  excellent,  are  no  longer  true  to 
type  and  disappear  from  the  market.  The  orange  trees  found  formerly  in 
European  gardens  as  most  vigorous  old  specimens  become  diseased  every- 
where in  spite  of  the  greatest  care.  The  celebrated  orangeries  at  Sanssouci. 
Dresden,  Cassel,  Versailles  etc.  have  vanished  or  are  represented  only  by  a 
few  often  sickly  trees.  Indeed,  even  in  Italy,  large  plantations  of  lemon  and 
orange  trees  have  been  attacked  by  diseases  at  present  apparently  incurable. 
The  cause  is  said  to  be  a  weakness  of  growth  w^hich  makes  itself  gradually 
increasingly  felt,  together  with  a  diseased  condition  of  the  root.  The  same 
may  be  affirmed  of  grape  vines  and  of  olive  trees,  pomegranates,  the  Ericas 
(heathers)  of  Cape  Colony,  the  Australian  Papilionaceae  and  Myrtaceae. 
which  formerly,  as  "Javanese"  plants  in  special  conservatories,  formed  the 
decoration  and  pride  of  gardeners.  Even  in  our  species  of  grains,  we  have 
noticed  the  disappearance  of  the  good  old  varieties.  This  is  the  opinion  of 
the  representatives  of  the  theory  of  degeneration. 

The  theory  of  the  continuity  of  an  individual  through  a.\\4he  scions,  for 
Avhich  the  stock,  or  the  parent  plant  rather,  serves  only  as  nurse,  is  based  on 
the  presupposition  that  this  individual  retains  all  its  characteristics  un- 
changed during  its  whole  existence  as  a  variety  wherever  grown  and  on  the 
different  stocks.  For,  at  the  moment  when  it  must  be  granted  that  the  habi- 
tat or  stock  may  change  any  peculiarities,  a  variation  in  the  length  of  life 
due  to  different  nutrition  must  also  be  considered  a  possibility.  For  this 
reason  those  who  defend  the  theory  of  degeneration  and  a  fixed  life  period 
of  varieties  (especially  Jensen  among  botanists)  insist  upon  the  fixity  of 
characters  and  support  their  theory  by  the  fact  that  the  varietal  character 
always  remains  constant  in  seeds  and  in  cuttings  as  well  as  in  grafts.  Defi- 
nite shoot  variations  produced  on  any  one  specimen  (variegated  leaves,  split 
leaves,  forms  with  weeping  branches,  fasciations  etc.)  which  can  always  be 
transmitted  by  grafting  on  new  stock  are  proofs  most  often  stated. 

1  "Wearing  out  of  varieties,"  Gardeners  Chronicle  1875.  "Do  the  varie- 
ties wear  out?"  ibid.  "Degeneration  from  senility"  in  the  Fruit  Manual  1875. 
"Golden  Pippin  degenerated"  in  Gardeners'  Chronicle  1875.  Compare  "Bericht  uber 
die  Verhandl.  d.  Sektion  fur  "Weinbau  in  Trier,"  1875,  etc.,  etc. 


36 

Such  statements  are  refuted  by  the  increasing  results  of  grafting  which 
show  the  mutual  influence  and  change  in  individuals,  incited  by  grafting.  It 
IS  known  that  a  form  of  albinoism,  i.  e.  the  condition  of  having  white  leaves, 
which  we  can  perhaps  call  "marbled,"  is  transmissible  from  scion  to  stock. 
Differences  in  the  development  of  a  scion  dependant  upon  its  being  grafted 
on  dwarf  species  or  wild  stock  are  known.  Just  as  abundant  are  the 
examples  of  changes  in  size,  structure,  coloration  and  taste  of  the  fruit  ac- 
cording to  the  habitat  and  climate.  Finally  it  should  not  be  forgotten,  that, 
in  extensive  cultivation  of  varieties,  we  always  find  some  which  "do  not 
hold,"  that  is,  which  from  the  time  of  germination  show  so  weak  a  growth 
that  they  soon  disappear.  This  indicates  a  dying  out  of  very  young  varieties. 
In  this  instance  the  theory  of  senility  does  not  hold. 

In  connection  with  the  statement  that  varieties  of  fruit  formerly  highly 
prized  no  longer  thrive  and  simultaneously  run  out  wherever  grown,  it  is 
interesting  to  compare  some  reports  dating  from  the  time  when  the  question 
of  degeneration  became  one  of  paramount  importance,  which  concern  directly 
j-ome  of  the  varieties  of  fruit  said  to  be  running  out.  Hogg  stated  in  1875, 
in  "the  Fruit  Manual,"  that  Knight  had  complained  of  the  "English  Golden 
Pippin"  as  a  variety  at  that  time  degenerating  because  of  senility.  He  says 
that  Mortimer,  almost  a  hundred  years  before  Knight,  had  spoken  similarly 
of  the  "Kentish  Pippin."  Healthy  specimens  of  both  varieties,  however,  are 
still  found  in  England.  The  length  of  life  and  strength  of  cultivated  varie- 
ties (says  Hogg)  may  be  proved  by  the  "Winter-Pearmain,"  which  may  be 
taken  as  the  oldest  English  variety  of  apple,  since  it  was  mentioned  in  manu- 
scripts as  early  as  about  T200.  The  Borsdorfer  apple  and  the  well-known 
plum  "Reine  Claude,"  are  very  old.  According  to  Bolle\  the  "Reine 
Claude"  must  have  originated  in  the  15th  Century  since  it  was  named  in 
honor  of  Claude,  the  consort  of  Louis  the  XII  (1490). 

These  fe#  examples  show  that  the  theory  of  degenerati(Mi  due  to  sen- 
i-ity  of  individual  cultivated  varieties  or  due  to  other  causes  has  been  formu- 
lated because  a  persistent  retrogression  has  been  observed  in  production  and 
liealthfulness  from  time  to  time  in  many  localities,  from  which  observations 
general  conclusions  have  been  drawn.  The  fact  that  in  many  regions  culti- 
vated, well-preserved  forms  no  longer  show  a  thrifty  growth  and  may  be 
replaced  by  others,  is  undeniable.  But  this  fact  only  proves  that,  since  each 
cultivated  form  makes  definite  demands  in  soil  and  climate,  these  demands 
can  not  be  satisfied  further  in  many  places.  Degeneration  may  be  spoken  of 
when  a  cultivated  variety  runs  out  universally,  even  in  places  where  suitable 
conditions  have  been  retained.     However,  proof  of  this  is  lacking. 

The  breaking  down  of  tiie  varieties  after  long  cultivation  may  be  due 
to  twofold  causes,  either  the  cultural  conditions  have  been  changed  or  the 
character  of  the  variety  has  become  different.  In  the  first  place,  the  fact  that 
cultural  conditions  in  any  one  locality  are  different  every  year  is  one  to 


1  Quoted   in    Oberdieck,    Pomolog.    Monatshefte    1875,    p.    240,    Bouche   and    Bolle, 
Monatsschrift  d.   Ver.  z.  Beford  d.  Gartenb.   1875,  p.  484. 


37 

which  we  usually  pay  too  little  attention.  Aside  from  the  fact  that  the 
weather  of  one  year  always  varies  from  that  of  the  preceding  year,  the  soil 
too  is  always  dififerent ;  indeed  partly  because  the  time  and  method  of 
working  as  well  as  the  fertilization  and  previous  cropping  in  themselves 
always  effect  changes,  and  partly  because  this  changed  arable  land  is  also 
subjected  to  changed  weather  conditions,  so  that  it  diiTers  every  year  physi- 
cally and  chemically  for  the  same  variety.  In  the  main  portion  of  the  book 
a  sufficient  number  of  examples  of  the  influence  of  planting,  previous 
cropping,  mechanical  soil  constitution  and  such  factors  will  be  cited  and  it 
will  be  shown  how  these  can  influence  the  character  and  power  of  resistance ; 
as,  for  example,  to  frost. 

In  the  second  place  we  think  that  the  running  out  of  a  cultivated  variety 
can  also  arise  because  the  variety  itself  changes  its  character.  According  to 
our  hypothesis,  there  is,  in  all  organisms,  no  stability ;  there  is  no  strict  ma- 
terial or  formal  repetition  of  any  process,  because  the  organism  changes  in 
the  smallest  unit  of  time,  at  each  moment  confronts  the  same  factors  of 
growth  as  a  dififerent  organism  and  strides  forward  to  adjustment.  Thus 
each  variety,  like  every  term  of  relationship  or  of  classification,  is  only  a 
frame  work  made  up  of  common  characteristics  in  which  individuals  con- 
stantly fluctuate  because  of  lesser  variations. 

An  excess  of  nitrogen  develops  a  plant  substance  ditterent  from  that 
produced  by  moderate  nitrogen  nutrition,  a  deficiency  of  potassium  makes 
an  organ  dififerent  from  that  grown  with  an  abundance  of  potassium.  Abun- 
dance of  light  and  deficiency  of  light  develop  the  cell  wall  in  different  ways, 
great  warmth  produces  more  sugar  than  scanty  amounts  of  heat,  etc.  Exact 
examples  are  given  in  the  chapters  on  the  action  of  individual  factors  of 
growth.  Therefore  the  organism  is  like  wax  which,  because  of  the  thrusts 
of  the  individual  vegetative  factors,  is  constantly  pressed  into  other  material 
forms. 

The  material  constitution  of  the  plant  body,  however,  is  changed  by  the 
variations  of  the  molecular  arrangement  which  we  call  chemical  changes,  as 
well  as  by  the  mechanical  ones  in  which  the  chemical  composition  remains 
constant.  The  mechanical  disposition  of  water  in  the  tissues,  the  substances 
carried  in  in  the  water,  the  tension  conditions  in  the  cell  wall  and  the  cell 
contents,  are  all  factors  which  change  constantly  and  as  constantly  influence 
each  other  dififerently.  The  slightest  increase  in  the  supply  of  light  is  a 
thrust  which  not  only  influences  the  assimilatory  process,  but  must  also  in- 
directly exercise  an  effect  on  all  other  functions.  This  does  not  depend  at 
all  upon  whether  we  can  define  these  effects ; — the  proof  that  they  must  take 
place  is  enough. 

Let  us  now  consider  how  the  thrusts  of  individual  factors  of  growth  act 
normally  on  the  plant  body.  Here  we  notice  a  peculiar  alternation.  At  day- 
break the  action  of  light  begins ; — assimilation,  evaporation,  thickening  of  the 
cell  wall  etc.  are  increased,  the  whole  structure  reflects  all  the  phenomena  of 
the  light  reactions.     At  nightfall,  when  the  after  eft'ects  of  the  light  have 


38 

ceased,  processes  of  oxidation  come  to  the  front,  phenomena  of  increased 
turgidity,  conversion  of  starch  and  the  Hke.  The  same  changes  may  be  ob- 
served in  the  media  surrounding  the  plant,  in  the  air  and  soil.  A  decrease 
of  warmth  and  increase  of  water  content  must  act  powerfully  on  the  plant 
body.  With  the  change  between  day  and  night  is  associated  the  influence  of 
the  seasons,  which  forces  upon  the  plants  a  period  of  rest  after  a  time  of 
production.  Therefore  we  find  in  nature  a  "corrective  pcriodicUy."  Amid 
these  regularly  alternating  fluctuations  of  the  vegetative  factors,  the  plant 
balances  its  growth  and  completes  its  normal  course  of  development. 

Since  the  duration  and  action  of  these  periods  in  each  year  differ,  the 
production  of  each  plant  differs  also  and  the  individual  years  are  thus  char- 
acterized. We  speak  of  dry  and  wet  years  and  know  from  experience  that 
in  the  former,  the  yield  of  grain  is  noticeably  large,  while  the  straw  yield  is 
less  on  account  of  the  shortness  of  the  stalks.  In  wet  years  this  is  reversed. 
And  although  the  farmer  then  complains  that  the  baking  quality  of  the  flour 
lias  suffered,  yet  he  emphasizes  the  fact  that  he  finds  compensation  in  the 
greater  straw  harvest. 

This  example,  taken  from  general  practice,  shows  how  great  single  vari- 
ations in  the  average  periodicity  at  once  becomes  noticeable  since  the  prefer- 
ence is  shown  for  different  peculiarities  of  the  plant  body.  As  long  as  this 
kind  of  one-sideness  in  development  does  not  threaten  the  existence  of  the 
individual  plant  we  may  leave  the  results  out  of  consideration  and  seek  to 
equalize  possible  cultural  variations  (as,  for  example,  by  the  crossing  of 
grains  possessing  poorer  baking  qualities  with  those  rich  in  gluten  which 
come  from  dry,  warm  regions). 

However,  the  single  prevalence  of  a  definite  atmospheric  factor  can  also 
lead  to  direct  disease  since  the  effects  are  cumulative.  Such  an  accumulation 
of  effects  may  be  compared  to  the  increase  in  celerity  in  falling  bodies  where 
the  distance  of  the  fall  equals  the  square  of  the  time.  If,  instead  of  gravity, 
we  assume  another  factor,  such  as  v/et,  cloudy  weather,  it  will  in  one  day  in- 
crease the  water  content  of  the  tissue  while  the  wall  thickening  remains  be- 
low normal.  On  the  second  day,  the  first  day's  action  is  doubled  and  the 
already  porous  tissue  becomes  still  more  porous.  The  thrust  against  the 
plant  body,  which  in  itself  would  not  produce  disease,  is  cumulative  to  an 
extent  ultimately  threatening  the  plant's  existence.  Practically  we  find  this 
even  within  one  vegetative  period,  as,  for  example,  lodging  of  the  grain  in 
rainy  seasons.  The  moisture  has  lengthened  consideral)ly  the  cells  at  the 
base  of  the  stalk  while  the  deficiency  of  light  has  essentially  arrested  the 
thickening  of  their  walls.  The  result  is  that  the  weakened  base  is  not  able 
to  sufficiently  resist  the  strain  of  the  wind  and  gives  way.  The  development 
of  the  grain  is  weakened  or  inhibited,  according  to  the  extent  of  this  lodging 
and  the  phenomena  resulting  from  it,  so  that  the  stalk  iself  is  also  brought 
to  a  premature  death. 

Corresponding  to  the  above  mechanical  changes  in  the  wall,  the  cell 
contents  are  subjected  to  changes  leading  to  a  diseased  condition  in  the  case 


39 

of  other  influences  on  the  part  of  the  vegetative  factor  which  accumulate 
along  one  line.  We  find  in  heavily  fertilized  nurseries,  whole  plots  of  lux- 
uuriantly  growing  sweet  cherries  with  open  or  hidden  gum  spots  and  in 
forests  whole  tracts  and  healthy  looking  beds  of  conifers  which  show  in  their 
wood-tissue  the  beginnings  of  a  resinous  condition.  In  garden  cultures 
especially,  which  on  an  average  are  worked  with  the  largest  quantities  of 
nitrogen,  whole  plantations  suddenly  become  diseased  and  are  abandoned 
because  the  "plants  will  not  grow."  Enough  cases  of  this  kind  have  reached 
me,  in  which  individual  breeders  have  announced  that  Begonias,  Primula 
sinensis  fl.  pL,  carnations,  lilies-of-the  valley,  cyclamen  and  others  which  at 
other  times  under  the  same  cultural  methods  had  always  been  produced  in 
the  greatest  perfection,  re-trogress  from  year  to  year  and  "degenerate."  Sim- 
ilar conditions  may  be  observed  in  field  cultures.  Entire  fields  of  potato 
varieties  which  formerly  gave  faultless  crops  now  easily  become  black 
specked.  Sugar  beets  grown  in  the  soil  best  suited  to  them  tend  to  root  rot. 
It  has  been  observed  in  the  root  rot  of  beets  that  plants  grown  from  trans- 
plants became  diseased  especially  easily,  while  seedlings  from  the  best  and 
heaviest  sugar  beets  showed  almost  no  root  rot.  Cucumbers  forced  under 
glass,  and  those  grown  in  fields  in  v/et,  cold  years  are  spoiled  by  gummosis, 
and  the  like. 

My  experience  in  remedying  such  occurrences  leads  to  the  conclusion 
that  an  increase  of  one  definite  line  of  development  is  concerned  in 
these  cases  which  is  usually  called  forth  by  excess  of  nitrogen  and  water. 
Our  constantly  increasing  intensive  cultivation  not  infrequently  leads  to  a 
showy  luxuriance  of  the  plants  and  then  to  a  sudden  collapse,  if  the  equaliz- 
ing factor  is  not  able  to  act  in  a  corresponding  amount.  Accordingly  in 
cases  of  a  shown  great  nitrogen  supply,  I  found  the  use  of  calcium  phosphate 
to  be  very  advantageous. 

Such  one-sided  lines  of  development  will  also  appear  necessarily  in  the 
development  of  the  seed.  If  it  is  cultivated  from  generation  to  generation 
under  the  same  nutritive  conditions,  as  when  first  produced,  definite  peculiari- 
ties of  its  place  of  growth  must  become  hereditary  through  habit.  Accord- 
ing to  our  theory  that  all  peculiarities  of  an  organism  represent  dynamic 
conditions  and  molecular  vibration-groupings,  the  habit  would  necessarily 
be  explained  as  inertia.  The  law  of  inertia  of  all  matter  requires  that  it  re- 
mains exactly  in  the  same  course  and  at  the  same  rate  of  motion.  Thus  the 
organism  keeps  on  vibrating  as  it  has  once  been  impelled,  until  some  factor 
of  vegetation  changes  the  rate  of  its  growth  or  the  direction. 

Practice  utiHzes  this  circumstance  in  the  "change  of  seed,"  that  is,  in  the 
use  of  seed  from  other  places  which  have  developed  a  definite  desirable 
peculiarity.  Thus  the  use  of  Swedjsh  grain  by  Middle-European  agricul- 
turalists has  become  more  extensive  because  it  is  desirable  to  take  advantage 
of  the  shorter  vegetative  period  of  the  northern  varieties.  While  an 
especially  developed  mealy  condition  is  typical  of  English  wheat,  regions 
with  opposite  climate  conditions  produce  chiefly  hard  wheat  etc. 


40 

Just  as  useful  types  of  grain  arise  as  the  products  of  atmospheric  and 
soil  conditions,  weakened  conditions  of  the  cultivated  plants  may  also  be 
produced  locally  and  transmitted  through  seeds.  If  these  weakened  con- 
ditions are  repeated  from  generation  to  generation  by  the  persistence  of 
causes  and  accumulate,  they  may  lead  in  the  end  to  a  complete  decline  and 
to  premature  death. 

Yet  this  is,  however,  no  degeneration  of  the  species  or  variety,  for  all 
these  characteristics  may  be  reproduced  under  other  cultural  conditions.  We 
perceive  this  from  the  fact  that  the  useful  special  characteristics  introduced 
by  a  change  of  seed,  are  retained  only  a  few  years.  Then  the  imported  culti- 
\ated  forms  become  changed  and  assume  characteristics  such  as  are  due  to 
the  climatic  and  soil  conditions  in  the  place  where  they  are  cultivated.  Such 
is  also  the  experience  in  practice  work  which  constantly  attempts  in  some 
way  to  accustom  (acclimate)  highly  productive  species  of  a  different  climate, 
to  some  one  cultural  region. 

If  it  seems  desirable  to  apply  the  term  "degeneration"  to  the  above  cases 
of  the  accumulation  of  peculiarities  leading  to  a  weakening  of  production 
and  to  premature  death,  it  is  possible  at  most  only  to  speak  of  local  transi- 
tory degeneration  of  a  number  of  individuals.  It  is,  however,  really  only 
a  depression  of  the  direction  of  development,  which  can  be  raised  again  by 
external  factors,  such  as  cultural  methods.  A  persistent  depression  in 
growth  as  a  result  of  the  senility  of  an  originally  long-lived  variety,  is  not  to 
be  assumed  within  any  definite  epoch.  The  disappearance  of  cultural  varie- 
ties is  explained  by  a  decreased  profitableness  resulting  from  a  deficient 
power  of  adjustment  to  our  agricultural  methods,  which  arc  con;-tantly  be- 
coming more  intensive. 


SECTION  2. 


HISTORICAL  SURVEY. 

In  any  branch  of  knowledge  so  young  as  phytopathology,  any  history 
of  the  science  can  scarcely  be  presupposed.  And  in  fact  the  date  after  which 
the  teaching  of  plant  disease  was  set  up  as  a  special  branch  is  so  recent  that  we 
are  still  able  to  survey  completely  the  course  of  its  development. 

If,  however,  the  form  of  investigation  is  still  new,  the  material,  viz., 
leports  on  plant  diseases,  is  very  old,  extending  far  back  in  history.  We  can 
not  go  astray  in  assuming  that  there  have  been  diseases  since  the  existence  of 
the  plants  began  and  that  observations  on  these  began  with  their  cultivation. 
For  we  constantly  see  what  heavy  injuries  are  produced  by  atmospheric  ex- 
tremes, and  indeed  not  only  by  those  disturbances  which  instantly  kill  the 
plant,  but  rather  by  such  as  weaken  the  individual  in  structure  and  form, 
and  slowly  lead  it  toward  a  premature  death, — i.  e.  make  it  sick.  The  action 
of  injurious  atmospheric  conditions  must  have  existed  always  and  have 
made  themselves  evident  in  different  forms. 

One  of  the  oldest  names  which  we  find  for  certain  forms  of  sickness, 
is  "blight."  On  this  account  we  will  attempt  to  trace  the  growth  of  our 
branch  of  knowledge  by  following  the  observations  of  the  diseases  which 
this  name  connates. 

As  the  later  reports  show,  at  first  all  those  phenomena  were  character- 
ized as  "blight,"  which  appeared  to  the  eye  to  have  the  color  of  burned  or 
charred  matter,  that  is,  black.  Accordingly  "blight"  comprised  on  the  one 
hand  the  groups  of  tree  diseases,  in  which  the  dead  bark  assumed  a  black- 
ened appearance,  on  the  other  hand  also  the  injuries  to  grain,  the  causes  of 
which  we  trace  back  to  smut  and  rust  fungi. 

If  we  look  first  in  the  Bible  for  mention  of  diseases  and  especially  of 
"blight,"  we  find,  for  example,  the  following: — ^"If  there  be  in  the 
land  famine;  if  there  be  pestilence,  blasting,  mildew,  locust,  or  if  there  be 
caterpillar;  if  their  enemy  besiege  them  in  the  land  .  .  .  ."  Again: — 
-"The   Lord   shall   smite   thee   with    consumption   and   with   a    fever,   and 


1  First  Book  of  Kings,  Chapter  VIII,  37.     Second  Booli  of  Clironicles,  Chapter 
VI,  28. 

2  Deuteronomy,  Chapter  XXVIII,  22 


42 

with  an  inflammation,  and  with  an  extreme  burning,  and  with  the  sword 
and  with  blasting  and  with  mildczv;  and  they  shall  pursue  thee  until  thou 
perish." 

From  these  verses  Eriksson*  concludes  that  these  statements,  which 
are  more  than  two  thousand  years  old,  refer  to  smut  and  rust  in  grain. 
He  cites  the  word  Schiddafon  (heat)  for  mildew  or  blight  and  Jerakon 
(yellowness)  for  rust.  The  following  sentences  already  quoted  by  Pammel- 
point  to  mildew  in  grain : — "I  ha\  e  smitten  you  with  blasting  and 
mildew:  when  your  garden  and  your  \ineyards  and  your  fig  trees  and  your 

olive    trees    increased,    the    palmer-worm    devoured    them "^ 

Descriptive  of  the  extent  of  the  failure  in  the  harvest  is  the  verse  in 
Haggai* :  "Since  these  days  were  when  one  came  to  an  heap  of 
twenty  measures,  there  were  but  ten : — when  one  came  to  the  pressf at  for 
to  draw  out  fifty  vessels  out  of  the  press,  there  were  but  twenty.  I  smote 
you  with  blasting  and  with  mildew  and  with  hail  in  all  the  labors  of  your 
hands     .     .     .     ." 

Among  the  Greeks,  Aristotle  (384-322  B.  C.)  mentions  the  years  of 
rust  and  Theophrastus  of  Eresus  (371-286  B.  C.)  recognized  the  varying 
susceptibility  of  the  different  varieties  of  grain  to  rust\  He  reports 
also  a  second  kind  of  phenomena  termed  blight,  i.  e.  the  bark  blight  of  trees, 
since  he  says  (Book  14,  Chapter  14)  that  the  cultivated  tree?  are  subject  to 
several  diseases.  Among  these,  some  are  common  to  all  trees  while  others 
attack  only  certain  tree  species.  One  universal  disease  is  the  attack  by 
worms  or  by  blight. 

Theophrastus,  whose  statements,  according  to  Kirchner®,  are  certainly 
based  on  his  own  observations,  speaks  especially  of  the  blight  and 
canker  of  fig  trees  and  mentions  in  this  connection  that  diseases  of  trees  (as 
of  animals)  seem  to  be  determined  by  climate,  since  in  some  regions  these 
same  trees  are  healthy.  The  fig  tree,  jie  says  further,  is  attacked  mostly  by 
blight  and  canker.  Blight  (Sphakclisfiios),  however,  is  spoken  of  when  the 
roots  become  black,  canker  (Krndos)  when  the  branches  become  so.  The 
zvild  fig  tree,  on  the  contrary,  has  neither  canker  nor  blight. 

The  statement,  that  some  fatalities  are  due  to  the  intluence  of  atmos- 
phere and  habitat,  indicates  to  us  the  cause  of  the  disease.  Such  phenomena 
can  not  really  be  termed  disease,  as,  for  example,  freezing  and  what  some 
call  blight.  In  some  places  certain  winds  also  kill  and  burn  the  plants,  as  at 
Chalcis  in  Euboea,  where  the  northwest  wind  is  cold,  if  it  blows  shortly  be- 
fore the  solstice.    It  blasts  the  trees  and  dries  them,  almost  more  than  the  sun. 


1  Eriksson,  Die  Getreideroste.    Stockholm  1894,   p.   8.      (Here  detailed  historical 
reports  on  rust). 

2  Pammel,    L.   H.,   Weems,   J.   B.    and   Lamson-Scribner,    The   Grasses   of   Iowa. 
Des  Moines,  Iowa,  1901. 

3  Amos,   Chapter  IV,   9. 

4  Haggai,  Chapter  II,  16-17. 

5  Naturgeschichte  der   Gewilchse.     Translated  and   explained  by   Sprengel.   Al- 
tona  1822.  I. 

6  Kirchner,    Die    botanischen    Schriften    des    Theophrast    von    Eresos.       Sond. 
Jahrb.  f.  klassische  Philologie.     Leipzig,  1874. 


43 

It  is  doubtful  whether  the  disease  mentioned  here  as  canker  bears  any 
resemblance  to  the  outgrowths  at  present  called  canker.  It  is  certain,  how- 
ever, that  woody  excrescences  were  also  observed.  If  actual  canker  swell- 
ings are  not  concerned  here,  yet  the  phenomena  may  well  have  been 
meant,  which  we  would  now  call  knarls.  Theophrastus  found  this  kind  of 
swellings  in  olive  trees  and  called  them  nails  or  scurf  (loxas-lopas)  because 
they  represent  bowl-shaped  nails  on  the  trees.  Sprengel  says  of  these  nails, 
that  they  have  occurred  recently  very  abundantly  on  the  olive  trees  in  Italy. 
They  appear  as  round,  warty  outgrowths  of  the  bark,  depressed  in  the  centre 
like  a  bowl.  Among  them  may  also  be  found  similar  swellings  of  the  wood 
body. 

It  is  scarcely  credible  that  the  points  of  view  expressed  by  closely  ob- 
servant scholars  of  Aristotle,  concerning  the  phenomena  of  disease  here  men- 
tioned, changed  essentially  in  the  course  of  the  following  centuries,  for  other- 
wise the  celebrated  encyclopaedist  Plinius  Secundus'.  who  lived  from 
23  to  79  A.  D.  and  who  possessed  a  wide  knowledge  of  literary  sources, 
would  have  brought  forward  further  material  at  the  time  he  recorded  scien- 
tifically the  statements  of  Cato  (de  re  rustica)  and  others  as  to  the  influence 
of  the  stars  and  the  death  of  trees  resulting  from  cold,  heat,  unfavorable 
position,  soil,  fertilization,  incorrect  pruning  and  the  like.  The  discoveries 
set  down  in  his  "Natural  History"  contain  much  worthy  of  notice  regarding 
the  influence  of  atmospheric  factors,  cultural  mistakes,  circumstances  pre- 
disposing to  disease  etc. 

In  the  edition  of  the  "Romischen  Prosaiker"  by  Osiander  and  Schwab, 
the  translator  of  PHny  (Kiilb)  has  given  a  summary  of  Pliny's  sources  and 
special  remarks  on  the  authors  instanced  in  his  "Natural  History."  There 
is  rich  material  here  for  a  complete  history  of  phytopathology.  We  must 
content  ourselves  with  a  reference  to  these  carefully  collected  Greek  and 
Roman  sources  and  perhaps  show  by  only  a  fev/  more  quotations  what  exten- 
sive discoveries  had  been  made  at  the  beginning  of  our  era.  According  to  this, 
there  may  be  found  in  the  seventeenth  book  of  Pliny's  "Natural  History," 
Part  XXXVII.,  his  statement  of  the  action  of  frost.  He  says,  "Not  the  weak- 
est trees  are  endangered  by  frost,  but  the  largest  ones,  and,  therefore,  when 
they  do  sufifer,  the  highest  tips  become  blasted,  because  the  sap  arrested  by 
the  cold  can  not  reach  that  point."  We  find  the  following  note  about  the 
phenomena,  which  we  would  now  call  "frost  blight," — "The  evil  influence  of 
the  stars  depends  entirely  on  the  Heavens ;  on  this  account  there  must  also  be 
included  among  these  efl^ects,  hail  as  well  as  blight  and  the  injury 
caused  by  white  frost.  The  blight  especially  attacks  tender  plants  if,  enticed 
by  the  warmth  of  spring,  they  venture  to  break  through  the  ground  and  it 
singes  the  juicy  buds  of  germinating  plants.  In  blossoms  this  is  called 
blasting." 

In  regard  to  carefully  cultivated  grape  vines,  one  reads — "Another  bad 
influence   of   the   stars    (atmospheric    factors)    is   the   covering   with    dew 


Plinii  Secundi  naturalis  Historiae  libri  XXXVII  edit.    Janus.  Book  17,  Chap.  37. 


44 

(roration,  the  falling  on  them  of  cold  dew.  Kiilb)  while  they  are  in 
bloom,  or  when  the  berries  become  hard  grains  and  spoil  before  they  mature. 
They  also  become  diseased,  if  they  freeze  and  the  blight  injures  the  buds 
after  pruning.  Untimely  heat  has  the  same  results,  for  everything  has  its 
definite  measure  and  goal."  At  present  we  summarize  the  experiences  more 
exactly  in  our  teaching  of  an  optimum  and  of  minimum  and  maximum  limits 
for  the  factors  of  growth. 

In  reference  to  defective  cultural  methods  it  is  stated  that  diseases  arise 
when  the  vine-dresser  ties  the  vines  too  tightly  or  injures  the  roots  when 
digging  around  them  and  barks  or  bruises  the  trunk.  Under  all  these  con- 
ditions they  (the  vines)  endure  wet  and  cold  much  less  easily  because  each 
mjury  penetrates  into  the  wound  from  without.  Scarifying  is  recommended 
as  a  remedy  because  the  thickening  bark  fastens  the  stems  together  and  plugs 
them.  As  a  protection  against  the  frosts  of  winter,  is  mentioned  the  method 
by  which  water-ditches  are  dug  about  the  grape  vines  in  winter,  when  the 
ground  is  covered  with  snow,  so  that  the  cold  can  not  blight  them. 

The  most  abundant  information  as  to  cultural  methods  and  the  evils 
attendant  on  them  may  be  found  in  the  collection  of  excerpts  from  old  agri- 
cultural authors,  which  was  made  in  the  tenth  century,  the  "Geoponika." 
We  base  our  discoveries  here  on  the  books  of  the  four  well-known  Roman 
Geoponicists,  Marcus  Cato,  Terentius  \^arro,  Palladius  and  Junius  Modera- 
tus  Columella,  in  which  special  attention  is  paid  to  the  practice  of  fertilization 
and  grafting.  A  compilation  of  the  books  on  agriculture  by  the  authors 
here  named  appeared  in  Cologne  in  1536'. 

From  this  work  I  will  choose  those  places  which  show  that  the  term 
"rust"  as  a  cause  of  disease  is  of  very  early  origin.  Thus  Varro  mentions 
in  the  first  chapter,  among  the  gods,  "qui  maxime  agricolarum  duces  sunt" 
.  .  .  .  "Quarto  Robigum,  et  Floram.  quibus  propitiis,  neque  rubigo  fru- 
menta,  atque  arbores,  corrumpit,  neque  non  tempestive  florent.  Itaque 
I'Uljlicae  Robigo  feriae,  robigalia,  Florae  ludi,  floralia  instituti."  The  ex- 
pression "rust"  was  used  probably  for  all  rust  colored,  diseased  discolor- 
ations  in  plants,  for  we  find  the  word  Robigo  used  by  Columella  to  designate 
a  disease  of  grapes  which  can  be  avoided,  when  frost  threatens,  by  smudging 
the  vineyards.  In  his  book,  "de  arboribus,"  Chapter  XIII  treats  of:  Ne 
rubigo  vineam  vexet.  It  is  recommended  "Palearum  aceruos  inter  ordines 
uerno  tempore  positos  habeto  in  uinea :  cum  f  rigus  centra  temporis  con- 
suetudinem  ne  intellexeris,  omneis  aceruos  incendito,  ita  fumus  nebulam 
et  rubiginem  remouebit."  The  following  place  is  found  in  the  "Enarratio 
priscarum  vocum"  in  regard  to  the  interchangeable  usage  of  "Robigo"  and 
"Rubigo" ;  "Robigo,  deus,  quern  putabant  rubiginem  auertere,  est  aute  Rubigo 
morbus  segetum"-. 


1  De  re  rustica  M.  Catonis  liber  I.,  M.  Terentii  Varronis  lib.  III.,  Palladii  lib. 
XIV.  et  I.  M.  Columellae  lib.  XIII.  Priscarum  vocum  in  libris  de  re  rustica  enar- 
rationes,  per  Georgium  Alexandrinum.  Coloniae,  Joannes  Gymnicus.  Anno 
MDXXXVI. 

-  Here,  as  in  the  following-  citations,  we  will  follow  our  sources  exactly. 


45 

The  next  fifteen  hundred  years  accepted  the  obsers  ations  and  theories 
of  the  Romans,  which  may  be  found  collected  in  Pliny.  For  E.  Meyer^ 
reports  from  Petrus  de  Crescentiis  who  wrote  his  great  work  in  1305, 
the  first  eight  books  of  which  treat  of  agriculture,  that  since  Palladius 
no  one  had  written  anything  in  Latin  on  agriculture.  Only  fragments  of 
the  Greek  collection  of  the  Geoponika  were  to  be  found.  The  older  works 
of  Varro  and  Columella  we'-e  no  longer  suited  to  existing  conditions,  so  that 
there  was  need  of  an  up-to-date  book  on  agriculture.  Yet  the  book  by  Petrus 
de  Crescentiis  actually  contained  less  than  the  books  of  the  older  authors,  al- 
though he  strived  for  a  scientific  foundation  for  agriculture  and  gave  num- 
erous directions  for  grafting  various  kinds  of  trees,  in  accordance  with  the 
favorite  pursuits  of  antiquity  and  of  the  middle  ages.  Tn  the  same  way  in 
1600  Colerus-  also  only  repeated  the  earlier  statements  regarding  the 
outpushings  of  the  bark. — "Inflammation  of  trees"  ("Schwulst  der  Bewne") 
under  which  there  develops  a  putrid  liciuid.  In  this  book  the  influence  of  the 
stars  was  believed  in,  with  unshaken  firmness.  For  example,  in  his  "Horti- 
cultura"  published  in  1631,  the  renovvmed  Professor  Peter  Tauremberg-^  of 
Rostock  relates  that  certain  stars  like  Orion,  the  Pleiades  and  others  exert 
an  especially  injurious  influence  and  that,  as  a  result  of  injurious  atmos- 
pheric influences,  the  so-called  "secret  evils"  arise,  among  which  belong  rust, 
carbuncle  and  mildew. 

We  can  naturally  expect  to  find  progress  in  the  recognition  of  the  sig- 
nificance of  disease  among  practical  workers,  whose  cultural  efl^orts  are  most 
sensitively  disturbed  by  injuries  making  themselves  felt  in  their  work.  The 
book  of  the  "Electoral  Superintendent  of  Gardens," — Heinrich  Hesze"', — 
which  was  famous  in  its  time,  is  interesting  in  this  connection.  He 
speaks  of  the  blasting  of  the  branches  which  he  calls  "blight  and  cold," 
"otherwise  there  are  three  chief  causes  for  the  blighting  of  trees.  First, 
superfluous  moisture  which,  with  inflammation  of  the  sap,  is  collected  be- 
tween wood  and  bark,  distending  the  latter  and  blighting  and  blasting  it.  The 
second  is  this, — that  of  times,  thoughtlessly  and  with  a  lack  of  judgment,  the 
tree  is  set  in  a  postion  dififerent  from  the  one  in  which  it  stood  before.  This  is 
very  injurious,  since  the  bark  where  it  is  brownish  and  has  been  exposed  to 
the  east  or  south,  is  therefore  much  harder  than  on  the  sides  toward  the 
north  or  west.  These  are  generally  green,  tender  and  immature.  There-fore, 
some  injury  must  inevitably  arise  from  this,  since  the  north  side  is  not  at 
all  accustomed  to  the  southern  sun  and  is  not  only  blasted  by  the  great  heat 
but  in  the  spring  is  injured  by  the  hard  frosts  ;  the  bark  is  raised,  then  later 
in  the  day  dried  up  and  scorched  by  the  sun.  From  this  the  bUght  at  once 
arises,  since  it  is  commonly  noticed  on  the  southern  side."  Flere  we  have  posi- 
tive personal  observations.     The  author  relates  further  that  he  has  never- 


1  Geschichte  der  Botanik.    Vol.  IV,  p.  148. 

^  M.  .loannis  Coleri,  Oeconomia  und  Haussbuch  etc.     Ander  Theil.     Wittenberg- 
1600.     Book  V.    Chapter  12. 

3  Petri  Laurembergii,  Rostochiensis  Horticultura.   Francofurti  1631.    Cap.  XXXV. 

4  Heinrich    Heszens,    Neue   Gartenlust   etc.,    enlarged    and    provided    with   three 
useful  indices  by  Theodorum  Phytologum.    1690.    Chapter  VIII. 


46 

Iheless  preserved  trees  thus  reversed  in  position  by  placing  a  covering  of 
cow  manure,  oat  chaff,  gkie  and  ashes  on  the  side  of  the  tree  unwisely  turned 
toward  the  south.  "The  third  case,  however,  arises  when  a  bread  knife  is 
used  in  grafting  etc."  Perhaps  Hesze  has  in  mind  here  some  parasitic  in- 
fection and  attempts  to  explain  it. 

Hesze  (p.  312)  writes  "that  canker  ("Krcbs")  really  orginates  from  the 
grafting  of  a  tree  at  the  time  when  the  moon  lies  in  the  sign  of  the  crab  or 
scorpion  .  .  .  ."  "This  disease  may  be  recognized  by  the  fact  that  here  and 
there  the  bark  throws  up  little  hummocks  under  which  the  tissue  is  dead  and 
black.  This  spreads  further  and  further,  ultimately  infecting  the  whole  trunk. 
Many  scattered  causes  of  canker  have  been  brought  forward,  but  the  one 
given  above  is  the  most  probable  of  all."  The  Editor  makes  the  following 
addition  to  this  statement, — "So  far  as  canker  is  concerned,  no  one 
can  deny  that  it  often  arises  high  up  on  the  trees,  and,  in  fact,  in  the  accumu- 
lations of  dirt  which  collect  between  the  trunk  and  the  branches  at  their 
crotches.  On  this  account,  it  is  most  necessary  that  the  crotches  always  be 
kept  clean  and  freed  from  all  dirt.  Thus  the  canker  often  arises  from  the 
same  rising  sap  which  produces  blight  and  the  two  diseases  often  have  but 
one  cause." 

The  author  clearly  describes  the  phenomenon  which  we  now  term  limb 
canker  and,  instead  of  "ascending  sap,"  we  insert,  injuries  due  to  frost  with  a 
subsequent  infection  by  Nectria  ditissima ;  his  presentation  corresponds  with 
our  present  conception  of  blight  and  canker. 

About  this  time  in  France,  de  la  Quintinye  wrote  "T^e  parfait  jardinier"^ 
which  is  still  much  sought  after.  In  this  we  find  canker  briefly 
mentioned  as  a  kind  of  gall  (signifie  une  manierc  de  ga1le  ou  dc  pourriture 
seiche),  formed  in  the  bark  and  the  wood  and  often  found  on  pears  (Poire 
oe  Robine,  Petit  Muscat,  Bergamotte),  on  trunks  as  well  as  branches.  The 
conception  of  the  swellings  of  the  wood  indicated  by  the  term  "canker"  is 
found  further  in  the  writings  of  later  horticultural  authors,  as,  for  example, 
in  Fischer-.  * 

The  boastful  Agricola'^  (born  1672)  stands  independent,  that  is, 
on  his  personal,  repeated  and  practical  experience.  His  actual  service  is 
found  in  his  numerous  experiments,  carried  out  from  1712-1715,  on  the  vege- 
tative reproduction  of  plants  (especially  by  roots).  He  devotes  the  fifth 
chapter  to  "occurrences  and  diseases"  and  expresses  himself,  for  example, 
as  follows : — "Mildew,  Rubigo,  however,  prevails  at  times,  as  a  pestilence 
among  trees.     In  spring,  when  the  earth  opens  and  the  enclosed  vapors  be- 


1  I^e  parfait  jardinier  otc.  Par  feu  Mr.  de  la  Quintinve.  Parish  1695.  Vol.  I., 
p.  31. 

^  R.  P.  Christophori  Fischefi  soc.  j,  Fleissiges  Herrenauge  etc.  Niirnberg-  1719.  5 
Section   I.,   p.   168. 

3  Georg-  Andrea  Agrricola.  Philosophiae  et  Medicinae  Doctoris  und  Physici 
Ordinarii  in  Regensburg,  Versuch  einer  allgemeinen  Verhmehrung  aller  Baume, 
Stauden  and  Blumengewiichse  anjetzo  auf  ein  neues  libersehen  uhw.  von  C.  G. 
Brausern.  Regensburg  1772.  The  original  title  read,— "A  new  and  unheard  of  ex- 
periment, well  founded  in  nature  and  in  reason,  for  the  universal  increase  of  all 
trees,  bushes  and  flowering  plants,"   1716. 


47 

gin  to  rise,  it  injures  most  of  them  and  is  nothing  else  than  a  very  sharp  and 
biting  dew,  originating  in  the  earthy  vapors  and  conducted  from  them  .... 
In  the  third  place  a  disease  occurs  among  trees,  which  is  called  sunblight,  or 
blight,  urcdo,  which,  however,_may  be  of  two  kinds.  First,  when  a  fine  rain 
or  dew  falls  or  settles  on  the  leaves  while  the  sun  shines,  the  ducts  or  tubes, 
becoming  flabby  and  distended,  are  contracted  at  once  by  the  heat  of  the  sun. 
Thus  the  leaves  are  scorched,  begin  to  turn  brown  and  black  and  fall.  In 
the  second  case,  the  urcdo  or  blight  is  found  in  the  inner  parts  of  the  trees, 
in  the  pith  ....  The  true  cause,  however,  for  the  blighted  pith,  when 
the  tree  is  transplanted,  may  well  be,  that  the  common  gardeners  have  the 
habit,  in  transplanting,  of  pruning  all  the  roots  and  do  not  understand  how 
much  they  are  injuring  the  tree.  For  the  smallest  roots  draw  the  most  sap 
from  the  earth,  and  these  are  the  ones  they  cut  off  ....  Now  because 
the  root,  together  with  the  pith,  is  open  and  exposed,  moisture  can  penetrate 
and  injure  the  pith     .     .     .     ." 

In  regard  to  canker,  we  find  the  "ascending  sap"  emphasized  as  its 
cause  in  the  horticultural  lexicon  by  Riedel  published  in  175 1".  "Can- 
ker, tree-cancer,  canker,  devourer,"  thus  is  listed  the  injurious  attack 
on  the  trees  which  appears  in  the  bark, — since  it  forms  hummocks  here  and 
there  and  springs  up. — And  therefore,  if  the  devouring  evil  is  not  overcome 
in  time,  one  branch  after  another,  and  eventually  the  whole  tree,  is  ruined 
.  .  .  .  The  real  cause,  however,  of  this  injurious  attack  on  the  trees  is 
cither  the  evil  peculiarity  of  the  earth  and  the  evil  juices  produced  or  arising 
from  it  which  become  so  inflamed  within  the  bark  that  this  looks  black  when 
removed,  or  the  ascending  superfluous  rank  juice,  which,  finding  no  escape, 
must  clog  and  spoil,  thus  becoming  the  cause  of  the  out-pushing  and  bursting 
of  the  bark." 

Instead  of  the  ascending  sap,  the  expression — "congestion  of  the  sap," 
is  used  at  present. 

As  a  remedy  for  canker,  this  author  recommends  cutting  out  the  dis- 
eased places  and  coating  with  grafting  wax.  If  the  cause  lies  in  the  soil,  this 
should  be  removed  up  to  the  roots  and  replaced  by  new  soil.  When  the  sap 
is  excessive,  the  base  of  the  tree  trunk  should  be  bored  in  February,  and  the 
hole  wedged  open  for  i  to  2  days  with  a  firm  wooden  peg  or  a  strong  root 
should  be  split,  "  since  the  superfluous  sap  will  then  be  drawn  downward." 

Philipp  Miller-  traces  phenomena  of  disease  directly  back  to  frost, 
and  calls  them  "blight."  Miller's  decisions  are  essentially  a  repetition 
of  Hale's  theories  that  by  blight  (blast)  not  only  frost  but  also  sun  scorch 
etc.  are  understood.  Hale's''  statements  are  important  because  he  men- 
tions the  transmissabiHty  of  canker  in  budding  and  of  its  occasional  heal- 
ing by  being  cut  out.     The  observation  of  this  English  experimentor  on  the 


1  Riedel,  Kurz  abgefafstes  Gartenlexiron  usw.     Nordhausen  1751.    p.  420. 

2  The    English    Garden    Book    or    Philipp    Miller's    "Gardener's    Lexicon      etc. 
From  the  Fifth  Edition  translated  into  the  German  by  Huth.  Nurnberg  1750.  p.  136. 

3  Statical  Essays  containing-  Vegetable  Statics  etc.  by  Steph.  Hales.  2nd  edition. 
London  1731.    L  35ff.,  147,  369;   II,  265. 


48 

influence  of  the  dry  spring  winds,  which  scorch  the  foHage  is  worth  noting: — 
"The  considerable  quantity  of  moisture  which  is  given  off  from  the  branches 
of  trees  during  the  cold  winter  season,  plainly  shows  the  reason,  why,  in  a 
long  series  of  cold,  northeasterly  winds,  the  blossoms  and  tender  young  set 
fruit  and  leaves  are  so  frequently  blasted  in  the  early  spring,  \\z.  by  having 
the  moisture  exhaled  faster  than  it  can  be  supplied  from  the  trees." 

DuhameP  pays  great  attention  to  injuries  from  frost  and  states 
that  trees  are  often  attacked  by  swellings  which  may  be  more  easily  healed  in 
younger  than  in  older  trees.  At  some  place  on  the  trunk,  the  bark  is  loosened 
from  the  wood  and  a  devouring  pus  occurs  between  the  two.  Devouring  ab- 
scesses of  this  kind  are  called  "canker"  which  is  counted  among  the  diseases 
j/roduced  by  a  superfluity  of  sap.  Das  Xiedersachsische  Gartenbuch-  finds 
the  cause  from  blight  and  canker  in  too  thick  standing  of  the  trees,  in  un- 
favorable soil  etc. 

While  in  ancient  times  and  in  the  middle  ages  observations  on  plant  dis- 
eases were  usually  limited  to  a  perception  of  the  mature  phenomena  visible 
to  the  naked  eye  and  the  solution  of  the  questions  of  plant  life  were  sought 
almost  entirely  among  experiments  of  budding,  we  find  that  the  experiment 
itself  attained  its  own  importance  with  Hales  and  Duhamel. 


Simultaneously  with  experimental  physiology  came  the  wider  classifi- 
cation of  plant  diseases. 

We  follow  here  Seetzen's"  treatment  of  the  subject  and  its  history. 
Seetzen  states  that  Tournefort  had  a  finished*  system*.  His  first  class 
includes  the  diseases  due  to  internal  causes,  as  opposed  to  the  sec- 
f)nd  class,  the  diseases  produced  by  external  causes.  To  the  first  class  he  as- 
cribes: —  i-La  trop  grande  abondance  du '  sue  nourricier ;  2-le  defaut  ou 
manque  de  ce  sue;  3-quelques  mauvaises  qualites  qu'il  pent  acquerir;  4-la 
distribution  inegale  dans  les  diflferentes  parties  des  plantes.  In  the  second 
class  belong: — i-La  grele ;  2-la  gelee ;  3-la  moisissure:  4-les  plantes,  qui 
naissent  sur  d'autres  plantes ;  5-la  piqueure  des  inscctes :  Ti-dififerentes  taillcs 
ou  incisions,  que  Ton  fait  aux  plantes. 

We  find  T(~»urnefort's  point  of  view  in  our  modern  systems.  \\'e  group 
the  diseases  caused  by  excess  or  deficiency  of  water  and  food,  with  injuries 
produced  by  weather  extremes  (frost,  hail)  etc.  In  the  same  way.  we  treat 
wounds  as  a  separate  division.  The  parasitic  diseases  appear  for  the  first 
time  as  such  in  Tournefort's  book. 

Less  fortunate  is  Zwinger's"  system  which  appeared  shortly  after 
Tournefort's  and  which  also  is  formed  of  two  main  groups, —  (i)   General 


1  La  physique  des  arbres  par  Duhamel  du  Monceau.    Pari.s  1758.    p.  339. 

-  Caspar  Bechstedt.  VolKstandises  niedersachsiches  Land-  und  Gartenbuch. 
Flensburg  und  Leipzif?  1772.  I,  p.  151. 

■'  Systematum  g^enoraliorum  de  morbis  plantarum  brevis  diiudicatio.  Publico 
examini   submittit  Ulricus  .Jasper   Seetzen.     Gottingae   MDCCLXXXIX. 

4  Observations  sur  les  maladies  des  plantes  par  M.  Tournefort.  Mem.  de  I'Ac. 
Roy.  des  Sciences  a  Paris  1705,  p.  332. 

5  Jo.  Jac.  Zwingeri,  Diss.  med.  inauguralis  de  valetudine  plantarum  fecunda  et 
adversa.    Basileae  1708. 


49 

and  (2)  Specific  diseases.  The  first  includes :— La  gangrene— le  desseche- 
ment — la  surabondance  de  sue — le  branchage  excess! f — une  espece  de  galle, 
qui  manche  I'ecorce.  In  the  second  main  group  we  find: — Le  dessechement 
des  racines — la  separation  de  leur  ecorce — la  grosseur  excessive  des  racines. 
qui  retienent  tout  le  sue  de  la  plante — les  excroissances — les  coups  et  les 
biessures.  It  is  evident  from  this  division  of  closely  related  phenomena  that 
the  author  had  not  fully  mastered  his  material. 

Eysfarth's^  system  gives  a  classification  which  the  layman  easily 
grasps.  It  uses  as  its  basis  the  different  periods  of  the  plant's  Hfe.  In 
the  first  class  are  the  diseases  of  the  period  of  germination ;  in  the  second, 
those  of  the  actual  vegetative  period  and  in  the  third  class,  the  disturbances 
of  the  sexual  period.  Under  each  class  are  discussed  the  influences  of 
weather  extremes,  injuries  due  to  animals  and  other  wounds.  In  this  book 
there  is  also  a  chapter  "a  rubigine  aut  pruina."  The  thoroughness  of  the 
classification  shows  that  the  author  had  well  worked  out  his  material. 

Adanson-  returns  to  Tournefort's  division  since  he  sets  up  as  his 
first  main  group  the  "maladies  dues  a  des  causes  externes,"  and  as  the 
second,  the  "maladies  dues  a  des  causes  internes."  Even  the  introduction 
shows  the  advance  in  microscopic  investigation  and  the  increased  attention 
paid  to  parasitic  fungi ;  under  the  first  main  group,  the  dififerent  chapters 
take  up,  for  example,  Le  givre  ou  Jivre  (Erysiphe  Fabricii) — la  rouille 
kgu(f[(nrj  Theophr.  (Rubigo) — le  charbon  (Ustilago) — la  pourriture  (Caries 
Fabr.)  etc. 

Adanson  often  uses  the  terminology  of  Fabricius  who  probably  had 
published  his  studies  in  separate  treatises  before  his  classification  had  ap- 
peared as  a  whole,  for  his  complete  classification  did  not  appear  until  1/74^'. 

Fabricius  certainly  based  his  views  on  his  own  observations.  This  is 
less  noticeable  in  the  formation  of  the  main  groups  than  in  the  sub-divisions 
of  the  dififerent  chapters,  in  which  a  classification  of  the  cases  according  to 
their  dififerent  causes  has  been  stated,  even  when  the  external  appear- 
ance was  similar.  Thus,  for  example,  we  find  in  the  first  main  group : — 
"Vf rugtbargiorende  Sygdomme,"  i.  e.  the  disturbances  leading  to  sterility  ; 
a  section  "Dovhed"  which  may  be  translated  by  etiolation  or  the  yellows. 
This  is  divided  into  D.  af  Regn,  af  Kulde,  af  Rog  etc.  His  observation  that, 
besides  rain,  cold  and  other  factors,  "yellows"  may  be  produced  by  smoke 
is  also  worth  notice.  In  the  second  main  group,  "Udtaerende  Sygd,"  i.e.  the  at- 
rophias, there  is  found  under  the  section  "Quaelelse,"  etiolation  from  "stedets 
Indslutning"  (too  close  planting),  from  "paa  Lys"  (lack  of  light)  and  from 
clinging  plants  and  insect  injuries.  x\nother  group  is  separated  from  these 
phenomena, — ^"Taering"  (Tabes,  Jaunisse  in  Adanson)  where  the  yellowing 
is   due  to   insufificient   nutritive   substances,  unsuitable   soil   conditions,   ex- 


1   Christ.  Sigismund  Eysfarth,  Diss,  pliys.  de  morbis  plantarum.    Lipsiae  1723.  4  . 

^  Adanson,  Sur  les  maladies  des  plantes;  in  "Families  des  Plantes."  Vol.  I,  p.  42. 
1763.     8°. 

3  Forsfig  til  en  Af  handling-  om  Planternes  Sygdomme  ved  Joh.  Christ  Fabricius; 
ind  der  kongelige  Norske  Videnakataers  Selskab  skrifter  femte  Deel.  Kjobenh.  1774. 
Sid.  431-492. 


50 

cessive  evaporation  after  transplanting  etc.  The  third  main  group  is  taken 
up  with  "Flydende  Sygdomme,"  that  is,  sap-currents,  under  which  is  included 
honey-dew.  In  the  fourth  group  are  found  the  "Raadnende  Sygdomme" 
which,  according  to  our  point  of  view,  might  be  termed  soft  rot,  putrefying 
hacteriosis  or  scrofula.  Among  the  causes  figure  also  the  "Snylte-Planterne," 
i.  e.  parasitic  plants.  In  the  fifth  and  sixth  groups,  wounds,  frost  splits,  galls 
and  monstrosities  are  treated. 

In  1779  appeared  the  German  translation  of  the  Zallinger^  classi- 
fication with  the  evident  endeavor  to  utilize  the  terminology  of  animal  path- 
ology in  plant  pathology.  Zallinger  makes  five  classes: — (i)  Phlcgmasiac 
or  inflammatory  diseases;  (2)  Paralyses  sen  debilitates,  laming  gouts  or  de- 
bility; (3)  discharges  and  draining;  (4)  Cachcxiae,  bad  constitution  of  the 
body;  (5)  chief  defect  of  the  dififcrent  parts.  In  order  to  characterize  his 
theory,  let  us  look  for  the  disease  which,  with  blight,  forms  the  main  example 
in  our  entire  presentation, — viz.  canker.  Zallinger  puts  this  in  the  class  of 
the  Cachexiae,  in  the  subdivision  of  the  ulcers,  under  which  he  includes  rachi- 
tis or  abortive  growth,  leontiasis  or  rough  warts  on  the  skin  and  others.  lie 
mentions  blight,  Gangraeno  s.  Sphacelus  as  an  abnormal  Cachexia,  together 
with  Phthiriasis  or  lousy  disease  and  Vermiculatio,  the  production  of  worms. 
From  this  classification  it  may  be  concluded  that  the  author  has  let  himself 
be  guided  by  the  frequently  similar  appearance  of  the  phenomena,  for  the 
dead  places  in  the  bark  offer  a  favorable  centre  of  attack  by  insects.  What 
we  now  term  grain  smut  is  found  as  Ustilago,  or  deformity  of  the  seed,  under 
the  class  of  draining.  Fabricius  had  placed  "Kraebs,"  Cancer,  in  the  class 
of  diseases  of  decomposition. 

Batsch^,  in  his  introduction  to  the  knowledge  of  plants,  also  pub- 
lished a  survey  of  the  diseases  which  he  divided  into  those  based  on  the  "de- 
composition of  the  firm  and  fluid  parts,"  i.  e.  on  the  constitution  of  the  plant, 
and  into  those  caused  ]:)y  "animals  and  plants." 

Any  one,  however,  looking  for  our  cryptogamic  parasites  in  the  latter 
section  would  be  deceived.  These  are  rather  to  be  found  in  the  first  class,  in 
agreement  with  the  conviction  already  advanced  by  Zallinger  Cs.  Ustilago). 
that  the  parasitic  organisms  are  not  independent  plants  but  only  develop- 
mental forms  of  the  higher  plants.  Thus  Batsch  under  constitutional  dis- 
eases has  one  group  "Brandige  Veranderung  des  Wesens,"  change  of  char- 
acter due  to  blight,  the  first  family  of  which  includes  the  phenomenon,  where 
a  decomposition  of  the  tissue  into  powder  "smut,  Ustilago"  takes  place.  The 
second  family  contains  the  transformation  of  the  tissues  into  "a  spongy  mass 
(Ergot,  Clavus)." 

These  views  remained  in  force  for  some  time,  as  will  be  seen  from  the 
following  section. 


1  Abhandluns-  iiber  die  Krankheiten  der  Pflanzen,  ihrer  Kenntnis  und  Heilung; 
translated  from  the  Latin  by  .loh.  Count  v.  Aauer.sperg-.     Augsburg  1779.    8°. 

-'  A.  J.  G.  C.  Batsch.  Versuch  einer  Anleitung  zur  Kenntnis  and  Geschichte  der 
Pflanzen  etc.    I.  Theil.  Halle  1787.    p.  284. 


EDGAR  TULLIS 

51 

By  means  of  the  works  of  the  authors  mentioned  and  the  discoveries  of 
practical  horticulture,  as  well  as  the  great  sensation  called  forth  by  the  tree 
wax  for  injured  trees  which  was  discovered  by  William  Forsyth  in  1791  and 
universally  overestimated,  the  conviction  of  the  agricultural  significance  of 
plant  diseases  was  extended  over  so  wide  a  circle  that  special  books  could 
now  be  published  for  this  branch  of  knowledge. 

The  year  1795  makes  us  acquainted  with  three  such  works.  The  first 
one  written  by  Plenk^  treats  of  the  diseases  of  all  cultivated  plants 
of  importance  at  that  time  and  is  based  on  thorough  observations.  He  de- 
scribes thus : — "d.  spongy  large  outgrowth  at  some  place  on  the  trunk  from 
which  exudes,  even  in  the  most  scorching  weather,  a  caustic  moisture  which 
corrodes  the  whole  extent  of  the  swelling."  Thus  Pyriis  Cydonia,  standing 
near  a  swamp,  was  attacked  by  tree  canker  while  other  quince  trees  planted 
in  a  higher  place  were  healthy.  The  sap,  it  seems,  becomes  so  caustic  from 
the  acidity  of  the  standing  water  that  it  eats  up  the  ducts.  There  are  two 
kinds  of  tree  canker  determined  by  the  diflFerence  in  the  location  of  the  dis- 
ease; first,  open  tree  canker,  when  the  canker  knots  appear  on  the  external 
surface  of  the  bark ;  second,  hidden  canker,  when  a  sharp  cancerous  pus 
collects  between  the  bark  and  the  wood  but  does  not  escape  from  the  bark 
in  any  place.  In  both  cases  the  tree  becomes  incurably  wasted,  when  the 
parts  attacked  by  canker  are  not  cut  out  at  once  and  covered  with  wound 
wax.  In  this  blight  Plenk  distinguished  between  a  dry  and  a  moist  blight. 
By  the  first  he  means  "a  black  and  dry  wilting  of  the  leaves  or  of  some  other 
part  of  the  plant"  and  by  "moist  blight"  he  designates  the  "moist  and  soft 
degeneration  of  the  plants  into  a  putrid  pus." 

We  find  almost  the  same  terminology  in  the  explanation  of  canker  in 
Schreger's-  book  which  otherwise  gives  many  of  his  personal  obser- 
vations. In  regard  to  the  phenomena  of  blight  in  which  the  bark  or  other 
parts  of  the  tree  appear  black  and  soft  and  are  consumed,  he  says,  "Such 
black  spots  of  the  bark  grow  further  and  further  round  about  themselves 
even  attacking  the  wood  so  that  the  bark  itself  at  last  splits  off,  as  if  dead, 
and  the  wood  appears  dry  and  black,  as  if  burned."  This  explanation  cor- 
responds exactly  with  the  phenomena  which  we  perceive  when  frost  causes 
considerable  injuries  to  the  bark.  In  fact  this  observer  arrives  at  the  same 
conclusion  as  we  do  in  regard  to  the  cause.  "Bruises  from  hailstones  give 
rise  to  its  production  and  also  cold  frosts.  This  frost  is  more  injurious  in 
low  and  moist  regions  than  in  high  dry  ones.  For  this  reason  there  is  less 
injury  from  frost  on  windy  nights  than  on  clear,  cold  ones.  If  the  trees 
freeze  in  winter  and  die,  the  cause  of  their  death  is  usually  a  blight  induced 
by  this  freezing.  This  happens  sometimes  when  the  severe  cold  comes  too 
early  in  the  autumn  while  the  sap  is  still  flowing  actively ;  sometimes  in  the 
spring  when  the  sap,  so  to  speak,  has  begun  to  run.     The  latter  case  is  the 


1  Plenk,  Physiologie  und  Pathologie  der  Pflanzen.    Wien  179.5.     ^ 

2  Erfahrungsmassige  Anweisung  zur  richtigen   Kenntnis   der   Krankheiten   der 
Wald-   und  Gartenaume.    Leipzig  1795. 


52 

most  dangerous  of  all.  Even  in  midwinter  with  very  great  cold  they  rarely 
freeze ;  it  might  be  when  it  has  rained  the  day  before."  On  pages  420  and 
500,  he  says  of  api)le  and  pear  trees  that  "an  excess  of  fatty,  oily  fertilizers 
easily  develops  blight  and  canker,"  i.  e.  creates  a  predisposition. 

The  third  one  of  the  books  published  in  1795,  the  one  by  Rittcr  v.  Khren- 
fels'  is  even  more  specialized,  for  he  treats  only  of  fruit  trees.  He 
declares  that  all  kinds  of  trees  would  be  subject  to  blight  and  that  "this  decay 
which  appears  first  in  the  bark  and  then  in  the  wood"  is  the  most  common 
disease  of  trees  and  in  some  books  is  termed  canker.  The  description  which  he 
gives  is  so  clear  that  it  can  be  identified  as  the  phenomenon  now  known  as 
iVectria-canker.  He  says,  "the  indication  of  this  evil  attack  is  first  of  all  a 
black  or  blackish  bark  which,  six  or  eight  days  after  its  appearance,  is  often 
pushed  out,  forms  little  splits  and  gradually  loses  its  connection  with  the 
trunk  of  the  tree  so  that  it  clings  only  loosely  to  the  shaft.  After  some  time 
the  loose  bark  is  entirely  separated  from  the  trunk  and  exposes  the  wood. 
In  this  new  stage  the  vitality  of  the  '^ick  plant  docs  its  very  licst  to  help  itself 
and  unceasingly  throws  off  the  unfa\oral)lc  or  sick  parts,  but  this  vitality 
finally  becomes  weakened  and  the  tree  dies.  The  tree  attempts  to  form  a 
new  bark  which  grows  in  folds  more  or  less  overlapping  and  tries  to  cover 
the  exposed  places"  ....  He  ascribed  the  cause  to  injuries  as,  for 
example,  from  injudicious  pruning,  injuries  due  to  insects  and  the  like,  "even 
at  times  the  tendency  to  blight  lies  in  the  disposition  of  the  tree  itself, — a 
disposition  which  the  trees  obtain  from  the  soil  in  wliich  thev  grow,  from 
(heir  descent  and  from  an  unwise  cultivation." 

In  the  pomological  glossary  published  at  the  beginning  of  the  la.st  cen- 
tury, Christ-  added  to  the  above  by  the  further  statement,  that  the  blight 
"often  is  due  to  freezing  in  winter." 

Burdach''  also  bases  his  statements  on  his  own  observations  and 
says  of  blight,  "this  disease  is  an  indirect  result  of  weakness  and  commonly 
arises  in  those  trees  whose  growth  has  been  hastened  by  strong  forcing  and 
fertilizing  or  which  have  been  transplanted  to  a  poor  garden  soil  where  only 
the  upper  part  of  the  ground  has  been  improved.  In  cherry  trees,  still  an- 
other evil  effect  arises  from  the  same  cause,  viz.  the  exudation  of  resin  or 
gum." 

The  theory  of  the  inHucncc  of  llie  soil  and  fertilization,  as  among  the 
most  important  causes  of  plant  diseases,  is  now  laid  aside  for  some  time  and 
attention  is  given  to  the  manifold  and  extensive  investigation  of  the  province 
of  fungus  life. 


Although   anli(juity   had   already   recognized   a   number   of   edible   and 
poisonous  fungi,  yet  their  attentive  observation  and  systematic  study  began 

1  Ritter   v.    Ehrenfels,    Ueber   die    Krankheiten    und    Verletzunsen    der    Frurht- 
und  Gartenbiiume.     Bresslau,  Hirshberg  und  Lissa  1795. 

2  Pomologisches  theoretisch-praktisches  Handworterbuch.     Leipzig  1802. 

3  Systematisches  Handbuch  der  Obstbaumkrankheiten.     Berlin  1§18, 


53 

first  in  the  Middle  Ages  with  the  foundation  of  classification  of  tlie  vegetable 
kingdom.  According  to  the  statements  of  Corda\  Andreas  Caesalpinus 
(1583)  was  the  first  to  gather  together  the  fungi  in  his  celebrated  book  "De 
plantis."  He  describes  sixteen  genera,  Tuber,  Peziza,  Fungus,  Boletus,  Suil- 
lus,Prunualus,  Prateolus,  Familiola,  ScorogVm,  Fungus  marinus,  Gallimaceus, 
Fungus  panis  similis.  Lingua,  Digitellus,  Igniarius  and  Agaricum.  As  it 
seems,  even  marine  animals  have  been  included  here.  After  almost  one  hun- 
dred years  appeared  Joannis  Raji's  "Methodus  plantarum"  Londini  1682.  In 
1710  Boerhave  followed  with  his  "Index  plantarum  horti  Lugdano-Batavi" 
and  in  1719  Tournefort  appeared  with  his  "Institutiones  Rei  herbariae." 

The  chief  work  to  which  modern  mycology  must  refer  appeared  in  1729 
in  Micheli's  "Nova  plantarum  genera"  in  which  the  fungi  are  most  carefully 
described  and  illustrated  in  more  than  100  pages  and  with  12  plates.  Micheli 
studied  their  life  phenomena  more  closely  and  was  the  first  to  observe  the 
attachment  and  dissemination  of  spores.  Among  the  genera  there  described 
are  found  those  which  are  considered  in  plant  diseases,  Aspergillis,  Botrytis, 
Puccinia  (now  Gymnosporangium),  Mucor  and  Lycogala. 

There  now  follow  in  quick  succession  "Methodus  fungorum"  by  Gled- 
itsch  (1753)  and  the  "Fungorum  agri  ariminensis  historia"by  Battara  (1755), 
in  which  a  special  chapter  treats  of  the  usefulness  and  injuriousness  of  fungi. 
The  close  systematic  description  of  the  different  genera  and  species  begins 
with  Linnaeus'  "Systema  Naturae"  (1735),  the  "Methodus  sexualis,"  the 
"Genera  plantarum,"  the  "Corollarium  generum"  and  the  "Philosophia 
botanica."  The  third  edition  of  this  book,  published  in  1790  by  Willdenow, 
contains  an  exact  list  of  all  botanists  up  to  1788.  The  work  also  mentions 
a  number  of  diseases  (Fames,  Polysarchia,  Cancer,  etc.).  On  page 
245  of  the  present  edition  by  Willdenow,  are  found  the  following  remarks 
on  parasitic  diseases: — "Erysiphe  Th.  est  Mucor  alhus,  capitulis,  fuscis  ses- 
silibus,  quo  folia  asperguntur,  frequens  in  Humulo,  Lamio.  A  cere"  etc.  .  .  . 
"Rubigo  est  pulvis  ferrugineus,  foliis  subtus.  adspersus,  frequens  in  Alche- 
milla,  Rubo  saxatili  .  .  .  ."  "Ustilago,  cum  fructus  loco  seminum  fari- 
nam  nigram  proferunt.  Ustilago  Hordvi  C.  B.,  Ustilago  Avcnae  C.  B."  .  .  . 
Then  follow  notes  on  Ergot,  galls  and  other  malformations,  changes  in  color 
etc.  It  is  of  importance  to  pathology  that  this  exact  systematist  can  not  sup- 
press the  fact  that  really  no  two  individuals  resemble  one  another  and  that 
climate  as  well  as  soil  constantly  act  in  a  modifying  way  on  the  organism.  It 
is  stated  in  fact  in  the  Philosophia  botanica,  "Varietates  tot  sunt  quot  diiTer- 
entes  plantae  ex  ejusdem  speciei  semina  sunt  productae.  Varietas  est  planta 
mutata  a  causa  accidentali :  climate,  solo,  calore,  ventis  etc. ;  reducitur  itaque 
in  solo  mutata."  ....  Scopoli's  book  "Dissertationes  ad  scientam 
naturalem  pertinentes"  (1772)  treats  especially  of  subterranean  plants.  In 
1780  the  publication  of  Bulliard's  "Herbier  de  la  France"  was  begun  in 
Paris,  in  which  the  different  genera  are  illustrated  on  6co  colored  plates, 
( among  others  Mucor,  Trichia,  Sphaerocarpus,  Nidularia,  Hypoxylon ) .  After 


Anleitung-  zum  Studium  der  Mykologie. 


54 

Batch's  "Elenchus  fungorum"  had  appeared  in  1783  in  Jena  and,  between 
1788  to  i79i,Bohon's  "Historia  fungorum,  circa  Hahfax  sponte  nascentium," 
in  which  only  Linnean  genera  are  described,  there  was  published  in  1790  in 
Liineburg  Tode's  valuable  work  which  abounds  in  personal  observations, 
"Fungi  mecklenburgenses  selecti."  The  extremely  careful  illustrations  include 
among  others,  the  genera  Acrospermum,  Stilbum,  Ascophora,  Tubercularia, 
Helotium,  Volutella,  Hysterium,  Vermicularia,  Pilobolus  which  we  now  find 
among  the  excitors  of  disease.  A,  v.  Humboldt,  in  his  "Florae  fribergensis 
specimen"  (1793)  has  also  described  a  considerable  nnni!)er  of  genera. 

But  all  these  works,  nevertheless,  are  to  be  considered  only  "contribu- 
tions." A  comprehensive  methodical  classification  was  first  given  by  Per- 
soon's  "Synopsis  methodica"  (Gottigen  1801),  for  long  a  standard.  There 
appeared  in  England,  from  1797  to  1809,  a  work  by  James  Sowerby  con- 
taining 439  plates  of  valuable  illustrations  with  the  title  "Colored  Figures  of 
English  Fungi  or  Mushrooms." 

Mycologists  now  tended  more  and  more  toward  the  study  of  the  mi- 
croscopic fungous  forms  even  if  the  optical  instruments  of  the  time  did  not 
make  possible  more  exact  observations.  This  applies  first  of  all  to  Linck's 
"Observationes  in  Ordines  plnntarum  naturales"  published  in  the  "Schriften 
naturforschender  Freunde  zu  Berlin"  (3.  Jahregang  1809-1810)  and  the 
illustrated  work  by  Nees  v.  Esenbeck,  abounding  in  copies  from  earlier  books, 
"System  dcr  Pilze  und  Schwiimme,"  Witrzburg  1817,  which  contains  a  sum- 
mary "of  the  theories  of  the  lower  vegetation  stages  in  historical  fragments." 
Here  also  are  the  statements  of  investigators  believing  in  sponiancoits  gene- 
fation.  The  author  himself,  if  we  understand  correctly  his  grandiloquent 
natural  philosophical  presentation,  considers  the  parasitic  fungi  in  the  lowest 
possible  groups  as  structures  produced  from  the  mother  plant  itself.  Thus 
he  says,  for  example,  of  the  Entophyt.es,  "Their  most  peculiar  characteristic 
is  that  they  belong  to  the  overloaded  or  exhausted  life  and  generally,  if  not 
always,  develop  first  under  the  common  covering  without  any  mixture  ex- 
tending over  the  whole,  and  originally  only  in  isolated  places,  formed  in- 
dividually from  the  life  of  the  whole.  The  dependence  of  the  infusorial  cell 
on  the  higher  organisms  is  always  shown  by  its  superior  position,  due  to  its 
more  or  less  lengthened  stem.  The  cell  grows  before  it  has  become  free  and 
its  elongation  on  this  foundation  is  the  expression  of  the  condition  of  polar- 
ity which  has  been  brought  about,  not  suddenly  but  organically,  and  which 
passes  over  into  the  cell  from  the  main  plant."  Under  the  genus  Cyathus 
(one  of  the  puff  balls)  (p.  141)  it  is  said  "the  whole  trunk  species  which 
we  have  described  is  only  a  thread  of  dust  originating  from  the  earth  itself. 
The  dust  of  the  puff  balls  begets  itself     .     .     .     ." 

At  this  time  Elias  Fries^  classic  work  was  published  including  all 
the  known  varieties  of  the  fungus  kingdom  with  clear  diagnoses  of 
genera  and  species. 


1   Systema  mycologicum  T.  I  to  III.     I.iindae  1821,  Gryphiswaldiae  1829  to  1832- 
Elenchus  Fungorum.     Gryph.   1828. 


55 

The  literature  now  begins  to  be  increased  by  single  works,  scientific  as 
well  as  practical  manuals  and  writings  on  both  agriculture  and  horticulture 
which  treat  of  diseases  (Tessier,  Jager,  Hopkirk,  the  text  books  of  Willde- 
now,  Nees,  de  CandoUe,  Wenderoth,  Reichenbach,  Re  and  Kieser)  to  such 
an  extent  that  we  can  now  emphasize  only  those  publications  which  deal  most 
fully  with  the  history  of  pathology. 

Among  these  belong  primarily  F.  Unger's^  "Exantheme  der  Piianzen" 
published  in  1833  and  giving  the  results  of  the  most  industrious 
and  conscientious  studies.  This  physician,  living  in  a  small  isolated  Alpine 
valley,  supplements  his  observations  by  many  very  careful  original  drawings, 
true  to  nature,  on  which  he  constructs  his  theory  of  disease.  "Most  plant 
diseases  are  located  in  the  juices  ....  The  faulty  formation  and  the 
numerous  abnormalities  in  the  chemical  process  of  the  nutritive  juice  as  well 
as  similar  faults  in  the  more  highly  active  life-sap,  are  the  causes  of  innumer- 
able diseases  which  become  evident  in  a  scanty  formation  of  the  plant  sub- 
stance, the  accumulation  of  excretory  substances,  the  breaking  up  of  the 
parenchyma,  the  changed  constitution  of  the  secretions  etc.,  or  by  conditions 
of  an  opposite  character.  In  every  case,  most  of  the  quantitatively  and  quali- 
tatively changed  processes  of  the  vegetative  "chylopoese"  might  be  taken 
as  the  source  of  diseases  which  may  be  recognized  from  the  change  in  sub- 
stance rather  than  from  that  of  form.  The  position  into  which  a  large 
number  of  the  plants  are  transplanted  often  acts  so  detrimentally  upon  them 
that  at  least  the  greater  part  deserve  to  be  called  diseased." 

Although,  according  to  this  presentation,  we  must  suppose  on  the  whole 
that  Unger  would  consider  diseases  as  functional  and  formal  variations  in 
the  life-history  of  the  organism,  he,  nevertheless,  arrives  at  the  conclusion 
that  disease  is  something  foreign.  "For  just  as  the  cosmic  and  elementary  is 
related  to  the  organic,  child-like,  antitypical,  as  something  parental  or  typical, 
in  the  same  way  the  organism  is  related  to  the  disease  tvhich  is  nothing  else 
than  a  second  lozuer  organism  whose  elements  already  lie  hidden  in  some 
other  higher  one."  In  this  theory  lies  the  continuation  of  the  thought  ex- 
pressed by  Batsch  on  the  nature  of  the  parasitic  organisms. 

Unger  states  that  "among  the  plant  diseases  least  betraying  any  depen- 
dence upon  the  organism  attacked  and  which  in  their  root  formations  are 
still  so  intimately  interwoven  with  this  organism,  there  belong  indisputably 
those  forms  which  we  designate  by  etiolation,  dropsy  (anasarca),  jaundice 
(icterus),  tympanitis,  tabescence  (tabes),  failure  of  crops,  proflu  via  and  others. 
Ihese  form  in  fact  by  far  the  majority.  Greater  independence  is  shown  by 
the  vast  army  of  malformations,  at  the  basis  of  which  always  lie  deficiencies 
in  the  amount  of  sap  and  therefore  a  retardation  in  lower  developmental 
stages.  Honey-dew  (Saccharogensis  diabetica)  is  more  important  than  these. 
Its  pathological  course  was  first  recognized  by  L.  Treviranus  and  its  more 
universal  significance  by  Dr.  H.  Schmidt.     Mildew  is  indisputably  related  to 


1  Die  Exantheme  der  Pflanzen   und   einige   mit  diesen  verwandte    Krankheiten 
der  Gewachse.    Wein   1833. 


56 

this  disease :  the  straining  toward  a  more  complex  organization  of  the  exuded 
juices  is  made  evident  here  l)_v  organic  formations  winch  are  missing  in 
honey-dew.  These  organic  formations  are  still  more  independent  in  rust 
dew  (Ftil'ujo  vagans).  iMnally  the  disease  organism  appears  in  the  excre- 
tions and  the  forms  nearly  related  to  them  as  a  peculiar,  complete  entity. 
Parasites  belong  here — the  highest  among  them,  such  as  some  kinds  of  I^)r- 
anthus,  seeming  to  have  separated  themselves  entirely  from  the  mother 
liody." 

Unger's  views  are  also  shared  hy  Xees  v.  Esenbeck  and  A.  Henry' 
who  state  in  regaril  to  puff  balls  that  "the  fungi  clearly  stand  here 
at  the  lowest  level  .  .  .  ."  "They  are  correctly  considered  as  the  ma- 
terial of  disease,  as  secretions  of  the  higher  plants."  "The  leaf  fungus  is 
formed  in  general  by  a  coagulation  of  the  juices  discharged  into  the  inter- 
cellular passages." 

Theodor  Hartig  also  wrote  his  work  on  the  red  and  white  rots  of  the 
]-iiie  under  the  influence  of  this  theory.  In  this  he  confirmed  first  of  all  the 
co-operation  of  fungi  (Nyctomyces)-.  He  traced  the  production  of  these 
fungi  to  a  decomposition  of  the  cell  walls. 

Of  the  works  which  take  up  general  constitutional  diseases  and  scarcely 
touch  upon  the  fungi,  we  will  name  those  by  Geiger-'  and  Lindley* 
which  in  all  essentials  are  based  upon  practical  experience.  On  the 
ether  hand,  however,  Wiegmann's"'  statements  are  evidently  based 
on  microscopic  studies  and  the  bearings  of  chemistry,  for  example,  he 
states  that  the  pus  of  the  blight,  as  well  as  that  of  canker,  contains  putric  and 
humic  acids,  but  that  that  of  the  blight  contains  more  putric  acid.  To  him 
both  diseases  appear  non-parasitic  in  nature  and  he  thinks  canker  (Caries, 
Necrosis)  always  arises  from  "a  stoppage  and  deterioration  of  the  juices, 
even  if  these  were  never  present  in  excess."  Among  the  causes 
mentioned  are  injuries  to  the  roots,  or  injuries  from  frost  and  unfavorable 
soil  conditions,  as,  for  example,  "H  the  subsoil  is  moist,  sour,  stony  or  other- 
wise unfertile,  or  contains  swamp  ore." 

Meanwhile,  after  Corda's"  great  work  on  fungi  had  begun  to  ap- 
pear, Meyen's'  "Pflanzenpathologie"  was  published  as  a  standard,  which 
even  now  warrants  consultation.  He  divides  his  material  into  "External 
Diseases"  and  "Internal  Diseases."  Among  the  former,  besides  the  injuries 
due  to  man  and  to  animals,  the  formation  of  gnarls  and  galls,  he  includes 
also  phanerogamic  and  cryptogamic  parasites,  of  which  the  Ustilagineae 
and  the  Uredineae  as  well  as  other  fungi  are  treated  in  detail,  according  to 


1   Das  System  der  IMlze,  Section   I.     Bonn   1S37. 

-  Abhandlung  iiber  die  Verwandlung  der  polycotylen  Pflanzenzelle  in  Pilz  und 
Schwammsebilde  und  die  daraus  hervorgehende  sogenannte  Fiiulniss  des  Holzes. 
Berlin  1833. 

3  Die  Krankheiten  und  Feinde  der  Obstbaume.     Miinchen   1825. 

■*  The  Theory  of  Horticulture.     London  1840. 

5  The  Krankheiten  und  krankhaften  Mifsbildung-en  der  Gewachse  von  Dr.  A.  F. 
Wiegmann  sen.     Braunschweig  1839. 

«  Icones  Fungorum   hucusque  cognitorum.     Prague  1837  to  1854. 

"  Pflanzenpathologie.  Lehre  von  dem  kranken  Leben  und  Bilden  der  Pflanzen. 
Published  after  the  death  of  the  author  by  Dr.  Gottfr.  Nees  v.  Ksenbeck,  Berlin  1841 


57 

the  standpoint  of  the  time.  Ivleyen  no  longer  shares  Unger's  view  that  the 
parasites  as  excrement-organisms  are  the  product  of  a  formative  development 
latent  in  each  plant,  the  disease  occurring  in  a  more  or  less  developed  form 
and  state  of  independence  according  to  the  constitution  and  strength  of  the 
host-organism.  On  the  contrary,  his  Plant-Pathology,  in  the  discussion  of 
smut  fungi,  emphasizes  especially  that  "observations  on  the  production  of 
the  smut  show  most  clearly  that  we  have  to  do  here  with  true  entophytes : 
we  will  find  that  some  smut  species  are  shown  as  particular  parasitic  growths 
in  the  interior  of  the  cells  of  the  plants  attacked  by  them  and  that  the  smut 
mass  is  not  to  be  compared  with  animal  pus." 


The  whole  title  of  Meyen's  "Plant  Pathology"  really  reads : — "Hand- 
buch  der  Pflanzenpathologie  und  Pflanzenteratologie"  edited  by  Dr.  Chr. 
Gottfr.  Nees  v.  Esenbeck.  Vol.  I.  "Plant  Pathology."  According  to  this, 
a  second  part.  Teratology,  was  to  be  expected.  j\Ieyen  himself  intended  to 
work  up  such  a  volume,  but,  according  to  the  Editor,  left  no  material  for  it. 
Just  as  Nees  v.  Esenbeck  was  about  to  undertake  this  himself,  there  appeared 
tlie  "Elements  de  Teratologic  vegetale,  au  Histoire  abregee  des  anomalies  de 
I'organisation  dans  les  vegetaux;  par  A.  Moquin  Tandon,  Doct.  scienc.  et 
med.  etc.,  director  du  jardin  des  plantes  de  Toulouse.  Paris  1841."  C.  F. 
Jaeger  "Ueber  die  Missbildungen  der  Gewachse"  (1S14)  and  Thomas  Hop- 
kirk.  "Flora  Anomala"  (1817)  should  be  mentioned  as  forerunners  of  this 
work.  We  learn  from  the  German  translation  of  Moquin  Tandon's^  book, 
that  the  translator,  C.  Schauer,  was  able,  as  specialist,  to  call  attention  to 
many  misunderstandings  and  errors  made  by  the  author,  especially  in  the 
German  citations  and  to  make  additions  from  his  own  observations.  Moquin 
Tandon  says,  "By  the  expression  'malformations',  'monstrosities'  (monstra) 
is  generally  understood  innate,  more  or  less  important  and  complicated  vari- 
ations from  the  type  of  a  species,  which  are  disfigurations  and  oppose  the 
regular  course  of  a  functioning  by  hindering  or  arresting  it."  We  are  better 
satisfied  by  de  CandoUe's  definition  (Theor.  element.  I.  ed.  p.  406),  by  which 
monstrosity  is  any  disturbance  in  the  economy  of  a  plant,  which  is  followed 
by  a  change  in  organic  form  and  arises  from  an  internal  disposition,  almost 
never  from  a  visible  cause.  Moquin  Tandon's  book  is  still  indispensible  to 
every  specialist  because  of  its  admirable  bibliographical  references. 


About  this  time,  the  science  of  infectious  diseases  received  a  new  im- 
petus because  of  the  rapid  spread  of  the  potato  disease  which  is  still  worthy 
of  especial  attention.  It  is  one  of  the  most  dreaded  enemies  of  agriculture, 
and  is  described  in  the  text  books  as  potato  Phytophthora  rot.  We  owe  one 
of    the    first    publications    on    this    subject    to    Martius-    and    from    that 


1  Pflanzenteratologie.  Lehre  von  dem  regelwidrigen  Waehsen  und  Hilden  der 
Pflanzen.  By  A.  Moquin  Tandon.  Translated  and  supplemented  by  Dr.  .J.  C. 
Schauer.     Berlin  1842. 

2  Die  Kartoffelepidemie   der   letzten   .Jahre.      Mtinchen    1842. 


5^ 

time  on  a  flood  of  publications,  proportionate  to  the  very  severe  injury  to 
national  property  from  these  diseases.  We  will  emphasize  among  these  pub- 
lications only  those  of  Focke',  Paycn-',  Schacht",  Speerschncider*,  v.  Holle'', 
Kiihn"  and  de  Bary".  (Further  bibligraphical  references  may  be  found  in 
the  detailed  discussions  of  the  different  diseases). 

It  was  natural  that  a  phenomenon,  such  as  the  potato  epidemic,  would 
necessarily  bring  fungous  diseases  into  prominence  and  increase  the  whole 
.'^tudy  of  mycology.  At  the  same  time  the  economic  importance  of  smut 
fungi  also  began  to  receive  greater  and  greater  consideration.  Tillet^,  Tes- 
sier",  and  Prevost^",  had  early  studied  the  smut  of  grains  and  at  present  we 
liave  acquired  a  considerably  extended  insight  into  the  nature  of  those  dis- 
eases and  also  into  the  means  of  combatting  them  from  de  Bary's^^  investi- 
gations and  Brefeld's  studies,  extending  over  many  years.  The  prevalence 
of  smut  diseases  lias  led  to  the  develojMiient  of  the  sterilization  of  seed. 

In  the  second  volume  of  this  work,  which  treats  of  parasitic  diseases, 
ihe  overpowering  number  of  mycological  works  will  be  mentioned, — we  will 
here  mention  only  some  of  the  most  important  ones,  treating  of  fungus 
families  as  a  whole.  Elias  Fries'  great  work  completed  in  1832,  has  already 
been  considered.  In  1831  the  first  part  of  Wallroths  "Kryptogamenflora"'- 
appeared  and  in  1833  the  second  part.  In  this  book  the  cryptogams 
were  worked  up  by  Math.  Joe.  Bluff  and  Carl  Ant.  Fingerhuth.  In  1842 
Rabenhorst's  "Kryptogamenflora"^^  began  and  in  1851  Bonorden's  "Hand- 
buch  der  Mykologie"^*,  which  has  proved  to  be  very  useful  because 
of  its  cuts  of  microscopic  fungus  forms,  although  these  had  been 
sufficiently  considered  in  the  illustrations  of  Schiift'er,  Persoon,  Greville, 
Sowerby,  Sturm,  Krombholz  and  Nees  sen.  To  be  sure  Corda's  "Icones 
fungorum"  had  already  been  published  and  his  "Anleilung  zum  Studium  der 
Mykologie"^'^  which  is  provided  with  very  small  drawings;  leaving  the 
peculiarity  of  his  classification  out  of  the  question,  however,  Corda  limit- 
ed himself  to  the  easily  visible  developmental  stages,  while  Bonorden  sought 
to  determine  the  tissue  structure.  This  author,  in  opposition  to  Unger,  em- 
phasized the  fact  that  parasitic  fungi  are  unquestionably  independent  organ- 


I  Die  Krankheit  der  Kartoffeln  im  Jahre  1845.     Bremen  1846. 

^  l^es  maladies  des  pommes  de  terre,  des  betteraves,  des  bles  et  des  vig-nes. 
Paris  1853. 

3Schacht,  Bericht  liber  die  Kartoffl^pflanze  und  deren  Krankheiten.    Berlin  1854. 

*  Das  Faulen  der  Kartoffelknollen.    Flora  1857.    Bot.  Z.   1857. 

0  Ueber  den  Kartoffelpilz.  Bot.  Zeit.  1858. 

«  Die  Krankheiten  der  Kulturgewachse,  ihre  Ursachen  und  \'erliiitung.  Berlin 
1858. 

'    Die  Kartoffelkrankheit.     Leipzig  1861. 

«  Dissert,  sur  la  cause  qui  corrompt  les  graines  de  hie,  1755. 

"  Traite  des  maladies  des  graines,  1783. 

10  Memoire  sur  la  cause  de  la  carie  des  bles,  1807. 

II  Untersuchung-en  iiber  die  Brandpilze.     Berlin  1853. 

12  Flora  cryptogamica  Germaniae  auctore  Ferd.  Guil.  Wallrothio,  Med.  et  Chir. 
Doctore  etc.     Norimbergae  1831-33. 

13  Kryptogamenflora  von  Deutschland,  Vol.  I.,  Leipzig-  1844.  2nd  Edition.  I-VII. 
1884-1903. 

1*  Handbuch  der  Allgemeinen  Mykologie  etc.  with  12  plates.     Stuttgart  1851. 
15  Anleitung-  zum   Studium  der   Mykologie   nebst  kritischer   Beschreibung-  aller 
bekannten  Gattungen.     Prag  1842. 


59 

isms,  but  maintained  that  "it  is  the  stomata  which  take  up  the  spores  and 
bring  them  to  development  in  the  air  cavities  connected  with  them."  He  said 
that  algae,  lichens  and  mosses  which  have  no  stomata  and,  for  the  same  rea- 
son, young  branches  and  twigs  are  free  from  parasites.  He  expresses  his 
point  of  view  in  regard  to  the  action  of  parasites,  as  follows : — "That  they 
6rst  cause  an  hypertrophy  and  degeneration  of  the  parts  heavily  infested  with 
them  but  when  isolated  they  do  not  disturb  the  growth  of  the  leaves."  Ac- 
cording to  him,  dry  weather  is  essentially  propitious  for  the  spread  of  the 
parasites,  "because  it  favors  the  scattering  of  the  spores.  On  this  ac- 
count Caeoma  and  Phragmidium  are  never  found  more  abundant  than  in 
dry  summers,  as  also  the  Caeoma  ccrcalium,  the  yellow  corn  smut  so  in- 
jurious to  seeds,  which  caused  such  great  damage  in  1846." 

Kiihn  in  his  "Krankheiten  der  Kulturgewachse"  (Berlin  1858)  attained, 
in  the  happiest  manner,  the  end  for  which  Meyen  strove,  viz.  of  uniting 
scientific  studies  with  practical  experience  in  the  treatment  of  plant  diseases. 
However  necessary  and  important  purely  scientific  investigations  may  always 
be  in  phytopathology,  yet  they  achieve  their  full  significance  only  by  being 
tested  in  practical  agriculture.  Only  by  practical  work  can  it  be  decided 
whether  the  conditions  of  nature  and  of  the  laboratory  favor  the  develop- 
ment of  the  same  parasites  or  other  excitors  of  disease.  So  it  is  necessary  to 
build  phytopathology  upon  a  practical  knowledge  of  agriculture  and  horti- 
culture. The  differences  which  have  developed  in  medicine  between 
the  scientific  investigator  and  the  practicing  physician  must  also  necessarily 
arise  in  the  science  of  plant  diseases.  We  term  this  practical  side, — the  pro- 
fession of  "Plant  Protection." 

Mycological  studies  are  a  part  of  the  indispensible  fundamentals  of  plant 
protection  and  for  this  reason,  we  have  given  them  the  greatest  possible  at- 
tention in  the  history  of  phytopathology.  Continuing  with  this  in  view  we 
will  name  first  of  all  the  masterly  plates  in  the  book  by  the  brothers  Tulasne 
"Selecta  fungorum  carpologia,"  Paris.  The  English  work  by  Berkeley 
"Outlines  of  British  Fungology,"  London  i860,  is  most  welcome  as  a  col- 
lective work  although  it  is  mostly  provided  with  very  rough  illustrations. 
De  Bary's  works  continue  to  be  of  especial  value.  His  results  in  this  con- 
nection may  be  found  summarized  in  the  "Morphologic  und  Physiologic  der 
Pilze,  Flechten  und  Myxomyceten,"  Leipzig  1866. 

We  owe  further  important  investigations  to  O.  Brefeld,  in  his  "Unter- 
suchungen  iiber  die  Schimmelpilze,"  Leipzig  1871,  1872  and  following,  and 
Cohn  for  his  "Biologische  Mitteilungen  iiber  Bakterien,"  Schlesische  Ges.  f. 
vaterl.  Kultur,  1873,  as  well  as  for  his  "Untersuchungen  iiber  Bakterien" 
1875  and  for  other  studies  contained  in  his  "Beitrage  zur  Biologic  der  Pflan- 
zen."  In  these  Cohn  has  successfully  advanced  the  history  of  the  develop- 
ment of  Bacteria.  His  pupil,  Zopf,  essentially  extended  these  studies  in  the 
work  "Die  Spaltpilze,"  Breslau  (3rd  Ed.  1885).  Among  the  summaries  of  this 
time  mention  should  be  made  of  Eidam  "Der  gegenwartige  Standpunkt  der 
Mykologie  mit  Riicksicht  auf  die  Lehre  von  den  Infektionskrankheiten," 


6o 

Berlin  (2nd  Ed.  1872)  and  further  Winter,  "Die  Pilze  Deutschlands,  Oester- 
reichs  und  der  Sdnvciz,"  Leipzig  1884.  Rabcnborst's  "Kryptogamenflora" 
brings  the  subject  to  completion. 

The  most  comprehensive  systematic  summary  of  all  the  fungi  is  con- 
tained in  1'.  A.  .Saccardo's  "Sylloge  Fungorum."  The  eleventh  volume  with 
a  ".Supplementum  universale"  was  published  in  Pavia  in  1895.  Sydow's  "In- 
dex universalis  et  locupletissimus  nominum  plantarum  hospitium  speciarum- 
(jue  omnium  fungorum,"  Berolini,  Fratres  Horntraeger  1898,  carries  the  work 
further.  This  book  contains  all  the  fungi  known  up  to  1897.  Further  sup- 
plemental volumes  (XI\'-X\T)  were  published  in  1899-1902  and  others  arc 
to  follow.  Saccardo  supplemented  this  great  work  on  fungi  with  1500  illus- 
trations which  were  published  from  1877-1886  under  the  title  "I'ungi  italici 
autographice  delineati,"  Patavii. 

In  place  of  the  sketchy  drawings  of  this  work,  A.  N.  lierlese  began  to 
publish  a  series  of  most  careful,  colored  illustrations  under  the  title,  "Icone*^ 
fungorum  ad  usum  Sylloges  Saccardianae  adcommodatae,"  Abellini.  The 
Sphaeriaceae  Hyalophnujmiae  were  furnished  in  parts  I  V-\\  which  appeared 
in  1894.  To  our  knowledge,  the  author  had  not  finished  the  work  at  the  time 
of  his  untimely  death.  In  the  same  way,  we  find  colored  illustrations  in 
Cooke's  "Mycographia  scu  Icones  fungorum,"  London : — the  first  part  ap- 
peared in  1879  with  cuts  of  the  discomycetes. 

The  publications  on  fungi  and  bacteria  now  become  so  numerous  that 
they  are  no  longer  to  be  mastered  and  make  any  further  citations  impossible. 
This  compels  us  to  refer  to  the  "Botonischer  Jahresbericht"  which  has  been 
appearing  since  1873. 

It  is  natural  that  Teratology  has  also  developed  further  since  Moquin 
1  andon.  Among  the  works  treating  of  the  material  as  a  whole,  emphasis 
should  be  laid  on  M.  Master's  "Vegetable  Teratology,"  London  1869  and  C). 
Penzig,  "I'flanzenteratologie,"  systematisch  geordnet,  (ienua  1890-94,  which 
may  be  designated  as  the  most  complete  book  of  reference  on  this  subject. 

Pecause  of  limited  space  we  must  forego  all  further  citations  of  my- 
cological  literature.  The  reader  will  find  the  desired  sujiplementary  infor- 
mation in  the  second  volume  of  this  work.  However,  a  brief  reference  to 
the  numerous  ])ublications  descriptive  of  fresh  and  herbarium  material  must 
be  made  in  a  presentation  of  the  history  of  the  development  of  this  science. 
Among  the  herbaria  which  pay  especial  attention  to  plant  diseases,  there 
should  be  mentioned  here,  F.  v.  Thiimen,  "Herbarium  mycologicum  oeco- 
nomicum,"  Teplitz,  1873-79,  Rabenhorst,  "Fungi  europaei  exsiccati"  con- 
tinued by  Winter  and  Patzschke ;  L.  Fuckel,  "Fungi  rhenani  exsiccati,"  2nd 
lulition  1874;  Jak.  Eriksson,  "Fungi  parasitici  scandinavici,"  Stockholm 
1882-1895;  G.  Briosi  et  F.  Cavara,  "J  funghi  parassiti  delle  piante  coltivate 
ed  utili  essicati,  delineati  e  dcscritti,"  Pavia,  fasc.  I-XII  (1897)  ;  W.  Krieger, 
"Schadliche  Pilze  unserer  Kulturgewachse,"  fasc.  I.  1896;  A.  B.  Seymour 
and  F.  S.  Earle.  "Economic  Fungi,  Cambridge.  Following  in  close  connec- 
tion with  Rehm's  ascomycete  collection,  published  many  years  ago,  are  many 


6i 

Herbaria  representing  the  general  fungus  flora  of  different  countries,  as, 
for  example,  those  by  Saccardo,  Sydow,  \"estergren,  J.  B.  Ellis,  Jaap,  Bubak 
and  Kabat,  Posch  etc. 


Although  the  science  of  plant  diseases  would  refer  to  teratological  phe- 
nomena only  when  it  can  prove,  or  at  least  suppose  as  a  cause  of  the  indi- 
vidual phenomena,  some  definite  disturbance  of  nutritive  or  structural  con- 
ditions, it  has  been  forced  to  take  the  animal  world  more  and  more  thor- 
oughly into  consideration.  The  following  publications  summarize  the  entire 
material  or  the  larger  part  of  it,  are  comprehensive  and  should  be  used  for 
further  study: — Ratzeburg,  "Die  Forstinsekten,"  Berlin  1839-1844  and  "Die 
Waldverderbnis,"  Berlin  1866-1868;  A  Gerstacker,  "Handbuch  der  Zoolo- 
gie,"  Vol.  II.,  Arthropoden,  Leipzig  1863  ;  E.  L.  Taschenberg,  "Entomo- 
gie  fiir  Gartner  und  Gartenfreunde,"  Leipzig  1871,  and  "Die  der  Landwirt- 
schaft  schadlichen  Insekten  und  Wiirmer,"  Leipzig  1865.  Further  Nordlinger, 
"Die  kleinen  Feinde  der  Landwirtschaft,"  Stuttgart  1869.  Kaltenbach,  "Die 
Pflanzenfeinde  ans  der  Klasse  der  Insekten,"  Stuttgart  1874,  and  Ritzema 
Bos,  "Tierische  Schadlinge  und  Niitzlinge,"  Berlin  1891.  The  "Handbook  of 
the  Destructive  Insects,"  by  C.  French,  published  in  Melbourne  in  1891  by 
order  of  the  Department  of  Agriculture  of  Victoria,  is  less  rich  in  material  but 
better  adapted  to  the  practical  needs  of  the  layman,  because  of  its  colored 
plates. 

In  the  same  year  H.  R.  v.  Schlechtendal  published  a  smaller  special  work 
on  gall  formations. — ^"Die  Gallbildungen  (Zoocecidien)  der  deutschen 
Gefasspflanzen,"  Zwickau  1891.  Ten  years  later  G.  Darboux  and  C.  Houard 
published  a  comprehensive  systematic  work, — "Catalogue  systematique  des 
Zoocecidies  de  I'Europe  et  du  Bassin  mediterraneen,"  Paris  1901. 

The  "Forstliche  Zoologie"  by  K.  Echstein,  Berlin  1897,  "lay  be 
especially  recommended  because  of  many  careful  original  drawings.  The 
popular  writings  of  H  v.  Schilling  are  especially  useful  for  horticuhure  ; 
we  recommend  "Die  Schadlinge  des  Obst-und  Weinbaues,"  "Die  Schadlinge 
des  Gemitsebaues,"  Frankfort  a.  O.  1898  and  the  "Practischer  LTngezieferk- 
alender,"  Frankfurt  a.  O.  1902.  The  "Schutz  der  Obstbaume  gegen  feind- 
liche  Tiere"  by  E.  L.  Taschenberg  (3rd  Edition  by  O.  Taschenberg),  Stutt- 
gart 1901,  is  also  well  adapted  for  practical  needs. 

As  the  science  of  plant  protection  develops  there  is  a  corresponding  at- 
tempt to  produce  reference  books  treating  some  of  the  most  important  culti- 
vated plants,  such  as  Eisbein  "Die  kleinen  Feinde  des  Riibenbaues,  1882,  with 
carefully  prepared  colored  plates  and  Emile  Lucet  "Les  insectes  nuisibles 
aux  Rosiers  sauvages  et  cultives  en  France,"  Paris  1898,  with  numerous 
plates  in  black  and  white.  Most  complete  is  the  work  being  done  in  the 
United  States  in  protecting  plants  from  these  animal  enemies.  The  Zoolo- 
gists in  the  several  State  Experiment  Stations  and  the  "Bureau  of  Entomol- 
cgy"  of  the  Federal  Department  of  Agriculture  in  Washington,  are  advanc- 
ing rapidly  the  study  of  the  enemies  of  cultivated  plants,  by  new  investiga- 


62 

tions  and  by  the  distribution  of  popular  treatises.  More  detailed  references 
to  zoological  literature  are  to  be  found  in  the  third  volume  of  this  manual. 

The  number  of  text-books  and  manuals  of  phytopatholoj^'  has  grad- 
ually been  increased  since  the  publication  of  Kiihn's  "Krankheiten  der  Kul- 
turgewachse,"  as  the  understanding  of  the  national  economic  significance  of 
phytopathology  has  increased.  First  of  all  comes  Orstedt's  "Om  Sygdomme 
hos  Planterne,  som  foraarsages  af  Snylteswampe,  navnlig  om  Rust  og 
Brand,"  Kjobenhavn  1863.  This  work  was  followed  in  1865  by  later  reports 
on  the  alternation  of  hosts  by  rust  fungi  (Gymnosporangium  Sahinae). 
About  this  time  Hallier's^  book  appeared  which  must  be  given  more 
especial  attention  in  a  history  of  plant  diseases  because  of  the  author's  stand- 
point. Hallier's  views  leading  to  sharp  literary  disagreements,  especially 
with  de  Bary,  may  be  found  in  extenso  in  his  later  writings'-.  In  his 
"Festkrankheiten  der  Kulturgewachse,"  he  gives  a  list  of  investigations  on 
the  Peronosporeae  and  believes  he  has  permanently  established  by  these 
the  correctness  of  his  "Plastidcn  Theory."  At  the  time  of  tiie  "Cholera 
meeting"  in  Weimar  (1868),  Hallier  first  made  the  assertion  that  the  forms, 
summarized  as  Fission  fungi  (Schizomycctcs)  by  Nageii  were  not  indepen- 
dent organisms,  but  represent  the  products  of  the  plasma  of  different  groups 
of  filament  fungi.  Hence  Nageli's  family  of  the  Fission  fungi  should  be 
stricken  out  of  the  classification  and  infectious  diseases  as  a  whole  be  traced 
back  to  the  action  of  such  plasma-products  ("Plastiden").  "In  order  there- 
fore to  discover  the  origin  of  infectious  diseases,  it  is  necessary  in  every  case 
to  ascertain  by  investigation  which  definite  fungus  produces  the  cells  of  con- 
tagion from  its  plasma  (bacteria,  micrococcus  etc.)  and  in  what  way  this 
takes  place."  In  regard  to  the  potato  disease  produced  by  Phytophthora,  he 
does  not  question  whether  this  fungus  is  the  cause  of  the  disease,  but  only 
whether  it  may  cause  it  less  directly  than  would  bacteria.  "I  have  proved 
first  and  foremost  that  the  bacteria  which  are  the  absolute  cause  of  the  pota- 
to pest,  are  produced  by  the  "Plastiden"  of  the  Phytophthora  and  that  these, 
when  once  formed,  are  absolutely  equal  to  the  production  of  the  plague;  that 
there  is  no  further  need  of  the  mycelium  and  buds  of  the  Phytophthora." 
His  numerous  experiments  ultimately  led  him  to  the  view  that,  in  all  in- 
fectious diseases,  human,  animal  and  vegetable,  three  main  points  undoubted- 
ly come  under  consideration:  (i)  The  absolute  cause;  (2)  External  or 
general  furtherance  (chance  causes  or  predisposition)  ;  ('3)  Personal  fur- 
therance (susceptibility  of  the  diseased  individual). 

Sorauer  in  the  first  edition  of  his  "Manual  of  Plant  Diseases,"  Berlin, 
Paul  Parey,  1874,  first  introduced  into  plant  pathology  the  view,  that  in  all 
diseases  not  only  the  direct  cause  but  also  the  earlier  preparatory  stages  and, 
in  parasitic  attacks,  the  accessory  conditions  favoring  the  development  of  the 
parasites,  including  the  disposition  of  the  host  organism,  should  be  taken 


1   Phytopathologie.     Die  Krankheiten   der  Kulturg-ewachse.     T^eipzig  1868. 
-  Die    Plastiden    der    niederen    Pflanzen.      Leipzig'    1895. — Die    Pestkrnnkheiten 
(Infektionskrankheiten)   der  Kulturgewachse.     Stuttgart  1895. 


63 

into  consideration.  This  statement  was  definitely  established  in  the  second 
edition  (1886)  and  in  an  abstract  written  especially  for  tlie  practical  agri- 
culturalist, "Die  Schaden  der  einheimischen  Kulturpflanzen,"  1888.  The 
delayed  acceptance  of  these  ideas  is  shown  by  the  text-books  which  im- 
mediately followed.  Of  these  the  one  especially  valuable  because  of  its  num- 
erous personal  investigations  is  "Lehrbuch  der  Baumkrankheiten"  by  Robert 
Hartig,  Berlin  1882  (2nd  Ed.  1889).  The  third  edition,  in  which  the 
author  rather  unreservedly  acknowledges  a  predisposition  and  differentiates 
local,  temporal,  individual,  acquired  and  morbid  predisposition,  appeared  in 
1900  wuth  the  title  "Lehrbuch  der  Pflanzenkrankeiten" — Berlin,  Julius 
Springer.  A  study  of  the  phenomena  of  the  decomposition  of  wood,  with 
the  title  "Wichtige  Krankheiten  der  \A^aldbaume,"  Berlin  1874,  is  an  intro- 
ductory work  for  this  textbook. 

Sorauer's  Manual  was  followed  first  by  Frank's  detailed  elaboration, 
"Die  Krankheiten  der  Pflanzen,"  Breslau  1880  (2nd  Ed.  1895).  The 
"Lehrbuch  des  Forstschutzes"  by  H.  Nordlinger,  Berlin  1884,  is  devoted 
especially  to  cultivated  forest  plants.  Solla's  book,  "Note  di  Fitopathologia." 
Firenze  1888,  is  more  comprehensive  and  contains  an  atlas.  This  was  pre- 
ceded in  Norway  in  1887  by  Brunchorst's  "De  vigtigste  Plantesydomme." 
To  this  decennium  belongs  also  a  number  of  noteworthy  articles  by  Jensen, 
among  which  (according  to  Rostrup)  is:  "Kartoffelsygen  kan  overvindes 
ved  en  let  udforlig  Dyrkningsmaade,"  Kjobenhavn  1882. 

While  up  to  this  time  scientists  had  classified  diseases  according  to  their 
proved  or  assumed  causes,  Kirchner  in  1890  published  "Die  Krankheiten  und 
Beschadigungen  unserer  landwirtschaftlichen  Kulturpflanzen,"  Stuttgart, 
arranged  especially  for  practical  use.  The  diseases  are  listed  here  ac- 
cording to  the  dififerent  cultivated  host  plants  and  described  according  to 
their  visible  habit  of  growth.  Systematic  scientific  supplements  are  collected 
at  the  end  of  the  book.  In  accordance  with  the  line  of  investigation  of  this 
author  there  appeared  in  1S95  a  richly  illustrated  book  treating  of  parasitic 
diseases  only,— "Pflanzenkrankheiten,  durch  kryptogame  Parasiten  verur- 
sacht,"  by  Karl,  Freiherr  v.  Tubeuf,  Berlin,  Julius  Springer.  Parastism  was 
here  developed  as  a  form  of  sym.biosis  and  thereby  referred  to  an  "internal 
and  an  external"  predisposition  for  becoming  diseased.  The  internal  predispo- 
sition depends  on  "the  energetic  condition  of  the  living  protoplasm  of  the  host 
cell,"  while  the  external  one  "is  determined  especially  by  anatomical  condi- 
tions." In  the  same  year  Prillieux  published  a  two  volume  work  abounding  in 
personal  investigations,  "Maladies  des  plantes  agricolcs  et  des  arbres  fruiticrs 
et  forestiers,"  Paris.  This,  the  most  comprehensive  work  in  French  on  the 
subject,  describes  only  parasitic  diseases.  They  are  treated  scientifically  and 
yet  the  practical  side  receives  attention  in  so  far  as  means  for  combatting 
disease  are  considered. 

An  unlooked-for  advance  in  the  studies  on  bacteria  resulting  from  their 
many-sided  economic  significance,  made  a  revision  and  enlargement  of  de 
Bary's  "Vorlesungen  iiber  Bakterien,"  necessary.     In  1900,  in  Leipsic,  Mig- 


64 

ula,  enabled  by  his  own  work,  prodiKX'd  a  new  edition  tfi  which  he  added 
exact  bibligraphical  citations. 

Meanwhile,  as  the  necessity  of  familiarizing  practical  circles  with  the 
nature  of  plant  diseases  became  increasingly  more  evident,  it  led  the  large 
German  Agricultural  Society  to  undertake  the  issuing  of  suitable  publica- 
tions. In  1892  appeared  the  first  edition  of  Sc^raucr's  "l^flanzcnschutz,"  and 
in  1896  its  second  edition,  revised  by  A.  !>.  JM-ank  and  1'.  Sorauer.  TIk' 
authors  strived  for  the  briefest  i)resentation  possible,  classified  the  diseases 
according  to  the  host  plants  and  treated  each  disease  under  three  headings  :— 
Recognition,  TToduction  and  Control.  "Phe  text  was  supplemented  l)y  num- 
erous illustrations  on  colored  plates.  In  the  same  way,  Frank  published  a 
more  detailed  work  with  the  title : — "Kanipfbuch  gegen  die  Schadlinge  un- 
serer  Feldfriichte,"  Berlin  1897  and  Sorauer  one,  entitled.  "Schutz  der  Obst- 
biiume  gegen  Krankheiten,"  Stuttgart  1900.  provided  with  numerous  figures 
in  the  text. 

Of  books  in  foreign  lar.guages,  there  a])peared  about  this  time.  W. 
Kriiger's  treatise  on  tlie  diseases  of  sugar  cane  in  the  "Bericht  der  \'ersuchs- 
station  fiir  Zuckerrolir  in  \\'est-ja\a,  Kagok-Tegal,"  published  in  \i>^j(}.  This 
treatise  took  up  thoroughly  the  Sereh  disease  with  a  conscientious  use  of  the 
pertinent  literature.  Subsequent  to  it  appeared  in  Leyden  in  1898,  H.  Wak- 
ker  and  G.  W^ent's  "De  ziekten  vom  het  suikerriet  op  !n\a."  which  should  be 
recommended  because  of  its  many  plates. 

Delacroix  treats  the  diseases  of  coffee  especial)}  in  his  ])ook.  "Les  mala- 
dies et  les  ennemis  des  Cafeiers,"  Faris  (2nd  Fd.  19(^0).  Two  years 
later  D.  McAlpine.  in  Melbourne,  published  "h\uigus  diseases  of  stone-fruit 
trees  in  .Atistralia." 

The  last  named  pulilication  considered  cultivated  plants  only.  The  need 
of  a  comprehensive  treatment  of  the  whole  field  of  diseases  was  shown  and 
after  a  long  interval,  a  response,  the  manual,  "Plantepatologi"  Haandbog  i 
Laeren  om  plante.sygdomme  af  F.  Rostrup,  was  published  at  Kjobenhavn  in 
1902.  This  book,  elegantly  gotten  up  and  attractive  because  of  its  many 
careful  original  drawings,  lays  emphasis  on  fungous  diseases,  the  known 
number  of  which  the  author  by  his  many  personal  observations,  published 
after  1871,  had  increased.  To  facilitate  the  consultation  and  discovery  of  the 
different  diseases,  a  list  was  placed  at  the  end  of  the  book,  arranged  accord- 
ing to  the  host  i)lants. 

In  1903  the  Japanese  published  a  book  which  shoidd  be  considered  as  a 
significant  cultural  advance.  We  have  a  German  translation  of  this  entitled 
"Lehrbuch  der  I'flanzenkrankheiten  in  Japan,"  b'in  Handbuch  fiir  Land- 
und  Forstwirte,  Gartner  und  P)Otaniker.  \dn  Arata  Ideta  (3rd  Fd.)  Tokio 
1903).  This  work  is  provided  with  a  glossary  of  technical  terms  in 
German,  English  and  Japanese  and  contains  13  plates  and  144  text  figures 
carried  out  in  fine  line-drawings  (mostly  after  Gerriian  authors). 

In  a  science  like  phytopathology,  in  which  the  results  of  all  investiga- 
tions are  intended  for  use  in  practical  industry,  the  need  is  at  once  felt  of 


65 

making  the  forms  and  causes  of  disease  more  easily  comprehended  by  the 
layman,  by  means  of  colored  illustrations.  On  this  account,  without  regard 
to  special  works  on  fungi,  we  often  find  the  text  supplemented  by  colored 
pictures  of  the  habit  of  growth.  An  attempt  to  present  the  most  important 
diseases  in  the  form  of  a  portfolio  with  short  descriptions  of  the  figures  on 
the  plates  could  be  undertaken  only  after  a  more  widely  extended  under- 
standing of  the  importance  of  this  branch  of  knowledge  had  insured  a  suf- 
ficient number  of  purchasers.  Accordingly,  since  1886,  Paul  Parey  of  Berlin 
has  issued  Sorauer's  "Atlas  der  Pflanzenkrankheiten,"  of  which  six  folio 
numbers  have  already  been  published.  The  especial  care  used  here,  in  hav- 
ing the  dififerent  colors  true  to  nature,  made  the  price  such  that  the  publica- 
tion had  a  smaller  circulation  among  practical  workers  than  in  scientific  in- 
stitutes, and  accordingly  a  need  was  gradually  shown  for  the  publication  of 
a  less  expensive  work.  This  appeared  under  the  title,  "Atlas  der  Krankhei- 
ten  und  Beschadigungcn  unserer  landwirtschaftlichen  Kulturpflanzen," 
edited  by  O.  Kirchncr  and  H.  Boltshauser  and  published  by  ITlmer,  Stutt- 
gart. This  is  now  completed  in  six  numbers.  ATcanwhile  the  Deutsche 
Landwirtschafts-Gesellschaft  discovered,  by  its  publication  of  "Pflanzen- 
schultz,"  that  at  present  the  time  is  ripe  for  the  extension  of  the  knowledge 
of  diseases  among  practical  agriculturalists,  and  that  it  can  be  carried  through 
most  successfully  by  such  brief  guides.  The  society  published  the  third 
edition  in  1904,  revised  by  Sorauer  and  Rorig,  with  seven  carefully  pre- 
I.ared  plates.  The  "Atlas  des  Conferences  de  Pathologie  vegetale"  by 
Georges  Delacroix,  Paris  T90T,  should  be  mentioned  as  of  special  service  to 
the  systematic  study  of  diseases.  This  gives  the  most  important  diseases  of 
cultivated  plants  in  56  plates  in  black  and  white.  In  1902  Delacroix  pub- 
lished by  order  of  the  French  Agricultural  Department  a  small  work,  "Mala- 
dies des  plantes  cultivees,"  Paris,  which  was  written  chiefly  for  general  use 
and  is  supplemental  to  the  above. 

The  most  significant  scientific  advance  is  the  publication  of  monographs 
covering  the  separate  fields  of  disease.  This  method  has  also  appealed 
especially  to  recent  workers  in  plant  pathology.  In  accordance  with  the  im- 
portance of  the  disease,  thorough  study  has  been  devoted  to  the  rust  fungi, 
especially  of  grain.  In  1894-95  the  German  edition  of  a  463-page  work  by 
Jakob  Eriksson  and  Ernst  PTenning  was  published, — "Die  Getreideroste, 
ihre  Geschichte  und  Natur.  sowie  Mafsregeln  gegen  dieselben,"  Stockholm. 
This  work,  which  attracted  much  attention,  appeared  as  a  volume  of  the 
"Meddelanden  fran  Kongl.  Landtbruks-Akademiens  Experimentalfalt,"  and 
its  13  colored  plates  show  clearly  the  diseases  due  to  grain  rusts.  It  proves 
the  specialization  of  parasitism  in  the  fungi  of  grain  rusts.  Besides  this,  the 
work  takes  up  the  discussion  of  the  determinative  factors  and  tests  the  posi- 
tion, the  physical  and  chemical  constitution  of  the  soil,  the  previous  cropping, 
time  of  seeding  etc. 

In  1904,  H.  Klebahn  published  an  equally  careful  work  with  a  larger 
field  and  based  on  his  personal  studies,  entitled :— "Die  wirtswechselndcn 


66 

Rostpilze,"  Versuch  einer  Gesamtdarstellung  ihrer  biologischen  Verhaltnisse. 
Berlin  1904.  Gebr.  Borntrager.  A  chronological  table  gives  a  list  of  the 
heteroecious  rust  fungi  discovered  since  de  Bary's  first  investigations  made 
in  1864  with  Puccinia  graiiiinis.  The  text  treats  in  the  greatest  detail  and 
with  pertinent  bibliographical  references,  gradation  of  differences,  hmi- 
tation  of  species,  specialization  and  theory  of  descent,  susceptibility  and 
transmission  of  rust  diseases  in  seed.  With  this  is  also  discussed  thoroughly 
the  mycoplasm  theory  brought  forward  about  1897  by  Eriksson.  This  point 
has  already  been  discussed  (see  p.  34).  Eriksson's  latest  studies  appeared  in 
1904  in  the  publications  of  the  Schwed.  Akad.  d.  Wissensch.  under  the  title : 
"Das  Vegetative  Leben  der  Getreiderostpilze." 

A  further  important  advance  in  the  creation  of  scientific  foundations  is 
eliown  in  the  "Pathologischc  Pflanzenanatomie"  by  Ernst  Kiister,  Jena  1903, 
published  by  Gustav  Fischer.  Guided  by  the  discovery  that  a  distinct  sepa- 
ration of  the  natural  forms  into  normal  or  abnormal  can  not  be  carried  out, 
Kiister  tests  the  phenomena  from  the  physiological  point  of  view,  i.  e.  as  to 
the  functional  efficiency  of  the  tissues.  "The  tissues  are  prevented  from  de- 
veloping into  functionally  efficient,  i.  e.  normal  tissues,  by  influences  of  some 
kind  or  functionally  efficient  tissues  undergo  subsequent  changes  in  which 
they  forfeit  entirely  or  partially  their  functional  ability,  or  new  tissues  are 
produced  in  the  plant  body  of  such  a  nature  that  its  diseased  and  deformed 
organs  either  accomplish  nothing  for  the  organism  as  a  whole,  or  less  than 
those  which  we  designate  as  normal."  We  find  in  this  work  a  successful 
attempt  at  presenting  the  developmental  mechanics  of  the  vegetable  organism. 


A  periodical  literature  developed  along  with  the  attempts  to  organize 
the  protection  of  plants.  The  guiding  principle  was  the  practical  question, 
how  the  spread  of  disease  and  the  enemies  of  cultivated  plants  may  best  be 
prevented  and  how  their  direct  control  can  be  most  advantageously  accom- 
plished. 

This  question  w^as  considered  more  closely  first  in  the  United  States  of 
North  America,  since  in  1887  stations  were  formed  by  the  Department  of 
Agriculture  for  the  study  of  phytopathology  and  of  insects.  These  most 
active  institutes  and  experiment  stations  first  of  all  issued  annual  reports  and 
then  later  special  publications  of  scientific  investigations.  The  report  of 
1889^  gives  a  closer  insight  into  the  organization  of  the  service.  W^e 
learn  from  it  that  the  Phytopathological  Division  published  its  investigations 
in  a  definite  periodical  "The  Journal  of  Mycology"  and  also  distributed  pop- 
ular bulletins  of  some  of  the  most  important  diseases.  Correspondence  con- 
sisting of  replies  to  queries  consumes  much  of  the  activity  of  these  stations. 
For  example,  in  1889  the  questions  sent  by  practical  agriculturalists  de- 
manded 2500  replies.     These  scientists  desire  chiefly  to  test  results  of  lab- 


1   Report  of  the  chief  of  the  Division  of  Vegetable  Pathology  for  the  year  1889. 
Published  by  the  authority  of  the  Secretary  of  Agriculture.     Washington  1890. 


■     6; 

oratory  studies  by  field  experiments.  With  the  intention  of  carrying  out  such 
practical  agricultural  experiments,  the  pathological  division  has  installed  cer- 
tain supervising  agents.  When  the  results  of  such  experiments,  conducted  in 
the  open  in  different  regions,  corresponded  sufficiently  Mrell,  general  conclus- 
ions were  drawn  and  the  results  published  as  speedily  as  possible. 

In  Germany  the  first  attempt  toward  organization  was  shown  at  the 
Agricultural  Congress  in  Vienna  in  1890,  where  Eriksson  and  Sorauer 
brought  forward  a  proposition  recommending  to  the  government  regulations 
similar  to  those  already  carried  out  in  America.  With  the  intention  of  work- 
ing out  a  special  plan  and  the  development  of  effective  activity,  an  "Inter- 
nationale phytopathologische  Kommission"  was  formed  by  representatives 
of  all  European  agricultural  countries  and  Sorauer,  as  secretary,  was  com- 
missioned to  bring  out  suitable  publications.  This  furnished  an  incentive 
for  the  foundation  of  the  "Zeitschrift  fiir  Pflanzenkrankheiten"  the  first 
annual  series  of  which  appeared  in  1891.  In  the  same  way  the  interest  in 
establishing  experiment  stations  and  similar  institutions  for  the  special  culti- 
vation and  the  protection  of  plants  in  different  countries,  Avas  stimulated  and 
successful.  In  iSSo^  Korn-Breslau  published  in  Prussia  a  very  thorough 
report,  "Ueber  die  Begrundung  einer  wissenschaftlichen  Centralstelle 
behufs  Beobachtung  und  Tilgung  der  Feinde  der  Landwirtschaft  aus  dem 
Reiche  der  Pilze  und  Insekten."  The  Imperial  Government  should  have  re- 
sponded to  such  stimuli  through  the  German  Agricultural  Council.  In  June. 
1889,  Julius  Kiihn,  through  whose  endeavors  the  experimental  station  under 
Ilollrung  was  established  in  Halle  a.  S.,  brought  this  same  subject  before  the 
German  Agricultural  Society  and  in  1890  the  Society  established  a  "special 
committee  for  the  protection  of  plants"  whose  Board  of  Directors  was  form- 
ed by  Julius  Kiihn,  A.  B.  Frank  and  P.  Sorauer.  This  special  committee  estab- 
lished a  net-work  of  information  bureaux  for  practical  agriculturalists  which 
covered  the  whole  German  Empire,  and  published  successive  "Annual  Re- 
ports from  the  special  committee  for  the  protection  of  plants,"-  after  Sorauer 
had  begun  in  1891  a  statistical  revision  of  the  rusts  of  grains. 

In  1890  the  Phytopathological  Laboratory  at  Paris  was  opened  under 
Prillieux  and  Delacroix  and  in  Amsterdam  on  the  nth  of  April,  1891,  the 
Netherland  section  of  the  International  Phytopathological  Commission  was 
established.  This  commission  called  Ritzema  Bos  to  Amsterdam  in  1895  as 
director  of  the  "Phytopathologisches  Laboratorium  Willie  Commelin 
Scholten."  In  this  year,  at  the  instigation  of  the  Holland  Phytopathological 
Association  and  of  the  Phytopathological  Division  of  the  Botanical  Society 
Dodonaea,  the  "Tijdschrift  over  plantenziekten,"  edited  by  J.  Ritzema  Bos 
and  G.  Staes  was  published.  Meanwhile,  an  experimental  station  was  found- 
ed at  the  Pasteur  Institute  for  the  purpose  of  combatting  injurious  animals 
by  means  of  contagious  diseases.  In  1894  this  was  placed  under  the  direction 
of  Metschnikofl.  As  director  of  the  "Experimentalfaltet"  at  Albano,  near 
Stockholm,  Eriksson  was  untiringly  active.     In  1895  he  published  test  ex- 

1  Archiv  des  Deutschen  Landwirtschaftsrates,  Part  8,  p.  307. 

2  Jahresberichte  des  Sonderausschusses  fiir  Pflanzenschutz.^ 


68    • 

amples  for  the  special  forms  of  grain  rusts  after  which,  in  February  1901, 
the  State  granted  him  a  fund  of  10,000  Kronen  because  of  these  studies. 
The  question  of  rust  which  is  also  of  the  highest  significance  in  Australia 
led  in  1888  to  the  annual  meeting  of  a  Congress  of  Members  of  the  Austra- 
lian Colonies  which,  for  a  considerable  number  of  years,  published  an  official 
report,  "Rust  in  wheat  Conference," 

In  Germany,  Sorauer's  "Zeitschrift  fiir  rilanzcnkrankheiten"  was  fol- 
lowed in  1892  by  C.  v.  Tubeuf's  Forstlich-naturwissenschafiliche  Zeit- 
schrift" which  devoted  especial  attention  to  plant  diseases.  In  1898  the"Kgl. 
bayrische  Station  fvir  Pflanzenschutz"  was  founded  with  von  Tubeuf  as  di- 
rector. Besides  this,  reports  in  the  collective  work,  "Just's  botanischer  Jah- 
resbericht,"  published  since  1873,  became  much  more  abundant,  since  a 
greater  number  of  periodicals  now  included  the  subject  of  plant  diseases  in 
their  programs.  Among  these  belongs  first  of  all  the  "Centralhlatt  fiir  Bak- 
teriologie,  Parasitcnkundc  und  Infektionskrankhciten"  issued  by  Uhlworm 
and  Hansen,  as  also  "Hedwigia,"  edited  by  Hieronymous  and  P.  Hennings, 
the  "Botanische  Centralhlatt,"  elaborated  by  Lotsy,  also  Biedermann's 
"Centralhlatt  fiir  Agriculturchemie,"  edited  by  Kellner,  the  "Naturwissen- 
schaftliche  Zeitschift  fiir  Land-und  Forstwirtschaft"  by  von  Tubeuf  and  L. 
Hiltner  and  the  "Practische  Blatter  fiir  Pflanzenhau  und  Pflanaenschutz" 
by  L.  Hiltner.  We  find  thorough  reports,  especially  on  tropical  cultivated 
plants,  in  "Tropenpflanzer,"  Zeitschrift  f.  tropische  Landvvirtschaft,  by  O. 
Warburg  and  F.  Wohltmann  as  well  as  in  its  "Beiheften"  (supplements) 
which  form  the  organ  of  the  "Kolonialwirtschaftliches  Komitee  zu  Berlin." 
In  the  German  East-African  colonies,  Zimmermann  is  especially  active  in 
pathological  fields  as  is  shown  by  his  "Mitteilungen  aus  dem  hiologisch-land- 
wirtschaftlichen  Institute  Amani."  In  Austria  the  "Zeitschrift  fiir  das  Land- 
wirtschaftliche  Versuchsivesen  in  Oesterreich"  was  founded  in  1898.  In  the 
following  year  P.  Nypels  began  a  series  of  publications  under  the  title  "Mal- 
adies des  plantes  cultivees"  Bruxelles.  In  1900,  v.  Istvanffi  published  the  first 
volume  of  the  "Annales  de  ITnstitute  Central  ampelologique  Royal  Hongrois" 
as  the  report  of  the  Central  Vineyard  Institute  which  had  been  placed  under 
his  direction.  Here  also  especial  attention  was  paid  to  diseases.  The  same 
is  true  also  of  the  "Jahresberichte  der  Kgl.  Lehranstalt  fiir  Obst-,Wein-und 
Gartenbau"  published  by  Gothe  and  later  by  Wortmann  in  Geisenheim  a.  Rh. 
and  the  annual  reports  of  the  "Deutsch-schweizerische  Versuchsstation  fiir 
Obst-Wein-und  Gartenbau  zu  Wadensweil,"  Zurich,  revised  by  Miiller- 
Thurgau. 

This  list  of  periodicals  which  in  part  review  German  and  foreign  litera- 
ture and  in  part  publish  original  articles,  gives  an  insight  into  the  unusually 
rapid  growth  of  material  which  necessarily  demands  a  unified  summary  in 
some  collective  work.  Hollrung  devoted  himself  to  the  working  out  of  such 
a  summary  and  since  1899  has  been  publishing  a  "Jahresbericht  iiber  die 
Neuerungen  und  Leistungen  auf  dem  Gebiete  der  Pflanzenkrankheiten," 
Berlin,  publishing  house  of  Paul  Parey. 


69 

Thus  the  new  science  of  phytopathology  has  taken  to  itself  the  same 
literary  methods  which  the  older  branches  of  knowledge  use  and  which  are 
undisputably  necessary  for  scientific  progress.  But  the  practical  side  of 
phytopathology,  viz.,  the  protection  of  plants,  has  also  found  a  desired  de- 
velopment. The  idea  of  estabhshing  special  institutions,  suggested  in  1880  by 
Korn,  actively  advocated  in  1889  by  Kiihn  and  further  developed  by  Sorauer 
at  the  International  Agricultural  Congresses  and  in  the  "Zeitschrift  fiir 
l^flanzenkrankheiten"  was  brought  in  1891  to  general  attention  in  the  Pruss- 
ian Abgeordnetenhause  (Chamber  of  Deputies)  by  Schultz-Lupitz  in  the 
form  of  a  motion.  On  the  27th  day  of  April  of  the  same  year  the  "Reich- 
sanzeiger"  gave  out  that  the  motion  of  Schultz-Lupitz  had  been  referred  to 
the  Royal  State  Administration  for  discussion  and  at  once  the  Department 
of  Agriculture  attempted  to.  test  the  question  in  how  far  the  production  of 
plants  could  be  advanced  by  the  enlargement  of  the  scientific  institutions  sub- 
ordinate to  that  purpose.  As  the  question  received  a  more  thorough  con- 
sideration, it  became  evident  that  the  best  interests  of  the  protection  of  plants 
could  only  be  had  from  an  Imperial  Institution.  Such  was  now  formed  in 
connection  with  the  Imperial  Board  of  Health  as  a  "Biologische  Abteilung 
fiir  Land-und  Forstwirtschaft"  and  since  1905  this  has  been  an  independent 
institution  of  the  Empire.  The  department,  at  present  under  Aderhold's  di- 
rection, possesses  in  Dahlem,  besides  the  proper  laboratories,  a  very  expensive 
experimental  field  and  has  published  its  results  at  indefinite  intervals  since 
1900.  Besides  these  scientific  works  the  "Biological  Division"  also  publishes 
popular  bulletins  and  colored  posters  and  in  this  way  promotes  the  knowledge 
of  the  most  abundant  animal  and  vegetable  agencies  injurious  to  plants.  In- 
formation as  to  their  control  is  also  distributed  gratis,  directly  to  these 
workers. 

Besides  the  above  mentioned  imperial  institution  which  now  bears  the 
title,  "Kais.  Biologische  Anstalt  fiir  Land-iind  Fortswirtschaft,"  we  find  in 
the  different  German  States  many  organizations  for  the  furtherance  of  plant 
protection,  which  in  part  are  associated  with  the  already  existing  high 
schools  and  experiment  stations  and  in  part  are  independent  establish- 
ments. Among  these,  besides  the  institutions  already  mentioned  at  Halle 
and  Geisenheim,  there  should  be  named  also  the  Anstalt  fiir  Pflansenschutz 
in  Hohenheim,  founded  in  1902  and  now  under  the  direction  of  Kirchner. 

We  also  find  in  the  other  European  countries  an  active  development  of 
the  study  of  plant  diseases,  proved  by  the  publications  of  many  institutions. 
Among  these  belong  the  "Bulletin  de  la  Station  Agronomique  de  I'Etat  a 
Gembloux,"  Bruxelles  (Em.  Marchal),  and  "Travaux  de  la  Station  de  path- 
ologie  vegetale,"  by  Delacroix,  Paris,  the  "Tijdschrift  over  Plantenziehten" 
(Ritzema  Bos)  already  mentioned  and  the  "Eandbouwkundig  Tijdschrift," 
the  "Oversigt  over  Landbrugsplanternes  Sygdomme"  Kjobenhavn,  in  the 
"Tijdsskrift  for  Landbrugets  Planteavl,"  Kjobenhavn  (Rostrup),  the  "Upp- 
satser  i  praktisk  Entomologi,"  Stockholm  (Lampa).  "Beretning  om  Skadein- 
sekter  og  Plantesygdomme,"  Kristiania  (Schoyen).   "Berattelse  ofver  skad- 


70 

einsekters  upptriidande  i  Finland"  (E.  Renter),  in  the  "Landbruksstyrelsens 
meddelanden,"  Helsingfors,  the  "Annual  report  of  the  consulting  botanist" 
(Carruthers)  in  the  "Journ.  Ro3al  Agric.  Soc,"  London. 

It  is  a  matter  of  fact  that  countries  outside  of  Europe  have  not  been 
backward  in  the  endeavor  to  increase  plant  protection.  This  branch  of 
knowledge  has  been  most  advanced  in  North  America  where  the  Department 
of  Agriculture  at  Washington  has  devoted  special  attention  as  well  to  animal 
enemies.  Besides  establishing  the  "Division  of  Entomology"  which,  by  its 
valuable  investigations,  contributes  essentially  to  the  knowledge  of  animal 
injuries,  the  organization  of  meetings  of  agricultural  zoologists  is  especially 
noteworthy.  In  these  meetings  questions  of  general  significance  are  dis- 
cussed. Besides  this,  many  investigators  in  the  Universities  and  Experiment 
Stations  are  working  along  these  lines  with  gratifying  results.  Of  the  latter, 
we  will  mention  the  Agricultural  Experiment  Station  of  the  State  of  New 
York  at  Ithaca  and  the  New  Jersey  Agricultural  College  Experiment  Station. 
l"\irther  statements  are  made  in  our  detailed  exposition  in  which  the  different 
bulletins  of  the  institutions  for  the  advance  of  plant  protection  are 
mentioned. 

Besides  the  numerous  publications  of  the  United  States  of  North  Ameri- 
ca, the  magazines  of  other  countries  also  furnish  noteworthy  contributions 
to  the  knowledge  of  the  diseases  of  cultivated  tropical  plants.  Among  them 
belong  the  "Mededeelingen  van  het  Proefstation  voor  Suikerriet  in  West 
Java,"  the  reports  of  the  "Proefstation  voor  Cacao  to  Salatiga,"  Malang,  the 
"Boletim  da  Agricultura,"  S.  Paulo,  "Boletim  del  Instituto  Fisico-Geograph- 
ico  de  Costa  Rica,"  "Queensland  Agricultural  Journal,"  "Australian  fungi" 
(McAlpine),  in  the  "Proceed.  Linnean  Society  of  New  South  Wales,"  "Ad- 
ministration Reports,  Royal  Botanical  Gardens,"  Ceylon,  "Report  of  the  De- 
partment of  Land  Records  and  Agriculture,"  Madras,  and  "The  Journal  of 
the  College  of  Science,  Imperial  University  of  Tokio,"  Japan.  We  must 
refer  to  the  "Botaniker-Adressbuch"  by  J.  Dorfler,  Vienna,  1902,  for  the 
numerous  other  institutions  and  indi\  idaul  investiirators. 


APPENDIX. 

In  the  above  statements  we  have  mentioned  not  only  the  literature  on 
the  subject  but  also  given  expression  to  the  leading  ideas  of  the  dififerent 
periods  in  order  to  show  how  the  science  has  gradually  developed  to  its 
present  standpoint.  To  be  sure,  changes  in  the  points  of  view  on  the  nature 
and  role  of  parasitic  organisms  are  not  without  interest,  but  no  less  interest- 
ing are  the  references  of  the  various  authors  to  the  influence  of  the  stars,  i.  e. 
the  atmospheric  factors,  which  may  be  traced  as  a  red  line  through  all  the 
reports.  On  this  account  we  have  often  restated  at  length  the  earlier  points 
of  view  and  find  a  striking  agreement  with  the  oldest  periods  since  emphasis 
is  always  laid  on  the  dependence  upon  climatic  and  soil  conditions  and  in  part 


71 

also  upon  cultural  habits  of  those  phenomena,  which  we  have  learned  to 
recognize  as  parasitic. 

This  idea,  which  is  also  the  guiding  principle  in  the  present  book,  has 
led  the  author  to  undertake  the  first  experiments  for  collecting  the  Statistics 
of  Plant  Diseases.  These  experiments  which,  as  already  mentioned,  were 
begun  with  the  help  of  the  German  Agricultural  Society  and  continued  by  its 
"Special  Commission  for  Plant  Protection,"  have  now  found  recognition, 
for  "the  "Kais.  Biologische  Anstalt  fiir  Land-  und  Fortswirtschaft"  beginning 
with  1905  has  assumed  the  collection  of  statistics  of  plant  diseases. 

Doubt  is  often  expressed  as  to  the  importance  of  such  statistics  for  our 
subject  and  reference  made  to  the  fact  that  our  most  dangerous  diseases  are 
constantly  present  and  the  statements  of  the  statisticians  concerning  the 
intensity  of  the  attack  and  the  amount  of  agricultural  loss  appear  to 
be  influenced  so  individually  that  all  certain  positive  figures  can  never 
be  attained.  In  opposition,  it  should  be  emphasized  that  I  did  not  undertake 
the  collection  of  statistics  in  order  to  obtain  precise  figures  as  to  the  dis- 
tribution and  agricultural  efifect  of  the  different  diseases.  (Besides,  in  this 
connection,  the  making  of  reports  will  gradually,  with  the  increased  educa- 
tion of  the  body  of  observers,  become  as  exact  as  it  is  in  all  provinces  of 
organic  life).  The  chief  undertaking  in  the  collection  of  statistics  lies  in  the 
proof  of  the  relations  which  the  different  diseases  bear  to  climatic  and  soil 
conditions  felt  locally  or  universally,  as  well  as  to  cultural  factors.  The  study 
of  the  extreme  forms  of  disease,  easily  verified,  and  the  determination  as  to 
which  factors  have  produced  these  extreme  forms  makes  up  the  productive 
field  of  the  statistics. 

In  these  studies  lies  the  future  of  pathology. 

However  valuable  in  themselves  the  observations  as  to  the  formal  po- 
sition and  the  life  requirements  of  the  parasitic  micro-organisms  may  be, 
nevertheless,  they  form  only  one  link  in  the  chain  of  investigations  and  be- 
come important  only  in  the  determination  of  their  relation  in  nature  and  in 
tJie  usual  practice  of  agriculture.  And  this  we  can  recognize  by  means  of  a 
carefully  arranged  statistical  office  showing  the  conditions  governing  the  in- 
crease or  decrease  of  diseases. 

This  knowledge  leads  to  the  prevention  of  diseases  by  means  of  an  ever- 
developing  plant  hygiene  and  plant  pathology  must  develop  further  in  this 
direction  in  the  future. 


DETAILED  EXPOSITION. 


SECTION  I. 
DISEASES  DUE  TO  UNFAVORABLE  SOIL  CONDITIONS. 


CHAPTER  I. 
THE  LOCATION  OF  THE  SOIL. 

Even  if  the  diseases  which  are  due  to  an  unfavorable  location  of  culti- 
vated land  are  better  understood  by  means  of  the  different  factors  because  of 
which  this  position  becomes  injurious  to  plant  growth,  we  have  still  con- 
sidered it  necessary  to  describe  in  the  following  section  the  general  conditions 
due  to  different  locations.  We  have  done  so  because  it  is  of  special  impor- 
tance to  the  guiding  principle  of  this  manual  and  to  any  reference  to  a  pre- 
disposition to  certain  diseases  which  is  developed  from  this  location  of  the 
soil  that  it  be  shown  how  the  material  and  formal  structure  of  any  plant 
species  changes  with  the  condtions  of  the  habitat,  how  thereby  separate  func- 
tions may  sometimes  be  suppressed,  sometimes  advanced,  and  how  accord- 
ingly the  different  localities  impress  their  definite  characteristics  on  the  plants 
which,  on  this  account,,  must  behave  very  differently  in  relation  to  the  differ- 
ent injurious  causes. 

I.  ELEVATION  ABOVE  SEA  LEVEL. 

a.     General  Changes  in  Habitat  in  Relation  to  Herbaceous  Plants. 

There  is  no  need  of  discussing  further  the  fact  that  the  temperature  al- 
ways falls  with  an  increase  in  elevation  of  any  cultivated  surface  above  sea 
level  and  that  this  fall  in  temperature  is  a  determining  factor  for  limiting 
vegetation,  on  which  account  the  time  of  harvest  in  mountains  must  always 
be  later  than  on  lower  levels.  It  is  an  universally  recognized  fact  that  this 
later  harvest  brings  with  it  great  difficulties  in  curing  the  grain  and  not  in- 
frequently makes  necessary  special  precautions  in  high  mountains,  and  that 
despite  these  precautions  there  often  takes  place  a  blackening  of  the  grain  as 
a  result  of  the  beginning  of  fungous  growth.    An  example  with  exact  figures 


73 

is  given  by  Angot^,  according  to  whose  observations  the  harvest  of  winter  r^'e 
in  France  is  delayed  on  an  average  about  four  days,  as  the  elevation  increases 
about  lOO  meters.  Attention  should  be  called,  however,  to  the  circumstance 
that,  with  increasing  height,  the  air  being  thinner  is  less  warm  so  that  there- 
fore it  must  have  an  appreciable  effect  on  the  development  of  vegetation. 
With  this  should  be  reckoned  conditions  of  moisture  which,  aside  from  the 
physical  constitution  of  the  soil,  are  different  for  plants  of  Alpine  regions  in 
lower  latitudes  than  for  those  from  plains  in  the  Arctic  zone.  Within  the 
same  degree  of  latitude  mountains,  as  colder  bodies,  will  condense  more 
water  vapor  and  thereby  bring  about  more  abundant  precipitation  than  takes 
place  on  plains.  On  this  account  more  snow  will  fall  and  the  warmth  needed 
to  melt  this  greater  mass  of  snow  is  withdrawn  from  vegetation.  Even  after 
the  snow  has  melted  in  spring,  the  plants  in  the  mountains  will  nevertheless  at 
first  be  less  able  to  benefit  from  the  sun's  warmth  than  those  on  the  plains 
since  the  inequalities  of  the  upper  surface  of  the  soil  become  efTective.  A 
square  meter  of  very  broken  ground  surface  has  a  much  greater  upper  sur- 
face, divided  into  many  slanting  levels,  over  which  the  same  amount  of 
warmth  must  be  distributed,  than  has  perfectly  level  land,  the  different  par- 
ticles of  which  are  raised  to  a  higher  temperature.  This  is  the  case  in  moun- 
tain chains  in  contrast  to  level  plains.  It  is  evident  from  these  statements 
that  with  increased  elevation  above  the  sea  these  processes  of  weathering  and 
decomposition  must  be  retarded  since  they  are  essentially  favored  by 
warmth.  It  is  also  evident  that  such  peculiar  combinations  of  vegetative 
factors  will  produce  characteristic  forms,  of  which  the  best  known  feature 
is  short,  repressed  growth.  Such  forms  of  growth  are  kept  constant,  first  of 
all,  in  the  seeds.  Climatic  forms  which  have  become  hereditary  in  this  way 
liave  been  termed  "Oecological  variations"'-. 

If  it  was  said  at  first  that  the  temperature  of  the  air  at  higher  levels  is 
lower,  it  must  also  be  emphasized,  on  the  other  hand,  that  at  higher  levels  the 
intensity  of  the  illumination  increases  and  produces  accordingly  greater  soil 
zvarmth.  On  this  account  climate  of  the  lower  and  middle  latitudes,  on  ac- 
count of  the  greater  intensity  of  light  and  greater  warmth  of  the  soil,  would 
differ  favorably  from  that  of  those  plains  in  a  Polar  zone  where  the  tem- 
perature of  the  air  is  the  same.  The  lesser  atmospheric  pressure  in  moun- 
tains must  result  in  an  increase  of  transpiration  as  stated  by  FriedaP 
and  the  increased  supply  of  light  in  an  increase  of  the  assimilatory  activity  of 
the  leaf.  Consequently  the  typical  mountain  plant  works  more  energetically 
and  in  this  way  is  explained  its  shortened  vegetative  period. 

According  to  the  observations  of  Bonnier*,  who  made  experimental 
gardens   on   Mt.   Blanc   and   in   the   Pyrenees,   in   Alpine   climates   with   a 


1  Der  Naturforscher,  1883,  No.   24. 

2  Lebensgeschichte  der  Bliitenptinnzen  Mitteleuropas.     Von  Kirchner,  Loew  und 
C.  Schroter.     Stuttgart,   Ulmer  1904.  p.   116. 

3  Friedal,  Action  de  la  pression  totale  sur  I'assimilation  chlorophyllienne.  C.  rend. 
1901.     Cit.  Bot.  Jahresb.   1901.     Section  II,  p.  221. 

*  Bonnier,  Etude  experimentale  de  I'influence  du  climat  alpin  sur  la  vegetation 
etc.     Bull.  Soc.  Bot.  France.     Vol.  XXXV.  35.     1888. 


74 

greater  number  of  herbaceous  plants,  the  shoots  became  shorter,  leading  to 
nanism.  In  specimens  from  high  mountains,  the  palisade  parenchyma  is 
more  strongly  developed  and  contains  more  chlorophyll.  Accordingly,  the 
assimilatory  work  has  been  increased.  If  the  leaves  of  the  same  species  from 
specimens  grown  on  plains  and  in  mountain  gardens,  are  cut  off  at  the  same 
time  and  tested,  the  leaves  from  the  high  mountains  showed  a  stronger  de- 
velopment of  oxygen  in  an  equal  length  of  time  for  equally  large  surfaces. 
It  is  said  that  such  Alpine  characteristics  can  be  artificially  bred  in  plants  by 
packing  them  in  ice  at  night  while  leaving  them  during  the  day  under  normal 
growing  conditions \ 

In  a  later  report,  Bonnier-  calls  si)ecial  attention  to  the  increase 
in  temperature  and  assimilation  which,  taking  place  in  Alpine  regions, 
may  easily  account  for  the  fact  that  plants  from  the  plains,  brought  into  an 
Alpine  climate,  develop  relatively  greater  amounts  of  sugar,  starch,  volatile 
oils,  coloring  matter,  alkaloids  and  other  products  of  chorophyll  activity. 

How  greatly  this  specific  climatic  character  immediately  influences  the 
mode  of  development  of  any  plant  species  is  shown  by  the  well-known  ex- 
periments on  structure  carried  on  from  1875  to  1880  by  Kerner  v.  Marilaun'' 
with  seeds  taken  from  the  same  parent  plant  which  had  been  grown 
with  precaution  against  cross-fertilization.  Part  of  the  seeds  were  sown  in 
an  Alpine  experimental  garden  on  the  top  of  Mt.  Blaser  in  the  Tyrol  (2195 
m.  elevation),  others  in  the  botanical  garden  in  Vienna.  The  germination  of 
the  seed  on  top  of  Mt.  Blaser  took  place  soon  after  the  melting  of  the  snow 
which  had  been  1.5  m.  deep,  between  the  loth  and  25th  of  June.  The 
germination  and  growth  of  the  seedlings  therefor-e  took  place  when  the  sun 
vvas  highest  and  the  days  longest.  The  seedlings  were  exposed  at  once  to  a 
temperature  which  was  just  as  high  or  perhaps  somewhat  higher  than  that 
furnished  the  experimental  plants  in  the  botanical  garden  at  Vienna,  when 
the  March  day  was  twelve  hours  long.  At  the  end  of  August  and  the  be- 
ginning of  September  blossoms  were  observed  on  the  plants  which  had  not 
been  killed  by  the  several  frosts  in  June,  July  and  even  in  August,  for  ex- 
ample, on  Satureja  hortensis,  Lepidium  sativum,  Agrostemma  Githago,  Cen- 
taurea  Cyanus,  Turgcnia  laUfolia  etc. 

The  plants  grown  in  the  Alpine  experimental  gardens  differed  from 
those  in  the  botanical  gardens  at  Vienna  in  that  they  were  strikingly  shorter 
and  their  stems  developed  a  greater  number  of  parts.  It  was  found  further 
that  in  the  Alpine  specimens,  for  instance,  Viola  arvcnsis,  blossoms  developed 
even  from  the  axis  of  the  third  and  fourth  leaves  while  at  Vienna  they  came 
only  between  the  seventh  and  eighth  leaves.  The  number  of  blossoms  was 
fewer  and  the  petals,  like  the  leaves,  were  smaller,  as  a  rule.    A  part  of  the 


1  Palladin,  Onfluence  des  changements  des  temperatures  sur  la  respiration  des 
plantes.     Revue  gen.  de  Botanique,  1899,  p.  242. 

2  Bonnier,  Gaston,  Influence  des  hautes  altitudes  sur  les  fonctions  des  vegetaux. 
Compt.  rend,  de  I'Acad.  scienc.  Paris.  Vol.  CXI.  1890.  Cit.  Bot.  Centralbl,  1891. 
No.  12. 

3  Pflanzenleben.     Vol.  II,  pp.  453  ff.     Wein.     1898. 


75 

annual  species  from  the  plains  which  had  had  sufficient  time  and  warmth  to 
develop  seeds  were  longer  lived  on  the  top  of  Mt.  Blaser  since  in  the  follow- 
ing year,  new  sprouts  were  developed  from  the  lower  part  of  the  stems.  An 
earlier  blossoming  could  also  be  observed. 

Corresponding  to  the  fact  that  the  intensity  of  the  sunlight  increases 
with  increased  elevation,  the  color  of  the  blossom,  depending  upon  the  antho- 
cyanin,  also  became  more  intense.  Blossoms,  which  were  white  on  the  plains, 
had  in  the  Alps  petals  which  were  violet  underneath.  The  glumes  of  grasses, 
green  on  the  plains,  or  only  pale  violet,  became  dark  brownish  violet  in  Al- 
pine regions  because  of  a  more  abundant  formation  of  anthocyanin^ 
The  leaves  of  Sedum  acre,  S.  album  and  S.  hexangulare  became  purplish  red. 
On  the  other  hand,  leaves  of  Orohiis  vermis,  Valeriana  Phu  and  Viola  cucitl- 
lata  turned  yellow  from  the  excess  of  light  in  the  Alpine  experimental  gar- 
dens while  in  the  valley  in  shaded  places  their  foliage  remains  green. 

The  mountainous  region  affects  not  only  temperatures  in  the  annual 
seasonal  average  but  especially  the  moisture  content  of  the  atmosphere. 
Warmth  and  humidity  in  their  total  amount  and  in  their  distribution  during 
the  seasons  together  with  the  supply  of  light  are  determinants  of  growth.  As 
already  mentioned,  atmospheric  moisture  influences  the  amount  of  light 
available  for  the  plant,  for  a  humid  atmosphere  absorbs  about  five  times  as 
many  light  rays  as  does  a  dry  atmosphere. 

Since  the  absolute  content  of  the  air  in  water  vapor  decreases  with  the 
elevation,  less  light  will  be  absorbed  in  the  mountains,  especially  since  the 
rays  of  light  have  a  shorter  distance  to  traverse  in  order  to  reach  the  earth  as 
compared  with  regions  at  sea  level.  The  fact  that  the  absolute  vapor  con- 
tent of  the  air  decreases  with  the  elevation  is  a  matter  of  course  for,  since 
the  temperature  becomes  lower  and  lower,  the  air  must  condense  its  water 
vapor  and  give  it  off  in  a  liquid  form.  But  the  relative  moisture  increases 
in  the  mountains  which  explains  why  we  call  a  mountain  climate  damp  and 
rainy.     Cloudiness  is  also  relative  to  the  moisture  of  the  air. 

This  increase  of  the  relative  moisture  and  the  decrease  of  temperature 
form  the  reasons  for  the  rapid  ending  of  our  cultural  efforts  so  far  as  these 
concern  the  obtaining  of  seeds  in  mountain  regions.  We  know  that  the  for- 
mation of  blossoms  and  seed  requires  an  increase  of  warmth  proportionate 
to  the  length  of  the  growth  period.  For  this  reason  we  find,  as  mentioned  at 
the  beginning,  that  grain  often  does  not  ripen  in  the  mountains  and  that 
therefore  clover  and  other  legumes  furnish  an  insufficient  amount  of  seed. 
Yet  another  condition  must  be  added  to  those  already  mentioned,  to  which 
Pax  has   called   attention-,   viz.,   that  the   insects   are   only  half   as   num- 


1  The  theory  that  anthocyanin  is  developed  for  the  protection  of  the  plant 
against  too  strong  sunlight  is  held  by  many  investigators.  Kerner  (1.  c.  Vol.  I, 
p.  508)  assumes  that,  in  the  reddening  of  blossoms  which  appears  with  a  lack  of 
heat,  the  loss  to  the  blossoms  of  the  directly  conducted  heat  is  compensated  "by  the 
heat  obtained  from  the  rays  of  light  by  means  of  the  anthocyanin."  We  believe  we 
have  observed  that  the  red  coloring  matter  indeed  does  develop  abundantly  with  a 
lack  of  heat,  but  can  also  set  in  with  an  abundance  of  heat  if,  in  proportion  to  the 
heat,  an  excess  of  light  makes  itself  felt  in  the  tissues  which  contain  sugar. 

-  Das  Leben  der  Alpenflanzen.     Zeitschr.  d.  d.-ostr.  Alpenvereins  1898,  p.  61. 


76 

crous  at  an  elevation  of  2300  m.  as  on  the  plains.  On  this  account  labiate 
plants  play  a  considerable  role  on  high  mountains.  Also  the  increased  diffi- 
culty of  insect  fertilization  is  partly  equalized  by  the  fact  that  an  asexual 
reproduction  also  takes  place  (Polygonum  v'wipanim,  Foa  alpina,  Saxifraga 
ccrnua) ;  further,  ten-elevenths  of  all  kinds  of  small  bushes  and  even  Viola 
iricolor,  an  annual  with  us,  become  perennial  in  the  Alps. 

Besides  this,  reference  should  be  made  to  the  fact  that,  with  unlimited 
cultural  experiments  at  high  elevations,  short-lived  mountain  varieties  are 
formed  which,  to  be  sure,  furnish  seed  in  smaller  amounts  but  more  satis- 
factory in  quality.  This  ofifers  greater  possibilities  of  yielding  a  good  har- 
Aest  in  the  mountains  and  (according  to  Schiebler)^  has  the  advantage 
of  retaining  at  lower  levels  its  shortened  period  of  growth  and  there- 
fore can  be  used  advantageously  in  Northern  climates. 

Development  of  the  Aerial  Axis  of  Woody  Plants. 

In  contradiction  to  a  widespread  opinion,  it  should  be  mentioned,  that 
dzvarf  growth  in  high  mountains  is  not  to  be  ascribed  to  the  pressure  of  the 
snow  since  we  have  tree-like  forms  in  those  regions  where  the  most  snow 
falls.  It  is  known  that  the  snow  cohering  does  not  become  thicker,  the  great- 
er the  elevation  of  the  mountain,  but  with  us  increases  up  to  perhaps  an 
elevation  of  2500  m.,  that  is,  only  to  the  upper  boundary  of  the  dwarf  coni- 
fers, dwarf  alders  and  the  Alpine  rose.  Higher  up  the  amount  of  precipi- 
tation decreases.  Spruces,  larches  and  the  cembra-pine  suffer  less  from 
snow  pressure  when  they  stand  alone  or  scattered  because  their  elastic,  slop- 
ing older  branches  let  the  accumulated  snow  slip  off  more  easily  when  the 
wind  blows.  Other  trees,  like  SalLv  serpyllifoUa  and  Rhamnus  pumila,  fre- 
quently escape  excessive  snow  pressure  by  their  growth  on  steep  rocky  cliffs 
from  which  the  snow  slides  rapidly.  However,  trees  exposed  to  the  full 
pressure  of  the  snow  can  scarcely  be  made  to  grow  closer  to  the  earth  be- 
cause of  the  burden  of  the  snow  or  of  windy  weiather.  Rather,  we  may  as- 
sume with  Kerner  that  it  is  the  soil  warmth  which,  in  the  immediate  prox- 
imity of  the  earth,  affords  them  the  best  conditions  for  existence.  In  the 
higher  Alpine  regions  the  soil  is  much  warmer  than  the  air  which  absorbs 
less  sunlight  on  account  of  its  increasing  thinness  and  its  rapidly  decreasing 
water  content.  The  above  quoted  author  cites  that,  for  example,  on  the  top 
of  Mt.  Blanc  (4810  m.)  the  intensity  of  the  sunlight  is  26  per  cent,  greater 
than  at  the  level  of  Paris.  On  the  Pic  du  Midi  (2877  m.)  a  temperature  of 
33.8°C.  was  observed  in  the  soil  on  which  the  sun  shone  while  the  air  showed 
a  temperature  of  only  io.i°C.  This  warmth  of  the  soil  together  with  the 
intensity  of  the  light  explains  the  speedier  development  and  blooming  of 
Alpine  plants. 

Vochting-,  in  opposition  to  Kerner,  thinks,  on  the  ground  of  his 
observations  with  Mimulus  Tilingn,  the  young  branches  of  which  at  a  defi- 

1   Schiebler,  Die  Pflanzenwelt  Norwegens.     AUg.  Teil.     Christiania  1873. 
-  Vochting-,  H.,  Ueber  den  Einflufs  niedriger  Temperatur  auf  die  Sprofsrichtung. 
Ber.  Deutsch.  Bot.  Ges.  XVI.  ]8?8,  p.  37. 


77 

nite  age  incline  downward  in  spring  when  the  temperature  is  lower  and 
straighten  up  later  with  increased  warmth,  that  the  creeping  habit  of  growth 
of  Alpine  plants  may  be  ascribed  in  part  or  entirely  to  the  influence  of  the 
low  temperature.    A\'e  can  not  agree  with  this  theory. 

RosenthaP  made  investigations  concerning  the  mode  of  growth 
of  trees  in  Alpine  regions.  He  found  that  in  all  the  species  of  wood  studied 
the  annual  ring  is  narrower  in  high  countains  than  in  the  lowlands.  The  ec- 
centricity of  the  branches  is  usually  very  great  but  the  direction  of  the  great- 
est increase  of  growth  varies.  The  vascular  system,  on  account  of  the  in- 
creased evaporation,  is  more  extensively  developed.  In  dicotyledons,  a 
higher  percentage  of  the  vascular  tissue  is  obtained  by  a  narrower  annual 
ring;  in  conifers  there  is  a  considerable  decrease  of  the  late  wood  ring. 

The  landslides  which  continually  take  place  in  mountains  because  of 
storm  conditions  displace  the  trees  and  thereby  change  their  woody  develop- 
ment. Hartig-  pointed  out  the  formation  of  broad  annual  rings  and 
so-called  "red  wood"  (wood  with  short  tracheids  and  strong  lignification) 
on  the  underside  of  the  trunks  and  branches  of  the  spruce  as  soon  as  they 
bend  toward  the  horizontal,  while  slender  annual  rings  and  "strain  wood" 
(long  tracheids  with  weak  lignification)  are  formed  on  the  upper  side.  Ac- 
cording to  Giovanozzi^  this  difference  in  the  formation  of  the  wood  ring 
of  conifers  is  made  use  of  in  hygrometric  measurements  by  the  inhabi- 
tants of  the  Piedmontese  Alps  since  the  small  celled,  thin-walled  red  wood 
possesses  hygroscopic  characteristics  very  dift'erent  from  those  of  the  strain 
wood.  The  red  wood  side  of  a  peeled  branch  becomes  concave  in  dry  air, 
convex  in  moist  air. 

According  to  the  investigations  of  Cieslar*  the  lignin  content  of 
spruce  wood  seems  to  be  less  near  the  upper  boundaries  of  the  tree  zone  than 
in  lower  positions. 

It  will  be  concluded  from  Cieslar's''  observations,  that  the  suppressed 
growth  in  Alpine  forms  is  hereditary  for  the  immediately  following 
generation,  according  to  which  spruces  from  seeds  of  trees  grown  in  moun- 
tainous regions  grow  more  slowly  when  cultivated  on  the  plains  than  do 
plants  raised  from  seeds  of  trees  from  the  plains  similarly  grown.  Engler  has 
made  the  same  observation  in  seeding  experiments  at  the  forestry  experimen- 
tal station  in  Zurich.  From  germination  experiments  with  the  seeds  of 
spruce,  pine  and  other  forest  trees,  M.  Kienitz*^  concludes  that  the  minimum, 
optimum  and  maximum  germinating  temperatures  of  spruce  seed  indigenous 
to  lower  regions  are  higher  than  for  seeds  grown  in  higher  positions. 


1  Rosenthal,  M.  Ueber  die  Au.sbildung  der  Jahresringe  an  der  Grenze  des  Baum- 
wuchses  in  den  Alpen.     Dissei-t.  Berlin,  ^it.   Bot.  Centralbl.   1904.  No.  43. 

2  Hartig,  R..  Holzuntersuchungen.     Berlin.   Springer  1901. 

a  Giovanozzi,     Sul    movimento    igroscopico  dei  rami  delle   Conifere.     Malpighia 
XV,  cit.  Bot.  Jahresb.  1901.     Sec.  II,  p.  191. 

4  Cieslar,  A.,  Ueber    den   Ligningehalt   einiger   Nadelholzer.      Mitt.    a.    d.   Forstl. 
Versuchswesen  Oestei-reichs  1897.     Part  XXIII. 

5  Centralbl.  f.  d.  gesamte  Forstwesen,  1894.     Vol.  20,  p.  145. 

6  Kienitz,    Vergleichende    Keimversuche    mit    Waldbaumsamen    aus    klimatisch 
verschieden  gelegenen  Orten  Mitteleuropas,  Ref.  Bot.  Zeit.  1S79.  p.  597. 


78 

In  plantations  in  high  altitudes,  however,  it  must  further  be  taken  into 
consideration  that  tlie  elevation  acts  differently  according  as  it  presents  iso- 
lated peaks  or  high  plateaux.  Since  the  earth's  illumination  and  radiation 
have  considerable  influence  on  the  temperature  of  the  layers  of  air  covering 
it,  vegetation  at  equal  heights  is  exposed  to  very  diverse  temperature  fluctu- 
ations. On  the  high  plateau  the  decrease  of  warmth  with  elevation  is  less, 
when  the  sun  shines,  than  on  the  mountain  peak  which  stands  alone.  If, 
however,  the  sun  disappears  and  radiation  becomes  determinative,  then  the 
lower  air  layers  above  the  high  plateau  also  cool  off  more.  Thus  the  daily 
fluctuations  in  temperature  are  much  greater  here  and  the  seasonal  ones  as 
well.  On  high  plateaux  the  temperature  can  fall,  even  to  frost,  while  the 
isolated  peaks  remain  protected.  The  same  relation  is  shown  between  valley 
and  heights ;  we  have  recently  observed  a  number  of  examples  from  Italy. 
Passerini  makes^  the  following  observations  from  the  neighborhood  of  Flor- 
ence and  cites,  as  an  especially  good  instance,  the  night  of  April  19-20,  1903, 
when  the  temperature,  which  on  the  15th  still  showed  +i8.3°C.  sank  to 
— i.i"C.  and  rose  again,  nine  hours  later,  to  -\-i2.2°C.  While  the  vegetables 
and  grains  were  not  injured,  the  leaves  and  blossoms  were  seriously  frozen. 
Only  50  m.  higher  the  injuries  were  no  longer  noticeable. 

In  mountainous  regions  clouds  and  mist  act  as  a  protection  from  frosts. 
Thomas-  observed  in  Thiiringen  that  the  young  beech  foliage  did  not 
suffer  from  frost  at  heights  covered  by  mists  while  in  the  valleys  and  gorges 
the  leaves  were  injured.  The  artificial  prevention  of  frost  by  the  production 
of  smoke  has  been  founded  on  the  peculiarity  of  mists  which  prevents  the 
sharp  fall  in  temperature. 

Adjustment  of  the  Root  Body  of  Woody  Pl.\nts. 

In  mountains  the  adaptation  of  the  wood  body  to  the  rocky  soil  and  the 
compensatory  structures  which  appear  on  this  account  are  especially  interest- 
ing. In  the  following  figure  i,  we  see  the  root  of  an  oak  which  has  made 
its  way  through  a  fissure  in  a  rock  and  by  its  continued  growth  in  thickness 
within  the  split  has  developed  into  a  flattened,  board-like  form.  After  leav- 
ing the  rock,  the  root  resumed  its  cylindrical  form.  This  example  shows 
first  that,  despite  the  pressure  which  the  strong  root  had  withstood  for  so 
many  years,  the  ability  to  conduct  water  and  plastic  material  has  not  been 
interrupted  in  the  board-like  part.  In  the  second  place,  we  notice  above  the 
board-like  flattening  the  appearance  of  adventitious  roots.  Both  processes 
correspond  to  the  phenomena  caused  by  artificial  constriction. 

So  far  as  we  have  been  able  to  investigate  roots  which  had  been  flatten- 
ed in  the  clefts  of  rocks,  we  could  observe  that  the  board-like  flat  places  in 
the  root  body  were  produced  because  the  wood  rings  formed  every  year  were 
very   strongly    developed   on    the    sides    where   they   could    develop    freely. 


1  Passerini,    Sui   danni   prodotti  alle   piante   del   shiacciato  etc.     Bull.   Soc.   Bot. 
ital.    1903.   p.    308. 

2  Thomas,  Fr.,   Srharfe  Horizontalgrenze  der  Frostwirkung-  an  Buchen.     Thiir. 
Monatsblatter.     April  1904. 


79 

therefore,  in  the  direction  of  the  split  surface,  but,  on  the  other  hand,  they 
were  reduced  to  a  minimum  on  the  side  where  the  roots  were  pressed  against 
the  rock  and  were  finally  irrecognizable.  On  the  free  side  of  the  wood  the 
vascular  bundles  developed  very  abundantly,  in  some  annual  rings,  in  fact, 
the  wood  was  very  broad  and  provided  with  a  thick  bark ;  on  the  side  of  the 
root  pressed  against  the  rock,  the  wood  lacked  all  vascular  formation,  was 
short-celled  and  formed   from  wood  fibres   inclined  diagonally  instead  of 


Fig-.  1.  Fig.  2. 

Roots  of  Quercus  Pedunculata  grown  between  rocks.      (After  Dobner-Nobbe.) 


running  vertically.  Finally,  differentiation  into  annual  rings  could  not  be 
observed  and  only  a  very  slender  cork  layer  is  seen  lying  on  the  occasionally 
formed  short-celled  parenchyma,  without  any  recognizable  differentiation 
into  medullary  rays. 

Nevertheless,  the  cambial  activity  was  not  lost  in  the  board-like  part  of 
the  root  as  was  evident  when  the  pressure  ceased,  for  the  flattened  part  grew 
normally  in  its  cylindrical  form.  Anatomical  changes  in  the  roots  pressed 
between  the  rocks  approximate  so  strikingly  the  results  obtained  by  artificial 


8o 

constriction  of  the  aerial  axis,  that  we  can  refer  in  this  connection  to  our 
subsequent  studies  in  the  chapter  on  "Wounds." 

Figure  2  shows  a  different  root,  also  from  Qiiercus  pedunculato,  which 
probably  has  only  been  pressed  between  stones.  In  meeting  with  this  ob- 
struction to  its  growth  in  length  it  was  bent  and.  when  growing  further,  be- 
came flattened.  With  increasing  age  the  pressed  root  surface  again  reached 
the  open  and  with  the  removal  of  the  pressure  came  an  increased  formation 
of  the  wdod  ring  in  great  luxuriance  like  callus  rolls.  The  .squeezing  which 
the  roots  had  undergone,  might  have  acted  like  girdling  and  have  produced 
in  this  a  kind  of  girdling  roll  above  the  place  of  pressure.  (See  Girdling  in 
the  chapter  on  "Wounds"). 

We  can  get  an  idea  as  to  the  anatomical  conditions  in  the  first  stages  of 
such  flattening  of  the  root  from  the  investigations  of  Lopriore^.  He 
observed  adventitious  roots  in  the  germinating  plants  of  Vicia  Paba  which 
were  forced  to  grow  under  the  lateral  pressure  of  cotyledons  which  had  not 
separated  from  each  other.  Within  the  sphere  of  pressure  these  tender  roots 
appeared  flattenedlike  ribbons  but  after  leaving  the  region  of  pressure,  they 
again  became  normally  cylindrical  just  as  was  noticd  in  the  oak  roots.  In 
the  very  young  roots  of  the  horse  bean  (Vicia  Paba)  Lopriore  found  that  the 
epidermal  cells  on  the  sides  not  pressed  upon  by  the  cotyledons  had  developed 
into  root  hairs.  On  the  compressd  sides,  however,  not  only  the  epidermal 
cells  were  tangentially  flattened  but  also  the  two  or  four  outer  layers  of  the 
bark  were  considerably  pressed  so  that  they  formed  a  kind  of  peripheral 
girdle  around  the  root  on  these  sides,  whereby  the  radial  walls  of  these  com- 
pressed cells  seem  folded  zigzag  as  in  a  bellows.  The  cells  subjected  to  the 
pressure  of  the  cotyledons  were  also  proved  changed  materially  since  their 
membranes  either  developed  into  cork  or  "together  with  their  lumina  were 
impregnated  with  a  kind  of  protective  gum." 

We  have  already  called  attention  to  the  fact  that  in  figure  i  several 
adventitious  roots  had  been  formed  above  the  board-like  flattening.  As  may 
be  seen,  the  root  had  made  a  curve  here  before  entering  into  the  split  in  the 
rock  and  under  the  influence  of  this  twisting,  a  new  formation  of  adventitious 
roots  had  been  started  on  the  free  convex  side.  We  perceive  in  this  a  result 
of  the  stimulus  of  twisting  which  XoU-  has  discussed  in  detail  in  his 
work.  It  is  easy  to  observe  that  roots  which  have  l)ecomc  twisted  because  of 
a  pressure,  hindering  tlieir  growth  in  length,  develop  new  side  roots  on 
the  convex  side  at  the  point  of  twisting.  In  water  cultures  in  glass  vessels 
this  phenomenon  may  be  observed  when  strong  roots  reach  the  bottom  of  the 
vessel  and  grow  against  it. 

In  mountains  emergency  precautions  are  met  with  in  the  flatly  growing, 
younger  tree  roots  if  the  tip  of  a  rootlet  has  been  lost  through  injury  or  from 


1  I^opriore,  G.,  Verbanderung  infolge  des  Kopt'ens.  Ber.  Deutsch.  Bot.  Ges. 
Vol.  XXII.  Part  5,  p.  309. 

-  Noll,  Vergleichende  Kulturver.suohe.  Sltzungsber.  d.  Niederrhein.  Ges.  f.  Na- 
turkunde.    Cit.    Hot     Jahresber.    1900.    II.  p.  304. 


8i 


drying  out  on  the  rock.  In  figvire  30,  we  see  such  a  compensatory  root  which 
has  been  developed  above  the  dead  tip  of  the 
main  root  A  A.  The  compensatory  organ  is 
much  stronger  and  fleshier  than  the  side  roots 
M'hich  had  been  formed  earUer. 

The  formation  of  adventitious  roots  as  a 
resuh  of  the  stimulus  of  twisting  or  of  injury 
to  the  root  is  constantly  utilized  technically  in 
the  cultivation  of  trees.  In  tranplanting  seed- 
lings of  forest  or  fruit  trees  the  main  root  is 
either  twisted  spirally  in  the  hole  where  it  is  to 
be  planted  or  it  is  shortened  about  a  third.  A 
stronger  cutting  back  is  not  advisable  because 
•adventitious  roots  always  develop  more  weakly 
the  older  the  parts  of  the  axis  which  are 
twisted  or  cut  back. 


Fig-.  3.  Branch  of  a  spruce 
root  on  which  a  fleshy  com- 
pensatory root  has  been  form- 
ed above  the  dead  tip.  (After 
Nobbe.) 


b.     .Special  Cases  of  Disease. 
Retrogression  in  the  Cultivation  of  the  Larch. 

As  a  striking  example  of  the  disadvantages  developed  by  the  cultivation 
of  plants  from  mountain  climates  when  grown  on  the  plains,  we  might  con- 
sider the  often  noticed  retrogression  in  larch  plantations.  Kirchner^ 
mentions,  when  describing  the  life  history  of  this  forest  tree,  that  it  is  a  true 
high  mountain  tree  of  the  European  Alpine  and  Carpathian  systems.  The 
natural  area  of  its  distribution  extends  from  Dauphine  through  Switzerland, 
past  Vorarlberg,  the  Bavarian  and  Salzburger  Alps  to  the  Moravian-Silician 
depression,  and  to  the  Carpathians,  up  to  the  hilly  country  of  Southern  Po- 
land. The  upper  limit  for  the  larch  is  about  2400  m.,  the  lower  one  in  the 
Alps  423  m.,  in  the  Sicilian  mountains  about  357  m.  AA'hile  it  thrives  in 
Scotland,  Sweden  and  Norway,  it  does  not  grow  very  well  in  Middle  and 
Northern  Germany  or  in  France.  When  growing  together  the  spruce  usually 
forces  out  the  larch  except  in  the  highest  altitudes.  When  the  spruce  grows 
on  dry  soil  it  is  shorter  than  the  larch.  Of  all  the  indigenous  conifers  the 
larch  needs  the  most  light.  It  exceeds  all  conifers  and  most  deciduous  trees 
in  its  transpiration.  Because  it  is  not  sensitive  to  cold,  as  shown  by  its 
natural  habitat,  it  is  much  more  dependent  upon  the  warmth  of  the  summer 
1.0  make  its  best  growth.  It  lives  in  regions  where  the  summer  is  constantly 
and  uniformly  warm,  where  there  is  abundant  circulation  of  air  and  a  win- 
ter's rest  of  at  least  four  months  with  a  short  spring  and  a  rapid  transition 
from  spring  to  summer.  Because  its  leaves  come  out  extremely  early,  it 
makes  the  most  of  the  very  short  period  of  growth. 

These  statements  are  based  on  the  observations  of  numerous  specialists 
and  may  on  this  account  be  acknowledged  to  be  thoroughly  reliable.    We  ob- 


1   Lebensgeschichtc   der   Bliitenpflanzen    Mitteleuropas. 
Stuttgart,  Ulmer  1904. 


Vol.   T.    Part 


p.    157 


82 

lain  an  insight  into  its  material  composition  from  the  works  of  \\^eber^ 
He  studied  sections  of  the  trunk  and  the  needles  of  the  larch  picked  in 
October  in  the  Bavarian  Alps,  in  the  Spessart,  from  the  plains  of  the  valley 
of  the  Main  etc.  Tn  spite  of  the  soil  differences,  the  results  agreed  entirely 
in  regard  to  the  influence  of  elevation.    A\'eber  summarizes  these  as  follows : 

The  organic  substance  of  the  needles  increases  with  noteworthy  regu- 
larity with  the  absolute  elevation  of  the  habitat  while  the  content  in  pure  ash 
decreases.  The  amount  of  ash  becomes  absolutely  greater  if  the  larch  grows 
on  the  plains  or  in  moderately  high  mountains  so  that  therefore  to  produce 
an  equal  amount  of  burnable  substance,  more  and  more  minerals  are  taken 
up  by  the  plant,  as  its  cultivation  descends  into  the  plains.  The  most  im- 
portant elements  of  the  ash,  potassium  and  phosphoric  acids,  show  a  regular 
increase  in  specimens  from  the  plains  in  contrast  to  Alpine  Larches.  In  re- 
gard to  the  calcium  content,  the  larch  of  the  plains  indeed  excels,  yet  the, 
constitution  of  the  soil  seems  to  be  very  determinative  here ;  magnesia  and 
sulphuric  acid  show  an  insignificant  increase,  while  ferric  oxid  and  silicic 
acid  show  a  considerable  increase. 

It  may  be  perceived  from.  Weber's  investigations  how  very  greatly  the 
life  habits  of  this  high  mountain  tree  and  its  mineral  composition  change 
with  its  descent  to  the  plains  and  the  question  now  becomes  pertinent  as  to 
whether  the  anatomical  structure  is  not  also  changed  by  the  entirely  differ- 
ent conditions  of  life  on  the  plains.  Primarily  the  plains  offer  strong  con- 
trasts from  the  most  intense  heat  of  summer  to  the  great  cold  of  winter.  To 
this  must  be  added  a  lengthened  spring  with  the  summer-like  days  which 
sometimes  begin  in  February,  always  in  March,  and  the  subsequent  relapses 
to  cold  weather.  However,  the  autumns  of  the  plains  may  be  of  decisive  sig- 
nificance when  a  relati\ely  warm,  dam])  period  not  infrequently  lasts  into 
December  and  does  not  permit  the  cessation  of  vegetation.  One  needs  think 
here  only  of  our  oaks  and  apple  trees  which  often  enough  retain  tlicir 
foliage  on  the  tips  of  the  brandies  throughout  the  whole  winter.  In  apple 
trees,  especially  in  trellis  and  trained  forms,  many  varieties  did  not  develop 
any  terminal  bud  in  autumn  but  the  last  leaf  simply  remains  in  the  winter 
in  an  unformed  stage  of  development. 

In  the  larch  these  long,  wet  and  relatively  warm  autumns  stimulate 
growth  so  that  after  the  normal  summer  end  of  the  annual  ring,  a  few  layers 
of  spring  wood  are  formed,  as  I  have  often  observed.  Therefore  in  such 
cases  on  the  plains  the  beginning  of  an  absolute  dormant  j^eriod  (which 
Kirchner  emphasizes  as  necessary  for  the  normal  development  of  the  larch) 
does  not  take  place  and  the  immediate  results  will  frequently  be  the  loss  of 
the  normal  or  usual  resistance  to  frost.  The  frost  wounds  make  possible  the 
entrance  for  all  wound  parasites  which,  in  the  often  dense  growth  of  larches 
on  the  plains  and  the  moist  motionless  air,  find  the  most  favorable  environ- 


1  "Weber,  R.,  Einflufs  des  Standortcs  auf  die  Zusammensetzung  der  Asche  vein 
Larchen.  Allg-em.  Forst-u.  Jagdzeitung  1873,  p.  368  nnd  in  Biedermanns  Centralbl. 
f.  Agriculturchemie,  1875,  p.  336. 


83 

ments  for  their  growth  and  distribution.  For  this  reason  the  fungus  of  the 
so-called  larch  canker,  the  Dasyscypha  (Pesk.a)  U'UlkommU,  is  so  abundant 
in  old  larch  plantations  and  the  trunks  of  the  young  cop'^e  wood  are  covered 
with  lichens. 

The  complaint  that  the  trees  in  northwest  and  middle  Germany  and  in 
France,  on  an  average,  show  no  satisfactory  growth  is  explained  by  these 
conditions  of  growth  on  the  plains  diametrically  opposed  to  the  nature  of  the 
tree.  This  is  also  the  reason  for  the  reaction  which  has  taken  place  in  the 
usual  enthusiasm  of  foresters  for  the  cultivation  of  the  larch. 

The  comprehension  of  our  mistakes  in  growing  the  larch  and  the  in- 
tenability  of  the  widespread  assum.ption  that  it  can  be  grown  in  any  place 
has  recently  been  gathering  force  in  forestry  circles.  A  little  paper  publish- 
ed by  the  First  Commissioner  of  Woods  and  Forests  in  Hameln^  is 
ot  the  greatest  significance.  He  observed  that  the  larch  canker  occurs  only 
\\'here  the  tree  is  grown  under  hindering  conditions  or  is  crowded  by  its 
neighbors.  The  point  which  he  makes  strongly  is  "that  the  sun  is  the  nurse 
of  the  larch."  Com.plete  agreement  with  this  discovery  has  com.e  from  an 
extensive  inquiry  on  the  part  of  the  English  Dendrological  Society  contained 
in  Sommerville's  reports-.  From  this  report  canker  seems  to  be  in- 
creasing in  England  on  the  larch  and  attacks  trees  from  seven  to  fifteen 
years  old  most  easily.  Dampness  in  dense  growths  favors  the  disease  which 
occurs  less  often  on  altitudes  than  in  hollows.  Many  practical  foresters 
maintain  that  the  disease  is  inherited  through  the  seed  ;  aiid,  while  Sommer- 
ville  does  not  share  this  point  of  view,  he  cannot  dispro\e  the  assumption  of 
an  hereditary  predisposition.  Also  the  assertion  that  nurseries  spread  the 
disease  may  not  be  repudiated  entirely. 

We  completely  understand  such  statements  also  heard  frequently  in 
Germany.  Such  predisposition  to  sickness  lies  in  the  changed  mode  of 
grow^th  which  is  a  result  of  the  removal  of  the  tree  frf-m  mountains  to 
plains,  thus  destroying  its  natural  immunity.  It  is  reasonable  that  nurseries 
with  their  rapid  forcing  of  the  seedlings  in  manured  soils,  excusable  because 
of  agricultural  reasons,  increase  this  weakening  of  the  larch.  W^e  find  simi- 
lar conditions  also  for  other  conifers  ;  for  example,  we  have  examined  pine 
seedlings  from  nurseries  and  forestry  seed-beds  which  had  begun  to  suffer 
from  leaf  cast,  and  we  have  always  been  able  to  prove  that  the  beginning  of 
resinosis  was  present  even  in  the  iirst  annual  ring. 

Weber^  observed  in  beech  foliage  conditions  similar  to  the  larch 
in  regard  to  the  difference  in  the  ash  content.  From  in\estigations  from 
eleven  different  habitats  it  was  found  that  the  percentage  of  ash  in  beech 

1  Die  Larche,  ihr  leichter  und  sicherer  Anbau  in  Mittel-und  Norddeutschland 
durch  die  erfolgreiche  BekJimpfung-  des  Larchenkrebses.    Leipzig-  1899. 

-  Report  by  Dr.  Sommerville  on  the  inquiry  conducted  by  the  Society  into  the 
disease  of  the  larch.  Transact,  of  the  English  Arboricultural  Society.  Vol.  Ill, 
Part  IV.    1893-94. 

3  Weber,  Einflufs  des  Standorts  auf  den  Aschengehalt  des  Buchenlaubes.  Allg-. 
Forst.-u.  Jagdzeitung-,  1875,  p.  221,  cit.  in  Beidermann's  Centralbl.  f.  Agrikultur- 
chemie,  1875,  II,  p.  325.  The  percentage  of  ash  content  and  especially  of  calcium 
and  silicic  acid  becomes  greater  the  more  slowly  the  plants  grow. 


84 

foliage  from  altitudes  over  looo  m.  above  sea  level  was  noticeabl}'  less  than 
in  that  from  lower  levels.  The  latter  showed,  however,  in  its  ash,  a  smaller 
amount  of  potassium,  phosphoric  acid  and  sulphuric  acid,  while  the  leaves 
collected  in  altitudes  were  proved  to  be  as  rich  in  these  substances  as  the 
young  foliage.  The  distribution  of  calcium  and  silicic  acid  v/as  the  opposite. 
The  size  and  weight  of  the  average  leaves  decrease  with  the  elevation.  In 
regard  to  morphological  changes,  H.  Hofifman^  states  that  the  young  sprouts 
of  Sali.v  herbacea  and  S.  reticulata  transplanted  from  high  mountains  to  low 
levels  grow  erect  instead  of  lying  flat  on  the  soil.  When  moved  from  low- 
lands to  high  mountains,  Solidago  J'^irga  aurea  becomes  an  aenemic  dwarf. 
riantaga  alpina  is  a  meagre  mountain  form  of  PL  maritima  not  coming  true 
to  seed  and  with  short  ears.  The  length  of  the  ears  increased  in  the  second 
generation  on  the  lowland  from  15  to  18  mm. ;  the  leaves  became  broader  and 
even  serated ;  there  were  fewer  blossoms  at  this  altitude  but  not  smaller. 
Hieraciun  alpimim  developed  on  the  lowland  isolated  specimens  with  tall, 
much  branched  stems.  Aster  alpinus  in  isolated  examples  developed  broad- 
er leaves.  Gnaphalium  Leonio podium,  the  Edelweiss,  loses  on  the  plains  its 
little  inflorescences  and  pubescence. 

The  facts  ascertained  when  the  larch  was  brought  from  the  mountains 
to  the  plains  seem  to  be  a  very  sharp  warning  to  consider  more  caiefully  the 
natural  requirements  of  the  trees  and  not  to  believe,  because  possibly  sup- 
ported by  soil  analysis,  that  each  tree  must  thrive  where  nutritive  substances 
are  abundantly  present  for  it.  The  great  physical  conditions,  such  as  venti- 
lation, illumination  and  dampness,  are  determinative  factors  which,  taken 
under  due  consideration,  preserve  the  natural  immunity  of  the  tree  and 
make  superfluous  a  petty  local  comliatting  of  the  parasites. 

Lack  of  .Success  with  Tropicai.  Plantations. 

Like  every  nation  at  tlie  beginning  of  its  colonizing  period,  we  must 
recognize  that  great  loses  occur  in  newly  organized  tropical  plantations.  An 
essential  factor  for  the  protection  from  agricultural  injury  is  to  be  found, 
we  believe,  in  the  insignificant  consideration  of  the  native  conditions  of 
growth  from  which  the  tropical  useful  plants  originate.  In  regard  to  the 
transplanting  of  plants  from  the  plains  into  an  altitude,  the  increase  in  the 
relative  dampness  is  of  especial  importance,  next  to  the  decrease  in  temper- 
ature. These  conditions,  for  example,  quickly  place  a  limit  for  the  culti- 
vation of  grain.  According  to  Fesca's  reports  (1.  c.  p.  42)  grain  species  do 
not  flourish  at  all  in  the  lower  regions  of  the  tropics  and  the  ripening  of  the 
grain  becomes  uncertain  in  the  higher  regions.  In  Java  and  Ceylon,  culti- 
vation of  our  species  of  grains  and  Leguminoseae  with  a  view  to  raising 
seeds  becomes  doubtful,  even  at  elevations  of  scarcely  2000  m. 

On  the  other  hand  a  smaller  difference  between  the  temperatures  of  win- 
ter and  summer  is  of  great  value,  especially  to  tropical  plants.     Many  plants 


Riickblick   auf  meine  Variationsversuche,   Bot.  Z.   1881,   p.  431. 


85 

for  which  the  plains  are  too  warm,  thrive  better  in  the  more  uniform  cli- 
mate of  the  higher  altitudes.  Thus  Fesca^  mentions  that  cocoa  thrives 
best  at  an  elevation  of  about  500  m.,  Arabian  Coffee  from  600  to  1200  m., 
and  more,  and  tea  from  1000  to  2000  m.  For  sugar  cane,  however,  places 
are  necessary  in  which  occur  periods  of  high  temperature.  Accordingly 
the  cultivation  of  sugar  cane  on  the  sub-tropical  plains  often  reaches  even 
to  the  35  parallel  of  latitude,  in  Mediterranean  regions  to  the  36  parallel  of 
latitude  where  the  heat  temperature  for  two  to  three  summer  months  rises 
above  25°C.  The  cultivation  of  sugar  cane  for  factories,  however,  even  in 
narrow  tropical  zones  is  seldom  successful  higher  than  300  m.  Indeed  it  is 
planted  higher  up  but  then  only  used  for  the  purposes  of  propagation  be- 
cause of  the  rapid  decrease  in  the  sugar  content.  At  such  heights,  however, 
the  cane  escapes  the  "sereh  disease"  so  much  feared  at  present  and  on  this 
account  it  has  been  proposed  that  the  plantations  for  the  sugar  be  regene- 
rated by  making  propagating  fields  with  the  proper  cultural  ^'arieties  at  high 
elevations  and  using  as  stock  the  material  from  these  for  cultivation  on  the 
plains. 

In  other  tropical  plants  the  uniformity  of  the  climate  is  not  the  decisive 
factor  but  the  high  summer  temperatures  necessary  for  the  maturing  of  the 
fruit.  Thus  in  the  narrower  tropical  zone  cocoa  palms  are  found  at  an  alti- 
tude of  1000  m.  but  fruit  is  rarely  produced  at  an  elevation  of  900  m.  In 
the  same  way  Fesca  cites  the  grape  fruit  which  endures  cooler  winter  tem- 
peratures but  requires  a  high  summer  temperature  to  mature  its  fruit.  On 
this  account  its  fruit  will  ripen  in  Japan  between  31  and  32  degrees  latitude 
Vv  ith  an  annual  mean  temperature  of  i6.5°C.  while  in  Bandoeng  on  Java  at  an 
elevation  of  714  m.  and  an  annual  temperature  of  22.7°C.  no  fruit  ripens. 
In  Japan  during  the  months  of  July  and  August  the  temperature  is  high 
enough  to  ripen  the  fruit  when  the  monthly  mean  temperature  exceeds  26° C 
and  even  in  September  is  more  than  24°C.  Such  temperatures,  however, 
are  not  found  in  Bandoeng. 

Tea  is  cultivated  advantageously  in  mountain  environments.  The  tea 
plant  loves  abundant  moisture,  hence  is  naturally  a  sub-tropical  plant.  Tak- 
ing advantage  of  the  climate  of  high  elevations,  it  can  be  grown  successfully 
in  the  tropics.  Thus  it  is  found  on  Java  and  Ceylon  and  in  India  up  to  an  ele- 
vation of  2000  m. ;  the  highest  plantations  in  the  Himalayas  often  lie  at 
about  2200  m.  Tea  from  the  higher  localities  is  in  fact  more  highly  prized. 
To  be  sure,  greater  quantities  of  leaves  are  harvested  on  tropical  plains  but 
the  quality  of  the  leaves  is  poorer. 

It  is  a  mistake  to  attempt  the  cultivation  of  coffee  on  plains  without 
other  shade.  Coffee  is  a  tropical  plant  from  high  elevations  demanding  uni- 
formity of  climate.  The  failure  of  the  crops  on  the  plains  m.ay  often  be 
traced  to  the  great  fluctuations  in  temperature  and  moisture  much  more 
noticeable  there  the  less  the  care  taken  for  shading.   In  the  sub-tropical  zone 


1  Der  Pflanzenbau  in  den  Troppn  und  Subtropen  von  Prcf.  Dr.  Fesca.     Vol.  I. 
Berlin,   Sufserott,   1904.,  p.   41. 


86 

the  summer  temperature  rises  so  high  and  the  winter  temperature  falls  so 
low  that  growth,  whicli  normally  should  be  continued  uninterruptedly,  ceases 
for  the  time  being. 

Cocoa,  however,  to  a  more  marked  degree,  requires  a  uniform  high 
amount  of  moisture  in  tlie  air  and  soil  together  with  shade  and  protection 
from  the  wind ;- — it  can  scarcely  ever  become  too  warm  for  cocoa.  Where 
ii  is  cultivated,  i.  e.  the  narrower  tropical  zone  up  to  an  altitude  of  500  m., 
it  developes  numerous  forms  but  in  all  ecological  varieties,  the  same  re- 
quirements are  felt  as  to  the  climate.  Fesca  (I.e.  p.  240)  recommends  the 
consideration  of  its  need  of  shade  especially  when  the  plantations  are  young. 
Zehntner^  describes  a  disease  affecting  these  plantations.  It  appears 
in  the  form  of  brown  specks  on  the  bark  of  two  or  three  year-old  sap- 
plings.  After  transplantation,  the  little  trunks  are  more  exposed  to  the 
wind  and  the  sun  and  the  bark  cracks  open  in  different  places. 

2.  SLOPE  OF  THE  SURFACE  OF  THE  SOH.. 

The  slope  of  the  surface  becomes  a  factor  which  must  be  considered 
when  the  local  changes  due  to  the  influence  of  the  geographical  position  are 
studied.  Inclinations  (^f  from  1°  to  10"  and  at  the  most  15°  are  the  most  im- 
portant, for  greater  incUnations  are  less  suitable  for  fields.  Noll-  has 
reported  an  advantageous  result  of  the  inclination  of  the  soil.  His  ex- 
periments showed  that,  on  rolling  land  artificially  made,  an  increase  of  the 
cultural  surface  is  obtained  which  in  growing  lettuce  increases  the  yield 
about  31  per  cent.  But  even  a  slight  inclination  has  disadvantages  since 
rainstorms  gradually  carry  off'  the  friable  earth  leaving  the  sub-soil  behind. 

The  point  of  the  compass  toward  which  the  cultural  land  slopes  is  also 
very  important.  Southerly  or  southeastern  slopes  are  most  subject  to  dis- 
aster because  of  the  great  weather  changes.  The  higher  temperature  pre- 
vailing here  forces  the  growth  rapidly  in  spring;  in  summer  the  danger  of 
drying  is  greater,  for  the  soil  is  exposed  not  only  to  the  south  winds  but  also 
to  the  dry  east  and  southeast  winds  and  anyway  to  the  cool,  damp  west 
winds,  but  is  protected  from  the  nortli  wind.  Since,  however,  dry  winds 
prevail  during  the  spring,  i.  e.  the  important  vegetative  period,  the 
southern  declivities  dry  out  very  especially  and  consequently  in  mountains 
the  southern  side  is  replanted  with  great  difficulty,  hence  is  usually  bare. 

The  advantages  of  the  southern  exposure  are  most  marked  in  short 
cool  summers.  Because  of  this  decli\ity  short  lived  plants  will  often  ma- 
ture their  fruit  only  in  such  positions ;  hence  these  slopes  are  best  used 
for  the  cultivation  of  such  plants  as  are  grown  on  account  of  their  fruits 
and  needing  the  increased  action  of  warmth  and  light.  A  colder  exposure, 
however,  would  be  used  to  better  advantage  for  such  plants  as  are  utilized 
for  foliage  and  wood. 


5   Proefstation  voor  Cactio  te   Salatiga.     Bull.   4. 

^  Noll,  Verg-leichende  Kulturversuche.    Cit.   P.ot.  Jahre.sb.    1900.  II,  p.   304. 


87 

When  cultivating  monocarpic  plants,  such  as  vegetables,  the  injury  due 
to  an  otherwise  suitable  exposure,  viz.,  injury  from  spring  frosts,  is  felt 
only  when  the  small  plants  are  put  out  early  in  spring.  There  is  still  greater 
injury  to  sensitive  polycarpic  plants  to  which  our  nut  trees  belong.  Here, 
with  a  favorable,  warm  exposure,  there  is  a  failure  of  the  harvest,  while  in 
the  same  year  nuts  are  produced  abundantly  with  raw  exposures.  In  the 
hrst  case  the  young  shoots  and  blossom  buds,  forced  out  earlier  by  the  great- 
er warmth,  are  blasted  by  the  night  frosts  which  have  not  harmed  the  less 
developed  specimens  found  in  high  raw  exposures. 

In  garden  plantations,  when  taking  advantage  of  such  positions,  ont 
attempts  to  avoid  the  disadvantages  of  the  spring  frosts  by  holding  tht 
plants  back  artificially.  This  is  done  by  leaving  them  covered  longer,  either 
by  heaping  snow  on  them  or  by  increasing  the  mats  and  litter.  With  fruit 
trees  snow,  ice  and  mulching  are  heaped  about  the  base  in  order  to  keep  the 
soil  cool  as  long  as  possible  and  thus  retard  the  root  activity. 

The  cold  northern  exposure  is  best  for  meadows  and  forests.  Eastern 
slopes  are  unsuitable  if  the  soil  is  sandy  because  they  dry  out  more  quickly. 
They  are  therefore  more  valuable  if  the  soil  is  heavy.  The  reverse  is  true 
of  the  damp  westerly  side.  Holzner\  comparing  a  slope  at  50°  north 
latitude,  inclined  about  10°  southerly,  v^-ith  another  with  a  10°  northerly  in- 
clination, also  took  into  account  the  difference  in  warmth  which  can  be 
called  forth  by  an  inclination  of  lo'^,  when  all  other  condtions  are  assumed 
to  be  equal.  The  sum  total  of  the  sun's  rays  falhng  upon  this  soil  bears  the 
proportion  on  the  south  and  the  north  slopes  of  approximately  three  to  two. 

Wollny's-  experiments  on  the  warming  of  field  lands  deserve 
especial  mention.  In  this  work  Kerner's"'  observations  are  cited,  show- 
ing how  differently  the  several  sides  of  a  hill  warm  up.  These  obser- 
vations follow  closely  upon  the  preceding  ones.  The  mean  found  by 
three  years  of  observation  showed  that  the  exposures  may  be  arranged  as 
follows,  decreasing  according  to  their  warmth.  The  warmest  exposure  was 
S.  W.  then  followed  S.,  S.E.,  W.,  E.,  N.E.,  N.W.  and  N.  This  scale  shows 
that  in  reality  the  different  exposures  do  not  act  as  one  would  first  suppose 
theoretically.  It  would  seem  first  of  all  that  with  the  sun  equally  high  above 
the  meridian  the  heating  would  be  equally  strong  and  that,  therefore,  the 
southeast  side  would  receive  the  same  amount  of  warmth  as  the  southwest 
side.  Kerner  explains  that  this  is  not  actually  the  case  by  stating  that  in  the 
afternoon  the  sun  at  the  same  height  acts  more  powerfully  because  the  satu- 
ration of  the  air  with  water  moisture  is  lower  then  than  in  the  morning  hours 
on  which  account  the  absorption  of  the  sun's  rays  is  less  in  the  afternoon. 
Lornez*    gives    still    another    reason.     On    the    southwest    side,    the    dew 


1  Holzner,  Die  Beobachtungen  iiber  die  Schiitte  der  Kiefer  oder  Fohre  und  die 
Winterfarbung-   immergriiner   Gewachse.     Freising    1877. 

-  Wollny,  Untersuchungen  iiber  den  Einflufs  der  Exposition  auf  die  Erwarmung 
des  Bodens.     Forschungen  auf  rtem  Gebiete  der  AgriPculturphysik.    Vol.  I,  p.  263. 

3  Kerner,  Ueber  Wanderungen  des  Maximums  der  Bodentemperatur.  Zeitschr. 
d.  osterr.  Ges.  f.  Meteorologie.    Vol.  \'I,  No.  5,  pp.  65  ff. 

4  Lorenz  und  Rothe,  Lehrbuch  der  Klimatologie.     Wien  1874,  p.  306. 


88 

and  moisture  from  the  rain  have  dried  up  more  than  on  the  south  and  south- 
cast;  it  has  previously  been  warmed  to  some  extent  and  the  same  amount  of 
warmth  falHng  on  a  drier  soil  correspondingly  warms  it  up  more. 

The  monthly  mean  temperature,  however,  and  in  any  case  the  maxi- 
mum warmth  in  the  different  seasons,  is  more  important  for  plants  than  is 
the  annual  average.  In  this  connection  Kerner's  thermometer  observations 
show  that  only  in  winter  (from  November  to  April)  is  the  maximum  soil  tem- 
perature found  on  the  southzvest  side  and  that  conversely,  from  May  until 
August,  the  southeast  side  shows  the  greatest  ivarmth;  in  September  and 
October  the  south  side  is  the  warmest.  This  shifting  of  the  maximum  may 
undoubtedly  be  explained  by  the  dry  east  and  southeast  winds  of  midsum- 
mer which,  a  similar  physical  composition  of  the  soil  being  assumed,  dry 
the  soil  more  quickly  and  thereby  make  it  more  capable  of  being  Avarmed  up. 

While  Kerner's  investigations  were  made  on  a  natural  hill,  consisting  of 
alluvial  sand  and  provided  v/ith  pretty  steep,  grass  slopes  near  Innsbruck, 
Wollny  experimented  with  an  artificial  hill  made  of  sifted  calcareous  sandy 
humus  whose  surface  formed  an  angle  of  15°.  Here,  therefore,  the  con- 
ditions were  adapted  to  a  land  whicli  could  be  used  agriculturally. 

Wollny's  observations  confirm  first  of  all  those  of  Kcrner,  that  the  max- 
imum of  warmth  shifts  from  southeast  in  summer  to  southwest  in  winter. 
Further,  in  general,  the  southern  slopes  (S.JV.,  S.,  S.E.)  are  exposed  to  great- 
er fluctuations  in  temperature  /ban  the  northerly  slopes  which  respond  to  the 
smallest  fluctuations.  In  another  series  of  experiments  ascertaining  the 
temperature  of  the  slopes  of  beds  set  at  different  angles  to  the  compass,  com- 
pared during  the  warmer  season  with  the  temperature  on  a  level  field  sur- 
face depressed  15  cm.,  gave  the  follov/ing  results.  The  south  side  is  the 
warmest,  then  follows,  as  the  medium,  the  level  worked  surface ;  then  in  the 
third  place  the  east  and  west  sides,  while  the  northern  exposure  of  the  bed 
seems  to  be  the  coldest.  If  now  the  bed  is  placed  east  and  west,  one  long 
surface  lying  to  the  south,  the  other  to  the  north,  these  two  surfaces  show 
the  greatest  difference  in  temperature  when  vegetation  can  still  be  found. 
Therefore,  if  the  field  is  to  be  laid  out  in  plots,  it  is  better  to  have  them  run 
north  and  south.  Cultivation  on  level  surfaces  with  a  lower  temperature 
than  on  the  slope  inclined  to  the  south  but  exceeding  that  of  other  exposures 
is  the  most  advantageous  on  account  of  the  even,  and,  on  an  average,  higher 
warming  of  the  soil. 

Later  experiments',  however,  show  the  advantages  of  a  position 
inclined  to  the  south,  but  these  are  only  evident  when  the  moisture  is  suffici- 
ent and  constant.  In  dry  weather  or  irregular  precipitation  the  harvest  is 
smaller.  Indeed,  in  extremely  dry  weather,  the  greatest  yield  is  from  the 
northerly  side,  which-  otherwise  gives  the  smallest.  In  fact  the  yield  becomes 
less  as  the  angle  of  inclination  increases.  Then  follow  the  west  and  east  ex- 
posures.   The  smallest  yield  was  usually  on  the  south  side. 

1  Wollny,  E.,  Untersuchumgen  liber  die  physikal.  Eigenschaften  des  Bodens  auf 
das  Produktionsvermogen  der  Nutzgewachse.  Forsch  Geb.  d.  Agrikluturphysik  XX, 
Part   3,    1899,    p.    291. 


Naturally  other  conditions  also  enter  into  the  question;  thus,  for  ex- 
ample, color  also  becomes  a  considerable  quantity  when  the  soil  is  sufficiently 
damp  and  has  a  favorable  mechanical  form.  The  darker  the  earth  the  more 
plant  growth  is  favored.  Mixed  soils  give  better  results  than  clear  peat, 
sand  or  loamy  soils. 

a.     Too  Steep  Slopes. 

Soil  surfaces  of  more  than  15°  to  20°  inclination  in  a  small  area  must  be 
used  so  far  as  possible  for  meadow  and  grazing  land  if  gardening  and  vine- 
yards do  not  warrant  expensive  terracing.  If  the  inclination  of  any  surface 
approximates  45°  it'is  urgently  advisable  to  retain  all  existing  vegetation  and 
to  attempt  forestration  or  to  complete  it  with  suitable  planting. 

This  utilization  of  surfaces,  at  such  an  inclination,  is  not  only  the  best 
method  but  also  the  best  protection  of  the  lower  adjacent  cultivated  land. 
Such  steep  slopes,  only  found  in  mountains,  rarely  have  a  deep  loam  even 
when  covered  with  forests.  Under  such  conditions  only  the  thickly  matted 
root  systems  of  the  trees  can  keep  off  the  destructive  gullying  and  washings 
after  heavy  rains  and  from  storms  after  continued  drought  if  the  soil  con- 
tains much  sand.  The  moss  cushions  of  forests  retain  moisture  necessary 
for  the  further  disintegration  of  the  rocks  and  increase  the  tendency  to 
form  springs ;  which  benefit  is  felt  only  on  the  plains.  It  is  easy  to 
observe,  that  the  pith  has  become  eccentric  when  the  trees  are  growing  on 
steep  declivities.  Mer\  studying  firs  and  spruces  of  the  Vosges,  ob- 
served that,  in  trees  growing  on  steep  cliffs,  the  annual  rings  are  more  strong- 
ly developed  on  the  side  toward  the  upper  incline  than  on  that  toward  the 
declivity.  This  occurs  especially  at  the  base  of  the  trunk.  On  cliffs  lying 
toward  the  north  and  east,  the  firs  and  spruces  were  not  only  taller  and 
stronger  but  the  annual  rings  of  the  individual  trees  varied  more  markedly 
in  the  same  points  of  the  compass.  If  the  trees  have  to  grow  twisted,  the 
annual  rings  show  a  stronger  development  on  the  convex  side  at  the  points 
of  twisting. 

Unfortunately  our  cultivated  lands  show  the  sad  results  of  the  deforesta- 
tion of  steep  slopes.  The  forest  was  here  the  product  of  consecutive  pro- 
cesses many  hundred  years  old,  which  probably  began  with  the  colonization 
of  lichen  encrustations  on  the  naked  rock.  Through  the  retention  of  the 
products  of  weathering,  these  and  gradually  larger  plants  began  to  form  a 
surface  soil  and  with  their  decomposed  bodies  furnished  the  first  humus 
substances,  making  the  soil  better  and  better  adapted  for  the  growth  of 
higher  plants.  Once  robbed  of  this  covering  of  vegetation,  the  bursts  of  rain 
sweep  the  surface  soil  downward,  exposing  the  stony  sub-soil  on  the  heights 
and  filling  up  the  tilled  land  on  the  plains.  With  greater  deforestation  of 
the  mountain,  the  water  supply  of  the  mountain  streams  becomes  the  more 
irregular  and,  with  more  frequent  spring  floods  in  the  lowlands,  covers  them 
with  sand;  also  in  dry  sum.mers  the  streams  are  without  water. 


1   Mer,   Des  causes   qui   produisent  I'excentricite   de  la  moelle   dans  les 
Compt.  Rend.  Vol.  CVl,   1888,  p.   313. 


go 

Aside  from  tlic  direct  injury  of  the  stones  carried  down  with  the  mass- 
es of  earth,  the  chief  destruction  Hes  essentially  in  the  covering  of  the  parts 
of  the  plants  which  hitherto  had  been  exposed  to  the  free  air.  Many  plants, 
however,  die  if  they  are  permanently  planted  too  deep  and  only  those  can 
withstand  being  covered  with  soil  which  possess  the  ability  of  readily  strik- 
ing adventitious  roots.  Among  herbacous  plants  the  grasses  growing  on 
dunes  should  be  emphasized  especially  as  having  this  quality  (Arundo 
arenaria  L.,  Elymus  arenarius  L.,  etc.)  ;  our  quack  grass  (Agropyrum  re  pens 
P.  B.)  also  easily  works  its  way  out  through  a  heavy  covering.  Among 
trees,  the  willows  and  poplars  withstand  such  a  covering  without  great  dis- 
advantage, and  especially  the  (Seekreuzdorn)  (Hippophae'  rhamnoides  L.), 
which  grows  on  gravel  and  sand,  is  found  on  the  coasts  of  Germany,  France 
and  England,  and  serves,  with  its  flat  lying  roots,  as  a  means  of  retaining 
the  dunes.  In  opposition  to  this,  the  bases  of  the  trunks  of  many  trees,  as 
for  example,  fruit  trees,  are  very  sensitive  to  deep,  lTea\y  soil  covering. 
Also  in  transplanting  trees,  or  in  grading,  a  change  in  level  covers  the  base 
of  the  trunk,  which  has  been  exposed  to  the  air,  leads  to  a  weakening  and 
shows  phenomena  of  disease  which  will  be  treated  of  more  in  detail.  In 
potted  plants  the  Ericas  are  most  sensitive  to  the  smothering  of  too  deep 
planting.  It  must  be  assumed  that  the  cause  of  death  is  a  lack  of  oxygen 
for  the  roots  which  have  been  set  too  deep  and  covered  by  large  amounts  of 
earth. 

Landslides,  besides  covering  the  lower  lands,  expose  the  roots ; 
which  fact  deserves  attention.  So  long  as  the  forest  remains  intact, 
interwoven  roots  form  a  network  with  such  small  meshes  that  the  soil  is 
held  firm.  If,  however,  holes  are  torn  in  this  by  the  h.and  of  man  or  by 
storms,  so  that  the  plants  are  uprooted,  then  the  soil  begins  to  push  down 
from  the  higher  places  and  in  fact  the  m^ore  quickly,  as  the  soil  is  more 
broken  and  the  wind  finds  the  more  access  to  the  torn  places.  Aside  from 
processes  of  this  kind  which  take  place  unceasingly  in  high  mountains  and 
before  which  we  usually  stand  powerless,  changes  in  the  forests,  even  on 
the  plains,  take  place  constantly  as  a  result  of  the  exposure  of  the  roots  from 
the  working  away  of  the  soil.  This  is  especially  the  case  in  forests  in  hilly 
places  when  streets  are  cut  through.  The  forest  soil  is  usually  porous  or 
becomes  so  by  drying  and  as  soon  as  the  street  cuts  through  a  hill  over- 
grown with  large  trees,  the  free  roots  are  found  at  the  edge  of  the  cut,  from 
between  which  the  soil  has  fallen  out  or  been  worked  away.  The  injury  is 
two-fold  since  the  exposed  side  of  the  root  crown  weakens  the  anchorage  of 
the  trees  and  the  decreased  supply  of  water  impairs  the  formation  of  the 
tree  top. 

The  statement  that  the  injury  caused  by  such  cutting  of  the  forest  for 
shortening  the  road  is  compensated  for  by  the  increased  growth  of  trees  is 
an  error.  To  be  sure  this  may,  under  certain  circumstances,  effect  a  con- 
siderable  increment  of  growth,   as,   for   example,   Hartig's^   investigations 

1  Havtig,  Ueber  den  Lichtstandszuwachs  der  Kiefer.  Allg.  Forst-  u.  Jagdzei- 
tung.  LXIV,  1888,  Januar. 


91 

show.  He  found  in  pines  147  years  old  which  had  been  standing  free  for 
seventeen  years,  that  the  growth  had  been  doubled  in  the  first  ten  years, 
especially  in  the  lower  part  of  the  trunk,  where  the  amount  of  wood,  that  is 
the  dry  weight,  had  also  increased.  But  he  also  demonstrated  that  the  in- 
crease fell  to  the  earlier  amount,  when  the  food  in  the  soil  was  taken 
up  by  spruces  which  were  set  out  there.  In  trees  whose  roots  are  exposed 
on  one  side,  there  is  a  less  water  content  of  the  soil  which  also  retards  the 
absorption  of  foods  and  the  influence  of  light  is  scarcely  able  to  cause  an 
increase  of  growth.  But  even  if  a  considerable  increase  of  growth  is  ob- 
tained by  the  sudden  thrusting  of  the  trees  into  the  light,  no  agricultural  ad- 
\antage  is  constantly  connected  with  it.  In  the  first  place,  the  branching  is 
increased  and,  in  the  second,  the  wood  due  to  the  rapidly  increased  growth 
is  coarse  grained.  This  is  deduced  from  the  observations  of  Cieslar  and 
Janka^  who  investigated  the  spruce  wood  produced  by  long-standing 
cultivation.  Produced  in  great  quantity  the  wood  was  of  strikingly  low 
specific  gravity  because  the  autumn  wood  made  a  scanty  growth  and  the 
tracheids,  in  the  main  part  of  the  annual  ring,  were  unusually  wide.  On 
the  other  hand,  the  danger  of  drying  of  the  top,  or  blight  of  the  tip,  often 
becomes  greater.  This  applies  also  to  deciduous  trees  grown  in  dense  plan- 
tations. The  crowns  are  suddenly  freed,  their  leaves,  in  structure  and  func- 
tion, are  adapted  to  a  moderate  amount  of  illumination,  can  not  endure 
the  increased  transpiration  and  the  excess  of  light  so  that  the  tips  of  the 
branches  partially  die  back.  Therefore  it  is  urgently  advised  in  the  interest 
of  retaining  old  tracts  of  woods,  specially  in  sandy  soil,  to  avoid  cutting 
through  the  hills  to  lay  out  roads,  preferably  to  lay  the  road  out  around  the 
hill.  According  to  Hartig-  the  shock  of  the  sudden  opening  may  also 
lead  to  injury  if,  with  the  increased  supply  of  light,  the  top  is  stimulated 
to  too  active  growth.  This  continues  some  years,  while  The  a\  ailable  quanti- 
ty of  nutriment  in  the  soil  lasts.  Because  the  leaf  material  is  increased  as  a 
result  of  the  intensity  of  the  light,  much  larger  amounts  of  mineral  stuifs 
naturally  are  required  than  with  growth  in  dense  tracts.  Hov/ever,  when 
parts  of  forests  are  exposed,  soluble  mineral  food  material  can  not  be  pro- 
vided in  sufficient  quantity  by  the  influence  of  the  atmosphere,  consequently 
after  a  good  growing  period  there  is  a  decrease  in  growth  due  to  the  "im- 
poverishment of  the  soil."  Following  a  scarcity  of  material,  however,  no 
matter  whether  due  to  an  actual  lack  of  the  substance  or  to  its  insufficient 
absorption  on  the  part  of  the  tree,  as  a  result  of  injuries  to  the  roots  or  a 
lack  of  water,  there  is  not  only  a  decrease  of  growth  but  also  the  constitution 
of  the  wood  is  weakened.  As  when  growth  is  forced,  only  the  thin-walled 
spring  wood,  the  vascular  tissue,  is  formed  and  but  little  or  no  strengthening 
tissue,  which  is  present  in  late  wood. 


1  Cieslar,  A.  und  Janka,  G.,  Studien  liber  die  Qualitat  rasch  erwachsenen  Fich- 
tenholzes.    Centralbl.  f.  d.  gesamte  Forstwesen  1902.    Part  8. 

-'  Hartig,  R.,  Ueber  den  Einflufs  der  Kronengrofse  und  der  Nahrstoffzufuhr  aus 
dem  Boden  auf  die  Grclfse  und  Form  des  Zuwachses  etc.  Forstl.  naturw.  Zeitschrift 
VII,    1898,    p.    78. 


92 

1).     Growth  of  Stilts. 

(i'.r.KVATIOX   OF  THE  RoOTS  OF  TrEKS.  ) 

In  this  connection  it  is  advisable  to  consider  still  more  closely  the  fact 
that  large  forest  trees  grow  with  their  older  root  branches  above  the  ground, 
so  that  the  base  of  the  stem  is  carried  on  a  number  of  stilts.  This  position 
gives  scantier  anchorage  to  the  trees  and  results  disadvantageously  since 
they  are  more  easily  blown  down  in  wind  storms.  In  addition  to  this  there 
is  a  smaller  provision  of  water  and  the  roots  are  peculiarly  sensitive. 

These  stilted  growths  form  two  types ;  first,  in  spruces,  where  the  base 
of  the  trunk  is  raised  high  above  the  soil  and  the  strong  branches  of  the 
root  crown  have  never  been  below  the  top  of  the  earth ;  second,  in  pines,  not 
rare  on  strongly  undulating  sandy  soil,  in  which  the  base  of  the  trunk  has 
previously  been  covered  with  soil  or  may  even  frequently  rest  on  its  surface 
so  that  part  of  the  crown  is  covered  with  earth,  while  the  other  part 
has  been  uncovered  by  the  washing  away  of  the  soil.  In  extreme  cases 
the  soil  slides  out  from  under  the  trunk  so  that  the  whole  tree  stands  on 
stilts. 

Examples  of  the  first  type  are  described  and  illustrated  by  L.  Klein^ 
(Figure  4).  He  explains  the  production  of  the  phenomenon  as  follows: — 
If  spruces  or  firs  have  been  felled  in  the  mountains  a  stump  is  left 
standing  which  weathers  gradually  on  its  upper  surface  and  becomes 
covered  with  moss.  Later  Vaccinia  etc.  infest  this  moss  cushion  beneath 
which  is  produced  a  thin  humus  layer.  If  self-sown  spruces  or  firs  begin  to 
grow  on  the  moss-covered  surface  of  the  stump,  the  little  young  growing 
roots  creep  under  the  moss-covering  in  all  directions  over  the  surface  of  the 
stump  and  then  down  its  sides  to  the  soil,  and  develop  further  there,  like  every 
other  root.  In  the  course  of  many  decades  the  roots  become  stronger,  the  old 
stump  slowly  rots  away.  Klein  answers  the  question,  as  to  why  one  usually 
finds  spruces  much  more  rarely  than  firs  and  never  any  deciduous  trees  with 
this  stilt-like  growth,  when  he  states  that  the  water  needed  by  deciduous 
trees  is  possibly  ten  times  as  great  as  that  of  conifers  and  that  on  this  ac- 
count the  seedling  of  a  deciduous  tree  would  not  find  enough  water  perma- 
nently on  the  surface  of  the  stump  for  its  development.  I'-ven  if  deciduous 
trees  do  not  grow  on  stilts,  yet  similar  structures  such  as  the  sheath  growth, 
may  nevertheless  be  found.  This  occurs  especially  in  willows.  Where  old 
willows  grow  along  country  roads,  one  finds  at  times  the  appearance  of  a 
new  trunk  growing  independently  out  of  the  decayed  heart  of  the  hollow 
old  trunk,  so  that  the  woody  cylinder  of  the  old  trunk  surrounds  the  young 
tree  like  a  wide  sheath.  Such  cases  are  easily  explained  in  the  pollarded 
willows  when  the  crown  is  entirely  cut  off  every  year  or  every  second  year,  in 
order  to  obtain  as  many  young  shoots  as  possible.  With  the  rapid  rotting  of 
willow-wood  on  large  pollarded  surfaces,  soil  accumulates  very  quickly  from 


1   Klein,  L,.,  Die  botanischen  Naturdenkmiiler  des  Grofsherzogtums  Baden  u.  ihre 
Erhaltung-.  Festrede.  Karlsruhe  190-1,  p.  13,  Fig.  7. 


93 

the  dust  blown  from  the  street  into  the  depressions  of  the  wounded  surface, 
in  which  seeds  of  all  kinds  of  weeds  find  instant  lodgment.  Now  if  a  wil- 
low-seed falls  into  one  of  these  accumulations  of  soil,  the  young  seedling 
finds  space  for  development  and  its  roots  finally  reach  the  soil  through  the 
rotted  wood  of  the  old  trunk.  When  an  adventitious  root  of  especial  length 
grows  downward  from  the  pollarded  surface  at  the  crown  of  the  tree,  with- 
in the  hollow  trunk,  it  has  the  appearance  of  a  young  trunk. 


Fig-.  4.  Stilted  spruce  near  Schc^iiinzach  in  Stiibewasen.  (After  L.  Klein.) 
A  case,  due  probably  to  the  same  conditions,  which  cause  the  stilt-like 
growth  of  spruces,  was  shown  as  recently  as  the  8o's  of  the  last  century  in 
Kohlhasenbriick  near  Neubabelsberg  (District  of  Potsdam).  The  stump 
of  an  old  oak,  about  75  cm.  high  on  the  village  street,  had  formed  a  broad 
hollow  cylinder  by  the  rotting  of  all  of  the  heart  wood.  This  was  half  filled 
with  rotten  wood  and  earth  and  a  healthy  oak,  possibly  thirty  years  old, 
stood  in  this  as  in  a  sheath. 

In  spruce  plantations  one  finds  at  times  the  so-called  "Harp-trees"  in 
which  a  number  of  side  branches  have  become  elevated  at  right  angles  to  the 


94 

main  trunk  wliich  tlie  wind  lias  blown  down,  part  of  whose  roots,  however, 
still  remain  in  the  soil,  and  therefore  are  still  livinj^.  Adventitious  roots 
serve  the  needs  of  these  growths  for  nutrition.  The  spruce  is  certainly  the 
one  of  all  the  conifers  which  can  most  easily  overcome  all  injuries  by  develop- 
ing adventitious  organs. 

It  also  withstands  pruning  \ery  well  and  can  therefore  be  used  ad- 
vantageously for  hedges,  only  the  hedges  must  be  thinned  constantly,  or 
they  become  bare  underneath.  The  ability  to  form  new  tips  when  the  old 
ones  have  been  removed,  a  characteristic  of  spruce  and  Araucaria,  is  taken 
advantage  of  in  horticulture,  in  propagating  by  cuttings. 

On  the  other  hand,  the  regeneration  ])henomena  of  the  older  i)ine  are 
most  stable  and  tixed.  The  secr)nd  type  of  stilt-growth  occurs  es[)ecially 
with  this  tree,  if,  in  a  hilly  place,  the  porous  sandy  soil  slides  downwards 
from  the  efifects  of  grading.  In  the  struggle  for  existcr.ce,  how^ever,  the 
pine  wdien  grown  from  seed  can  withstand  much  better  exposure  of  its  roots 
than  spruces  and  firs ;  this  is  because  the  roots  habitually  grow  perpendicu- 
larly into  the  ground.  In  the  two  illustrations  which  reproduce  two  examples 
of  Pinus  sihestris  from  the  Grunewald  (back  of  Paulsborn)  near  Berlin,  this 
perpendicular  downw^ard  growth  is  shown  especially  well  in  the  bide  roots.     . 

Figure  5  show^s  two  pines  standing  back  of  one  another  with  the  bases 
of  their  trunks  about  i  meter  above  the  ground.  The  strong  main  roots  send 
their  side  branches  (arising  directly  on  the  underside)  into  the  ground  in 
parallel  and  perpendicular  directions,  indicating  that  the  pine  roots  deeply. 
The  front  tree  is  possibly  60  years  old ;  the  specimen  behind  it  is  younger. 
Figure  6  is  taken  from  another  side  and  shows  the  side  roots  starting  at 
right  angles  from  the  main  branches  which  spread  horizontally  from  the 
root  crowns.  However,  in  the  middle  of  the  stilt  appearance,  may  be  dis- 
tinctly recognized  the  original  main  root  wdiich  as  a  prop  has  grown  directly 
into  the  earth  and  which  endures  the  chief  strain  of  anchoring  the  tree  in 
the  sandy  soil.    The  tree  is  still  w-ell  covered  with  needles. 

One  more  important  j)b,enomenon  must  be  mentioned  in  connection  with 
this  form  of  stilt-growth,  viz.,  nianv  woody  tubers  with  a  dense  cf)\'ering  of 
bark  grow  in  rows  on  the  ui)pcr  sides  of  the  strong  roots.  These  in  figure  7, 
reproduced  natural  size,  form  hemispherical,  wart-like  prominences  up 
to  1.5  cm.  high,  with  a  crater-like  depressed  centre.  They  correspond  wath 
the  rest  of  the  root  in  color  and  bark. 

It  is  supposed  that  this  arises  from  an  adventitious  sprout  formation 
in  which  the  young  shoots  have  died  immediately  and  a  heavy  scar  has  been 
formed.  The  fact  that  these  growths  come  only  on  the  upper  side  lends 
strength  to  this  supposition.  It  is  well  known  that  when  there  is  this  ten- 
dency toward  adventitious  growths  in  trees,  the  forniation  of  such  buds  of 
all  sizes  occurs  most  strongly  on  the  side  toward  the  light  (Tilia,  Acer). 
This  supposition  has  not  been  generally  confirmed,  as  the  cross-section  (Fig. 
8)  shows.  This  illustrates  a  seven  years'  overgrowth  of  a  centre  of  disease 
formed  by  a  homogeneous  mass  of  resin.    This  resin  gall,  produced  by  resin- 


95 


Fig.  5.     Stilted  pine  from  Gruiiewald  near   Berlin.      (Orig.) 


Fig-.  6.     Stilted  pine  from  Grunewald  near  Berlin,     (Grig-) 


96 


osis  of  the  wood,  ruptured  on  the  outsid 
ing  years.  The  edges  of  the  over- 
growth, still  connected  in  the  first  few 
years,  have  grown  back  farther  and  ' 
farther; — in  this  way,  a  crater-like 
opening  was  produced  at  the  top  of  the 
woody  tuber.  The  new  annual  rings 
turn  to  resin  every  year  and  always  in 
the  first  spring  wood,  which  consists  in 
part  of  parenchymatically  forme  1 
cells.  The  resin  holes  (H)  are  pro- 
duced by  the  drying  up  of  the  resini- 
fied  tissues,  in  part  also  by  exudation 
of  the  resin.  The  edges  of  the  over- 
growth are  further  apart  each  time  so 
that  the  last  ones  (U)  are  widely  sep- 
arated. In  this,  they  show  a  most  ir- 
regular construction  often  changing 
between  every  two  medullary  rays  in 
the  same  annual  ring.  In  the  drawing 
G  is  the  normal  wood  in  cross-sec- 
tion and  M  the  regular  course  of 
the  tracheids  in  longitudinal  section. 
These  are  in  the  same  annual  ring  just 
as  in  true  gnarls. 

I'^or  this  reason  these  structures 
musi  be  classed  with  the  resin  galls. 
So  far  as  their  production  is  concerned. 


e  and  was  overgrown  in  tlie  follow- 


,u 

H^^g^l^ 

^^ 

m. 

H 

HT 

Fig.   8.     Crcis.s-section  through  a  resin   gall  on   the 
stilt-like   root   of  the   pine.     (Orig.) 


Fig.  7.  Resin  galls  with  gnarl 
growth  on  the  upper  side  of  the  stilt- 
like root  of  the  pine  (natural  size). 
(Orig.) 


t  must  be  assumed  that  the  exposed 
root  shows  small  centres  of 
injury  from  extremes  of 
weather  on  its  upper  side, 
i.  e.  the  one  most  exposed 
to  such  extremes.  These 
centres  of  injury  have 
caused  a  resinosis  of  the 
tissues,  or  rather,  a  com- 
I)lete  resinous  liquefaction. 
We  may  assume  that  frost 
has  caused  the  injuries,  and 
especially  late  frosts,  since 
these  appearances  are  al- 
ways found  in  the  first 
formed  spring  wood.  The 
production  of  these  resin 
galls  shows  that  the  roots 


97 

exposed  in  the  stilt-like  growth  are  very  sensitive.  Tf  this  is  true,  less  extreme 
cases  Yi^ill  have  to  be  taken  into  consideration  and  a  further  warning  be 
given ;  when  possible  the  root  body  must  be  guarded  from  complete  exposure. 
When  roots  are  partially  exposed  their  bark  is  liable  to  be  broken  on  the 
upper  side  by  pedestrians,  with  the  result  that  much  stronger  annual  rings 
develop  on  the  under  side  which  is  protected  from  such  injuries  by  the  earth. 
The  cultivation  of  seedlings  of  the  different  species  of  our  common  coni- 
fers under  the  same  conditions  gives  the  best  demonstration  of  these  root 
systems.  Nobbe^  carried  his  experiments  out  with  the  following  re- 
sults : — Six  months  after  sowing,  the  pines  had  3135  root  fibres  with  a  total 
length  of  12  meters,  the  spruces  253  fibres,  all  together  2  meters  in  length  and 
the  fir,  134  fibres  with  a  total  length  of  i  meter.  In  one  year,  in  fertilized 
sandy  soil,  the  tap-roots  of  the  pine  seedling  penetrated  almost  one  meter 
deep,  while  the  spruce  and  fir,  under  absolutely  the  same  experimental  con- 
ditions, went  down  only  one  third  as  far.  At  the  same  time  the  young  pine 
developed  five  series  of  roots,  the  spruce  four  and  the  fir  three.  In  decid- 
uous trees,  oaks  and  beeches.  Tharandt's  experiments  showed  that  in  the 
same  way  they  form  even  in  the  first  year  a  widely  branched  root  system  with 
tap  roots  nearly  a  meter  long. 

Spruce  and  fir  with  their  weaker  root  apparatus,  which  almost  im- 
mediately spreads  out  flat,  need  a  moist  soil,  while  the  pine  can  do  without 
moisture,  in  fact,  easily  suffers  from  it.  In  seedling  plantations,  where  fir 
and  spruce  thrive,  the  pine  very  often  shows  pathological  resin  ducts  in  the 
wood  of  its  young  trunk.  The  deep  growth  of  the  pine  also  explains  its  so- 
called  "contentment"  and  its  healthy  growth  in  almost  sterile  sand.  Like 
the  lupin  it  understands  how  to  meet  its  need  for  water  and  food  from  the 
deep  layers  of  the  soil  but  it  demands  good  drainage. 

This  natural  advantage  of  a  tap  root  penetrating  at  once  to  great  depths 
is  made  use  of  only  where  seeds  are  planted  in  forests  without  necessity  for 
transplantation.  In  the  controversy  in  forestry  circles  as  to  the  best  methods 
of  planting,  in  considering  the  pine,  we  would  always  place  ourselves  on  the 
side  of  those  favoring  sowing  in  the  permanent  place.  For  the  spruce  and 
fir,  we  consider  transplanting  from  the  seed  bed  to  be  more  advantageous. 
In  any  event  the  method  of  seeding  is  not  the  only  factor  in  a  healthy  devel- 
opment, but  soil  and  position  are  often  decisive.  We  can  not  consider  ad- 
visable the  present  endeavor  to  plant  pines  everywhere,  because  they  give  the 
quickest  and  therefore  the  best  return  from  the  soil.  In  our  own  forests 
comparisons  of  the  trees  in  deep  lying  or  marshy  places  vvith  those  on  free, 
dry  regions  show  that  in  the  marshy  localities  there  is  an  impoverished  growth 
and  often  a  premature  dropping  of  the  needles,  and  that  in  hilly  sandy  soil, 
wnth  deep  lying  ground  water,  the  trees  develop  to  their  full  strength,  even 
l;eing  well-preserved  when  their  roots   are  exposed  on  stilts.    Rechinger^ 


1  Dobner's  Botanik  fiir  Forstmanner.    IV  Edition,  revised  by  Fr.  Nobbe,  Berlin. 
Paul   Parey.     1882,    p.    130.  ,         mno    t    „    qq- 

2  Rechinger,  Bot.  Beobacht.  in  Schur.  cit.  Bot  Jahresber.  1902,  1,  p.  66,- 


98 

mentions  the  occurrence  of  stilt-roots  in  marshy  forests,  in  which 
Alnus  glutinosa  predominates  while  isolated  Qnercus  pcdunculaia,  Rhamnus 
Frangula  and  Salix  cinerea  occur. 

A  tliird  cause  of  the  stilt-like  growth  still  remains  to  be  mentioned 
which  is  different  in  that  the  trees  are  positively  elevated,  while,  in  the  cases 
already  mentioned,  the  base  of  the  trunk  remains  at  the  place  where  the  seed 
was  sown.  White^  describes  occurrences  of  this  kind.  He  thinks  that  on 
rocky  soil,  where  the  roots  must  grow  flat,  the  trees  are  gradually  forced 
out  of  the  ground  by  periods  of  frost  and  draught  to  which  they  are  peculiarly 
susceptible. 

c.     Too  Deep  Planting. 

Too  Deep  Planting  of  Trees. 

Almost  all  our  trees,  in  their  later  life,  stand  in  a  position  different  from 
that  of  the  seed  beds  in  wdiich  they  develop.  For  fruit  trees  must  have  a  sec- 
ond transplanting  when  young  in  order  to  obtain  an  abundant  ramification  of 
the  root  body.  Since  these  trees  must  be  so  transplanted  great  care  should  be 
taken  that  they  are  not  planted  deeper  than  they  originally  stood.  Exper- 
ience teaches  that  trees  can  indeed  be  destroyed  through  a  disregard  of  this 
warning.  In  fact  many  practical  workers  recommend  that  each  tree  in  its 
new  position  be  oriented  exactly  as  before  in  regard  to  the  points  of  the 
compass,  since  they  think  that  many  kinds  of  bark  injuries  from  heat  and 
frost  can  thus  be  avoided. 

Otto-  has  attempted  to  decide  the  ciuestion  whether  the  branches  of 
apple,  pear  and  cherry  trees  develop  differently  in  the  several  points  of  the 
compass.  By  chemical  analysis,  he  found  essential  differences  in  the  com- 
position of  the  differently  oriented  one  year  old  branches.  The  water  and 
nitrogen  content  is  the  smallest  on  the  east  side,  while  the  content  in  dry  sub- 
stances is  the  greatest  there  ;  but  the  water  and  nitrogen  content  is  greatest  on 
the  north  side.  This  would  indicate  that  the  branches  were  not  so  fully  ma- 
tured here  as  on  the  other  side  of  the  tree. 

Kovessi^  considers  the  cause  of  a  decreased  formation  of  blos- 
soms to  be  the  greater  amount  of  water  and  the  lesser  ripening  of  the  wood 
of  the  branches.  The  number  of  blossoms  and  fruit  was  certainly  proved 
to  be  dependent  on  the  water  supply  of  the  previous  year.  The  tree  bears 
better,  if  the  water  supply  is  scant.  Anatomically,  the  differences  in  the 
maturity  of  the  branches,  according  to  the  points  of  the' compass,  can  scarce- 
ly be  determined  since  the  structure  of  the  same  annual  ring  fluctuates  too 
greatly  within  the  different  internodes  of  a  branch*. 


1  WTiite,  Theodore,  Mechanical  elevation  of  the  roots  of  trees.     The  Asa  Gray- 
Bull.    Cit  Bot.  Jahresb.  1897,  L  p.   85. 

2  Otto,  Arbeiten  der  Chemischen  Versuchsstation  zu  Proskau.     Cit.  Bot.   Cen- 
tralblatt  1900,  Vol.   82.  Nos.   10-11. 

3  Kovessi,   P.,   LTeber  die   Beziehung  des   Wassers   zur  Reife  der  Holzpflanzen. 
Biedermann's  Centralbl.  1902,  p.  161. 

*  Sorauer,  Beitrag  zur  Kenntnis  der  Zvveige  unserer  Obstbaiime.    Forsch.  a.  d. 
Gebiete  d.  Agrikulturphysik,  Vol.  Ill,  Part  2. 


99 

Also,  we  know  nothing  definite,  at  least  nothing  which  holds  good  in 
general,  of  the  anatomical  changes  taking  place  when  trees  are  planted  too 
deep.  In  some  cases  it  has  been  observed  that  the  ducts  are  filled  with 
brown,  gum-like  stifif  masses,  in  others  they  are  filled  with  tyloses  accom- 
panied by  a  brown  discoloration  of  the  walls.  Gummy  swellings  of  the  mem- 
branes are  not  infrequent.  But  these  are  all  only  occasional  observations 
and  experimental  study  of  the  question  is  still  needed. 

We  will  limit  ourselves  on  this  account  to  the  enumeration  of  the  dis- 
coveries already  made  as  to  the  influence  of  the  two  factors  occurring  most 
generally  when  trees  have  been  planted  too  deeply— the  lack  of  oxygen  and 
the  excess  of  carbon  dioxid.  We  know  that  plants  without  a  supply  of  oxy- 
gen gradually  die.  If  the  living  cell  can  take  up  no  oxygen,  it  changes  the 
direction  of  its  life-functions.  Later  it  passes  over  into  a  state  of  rigidity, 
since  the  phenomena  of  movement  cease  in  the  cytoplasm.,  the  sensitiveness 
to  stimuli  is  lost  and  growth  becomes  inhibited.  The  plant,  however, 
does  not  die  immediately.  It  continues  to  give  off  carbon  dioxid  for 
some  time  and,  with  a  renewal  of  the  oxygen  supply,  it  can  even  re-assume 
its  usual  functions  after  a  rather  long  apparent  death.  In  this  continuation 
of  life  without  oxygen  (anaerobic)  the  oxygen  necessary  for  the  life  pro- 
cesses must  be  furnished  from  the  substance  of  the  plant  itself  and  has  been 
called  intra-molecular  respiration. 

Lechartier  and  Bellamy^,  in  a  series  of  experiments,  have  proved 
that  alcohol  is  formed  in  the  parenchyma  cells  growing  without  a 
supply  of  oxygen,  not  only  in  our  pitted  and  other  fruits,  but  also  in  the  roots 
and  leaves.  Stocklasa  has  also  proved  most  recently  tliat  there  is  a  forma- 
tion of  lactic  acid.  Even  in  fungi  (Agaricns  campestris),  Muntz-  found 
alcohol  and  hydrogen  in  considerable  quantities  if  the  fungi  were  kept 
for  some  time  in  air  free  from  oxygen.  The  material  for  this  alcohol  can 
have  been  furnished  by  the  kind  of  sugar  alone  present  here,  named  man- 
riose,  while  in  other  fungi,  producing  only  alcohol,  (without  hydrogen)  in 
an  atmosphere  of  carbon  dioxid,  the  trehalose  must  have  been  fermented. 
If  the  fungus  is  not  kept  too  long  in  the  oxygen-free  air,  it  can  take  up  again 
its  normal  life-functions,  as  has  recently  been  proved  by  Krasnosselsky'' 
for  Mucor  spinosa  and  Aspergillus  .niger.  Adolf  Mayer*  had  earlier 
expressed  his  opinion  that  fermentation  produced  by  yeast,  is  a  re- 
sult of  respiration  in  the  absence  of  oxygen.  Pasteur"'  and  Bohm" 
had  really  proved  already  that  all  more  highly  organized  land  and  water 
plants  behave  in  a  very  similar  way,  since,  in  media  free  from  oxygen,  they 

1  De  la  fermentation  des  pommes  et  des  poires.     Compt  rond.  t.  I^XXIX,  p.  949.— 
De  la  fermentation  des  fruits  ib.  p.   1006. 

2  Comptes  rend.  KXXX  I,  p.  178. 

3  Krasnosselskv,    Atmung-    und     Garung    der    Schimmelpilze    etc.      C'entralbl.    f. 
Bakteriologie  etc.,  i904,  Vol.  XIII.    Nos.  22-23. 

4  Mayer,  A.,  Untersuchungen  iiber  die  alkoholische  Garung.    Landwirtsch.    Ver- 
suchsstationen,  1871. 

5  Faits  nouveaux  pour  servir  a  la  connaissance  de  la  th^orie  des  fermentations 
proprement  dites.     Compt.  rend.  1872,  p.  784. 

6  Bohm,  Ueber  die  Respiration  von  Landpflanzcn.     Sitzungsbcr.  d-  k.  Akad.  d. 
Wissensch.    67.    Section  I. 


reduce  a  part  of  their  substance  by  fermentation  to  carbon  dioxid  and  alco- 
hol, as  do  the  yeasts  in  self-fermentation.  The  green  parts  of  plants  at  any 
rate,  with  sufficiently  intensive  illumination,  can  establish  an  atmosphere 
suited  to  their  normal  respiration  by  decomposing  the  carbon  dioxid  which 
had  been  given  oflf  immediately  before.  Aerobic  and  anaerobic  respiration  are 
interdependent  and  anaerobic  is  able  to  withstand  total  destruction  for  some 
time,  even  if  growth  is  impossible  This  retardation  becomes  greater  as  the 
temperature  is  lower.  Thus,  for  example,  Pfefifer^  cites  the  observations  of 
Chudiakow,  that  the  failure  of  the  carbon  dioxid  production,  i.  e.  the  pos- 
.'^^ibility  of  living,  begins  after  twelve  hours  in  seedlings  of  maize  at  a  temper- 
ature of  40°C.,  after  24  hours  at  i8°C.  and  only  after  some  days  at  a  lower 
temperature.  If  an  organism  or  one  of  its  members  always  has  a  lower 
vitality,  it  also  will  keep  alive  longer  in  a  place  free  from  oxygen.  Thus, 
under  such  conditions,  apples  and  pears  at  a  moderate  temperature  have 
been  kept  growing  and  ripening  for  months  while  rapidly  growing  moulds 
and  aerobic  bacteria  went  to  pieces  quickly.  In  seedlings  of  phanerogamic 
plants  (Vicia  Faha,  Ricinus  etc)  there  is  an  increase  in  the  intra-molecular 
exchange, 

Stich's-  experiments  show  that  single  plants  at  times,  or  parts  of 
plants,  at  first  exert  no  influence  on  the  oxygen  content  in  the  air  by  their 
respiration  since,  in  a  hydrogen  atmosphere,  they  form  exactly  as  much  car- 
bon dioxid  as  in  air.  With  8  per  cent,  of  oxygen  in  the  air,  the  respiratory 
quotient  was  still  normal, — with  a  lesser  content  (2  to  4  per  cent.)  it  was 
changed  in  favor  of  carbon  dioxid  because  an  intra-molecular  respiration 
took  place.  When  the  plants  were  kept  for  a  longer  time  in  an  atmosphere 
poor  in  oxygen,  the  normal  respiratory  quotient  was  gradually  produced  to- 
gether with  a  decrease  of  the  absolute  amount  of  oxygen  and  carbon 
dioxid.  In  a  gradual  withdrawal  of  the  oxygen,  the  intra-molecular 
respiration  is  first  stimulated  by  a  considerably  lower  percentage  of  oxygen 
than  when  the  oxygen  diminution  is  sudden. 

Brefeld's-^  experiments  lead  to  the  conclusion  that  alcoholic  fer- 
mentation in  all  plants,  from  the  lowest  to  the  highest,  takes  place  as  soon 
as  the  oxygen  supply  ceases.  A  very  essential  difference  is  shown,  however, 
in  the  different  organisms  which  produce  alcohol.  While  generally  in  yeast 
(Saccharomycetes)  the  phenomenon  of  fermentation  is  to  be  considered  the 
climax  of  the  normal  activity  of  the  organisms  (which  actually  grow  during 
the  process  of  sugar  decomposition),  it  appears  in  the  cells  of  phanerogams 
as  an  abnormal  process  ending  prematurely  in  the  death  of  the  cell.  This 
differs  essentially  from  the  pure  fermentation  of  yeast  producing  only  alcohol 
and  carbon  dioxid,  by  the  appearance  of  further  products  of  decomposition 
among  which  fusel  oil  and  acids  are  especially  noticeable.    There  is  a  great 

1  Pfeffer,  Pflanzenphysiologie,  1897.  Vol.  I,  p.  544. 

2  Stich,  C.,  Die  Atmungr  der  Pflanzen  bei  verminderter  Sauerstoffspannung  und 
bei  Verletzuneren.     Flora   ISni,   p.   1. 

3  lUeber  Garung-  III,  Vorkommen  und  Verbreitung  der  Alkoholgarung  im  Pflan- 
zenreiche.     Bot.  Zeit.   1876,  p.  381. 


difference  in  the  ability  of  fungi  to  endure  alcohol,  as  is  shown  among  those 
which  still  introduce  an  actual  alcohol  fermentation.  For  Saccharomycetes,  12 
per  cent,  of  the  weight  is  the  limit  of  growth ;  14  per  cent,  the  limit  of  fermen- 
tation. In  Mucor  racemosus,  which  lives  on  sugar  without  free  oxygen,  the 
limit  of  growth  and  of  fermentation  lies  between  4}^  and  5>^  per  cent,  alco- 
hol ;  Mucor  stolonifer,  on  the  other  hand,  no  longer  grows  and  can  not  be- 
gin fermentation  with  1.5  per  cent,  alcohol.  It  should  be  concluded  from 
these  results  that  under  the  same  external  conditions  even  phanerogams 
succeed  in  forming  alcohol  of  very  different  percentages  and  endure  it  in 
dift'erent  amounts. 

Later  Muntz^  speaks  very  generally  of  alcohol  as  one  of  the  decomposi- 
tion products  of  organic  substances  formed  on  the  surface  of  the  earth  as 
well  as  in  the  soil  and  in  the  depths  of  the  ocean  and  distributed  in  the  at- 
mosphere according  to  the  laws  of  the  tension  of  gases. 

It  can  not  be  surprising  that  organic  acids,  among  others  acetic  acid, 
occur  in  the  fermentation  of  alcohol.  It  is  very  probable  that  the  accumu- 
lation of  such  acids  must  ultimately  act  as  a  poison  upon  the  organisms  and 
that  in  roots,  which  are  entirely  or  almost  entirely  cut  oft'  from  atmospheric 
oxygen,  there  will  begin  a  gradual  dying  back. 

When  trees  have  been  planted  too  deep  and  the  roots  need  an  abundance 
of  air,  perhaps  more  than  the  top  part  of  the  plant,  the  lack  of  oxygen  will 
be  felt  more  quickly  the  greater  the  power  of  the  soil  to  hold  water  and  the 
more  the  parts  are  cut  off  by  water-.  Water  near  the  living  roots 
becomes  more  and  more  a  source  of  danger  for  the  larger,  healthy  roots 
and  for  the  sunken  bases  of  the  trees,  since  the  water  becomes  more  and  more 
charged  with  carbon  dioxid.  If  healthy  plants  are  set  in  water  containing 
much  carbon  dioxid  they  begin  to  wilt  and  the  leaves  begin  to  die  back^. 
Kosaroff's*  studies  on  the  absorption  of  water  in  insufficiently  drained 
soils,  i.  e.  those  poor  in  oxygen  a..d  rich  in  rarbon  dioxid,  are  especial- 
ly interesting.  The  water  absorption  and  transpiration  were  proved  to 
be  repressed  by  the  carbon  dioxid.  Plants  whose  roots  remained  in  an  at- 
mosphere rich  in  carbon  dioxid  lost  their  turgidity  immediately  and  be- 
came limp ;  when  kept  there  longer  they  disintegrated.  In  experiments  in  an 
hydrogen  atmosphere  wdiere,  therefore,  only  the  lack  of  oxygen  becomes  de- 
pressing, it  was  shown  that  this  circumstance  does  not  act  in  any  way  as  in- 
juriously as  an  excess  of  carbon  dioxid. 

Therefore,  in  the  roots  of  trees  lying  too  deep,  death  by  poison  begins 
by  attacking  first  the  tender  organs,  later  the  older  ramifications  of  the  roots. 
At  the  same  time  the  putrid  products  of  decomposition  make  the  whole  soil 
unfit   for  the   growth   of   plants.    Bohm^"^    cites   an   exami)le    in   the   dying 

1  From  Compt.  rend.  Vol.  I.XXXXII,  p.  499.  cit.  in  Biedermann's  Contralbl.  ISSl. 
p.  709. 

2  Mayer,  Agrikulturchemie,  5th  Edition,  1901,  Vol.  I,  p.  116. 

3  Wolf.  W.,  Tageblatt  der  Naturforscher-Versammlung-  zu  Leipzig,  18.-,  p.  -"■'. 
i  Kosaroff,  Einfluss  verscliiedener  ausserer  Faktoren  auf  die  Wasseraufnahnie 

der  Pflanzen.     Dissert.  Leipzig,  1897,  cit.  Naturw.  Rundschau,  1S97.  No.  47. 

5  Bohm,  J.,  Ueber  die  Ursache  des  Absterbens  der  Gotterbaume  und  uber  die 
Methode  der  Neubepflanzung  der  Ringstrasse  in  Wein.    Faesy  &  Frick. 


Ailanthus  trees  of  the  Ring^strasse  in  \'ienna  wliich  liad  been  planted  too 
deep.  These  trees  years  before  had  fallen  olT  in  growth,  for  in  the  first  year 
after  they  were  planted,  their  annual  rings  were  more  than  3  cm.  broad,  in 
the  last  year  the  growth  was  0.5  cm.  At  the  time  of  death  the  earth  about 
the  roots  was  found  to  be  so  injurious  that  seeds  of  different  plants  sown  in 
the  soil  in  the  open  and  under  bell  jars  began  to  decompose  at  once.  Seeds 
developed  luxuriantly,  however,  after  this  soil,  repeatedly  washed  with 
water,  had  been  exposed  in  thin  layers  to  the  atmosphere  for  eight  warm 
days  in  July.  Similar  experiments  were  undertaken  by  Mangin^  w^ho, 
before  this  time,  had  ascribed  the  diseased  appearance  of  the  street  trees  in 
Paris  to  the  bad  composition  of  the  soil.  Seeds  and  tubers  sown  in  soil  re- 
moved from  around  diseased  roots  showed  an  interrupted  development. 

The  air  tests  made  near  the  diseased  roots  of  Ailanthus  showed  a  de- 
ficiency of  oxygen  and  a  preponderance  of  carbon  dioxid  and  Mangin- 
suspects  that  the  lack  of  oxygen  may  be  traced  back  to  a  reduction  by 
sulfids.  Certainly  numerous  micro-organisms  co-operate  in  the  decom- 
posing process  of  the  roots.  However,  such  an  attack  by  the  suitable 
bacteria  would  not  have  taken  place  if  the  oxygen  in  the  soil  had  not  begun 
to  be  deficient. 

When  trees  with  spongy  bark  have  been  planted  too  deep,  as  in  the 
above  mentioned  Ailanthus  trees  in  Vienna,  the  bark  under  the  soil  is  found 
entirely  rotted  away.  According  to  the  age  and  the  bark  structure  of  the 
tree,  as  well  as  the  physical  constitution  of  the  soil,  a  disturbance  of  the  ab- 
solutely necessary  circulaticni  of  the  air  will  appear  sooner  or  later  in  the 
buried  base  of  the  trunk.  This  disturbance  wdll  be  felt  also  in  both  the  ven- 
tilatory systems  of  the  trunk,  viz.,  in  the  vascular  system  of  the  wood  body 
and  the  bark  system  communicating  with  it  by  means  of  small  hollow  spaces. 
The  green  bark  parenchyma  protected  by  the  more  or  less  strongly  developed 
cork  is  bathed  by  the  atmospheric  air;  it  penetrates  through  the  lenticels 
into  the  intercellular  spaces  where  it  circulates.  The  air  penetrates  the  ducts 
of  the  wood,  partly  through  the  water  from  the  roots,  but  largely  by  diffu- 
sion from  the  sides  and  is  also  in  circulation,  as  mentioned  above.  In  fact, 
as  may  be  assumed  from  the  investigations,  of  O.  HohneP,  a  daily 
periodicity  probably  takes  place  in  this  circulation.  The  ducts  originally 
hlled  with  w^ater  are  partly  or  entirely  emptied  in  the  course  of  the  day, 
since  the  superior  and  surrounding  tissues  draw  away  the  water.  The  trans- 
piring leaf  body  of  the  tree  needs  a  very  large  amount  of  water  and  draws 
it  from  the  wood  tissues  of  the  branches  which  make  good  their  losses  from 
the  trunk,  in  w'hich  therefore  a  suction  wave  advances  down  toward  the 
base  and  thence  out  into  the  roots. 


1  Mangin,  L.,  Sur  la  vegetation  dans  line  Atmosphere  viciee  par  la  respiration. 
C.  rend.  1896,  p.  747. 

-  Mangin,  L..,  Sur  I'sieration  du  sol  dans  les  promenades  et  plantations  de  Paris, 
C.  rend.  1895,  II,  p.  1065. 

a  V.  Hohncl,  Beitrage  zur  Luft-  und  Saftbewegung  in  der  Pflanze.  Pringsh.  Jahrb. 
f.  wissensch.  Bot.  Vol.  XII,  Part  I,  p.  120. 


103 

Since  more  water  is  drawn  away  from  the  ducts  than  can  be  replaced 
instantly,  a  space  partially  filled  with  air  appears  in  these  ducts  causing  a 
negative  pressure  (suction)  which  is  so  much  the  greater  the  less  the  amount 
of  air  present  at  tlie  beginning  or  slowly  diffused  through  the  membranes,  for 
so  much  the  more  must  the  originally  small  volume  of  air  be  distended  to  fill 
out  the  hollow  space  which  is  always  becoming  greater.  In  the  night,  when 
the  evaporation  is  arrested  or  very  much  repressed,  the  ducts  of  the  trunk 
again  suck  up  great  amounts  of  water,  in  fact,  this  suction  is  often  increased 
by  the  pressure  proceeding  from  the  roots  which  can  press  so  much  water  into 
the  ducts  that  a  great  part  passes  through  the  membranes  into  the  surround- 
ing cells  and  intra-cellular  spaces.  If  this  liquid  drawn  up  from  the  root  body 
or  pressed  up  by  it  is  healthy,  a  considerable  infiltration  into  the  intercellular 
spaces  will  take  place  without  disadvantage  to  the  body,  as  has  been 
shown  by  Moll\  If,  however,  the  water  mass  is  already  laden  with  the 
products  of  fermentation  from  the  putrefying  root  tips,  we  see  that  these 
poisonous  substances  get  into  the  especiaUy  sensitive  sapwood  and  bark  and 
thus  the  dying  back  easily  spreads. 

Trees  planted  too  deep,  however,  usually  die  only  in  heavy  soil  per- 
manently loaded  with  water.  In  light  soils  they  suffer  but  do  not  die.  If  the 
heavy  soil  with  its  water  burden  surrounds  the  base  of  the  trunk  and  pre- 
A'ents  intercellular  ventilation  by  means  of  the  lenticels,  alcoholic  fermenta- 
tion and  the  formation  of  acetic  acid  must  naturally  appear  in  the  bark  cells 
and  lead  to  a  dying  back  which  is  continued  radially  to  the  cambial  zone  and 
the  young  sapwood  which  is  especially  active  in  conducting  water. 

Thus  there  remains  from  year  to  year  a  cylinder  of  heartwood  in  the 
middle  of  the  trunk  which  is  always  becoming  smaller  and  smaller  and  which 
usually  has  to  meet  the  water  need  of  the  aerial  part.  The  heartwood  which 
is  poor  in  water,  however,  is  less  suited  for  conducting  it  and  the  dead  tis- 
sues of  the  wood,  which  at  any  rate  can  still  conduct  water  mechanically, 
Vvill  not  be  able  with  their  help  to  meet  the  need  of  water  in  the  crown.  Con- 
sequently, the  tree  uhimately  wilts  or  fails  to  put  out  buds  in  spring. 

The  fact  that  the  non-parasitic  processes  of  decomposition  in  the  buried 
end  of  the  trunk  cease  near  the  upper  surface  of  the  soil  leads  to  the  theory 
that  processes  of  decomposition  are  not  able  to  attack  healthy  plant  cells  but 
only  those  weakened  and  functionally  abnormal.  Such  weakening  is  actually 
present.  It  was  mentioned  at  the  beginning  that  cells  full  of  life  and  rich  in 
content,  when  shut  away  from  the  oxygen  of  the  air,  begin  at  once  to  de- 
velop alcohol  through  the  activity  of  fermentation  (alcoholases)  which  was 
not  present  previously  and  which  disappears  again  if  the  plant  regains  its 
atmospheric  air.  It  has  been  proved  further  that  the  plant,  in  the  absence  of 
oxygen,  continues  for  some  time  to  eliminate  carbon  dioxid  in  considerable 
quantities    (respires  intra-molecularly)   but  that  these  amounts  of  carbon 


1  Untersuchungen  iiber  Tropfenausscheidung  und  Infektion,  18S0  p.  -8  Sep. 
aus  Verslag  en  Mededeeling  d.  Koninkligke  Akad.  Amsterdama,  cit.  in  Pfeffer, 
Pflanzenphysiologie,  1881,  I,  p.  159. 


104 

dioxid  are  still  smaller  when  the  experiments  are  continued  longer  than 
those  of  plants  respiring  in  air  which  contains  oxygen\  Since  the 
carbohydrates  (starch,  sugar)  furnish  the  material  for  respiration,  it 
should  be  assumed  from  the  above  facts  that  these  material  contents  of  the 
cell  are  made  use  of  abnormally  in  the  absence  of  oxygen.  With  Pfeffer- 
respiration  can  be  conceived  of  as  a  process  set  up  by  two  dove- 
tailing processes.  The  first  is  the  intra-molecular  respiration  ascertained  in 
the  phenomena  of  fermentation  which  Borodin^  named  internal  oxidation. 
The  second  process,  possible  only  with  a  supply  of  oxygen  from  with- 
out, is  the  immediate  further  oxidation  of  the  products  of  fermentation 
in  the  moment  of  their  production.  If  this  last  act,  absolutely  necessary  for 
the  life  of  the  cell,  is  suppressed,  not  only  the  zone  of  the  trunk  of  the  tree, 
planted  too  deep  and  lacking  oxygen,  loses  its  respiratory  material,  that  is, 
always  becomes  poorer  in  reserve  substance,  but  it  also  forms  those  products 
which  lead  to  decomposition  and  the  death  of  the  cell.  Insufficient  respir- 
ation therefore  is  a  necessary  preliminary  condition  for  the  dying  back  and, 
to  the  degree  in  which  the  buried  part  approaches  the  surface  of  the  soil, 
gradually  getting  more  and  more  oxygen,  the  fermentation  will  become 
weaker  and  weaker  and  pass  over  into  the  normal  process  of  oxidation  so 
that  decomposition  gradually  reaches  its  limit.  It  is  thus  only  a  question 
whether  the  tree  has  the  possibility  of  forming  new  roots  in  the  soil  above 
these  limits  in  order  to  meet  the  loss  of  water  produced  by  the  transpiration 
of  the  foliage.  The  stunted  production  frequently  observable  in  early  years 
disappears  as  the  more  plastic  material  can  pass  downward  and  be  used  for 
the  new  structures  in  the  wood  ring  of  the  trunk  and  the  roots.  The  more 
rapid  the  growth,  the  greater  the  energ}^-  of  respiration  (as  shown  by  Saus- 
sure)  and  the  more  the  flat  new  root  body  is  reached  by  light,  so  much  the 
more  will  the  production  of  carbo-hydrates  and  its  absorption  of  oxygen 
and  production  of  carbon  dioxid  increase*. 

The  behavior  of  the  trees  planted  too  deep  or  only  partially  buried  de- 
pends naturally  upon  their  specific  character.  In  willows  and  poplars,  for 
example,  the  part  sunk  in  the  earth  may  indeed  be  found  to  be  dead,  but 
near  the  top  of  the  soil,  the  decomposition  appears  to  have  been  stopped. 
Numerous  adventitious  roots  have  been  formed  from  the  tnuik  which,  some 
time  after  the  tree  has  been  buried,  starts  a  healthy  development  of  the  crown. 
The  tree  is  therefore  saved  if  it  is  able  to  produce  new  roots  quickly  near 


1  Wortmann  (Ueber  die  Beziehungen  der  intramolekularen  zur  normalen  At- 
mung  der  Pflanzen.  Inauguraldissertatiort.  Wiirzburg  1879)  states,  to  be  sure, 
that  the  amounts  of  carbon  dioxid  are  equally  large  in  intra-molecular  and  normal 
respiration;  it  seems  to  me,  however,  that  the  short  duration  of  his  experiments 
also  caused  the  observation  of  the  after  effects  of  a  previous  normal  functioning. 
He,  himself,  admits  (p.  31)  that  in  a  longer  period  with  no  addition  of  oxygen  a 
smaller  amount  of  carbon  dioxid  was  produced  by  the  plants  under  experimentation 
than  had  been  the  case  in  the  constant  presence  of  oxygen. 

~  Pfeffer,  Ueber  das  Wesen  und  die  Bedeutung  der  Almung.  Landwirtsch. 
Jahrb.    1878. 

3  Borodin,  Sur  la  respiration  des  plantes  pendant  leur  germination. 

*  Borodin,  INIemoires  de  I'Acad.  imp^riale  des  sciences  de  St.  Petersbourg.  VII 
s6rle.  1881. 


I05 

the  earth's  surface.  It  is  well-known  that  Ericaceae  and  Epacrideae  are 
especially  sensitive  to  too  deep  planting.  In  these  species  the  base  of  the 
trunk  dies  even  when  the  root  has  not  suffered  very  much.  When  the  sap- 
ling shows  moss  and  lichen  growths  at  the  base,  there  is  every  reason  for 
being  careful. 

In  nurseries  no  one  general^  rule  holds  good  in  regard  to  the  depth  of 
planting.  Aside  from  the  important  physical  composition  of  the  soil  much 
depends  in  grafted  trees  upon  the  stock.  Fruit  varieties  grafted  on  wild 
stock  should  be  so  planted  that  the  root  neck  remains  in  the  plane  of  the 
surface  of  the  soil  or  even  projects  a  little  above  it.  In  fact  in  marshy  soil, 
with  a  great  deal  of  moisture,  planting  is  made  in  hills.  Pears  grafted  on 
dwarf  stock  (on  quinces)  and  apples  (on  Doucin  and  Paradise  apples),  on 
the  other  hand,  must  be  planted  at  least  so  deep  in  the  soil  that  the  place  of 
grafting  is  found  at  the  surface  level  of  the  soil;  i.  e.,  the  whole  stock  under 
the  soil.  From  this  a  considerable  number  of  adventitious  roots  develop 
which  are  especially  useful  for  nutrition. 

Bouche^  has  given  a  splendid  summary  of  practical  experiments. 
He  refers  first  of  all  to  the  fact  that  in  old  healthy  trees  the  strong 
roots  are  seen  to  appear  above  the  soil  and  that  this  appearance  of  the  root 
neck  is  normal.  Many  trees  can  survive  deep  planting  when  young,  since 
they  put  out  new  roots  from  the  base  of  the  trunk  just  below  the  surface 
(elms  and  lindens)  ;  others,  on  the  contrary,  are  very  sensitive,  as,  for  ex- 
ample, pears,  maples,  oaks,  most  of  the  Rosaceae,  plane-trees,  walnuts,  red 
and  white  beeches.  Also  most  conifers  require  care  in  planting,  as,  for  ex- 
ample, the  genera  Pinus,  Picea  and  Abies  and  at  times  also  Thuja,  especially 
Thuja  (Biota)  orientalis  and  related  species,  while  deep  planting  has  been 
proved  to  have  been  endured  by  Thuja  occidentalis,  T.  Warreana,  T.  plicata. 
Bouche  found  trunks  5  to  8  cm.  thick  putting  out  a  number  of  new  roots  from 
tlieir  buried  bases  whereby  they  were  very  much  strengthened.  Juniperus 
communis  must  be  planted  shallowly  but  /.  Sahina  and  related  species  sur- 
vive deep  planting  with  advantage.  It  has  already  been  stated  of  poplars 
and  willows  that  deep  planting  is  counterbalanced  at  once  by  the  formation 
of  new  roots  on  the  surface  of  the  soil.  In  weak  trunks  it  is  often  found 
that  the  roots  formed  just  below  the  surface  get  the  upper  hand  over  the 
older,  deeper  ones.  It  is  actually  even  more  advantageous  to  plant  many 
bushes  deeper  than  they  stood  before  because  they  strengthen  themselves  by 
numerous  new  roots  from  the  buried  base  of  the  stems.  This  is  noticeable 
for  example  in  Calycanthus,  Cornus  alba  and  C.  sibirica,  Ribes,  many  kinds 
of  Spiraea,  Viburnum  Opulus,  Aesculus  macrostachya,  Symphoria,  Ligus- 
trum,  Rosa  gallica  etc.  On  the  other  hand  Caragana,  Berberis,  Colutea, 
Cornus  mascula  and  C.  sanguinca,  Corylus,  Cytisus,  Rhamnus,  Sambucus, 
should  be  planted  at  the  old  level. 


1   Bouche,   C  Ueber  das  Tiefpflanzen  --^on  Baumen  etc.     Monatsschr.  d.   Ver. 
Ford.  d.  Gartenb.,  v.  Wittmack,  1880,  p.  212  and  Wredow  I.e.  p.  75. 


io6 

In  ftlantlng  streets,  besides  the  embankment  which  sometimes  becomes 
necessary,  the  asphaltincj  and  cementing  of  the  street  causeways  is  also  very 
injurious  to  the  roots  of  the  trees.  The  injury  is  due  not  only  to  the  shutting 
off  of  the  atmospheric  air  but  also  the  loss  of  precipitation  from  the  air,  upon 
which  trees  in  large  cities  become  so  much  more  dependent,  as  the  level  of 
the  ground  water  has  fallen  because  of  canalization  and  the  workings  of  the 
subsoil  in  building.  Young  trees  which  are  planted  after  the  falling  of  the 
level  of  the  ground  ivatcr  strive  to  reach  this  despite  the  increased  depth  of 
the  springs.  Consequently  in  order  to  facilitate  this,  the  holes  for  planting 
the  trees  must  be  made  considerably  deeper  in  such  localities.  According  to 
Bouche,  this  increased  depth  amounts  to  60  cm.  in  Berlin  so  that  now  the 
holes  for  planting  trees  must  be  dug  i.  5  cm.  deep. 

Too  Deep  Sowing  of  the  Seed. 

The  discovery  has  also  often  been  made  that  from  a  plentiful  sowing 
of  good  fresh  seed  a  comparatively  small  number  of  plants  is  produced.  As 
is  generally  believed,  the  cause  lies  more  frequently  in  sowing  the  seeds  too 
deep.  When  harrowed  in  or  hoed  under  in  places,  as  is  customary  with 
barley\  some  seed  grains  necessarily  come  to  lie  too  deep,  others 
too  superficially.  Uniformity  can  be  obtained  only  by  planting  with  a  drill. 
But  even  the  gardener,  who  can  cover  his  seeds  very  uniformly  in  seed  pans, 
not  infrequently  obtains  only  a  low-  percentage  of  plants  in  sowing  very  fine 
seeds  even  if  the  seed  was  good  and  of  high  germinating  quality. 

The  processes  causing  the  loss,  however,  are  not  always  the  same,  and 
do  not  always  take  place  under  the  same  conditions ;  on  this  account  it  is 
impossible  to  generalize.  In  order  to  protect  oneself  from  injury  in  this 
connection,  there  is  nothing  to  be  done  except  to  understand  clearly  the  in- 
fluence of  the  different  factors  to  be  observed  in  sowing  seed  and  to  see 
which  combinations  exist  in  every  individual  case. 

There  are  three  phases  in  germination.  Each  can  be  disturbed  and 
cause  failure.  The  first  stage  consists  of  the  swelling  of  the  seed  and  is  a 
mechanical  process,  in  which  (probably  by  water  condensation)  an  increase 
in  temperature  has  been  observed.  This  introduces  the  second  stage,  the 
mobilisation  of  the  reserve  substances,  a  chain  of  chemical  phenomena,  and 
these  accompany  the  third  act,  that  of  the  formal  development. 

Disturbances  in  the  stage  of  swelling  have  often  been  observed.  Nobbe 
and  Haenlein-  found  especially  in  Papilionaceae  and  Caesalpiniacea, 
that  the  seed  shell  at  times  is  so  hard  that  water  can  not  enter,  that  the  seeds 
retained  the  embryo  for  years  without  development,  but  always  in  a  healthy 
condition.  The  seed  did  not  germinate  because  it  did  not  swell.  In  clover 
seed,  the  superficial  shell  or  hard   layer   containing  the   coloring  matter,   is 


1  Eggers-Gorow,  Versuche  iiber  den  Nutzen  oder  Nachteil  einer  flachen  oder 
tiefen  Bestellung-  der  Gerstenkorner.     Meoklenb,  landw,  Ann,  1874,  No.  23. 

-  Nobbe  und  Haenlein,  Ueber  die  Resistenz  von  Samen  .2:egen  die  aufseren 
Faktoren  der  Keimung.     Versuchsstationen  1877,  p.  71. 


107 

shown  to  be  so  impermeable  for  water  that  clover  seeds  can  lie  from  one  to 
two  weeks  in  English  sulfuric  acid,  and  for  years  in  water,  without  losing 
the  coloring  matter  which  in  itself  would  be  soluble  in  water.  In  such  cases 
cnly  mechanical  treatment  is  of  any  use.  Gaher  and  Klose^  mixed 
the  seeds  of  lucerne  (alfalfa)  and  varieties  of  clover  with  fine  sand  and  trod 
for  ten  minutes  on  the  bag  containing  the  mixture.  After  this  treatment, 
13.4  per  cent,  of  the  seeds  of  the  lucerne  were  found  to  be  more  capable  of 
swelling,  10.2  per  cent,  of  the  white  clover  and  37.8  per  cent,  of  those  of  the 
bird's-foot,  without  showing  any  especial  injury.  Nobbe  cites  examples- 
of  an  unexpectedly  long  retention  of  the  germinating  power.  32  per 
cent,  of  seeds  of  Pinus  silvestris,  gathered  in  1869,  after  having  been  kept 
5  years  in  closed  glasses  in  an  occupied  room,  still  germinated,  and  after  7 
}ears  12  per  cent.  With  red  clover  seeds  (Trifolium  pratense),  preserved 
in  the  same  way,  10.5  per  cent,  germinated  after  12  years,  peas  (Pisum  sati- 
vum) 47.7  per  cent,  after  10  years,  Spergula  arvensis  20  per  cent,  after  12 
3'ears,  flax  (Linum  usitarissimum)  49  per  cent,  after  6  years  and  3  per  cent, 
after  11  years.  Out  of  400  seeds  of  the  locust  (Rohinia  Pseud-Acacia)  after 
ten  days,  longer  than  which  the  time  for  practical  purpose  does  not  last, 
71  grains  germinated ;  at  the  end  of  the  year,  55  grains ;  in  the  next  year  18  ; 
in  the  following  year  7  and,  after  7  years,  one  seed ;  all  were  kept  contin- 
uously in  distilled  water  which  was  renewed  periodically.  From  these  ob- 
servations it  seems  credible  to  us  that  many  buried  seeds,  unimpaired  in  life- 
power,  survive  for  very  long  periods.  Even  in  the  locust  seeds  mentioned 
above,  the  remainder,  left  ungerminated  after  seven  years,  w^as  still  perfectly 
healthy.  A  slight  injury  to  the  seed  shell  resulted  after  a  few  hours  in  a 
swelling  up  and  also,  as  a  rule,  in  rapid  germination. 

Disturbances  of  the  second  phase  of  the  process  of  germination,  the 
stage  of  chemical  action  converting  the  solid  reserve  substances  into  the 
easily  transpired  constructive  matter,  are  observed  very  frequently.  The 
fact  that  many  hard  seeds  such  as  Crataegus,  Rosa,  Juglans,  Prunus,  lie  un- 
harmed for  a  year  in  the  soil,  is  not  to  be  confused  with  real  disturbances. 
The  difficulty  of  swelling  may  partly  be  to  blame  here; — during  the  dry 
time  in  summer  the  seeds  again  become  dormant.  On  the  other  hand  water 
may  have  permeated  them  already  and  have  given  rise  to  the  formation  of 
ferments,  which  lead  to  the  mobilization  of  the  reserve  substances.  But  this 
action  of  the  ferment  is  in  itself  too  slow,  up  to  the  beginning  of  the  dry 
summer  period,  to  sufficiently  nourish  the  embryo.  In  different  individuals 
and  varieties  of  all  species  which  germinate  with  difficulty,  germination  and 
development  is  found  the  spring  following  autumn  planting.  This  takes 
place  especially  if  the  seeds  are  sown  soon  after  harvesting  and  when  possi- 
ble with  the  entire  fruit.  "Stratification"  has  been  proved  still  more  effec- 
tive, i.  e.  the  placing  of  the  seed  in  layers  in  vessels  filled  with  sand  for  the 


1  Gaiter    und    Klose,    Quellungsunfahigkeit    von    Kleesamen.      Wiener    landw. 
Zeitschr.  1877,  No.  17,  cit.  Jahresb.  f.  Agrikulturchemie,  XX.    Year,  1S77,  p.  181. 

2  Dobner's    Botanik    fiJr    Forstmanner,    4th    Edition,    revised    by    Aobbe,    1SS_. 
p.  382. 


io8 

winter.  The  actual  disturbances  are  found  to  be  the  lack  of  external  con- 
ditions necessary  for  germination.  Besides  moisture  and  warmth  there  be- 
long here  the  unimpeded  supply  of  oxygen  and  the  observance  of  the  time 
when  the  seed  is  capable  of  re-acting. 

The  time  within  which  the  seed  responds  to  the  action  of  the  external 
conditions  necessary  for  germination  by  a  normal  transmutation  of  the  re- 
serve substances  and  the  development  of  the  embryo  varies  greatly,  for  the 
different  families  and  species,  even  for  individuals  of  the  same  variety.  It 
is  well-known  that  seeds  of  willows,  poplars  and  elms  must  be  sown  im- 
mediately after  harvesting,  since  they  lose  their  power  of  germination  after 
a  few  days  or  weeks,  while  cucumbers  and  melons  often  give  stronger,  more 
fertile  plants,  if  the  seeds  have  been  kept  for  a  year.  To  be  sure,  the  seeds 
of  many  of  our  fruit  and  forest  trees  usually  germinate  after  one  or  more 
years,  but  the  number  of  the  slow  growing,  weakened  specimens  increases 
with  the  age  of  the  seed. 

Oxygen  should  be  considered  the  most  important  factor  next  to  water, 
necessary  for  swelling.  For  germination  the  seeds  never  need  as  much  water 
as  their  substance  can  take  up ;  the  vegetative  activity  of  the  seedling  begins 
before  this  time\  If  in  the  beginning  there  is  a  scarcity  of  water 
which  can  be  taken  up  endosmotically,  the  seed  also  takes  water  up  hydro- 
scopically  from  the  atmosphere'-.  Water  vapor  also  condenses  on  the 
outer  surface ;  in  fact,  after  the  manner  of  all  porous  bodies,  it  condenses 
also  hydrogen,  nitrogen  oxygen  and  other  gases.  Deherain  and  Landrin-' 
found  that  the  swollen  seeds  take  up  comparatively  more  oxygen  than 
nitrogen  from  the  atmosphere  so  that  more  nitrogen  remains  in  the  en- 
closed space.  After  three  days  the  seed  begins  to  give  off  carbon  dioxid  and 
this  increases  so  fast  that  soon  more  carbon  dioxid  is  present  than  the  oxygen 
enclosed  in  the  volume  of  the  air  would  warrant,  the  oxygen  has  gradually 
disappeared.  The  excessive  production  of  carbon  dioxid  is  therefore  to  be 
considered  as  a  product  of  the  processes  of  oxidation  of  the  inner  burning, 
beginning  in  the  seeds. 

These  authors  pictured  to  themselves  the  beginning  of  the  chemical 
actions  in  the  seed  in  such  a  way  that  the  rapid  condensation  of  the  gas  de- 
termined at  first  for  the  various  seeds  will  necessarily  free  the  latent  warmth 
of  the  gas  and  this  warmth  sufficiently  increases  the  temperature  of  the  en- 
closed oxygen  so  that  oxidation  can  begin.  With  this  is  given  the  impetus  for 
the  normal  solution  of  the  reserve  substance  of  the  seed ;  the  heat,  freed  by 
oxidation,  favors  these  processes  more  and  more  and  they  become  evident 
externally  by  the  production  of  carbon  dioxid. 


1  Jahresb.  f.  Agrikulturohemie,  18.S0,  p.  213. 

-  Hoffmann,  R.,  in  the  Jahresbericht  der  agrikulturcheniischen  Untersuchung- 
station  in  Bohmen,  1864,  p.  6.  :ind  Haberlandt,  F.,  in  Zeitschrift  fiir  deutsclie  I^and- 
wirte,  1863,  p.  355.  Both  works  may  be  found  in  abstract  in  the  Jahresb.  f.  Agrikul- 
turohemie, Jahrg.  VII.  1864,  pp.  108  and  111. 

H  Compt.  rend.  1874,  Vol.  LXXVIII,  p.  1488,  cit.  in  Biedermann's  Centralbl.  f. 
Agrikulturchemie,  1874,  II,  p.  185. 


109 

The  preparation  for  the  germination  of  the  dormant  seed,  according  to 
this  theory,  is  the  loosening  undergone  by  the  shell  of  the  seed,  as  the  result 
of  its  swelling  with  water.  The  broken  cell  layers  which  have  become  per- 
meable for  gases  now  permit  their  rapid  penetration  and  their  condensation 
therefore  gives  the  first  impetus  for  the  process  of  oxidation  which  causes  the 
transformation  of  the  reserve  substances  into  diffusible  forms.  Since  it  can 
be  observed  with  the  seed  albumen  of  plants  that  the  breaking  down  of  the 
starch  in  the  seedling  begins  in  the  cotyledons  in  monocotyledons,  it  can  be 
assumed  that  the  part  richest  in  nitrogen,  i.  e.  the  embryonic  tissue,  under 
the  influence  of  oxygen  will  begin  the  metabolic  reactions  and  by  the  develop- 
ment of  abundant  enzymes  act  upon  its  surroundings. 

The  disturbance  in  the  second  phase  of  germination  can  result  only 
from  a  lack  of  oxygen  or  also  from  an  excess  of  carbon  dioxid.  The  state- 
ments of  Th.  de  Saussure  confirmed  by  Deherain  and  Landrin  show  that  no 
gas  is  so  detrimental  to  germination  as  carbon  dioxid.  Seeds  which  are  kept 
in  a  mixture  of  oxygen  and  hydrogen  germinate  just  as  in  atmospheric  air; 
yet  an  addition  of  a  few  hundredths  of  carbon  dioxid  to  an  atmosphere  of 
oxygen  is  enough  to  absolutely  inhibit  germination,  when  only  the  little  roots 
have  appeared.  If  the  amount  of  carbon  dioxid  is  very  considerable  seeds 
will  not  germinate. 

Carbon  dioxid  in  excess  is  very  injurious  to  other  dormant  parts  of  the 
plant.  Van  Tieghem  and  Bonnier^  found  in  bulbs  and  tubers  (Tuli- 
pa,  Oxalis  crenata)  which  respired  further  in  air  containing  a  great  deal  of 
oxygen,  and  therefore,  produced  carbon  dioxid,  that  they  formed  alcohol  in 
an  atmosphere  of  pure  carbon  dioxid.  Tulip  bulbs  which  had  been  kept  for 
a  month  in  air  free  from  oxygen  were  suffocated  and  remained  without  fur- 
ther development. 

When  seed  has  been  sown  too  deep  there  is  also  an  excess  of  carbon 
dioxid  and  a  lack  of  oxygen.  The  thick  soil  covering  brings  about  injuries 
and  hinders  the  germination  of  the  seed  but  can  not,  however,  be  expressed 
in  definite  figures.  Aside  from  the  different  requirements  of  the  different 
species,  the  optimum  thickness  of  the  covering  differs  for  the  same  species 
according  to  the  composition  of  the  soil,  the  amount  and  distribution  of  pre- 
cipitation etc.  On  this  account  the  results  of  the  experiments  often  under- 
taken to  ascertain  the  best  depth  for  sowing  differ  from  one  another  as  soon 
as  a  definite  statement  of  figures  is  undertaken.  They  all  agree,  however, 
that  in  doubtful  cases  it  is  better  to  sow  with  too  shallow  a  co^'ering  than  too 
deep. 

The  purpose  of  the  coz'erlng  is  to  hold  the  young  seed  firm  and  to  retain 
a  sufficient  degree  of  moisture.  The  shutting  out  of  light  comes  less  under 
consideration.  The  retention  of  sufficient  moisture  for  germination  must  be 
primarily  considered.  If  enough  is  present,  the  roots  themselves  will  pene- 
trate at  once  into  the  soil  even  when  the  seed  lies  superficially.     On  this  ac- 


1  Bulletin   de  la   societe  botanique   de  France.  Vol.   XXVII,    1880,    p.    83.   cit. 
V^^ollny's  Forschung-en  auf  dem  Gebiete  der  Agrikulturphysik. 


no 

count  a  perfectly  superficial  sowing  of  the  seed  would  be  advisable  if  periods 
did  not  occur  in  spring  which  dry  up  the  surface  of  the  soil  to  such  an  ex- 
tent that  a  temporary  or  even  a  permanent  inhibition  of  the  life  activity  takes 
place  in  the  seedling. 

The  more  porous  the  soil,  the  greater  is  the  danger  of  drying  out  and 
therefore  the  greater  the  depth  at  which  the  seed  must  lie.  In  regions  where 
the  spring  is  dry  a  heavy  soil  will  give  a  more  uniform  germination  even  if 
the  sowing  is  shallow.  The  same  soil  and  the  same  depth  of  sowing  become 
dangerous  when  strong  rainfall  and  great  heat  alternate  rapidly  and  form 
crusts  on  the  upper  surface  of  the  soil  cutting  off  nearly  all  access  of  air  to 
the  seeds  then  in  a  most  active  stage  of  metabolism.  The  air  enclosed  in  the 
seeds  does  not  last  long.  Ventilation  of  the  plant  body  is,  however,  absolute- 
ly necessary,  even  the  germinating  seed  sufil'ers  extremely  if  the  air  contained 
in  it  be  removed.  The  formation  of  heavy  crusts  on  the  soil  can  make  the 
depth  of  sowing  of  the  seed  become  the  cause  of  consideral'ly  injury,  which 
in  itself  would  not  be  injurious. 

How  much  the  lack  of  air  influences  the  germination  rapacity  of  seeds 
is  evident  from  de  Vries^  citations.  In  this  connection  Haberlandt  injected 
curly  beet  seeds  with  water  under  an  air  pump  and  observed  that  the  seeds 
took  up  71.13  per  cent. ;  of  these  seeds  thus  partially  deprwed  of  air  only  30 
per  cent,  germinated  as  against  90  per  cent,  of  the  normal  seeds  kept  as  a 
control.  In  a  second  experiment  all  the  air  was  replaced  by  water  forced  in 
by  the  air  pump  and  only  8  per  cent,  germinated  as  against  72  per  cent,  in  the 
control. 

Also  the  time  required  for  germination  was  shorter  in  the  normal  seeds. 
It  may  well  be  assumed  that  the  removal  especially  of  oxygen  from  the  seed 
and  the  hindered  diffusion  of  this  gas  in  new  quantities  into  the  intercellular 
spaces  is  the  cause  of  the  loss  in  germinating  power.  Dutrochet- 
found  even  in  mature  plants  that  death  often  occurs  if  water  is  injected.  In 
the  rapid  thaivimj  of  frozen  fleshy  parts  of  plants  which,  as  a  result  of  an 
infiltration  of  the  intercellular  spaces  with  water,  have  a  glassy,  translucent 
appearance,  the  exclusion  of  the  air  from  the  cells  by  water  may  contribute 
essentially  to  their  death. 

From  the  many  experiments  carried  out  practically  in  order  to  obtain 
precise  numerical  values,  for  the  best  depth  for  sowing  seeds,  those  of  Roes- 
tell,  Tietschert,  Ekkert  and  Wollny  are  the  most  thorough.  Roestell" 
gives  2  to  4.5  cm.  as  the  most  favorable  depth  for  porous,  strong,  field  soil. 

Tietschert*  experiments  endeavor  to  determine  the  maximum  boun- 
daries of  the  most  favorable  seeding  depths  in  soils  differently  con- 
structed physically; — 10  cm.  was  seen  to  be  the  rational  maximum  depth  for 


1  De  Vries,   Keimun,?s£reschichte  dcr  Zuckerriibe,  Landwirtsch,   .Tahrb.   v.   Thiel 
1879,  p.  20. 

2  Dutrochet,  Memorires  etc.  edition  Bruxelles  p.  211,  cit.  by  de  Vries  1.  c. 

3  Annalen  der  Landwirt.schaft,  Vol.  51,  p.  1. 

*  Tietschert,  Keimungsversuche  mit  Roggen  and  Raps.  Halle.  1871. 


sandy  soil,  8  cm.  for  humus  soil  and  5  cm.  for  clay  and  loamy  soil  containing 
lime. 

The  last  two  kinds  of  soil  suffer  from  dry  weather  so  that  shallow  seed- 
ing gives  poor  results.  The  experiments  repeated  later  in  the  year  (August 
to  September)  gave  for  all  kinds  of  soil  a  depth  of  2.5  cm.  as  very  unfavor- 
able because  of  drought ;  in  this  case  clay  soil  was  proved  most  favorable  in 
seeding  at  a  depth  of  10  cm.  It  is  evident  from  this  that  delinite  figures 
must  be  accepted  with  great  reserve.  Ekkert'  experimented  with  rye, 
oats  and  barley,  in  loam,  in  pond  slime  (silt),  in  sandy  soil  and  garden 
earth.  In  seeding  rye  in  separate  wooden  boxes  no  difference  in  the  growth 
of  the  plants  was  shown  between  2  to  8  cm.  of  covering  (as  a  result  of  uni- 
form ventilation  from  all  sides).  In  experiments  in  the  open  ground  stem 
formation  seemed  more  favored  by  a  lesser  depth  of  the  seed,  yet  this  refers 
more  to  the  time  of  the  appearance  of  the  sprout  than  to  its  quality.  Oats 
and  barley  survive  a  deeper  sowing  than  does  rye.  In  siunmer  a  deeper  sow- 
ing of  the  seed  is  better  than  in  winter.  The  minim.um  covering  for  grain 
m.ay  be  1.5  to  2  cm. ;  the  maximum  favorable  for  results  is  6  cm. 

Later  experiments  of  the  same  author-  bring  another  important 
factor  into  consideration  which  for  the  same  soil  acts  as  a  modifier  of  the 
favorable  depth  for  sowing.  The  quality  of  the  seed  is  at  times  decisive. 
The  quality  of  wheat  seed,  however,  with  which  the  first  experiments  were 
made  did  not  seem  to  have  any  influence  on  the  capacity  for  germination  but 
the  development  of  the  young  plant  with  equal  depth  of  sowing  was  better, 
the  better  the  quality  of  the  seed.  With  a  medium  5  cm.  depth  of  sowing 
(experiments  with  sandy  soil)  all  qualities  gave  the  longest  straw  and  the 
longest  heads.  The  relation  of  the  w^eight  of  the  grain  yield  to  that  of  the 
straw  is  lower,  as  the  seed  is  poorer  and  the  sowing  deeper.  Experiments 
with  barley  confirmed  the  results  obtained  with  wheat ;  the  less  the  depth  of 
sowing  and  the  better  the  quality  used  for  the  same  depth  the  earUer  the 
seed  sprouted.  The  sum  of  the  sprouted  plants  was  no  less  with  inferior 
seed  but  the  influence  of  the  depth  of  sowing  was  so  felt  in  this  quality  that 
a  shallow  sowing  gave  a  much  longer  straw.  In  general  it  must  be  said  that 
Ihe  depth  of  sowing,  conditions  otherwise  being  thought  equal,  will  influence 
first  of  all  those  developmental  stages  which  are  connected  with  the  early 
stage.  However,  the  quality  of  the  grain  depends  upon  the  early  develop- 
ment in  the  number  of  sprouts  and  the  length  of  the  heads  as  well  as  the  for- 
mation of  the  young  heads  and  is  therefore  influenced  by  the  depth  of  the 
sowing.  On  the  other  hand  the  quality  of  the  harvested  grain  depends  upon 
the  nutritive  and  weather  conditions  of  the  current  year,  and  will  therefore 
be  scarcely  more  influenced  by  the  first  development  or  inherited  peculiarity 
of  the  grain. 


1  Ekkert,  Ueber  Keimung,  Bestocking-  und  Bewurzelung-  der  Getreidearten  etc. 
Inauguraldissertation.     Leipzig-  1874. 

2  Ekkert,    Kulturversuch    mit   Weizen    und    Gerste    verschiodener    Qualitat    etc. 
Fuhling's  Landw.  Zeit.,  1875,  Part  1;   1S76.  Parts  1  and  2. 


Soaking  of  the  seed,  which  has  often  been  recommended  for  Hght  soils 
when  tlie  time  for  seeding  lias  been  continuously  dry,  should  be  used  with  due 
care.  If  the  weather  becomes  dry  and  the  water  which  has  been  taken  up  in 
swelling  is  not  enough  to  make  the  primar}-  rootlets  grow  into  the  soil,  then 
there  is  an  unavoidable  interruption  in  growth.  This  is  the  explanation  of 
WoUny's  discovery^  that  soaking  produces  plants  maturing  later. 

Wollny's^  studies  on  the  suitable  dei^th  of  sowing  are  most  thorough ; 
he    determined    for   grain    tliat    sowing    2    to    3    cm.    deep    furnishes    the 


Fig.  9.     Rye  seedling-  with  too  deep  sowing  of  the  seed  grain.     Klevation  of 
the  node  of  the  sprout  near  the  surface  of  the  soil.     (Orig.) 


best  results  in  yield.  Over  and  above  this  a  noticeable  retrogression  is  found 
already  especially  emphasized  by  Jorgensen\  The  last  named  author 
also  found  rye  to  be  the  most  sensitive  and  wheat  the  least  sensitive.  For 
most  of  the  Leguminoseae  the  depth  of  the  sowing  is  less  important.  In  con- 
trast to  this,  varieties  of  clover  and  rape  have  been  proved  very  dependent 


1   Bot.  Centralbl.,  Vol.  XXX,   No.   15,  1SS7,   p.   48. 

-   Wollny,  Saat  und  Pflege  der  landwirtschaftl.    Culturpflanzen.    Berlin,  1885. 
3  Jorgensen,    S.,    Versuche    liber    das    Unterhringen    der    Saat    etc.      Annalen    d. 
Landw.  in  d.  Kgl.   Preuss.  Staaten.     Wochenblatt   1873.    No.   11. 


upon  the  depth  to  which  the  seeds  are  covered.  It  seems  desirable  to  have 
this  still  less  tlYkn  for  grain  (0.5  to  2.(5  cm.).  Wollny's  experiments  showed 
that  in  dry  years  a  deeper  earth  covering  was  more  advantageous,  in  wet 
years,  a  lighter  one.  Corresponding  to  wet  and  dry  weather  the  time  of  har- 
\  est  w^as  retarded  with  an  increasing  depth  of  sowing,  the  number  of  plants, 
which  germinated  at  all  and  still  more,  the  number  which  came  to  harvest,  was 
decreased.  But  it  must  be  emphasized  again  and  again  that  precise  figures 
for  the  most  favorable  sowing  in  the  different  localities  can  be  collected  only 
directly  by  the  local' agriculturalist  since  not  only  the  composition  of  the 
soil  and  the  weather  but  also  the  character  of  the  variety  must  be  con- 
sidered in  the  matter,  as  has  been  shown  by  Stossner\ 

This  same  holds  good  for  tubers,  bulbs  and  pieces  of  roots  which  are 
used  for  seeds.  In  these  the  soil  conditions  have  an  especial  weight  because 
these  fleshy  organs  which  are  rich  in  water  are  essentially  and  quickly  in- 
fluenced by  the  soil  supply  of  oxygen  .  For  potatoes,  experiments  by 
Nobbe-  and  Kiihn'  have  shown  that  in  questionable  cases  the  more 
shallow  sowing  wall  be  the  most  advantageous  one.  In  the  forcing  of  bloom- 
ing bulbs  excessive  losses  arise  at  times  from  the  fact  that  the  bulbs  (hya- 
cinths) have  been  planted  too  deep  in  the  pot,  or  when  in  the  pots  are  cover- 
ed too  deep  with  earth  after  the  rooting  has  been  sufficient.  Especially  if  the 
soil  covering  is  heavy  and  damp  and  the  bulbs  have  not  matured  sufficiently 
the  year  before  on  account  of  wet  weather,  the  "Rotz"  (see  this  in  A^ol.  IT.) 
usually  appears  very  easily. 

The  automatic  regulation  of  the  depth  of  sowing  on  the  part  of  dift'erent 
plant  races  is  interesting.  In  grasses,  and  in  fact,  best  seen  in  our  grain 
species,  the  first  internode  is  the  part  which  is  destined,  when  the  seed  grain 
has  been  sown  too  deep,  to  push  the  second  node  which  hides  the  stem  eye 
and  the  side  buds,  i.  e.  the  node  which  forms  the  stem,  into  the  porous,  well 
ventilated  upper  layer  of  soil.  In  the  adjoining  figure  9  we  perceive  the 
seed  grain  which  is  already  almost  empty  and  its  weakly  retained  (primary) 
roots  which  had  been  formed  in  the  grain.  From  the  seed  grain  the  first 
(over-elongated)  internode  has  pushed  the  second  node  nearly  up  to  the 
upper  surface  of  the  soil.  In  this  favorable  position  the  secondary  roots, 
which  exist  during  the  whole  life  of  the  plant,  have  been  developed,  the  eyes 
of  the  side  shoots  have  attained  a  further  maturity.  In  shallow  sowing  both 
nodes  lie  close  to  one  another  and  give  in  cross-section  such  a  picture  as  is 
shown  in  figure  10.  The  nodal  tissue  seems  divided  radially  by  browned  vascu- 
lar strands.  The  vascular-bundle  cylinders  are  those  of  the  primary  roots  and 
become  diseased  during  or  soon  after  the  formation  of  the  secondary  roots. 
The  ground  tissue  of  the  node  shows  the  first  circle  of  vascular  bundles  fg) 
of  the  young  blade  close  to  the  pith  shield  fin )  with  its'  few  cells.  Branches 
of  these  bundles,  recognizable  from  their  wide  ducts  (g),  may  be  seen  fur- 


1   Stossner,  l^ntersuchungen  liber  den  Einflu.s§  verschiedener  Aussaattiefen  et< 
Landwirtsch.    Jahrbiicher  ISSi. 

-  Nobbe,  Handbuch  der  Samenkunde,  1876,  p.  184. 

3  Kiihn,  Berichte  aus  dem  physiolog.  Laborat.  Halle,  Part  I.,  p.  43. 


TI4 


ther  out  in  the  axis.  This  young  blade  possesses  on  the  side  marked  T* 
uniformly  connected  bark  tissue;  on  the  opposite  side /i,  however,  the 
first  sheath-formed  leaf  (sch)  which  remains  colorless,  and  the  bud  of  the 
next  higher  leaf,  the  first  green  one  (bl),  which  is  completely  developed  later, 
have  been  difYerentiated  from  the  bark  tissue.  In  the  axis  of  this  first  leaf  may 
be  seen  the  meristematic  position  of  the  first  lateral  bud  ^^nj which  pushes 
out  the  green  leaf  lying  in  front  of  it  with  its  already  clearly  developed  epi- 


Fig.  10.     Cross-section  through  the  lowest  node  of  a  young  rye  plant. 
Explanation  of  lettering  in  text.     (Orig.) 

dermis  (e )  ;  e  is  the  epidermis  of  the  sheath  leaf  which  is  already  being 
differentiated  from  the  axis.  If  the  (dotted)  tissue  of  the  bud  of  the  first 
green  leaf  (bl)  be  traced  backward  in  this  cross-section  toward  the  side 
marked  V  it  is  seen  that  this  passes  over  into  a  colorless  tissue  ring  char- 
acterized, however,  by  its  comparatively  large  intercellular  spaces  contain- 
ing air  (i) ;  the  bark  tissue  of  the  young  blade.  It  is  seen  from  this  that  each 
grain  leaf  is  a  direct  continuation  of  the  bark  of  the  blade.    This  bark  ring 


EDGAR  TULLiS 

PART  II. 


MANUAL 


OF 


Plant  Diseases 

BY 

PROF.  DR.  PAUL  SORAUER 


Third  Edition—Prof.  Dr.  Sorauer 

In  Collaboration  with 

Prof.  Dr.  G.  Lindau       And       Dr.  L.  Reh 

Private  Docent  at  the  University  Assistant  in  the  Museum  of  Natural  History 

of  Berlin  in  Hamburg 


TRANSLATED  BY  FRANCES  DORRANGE 


Volume  I 
NON-PARASITIC  DISEASES 

BY 

PROF.  DR.  PAUL  SORAUER 

BERLIN 


WITH  208  ILLUSTRATIONS  IN  THE  TEXT 


PART  II. 


MANUAL 


OF 


Plant  Diseases 

BY 

PROF.  DR.  PAUL  SORAUER 


Third  Edition-Prof.  Dr.  Sorauer 

In  Collaboration  with 

Prof.  Dr.  G.  Lindau        And       Dr.  L.  Reh 

Private  Docent  at  the  University  Assistant  in  the  Museum  of  Natural  History 

of  Berlin  in  Hamburg 


TRANSLATED  BY  FRANCES  DORRANCE 


Volume  I 
NON-PARASITIC  DISEASES 

BY 

PROF.  DR.  PAUL  SORAUER 

BERLIN 


WITH  208  ILLUSTRATIONS  IN  THE  TEXT 


Copyrighted,    1915 

By 

FRANCES  DORRANCE 


THE   RECORD   PRESS 
Wilkes -Barr^,  Pa. 


115 

is  connected  on  the  side  [''  with  the  tissue  of  the  sheath  leaf  and  it  is  worth 
noting  that  this  sheath,  even  in  so  young  a  stage  of  blade  differentiation,  must 
liave  finished  its  work  since  the  tissue  is  entirely  impoverished  and  begins  to 
be  full  of  holes  (I). 

While  therefore  in  the  Gramineae  the  accessory  apparatus,  which  with 
too  deep  sowing  brings  the  vegetative  tip  into  the  abundantl}^  aerated  par- 
ticles of  soil,  consists  in  the  elongation  (observed  up  to  9  cm.)  of  the  lowest 
internode  and,  in  case  of  necessity,  also  of  the  one  above  it,  we  find  in  the 
Leguminoseae  and  other  dicotyledons  a  different  arrangement.  In  beans, 
for  example,  we  notice  first  of  all  an  increased  elongation  of  the  hypocotyle 
corresponding  to  the  need,  so  that  finally,  with  very  different  depths  of  sow- 
ing, the  growing  tip  of  the  stem  in  all  plants  is  found  at  approximately  the 
same  height.  Naturally  the  strength  of  the  plant  from  the  same  kind  of  seed 
is  decreased  as  the  depth  of  sowing  is  greater.  The  more  the  hypocotyle  must 
be  lengthened,  in  order  that  its  upper  part,  comparable  to  the  curved  back 
of  the  burden-carrier,  can  break  through  the  load  of  the  soil  and  bring  the 
cotyledons  to  the  light,  the  more  reserve  substances  will  be  used  up.  It  is 
therefore  very  evident  that  plants  coming  from  greater  depths  are  weaker 
even  if  they  have  not  lost  reserve  substances  in  the  seed  through  strong 
intra-molecular  respiration.  Such  will  be  the  case,  however,  if  continued  wet 
weather  sets  in  after  too  deep  sowing  so  that  a  shortage  of  oxygen  results. 

The  experiments  by  Godlewski  and  Polzeniusz^  show  what  amounts  of 
reserve  substances  can  be  lost  through  intra-molecular  respiration  and  the 
formation  of  alcohol.  Sterilized  peas,  in  evacuated  air,  produced  in  the  first 
period  almost  as  much  carbon  dioxid  as  in  normal  respiration  in  the  air. 
The  whole  amount  exceeded  20  per  cent,  of  the  original  dry  substance  of  the 
seed.  The  amount  of  alcohol  formed  corresponds  to  that  of  the  carbon 
dioxid.  Only  during  the  sixth  week  did  the  production  of  carbon  dioxid 
cease  in  the  peas  which  lay  in  sterilized  water  and  up  to  that  time  possibly 
40  per  cent,  of  the  dry  substances  present  had  been  broken  down  to  alcohol 
and  carbon  dioxid.  This  is  also  the  case  in  grains.  In  grains  the  action  of 
the  secondary  roots  on  the  nodes  of  the  stem  counteracts  this  weakening. 
In  legumes  a  similar  process  of  self  assistance  can  now  take  place,  since,  as 
Wollny  proved,  adventitious  roots  are  formed  from  the  over-elongated 
liypocotyle  member.  He  observed  this  on  the  parts  of  the  stem  which  had 
been  covered  with  soil,  not  only  in  field  beans,  but  also  in  peas,  sweet  peas, 
lentils,  lupines  and  plants  of  other  families, — rape  and  sunflowers.  But  the 
legumes  often  are  not  capable  of  using  such  an  a'ccessory  apparatus  since, 
with  normal  depth  of  sowing  and  capacity  for  germination,  they  easily  suc- 
cumb to  other  dangers  which  will  be  described  in  the  section  on  "condition 
of  hard  shells." 


1  Godlewski  unci  Polzeniusz,  Ueber  Alkoholbildung  bei  der  intramolekularen 
Atmung  hoherer  Pflanzen.  Anzeig.  Akad.  d.  Wiss.  Krakau,  cit.  Bot.  Jahresb.  1897, 
p.  142. 


ii6 

Roots  From  the  Tip  of  Grain  Sf.kds. 

It  seems  best  to  add  here  an  account  of  a  case  which,  because  of  its 
pecuharity  and  rareness,  deserves  a  permanent  place  in  science. 

The  agricultural  teacher,  Wolfes  in  Dargun  (Mecklenburg-Schwerin), 
sent  me  in  1876,  fourteen  wheat  grains  in  which,  through  hypertrophy,  the 
embryo  did  not  lie  to  one  side  of  the  endosperm,  but  occupied  a  middle 
position.  The  grains  were  sown  in  the  fall  and  in  the  spring  they  had  partly 
rooted  but  without  developing  plumules.  They  were  either  slender,  pear- 
shaped  or  even  cylindrical  at  the  one  end,  tapering  rapidly  at  the  other  like 
the  neck  of  a  violin.  In  many  grains  (Fig.  11-12)  the  elongation  of  the 
slender  end  opposite  the  embryo  was  so  marked  that  a  neck  was  formed, 
possibly  2  to  3.5  mm.  long,  and  twisted  toward  the  upper  end. 

In  twelve  grains  the  length  of  which  varied  from  ^  to  1I4  cm.  the 
neck  bore  a  large  number  of  very  thin,  thread-like  roots  i  to  2  cm.  long, 
closely  arranged  like  a  brush.  These  were  pubescent  almost  their  entire 
length. 

Upon  attempting  carefully  with  a  needle  to  raise  the  wrinkled  and  oc- 
casionally ruptured  testa  of  the  grain  it  was  found  to  be  closely  attached  to 


Fig.   ]].     Wheat  grains  with  root.s  not  originating-  from  the  ■emljryo  but   springing 
from  the  hypertrophied  testa  at  tlie  tip  of  the  seed  grain. 

the  grain  in  different  places  and,  when  broken  off,  was  usually  of  a  darker 
color.  On  the  other  hand  its  upper  part  was  firmly  connected  with  the  beak- 
like growth  along  almost  its  whole  length  and  could  be  raised  from  the  grain 
proper  like  a  straw  cap  (Fig.  12).  The  neck  therefore  at  the  time  of  the 
investigation  was  not  connected  with  the  actual  grain  except  by  the  testa 
from  the  substance  of  which  it  also  seemed  to  be  formed.  In  the  fresh  con- 
dition of  the  grain  this  had  been  firmly  set  on  the  seed  since  various  concave 
places  on  the  inner  wall  of  the  cap,  perceptible  through  the  microscope,  fitted 
on  to  the  small  convex  elevations  visible  on  the  seed  grains. 

There  was  another  equally  noteworthy  phenomenon,  namely,  that  the 
fissure,  normally  present,  was  lacking  in  these  wheat  grains.  The  grain, 
which  had  been  dug  up,  also  failed  to  show  the  seedling  which  lies  at  the  base 
of  the  normal  grain  and  is  easily  recognizable  through  the  seed  coat;  it  was 
not  noticeable  in  the  seeds  observed.  The  endosperm  itself,  when  cut  apart, 
finally  showed  only  a  small  degree  of  the  white  color  of  the  healthy  grain. 
There  were  long,  glassy,  translucent  and  yellowish  streaks  extending  from 
the  edge  inward.  It  had  a  rancid  odor.  The  blue  iodin  reaction  for  starch 
was  strong  only  in  those  particles  of  the  grain  which,  on  the  freshly  cut 


117 


Fig.  12.     Wheat  grain  with  hypertrophied  testa  and  root  formation  at  its  tip.  Embryo 
central  instead  of  lateral.     Explanation  of  letters  in  the  text.     (Orig.) 


ii8 

surface,  were  found  to  be  wliite  and  mealy,  wliile  f»n  the  s^lassy  ])laces  there 
was  only  a  slight  reaction. 

The  glutinous  layer  in  the  Mecklenburg  grain  was  not  developed  at  all, 
the  thin  seed  shell  only  incompletely.  In  place  of  this  glutinous  layer  (Fig. 
12  k)  a  plate-like  parenchyma  was  found,  the  content  of  which  did  not 
differ  essentially  from  that  of  the  underlying  tissue. 

The  most  striking  thing  connected  with  this  abnormal  wlieat  grain  was, 
however,  the  position  of  the  embryo  on  the  opposite  end  from  that  which 
bore  the  roots  (Fig.  12  w)  and  exactly  in  the  middle  of  the  grain  (as  in 
Typhaceae)  equally  surrounded  on  all  sides  by  the  tissue  of  the  starch- 
containing  endosperm.  While  in  the  normally  constructed  wheat  grain  the 
seedling  lies  without,  at  the  base  of  the  grain,  and  is  connected  with  the 
endosperm  by  a  special  organ,  the  scutellum  (the  cotyledon),  the  seedling 
lies  here  (Fig.  12  e)  without  cotyledons  in  a  central  cavity  (Fig.  12  h)  of 
the  grain. 

This  cavity  in  some  of  the  grains  is  elliptical,  in  others  triangular.  In 
some  it  extends  possibly  to  the  middle  of  the  grain,  in  others,  becoming 
narrower  and  narrower  toward  the  top,  it  reaches  to  the  tip,  even  penetrating 
into  the  tissue  of  the  cap.  On  the  inner  side  it  is  lined  with  a  layer  formed 
of  two  plate-like  rows  of  cells  of  a  glutinous  content  (Fig.  12  a)  which 
clearly  resembles  the  glutinous  layer  deposited  in  healthy  grains  outside  the 
endosperm. 

The  young  leaves  of  the  seedling,  folded  over  one  another,  show  no 
essential  variation.  On  the  contrary,  the  number  of  secondary  roots  formed 
in  whorls  at  almost  equal  distances  (Fig.  12  r)  steadily  increases  up  to  6  to  8 
and  these  roots  appear  to  be  covered  by  a  parenchymatous  layer  arranged  in 
the  manner  of  cork  cells,  6  to  8  cells  thick  and  free  from  starch. 

On  this  tissue  lies  the  combined  and  modified  seed  coat  (Fig.  12  sf) 
which  in  dry  grain  becomes  thicker  walled  with  more  abundant  cells  toward 
the  tip  and  develops  imperceptibly  into  the  cap  which  the  root  bears  at  its 
tip  (Fig.  12  w). 

The  vascular  bundle  is  continued  into  the  cap  from  the  roots.  Here  are 
often  found  several  bundles  united  at  the  tip  of  the  cap  into  a  ring-like, 
thicker  network  of  ducts  running  horizontally  and  resembling  a  node  of  the 
stalk. 

Still  further  back  from  the  tip  these  vascular  bundles  (Fig.  12  g),  iso- 
lated near  the  outer  edge  of  the  inside  of  the  cap,  are  seen  to  run  backward 
(Fig.  12  gg).  The  endosperm  normally  has  no  fully  developed  vascular 
bundles  and  the  cotyledons  only  embrj^onic  ones.  Here,  however,  the  vas- 
cular bundles  take  an  often  irregular  course  through  the  endosperm  and, 
in  the  individual  grains,  surround  the  seedling  in  a  semi-circle  and  have 
not  developed  even  though  the  grains  lay  in  the  soil  over  winter. 

By  cutting  cross-sections  from  the  diseased  grains  and  submitting 
them  to  microscopic  investigation,  the  probable  cause  of  this  striking  mal- 


TI9 


friTn 


formation  was  seen  at  once.  The  inability  of  the  seed  covering  to  free  itself 
entirely  from  the  grain  was  due  to  a  connected  firm,  homogeneous,  some- 
what dark  mass   (Fig.  13)  ;  the  presence  of  thick,  much  ramified  mycelial 

threads,  often  provided 
with  short  skein-like  groups 
of  branches,  could  be 
proved.  The  threads  of  the 
colorless,  strongly  refrac- 
tive mycelium  grew  trans- 
versely through  the  very 
thick  w^alls  (Fig.  13  m)  of 
the  fruit  cells  and  seed  coat 
which  had  been  merged  into 
one  another.  The  mycelial 
threads  grew  more  thickly 
when  the  cells  were  richer 
in  content  and  thinner  wall- 
ed, entirely  filling  some  cells 
of  the  endosperm  (Fig.  13 
mm). 

Near  such  places  the 
starch  had  been  dissolved 
and  the  cytoplasm  had  be- 
come solid  as  if  it  had  been 
dried.  In  other  cells  a  firm 
network  of  protoplasmic  material  scarcely  distinguishable  from  starch  could 
be  seen.  These  were  almost  imperceptible  in  the  starch  grain  but  yet  were 
there.  This  substance  was  apparently  deposited  about  the  starch  grains  but 
upon  examination  there  were  no  grains 
present,  only  the  corresponding  cavities. 
In  some  such  way  originated  the  yellow- 
ish, translucent  places  between  which 
lay  groups  of  cells  especially  rich  in 
starch.  These  mixed  regions  gave  the 
proper  iodine  reaction  under  a  weak 
magnification. 

The  variation  in  the  structure  of  the 
diseased  grain  is  best  shown  by  compar- 
ing figures  13  and  14.  The  latter  repre- 
sents a  section  from  a  corresponding 
part  of  a  healthy  gain.     The  seed  coat 

(Fig.  13-14  fs)  in  the  diseased  grain  is  more  than  three  times  as  thick  as  in 
the  healthy  grain.  In  the  abnormally  developed  seed  coat  there  is  a  com- 
pletely developed  vascular  bundle  with  a  clearly  recognizable  sheath  (gs). 
In  the  diseased  grain  the  growing  fruit  membrane  passes  directly  over  into 


Fig-.  13.     Hypertrophied  testa  traversed  by  mycelia. 


Fig-.  14.  Normal  fruit  and  seed 
membrane  together  with  the  gluti- 
nous layer. 


the  endosperm  (e),  and  in  the  liealthy  one  the  gluten  layer  (Fig.  14  ^)lies 
between  the  two  tissues. 

Investigations  of  such  grains  in  the  "imported"  seed  show  a  similar 
condition.  The  seeds  seem  malformed  and  the  fact  that  the  malforma- 
tion manifests  itself  in  the  position  of  the  embryo  as  well  as  in  the  develop- 
ment of  the  endosperm  and  especially  in  the  thickened  growth  of  the  seed 
coat  proves  that  this  malformation  must  have  been  completed  when  the 
grain  was  forming  in  the  head.  Fertilization  has  nevertheless  taken  place 
normally  since  the  embryo  displays  leaves  and  growing  point  as  well  as  roots 
(the  latter  in  increased  numbers).  But  some  local  stimulus  must  at  once 
have  incited  a  cell  increase  in  the  fruit  tissue  and  thereby  displaced  the  em- 
bryo from  the  side  towards  the  middle  of  the  endosperm.  This  stimulus 
was  active  during  the  whole  development  of  the  seed  and  increased  the  vege- 
tative activity  so  that  the  character  of  the  endosperm  underwent  a  change, 
for  the  vascular  bundles  are  those  of  a  vegetative  axis.  We  observe  a  most 
important  numerical  increase  of  the  cells  in  the  tips  of  the  seed,  assuming 
the  character  of  a  vegetative  axis  and,  by  means  of  the  entangled  vascular 
bundles,  resembling  a  stalk  node.  Abundant  roots  develop  at  these  stalk 
nodes  and  it  is  not  improbable  that  leaf  buds  might  have  begun  had  there 
been  a  greater  aeration  of  the  soil  layers.  We  would  then  have  had  a  case 
similar  to  that  in  dicotyledonous  plants  when,  as  has  often  been  observed, 
vegetative  axes  develop  from  their  fruit  nodes. 

For  such  processes,  however,  the  seed  lay  too  deep.  There  was  no  ac- 
cessory apparatus  for  raising  the  seed  to  the  upper  surface  of  the  soil,  such 
as  the  elongation  of  the  first  internode  in  the  seedling.  As  a  result  bacterial 
decomposition  followed,  due  to  the  lack  of  oxygen,  as  was  shown  by  the 
rancid  smell  of  butyric  acid. 

This  is  the  reason  for  mentioning  the  present  case  here.  Had  it  been 
possible  to  determine  exactly  the  causative  fungus  the  case  w'ould  have  be- 
longed under  parasitic  diseases.  As  it  was  impossible  to  make  the  my- 
celium fruit,  the  case  becomes  hypothetical  as  to  the  nature  of  the  parasite. 
Only  one  thing  is  certain — viz.,  that  the  stimulating  mycelium  did  not  belong 
to  the  black  fungi  (Cladosporium,  etc.).  According  to  Bref eld's  latest  in- 
vestigations on  the  penetration  of  the  smut  into  the  blossoms,  it  is  highly 
probable  that  the  smut  spores,  which  have  entered  the  blossom,  germinate 
soon  after  the  fertilization  of  the  grain,  and  by  the  slow  advance  of  their 
mycelia  have  exerted  the  stimulus  on  the  seed  coat. 

3.     Greater  Horizontal  Differences. 

The  individual  development  within  the  same  plant  species  is  influenced 
by  horizontal  changes  in  the  place  of  cultivation  from  north  to  south,  or  east 
to  west,  as  well  as  by  the  vertical  elevation  of  the  habitat.    ]>.  Candolle^  laid 


1  Sur  la  methode   de   sommes   de   temperature   appliquee   aux   phenomenes   de 
v#g6tation.    Separatabzug  der  Bibliotheque  universelle  de  Gen§ve  1875. 


121 

down  the  principle  that  with  approximately  equal  latitude  and  elevation,  the 
temperatures  above  0°  in  shade  are  higher  for  the  same  developmental 
phase  (time  of  blossoming,  defoliation,  etc.)  in  the  western  parts  of  Europe 
than  in  the  eastern  ones.  Observations  show  that  in  Europe  the  length  of 
the  growth  period  decreases  toward  the  northeast  and  increases  towards  the 
southwest.  Because  of  the  many  mountain  chains  and  plateau-like  inter- 
ruptions the  phenomenon  is  less  clearly  evident  in  western  Europe  than  on 
the  great  level  plains  of  Russia.  Kowalewski's^  very  remarkable  work  re- 
ports on  this  phase.  This  is  based  on  the  statements  of  2200  agriculturalists 
scattered  throughout  all  parts  of  European  Russia,  who  had  reported  the 
time  of  sowing  and  harvesting  of  the  grain.  Since  cultivation  must  be 
adapted  to  climatic  conditions,  the  usual  times  for  sowing  and  harvesting 
show  the  existing  vegetative  conditions. 

The  sowing  of  winter  rye  takes  place  in  the  southern  part  of  the  Gov- 
ernment of  Kherson  on  the  15th  of  September-,  at  Archangel,  on  the  first  of 
August.  The  localities  of  simultaneous  plantings  of  winter  rye  do  not  run 
parallel  to  the  degrees  of  latitude,  but  are  inclined  from  N.  W.  to  S.  E.  ; 
therefore,  they  run  almost  in  the  same  direction  as  do  the  isocheims.  The 
difference  in  the  time  of  harvesting  winter  rye  in  the  far  north  (Archangel) 
and  in  the  south  (Kherson)  extends,  like  the  time  of  sowing,  over  a  month 
and  a  half.  The  seeding  period  for  summer  grain  in  the  far  north  is  one- 
third  to  one-fourth  as  long  as  at  the  southern  limit.  At  the  western  it  is  two 
to  two  and  a  half  times  longer  than  at  the  eastern.  The  time  of  harvesting  in 
the  north  is  hkewise  one-third  as  long  as  in  the  south ;  in  the  west  once  and 
a  half  to  twice  as  long  as  in  the  east.  The  localities  of  simultaneous  ripen- 
ing of  summer  grain  run  from  S.  W.  to  N.  E.,  corresponding  therefore  in 
their  direction  with  the  isotheres. 

The  growth  period  in  southern  and  southwestern  Russia  is  only  85  to 
no  days  for  rye,  buckwheat,  flax  and  barley, — but  no  to  125  days  for  sum- 
mer wheat,  millet,  oats  and  peas.  Sugar  beets,  maize  and  potatoes  have  the 
longest  growth  period, — 150  to  165  days.  Thus,  in  the  south,  the  longest 
growth  period  is  almost  twice  as  long  as  is  the  shortest.  On  the  other  hand, 
in  the  north,  the  periods  concerned  are  not  only  shorter  everywhere  but  are 
also  more  simultaneous.  In  the  far  north  and  northeast  the  difference  be- 
tween the  longest  and  the  shortest  growth  periods  does  not  exceed  10  to  20 
days. 

For  the  same  cultivated  plant,  in  European  Russia,  the  rate  of  develop- 
ment increases  on  the  average  with  the  latitude.  Thus,  for  example,  oats  in 
the  Government  of  Kherson  (south)  have  a  growth  period  of  123  days, 
wheat  and  barley  one  of  no  days.  In  the  north,  however,  (Archangel)  the 
growth  period  of  oats  decreases  to  98  days,  that  of  wheat  to  88  days,  of  bar- 


1  Kowalewski,  W.,  Ueber  die  Dauer  der  Vegetationsperiode  der  Kulturpflanzen 
in  ihrer  Abhangiglveit  von  der  geograpliischen  Breite  und  Lange.  Arb.  d.  St.  Peters- 
burger  Naturforscherges.,  XV,  1884  (russisch),  cit.  Bot.  Centralbl.,  1884,  No.  .^1, 
p.  367. 

2  All  dates  are  given  old  style  as  still  used  in  Russia. 


ley  to  98  days.    In  the  same  geographical  latitude,  a  longer  vegetation  period 
is  found  in  the  west  than  in  the  east. 

'Jhe  causes  of  the  shortening  of  the  growth  periods,  therefore,  cannot 
lie  in  the  warmth  which  the  plants  receive  at  a  corresponding  degree  of  lati- 
tude, for  otherwise  the  plants  in  the  south  would  have  passed  through  their 
development  considerably  more  quickly  than  in  the  north,  also  since  the 
southern  black  soil  is  raised  to  a  higher  temperature  than  the  heavier,  often 
clayey  and  damp  soil  of  the  north.  l)esides  this,  the  lack  of  moisture  in  the 
south  hastens  maturity  very  greatly.  Some  other  factor  must  therefore  be 
determinative.  Kowalewski  states  this  to  be  ihe  lerujth  of  the  insolation. 
He  now  assumes  May  5th  to  be  the  mean  time  for  sowing  oats  and  August 
20th  as  the  mean  time  for  harvesting  them,  finding  thereby  an  insolation 
period  of  2000  hours  for  the  98  days  of  vegetation  in  Archangel.  If  the 
period  of  bright  nights  be  added  to  this,  there  is  an  increase  amounting  to 
2240  hours.  Kherson  oats  are  sown  on  March  20,  harvested  on  July  20th. 
In  this  123  days  of  vegetation,  however,  only  1850  insolation  hours  obtain. 
Further,  as  Kowalewski  says,  it  must  be  noted  that  the  cultivated  species  of 
the  north  are  adapted  to  a  lesser  degree  of  warmth.  Therefore,  when 
brought  to  the  south,  they  ripen  comparatively  earlier.  This  result  agrees 
with  the  one  found  by  Schiibeler'  which  will  be  mentioned  later.  Similar 
observations  are  said  to  have  been  made  in  Canada  also. 

In  further  explanation  of  the  change  in  the  length  of  vegetation,  Kowa- 
lewski brings  forward  the  greater  intensity  of  illumination,  the  small  cloud 
masses  and  the  greater  humidity  of  the  atmosphere  and,  supported  by  Fa- 
mintzin's  investigations,  he  believes,  for  example,  that  the  light  optimum 
for  assimilation  is  exceeded  in  the  south  and  therefore  has  a  retarding  in- 
fluence. This  would  correspond  to  the  yellowing  of  the  shade-loving  plants, 
when  grown  in  high  mountains.  It  is  not  necessary  to  fall  back  upon  the 
theory  of  the  retarding  action  of  the  southern  excess  of  light,  if  Wiesner's 
theory  be  accepted.  In  explaining  the  utilization  of  light  on  the  part  of 
plants  in  the  far  north,  Wiesner-  emphasizes,  according  to  his  investigations, 
the  fact  that  in  regions  of  the  far  north  (Tromso),  with  an  equal  elevation 
of  the  sun  and  an  equal  clouding  of  the  sky,  the  chemical  intensity  of  the 
daylight  has  been  shown  to  be  greater  than  in  Vienna  and  Cairo,  but  less 
than  in  Buitenzorg  in  Java.  The  light  factor  of  the  far  northern  regions  is  dis- 
tinguished in  its  illuminating  quality  by  a  relatively  marked  equability  which 
obtains  in  no  other  locality  where  plants  flourish.  The  plants  of  the  arctic 
vegetative  zone  receive  the  greatest  amount  of  light  as  a  whole.  Here,  in 
the  low  growing  plants  there  is  no  self-shading  due  to  their  own  foliage, 
and  even  woody  plants  in  adjacent  southern  regions  show  only  a  minimum 
amount  of  shade-producing  branches. 


1   Schiibeler,  Die  Pflunzenv.elt  Norwegens. 

-  Wiesnor,  .1.,  Beitrage  zur  Kenntnis  des  photo-chemischen  Klimas  im  arktis- 
chen  Gebiete.     Sitz.  Akad.  d.  Wiss.  Wien  CVII,  cit.  Bot.  Jahresb.  1898,  I,  p.  r.86. 


123 

Wittmack  has  reviewed  earlier  cultural  experiments  as  to  the  behavior 
of  plants  indigenous  to  any  given  locality  when  artifically  introduced  to  a 
region  farther  souths  His  conclusions  follow; — plants  from  the  north  de- 
velop somewhat  more  slowly  in  middle  Europe,  catch  up  later  with  the  in- 
digenous ones,  however,  or  even  exceed  them.  It  is  evident,  therefore,  that 
the  short  growth  period,  which  has  become  habitual  in  the  north,  is  often 
still  more  shortened  by  the  increased  w^armth  of  the  southern  habitat,  pro- 
vided also  that  the  climate  be  dry.  The  damp  climate  of  England  with  its 
low^  maximum  temperatures  retards  ripening.  The  humidity  of  the  air  is  a 
1  actor  of  great  power  and  can  delay  ripening;  just  as,  conversely,  regions 
with  great  periods  of  drought,  the  climate  of  the  steppes  and  similar  con- 
ditions, not  dependent  on  the  degree  of  latitude,  form  limited  centres  where 
plants  ripen  prematurely.  Too  great  drought  certainly  retards  development, 
as  has  been  determined  experimentally.  Stahl-Schoder's  experiments,  cited  in 
the  chapter  on  "Excess  of  Water,"  treat  of  soil  dryness.  The  period  of  the  in- 
fluence of  heat  is  very  important  and  is  indeed  explicable.  Heat  in  July  and 
August  is  more  advantageous  than  in  May  and  June  but  the  reverse  is  true 
for  rain. 

Wittmack's  summary  in  general  shows  the  significance  of  the  physical 
structure  of  the  soil  in  relation  to  the  early  ripening; — that  the  vegetative 
time  in  eastern  regions  is  shorter  for  the  same  varieties  of  grain  than  in 
western  ones. 

Based  on  the  observation  that  the  varieties  cultivated  in  northern 
climates  retain  their  shorter  growth  period  in  the  immediately  following 
developmental  periods,  an  active  trade  in  northern  seed  has  been  developed. 
Meanwhile  the  quantity  of  the  harvest  should  not  be  lost  sight  of.  Abundant 
supply  of  nutrition  being  uniformly  assumed,  the  quantity  depends  always 
on  the  length  of  the  vegetative  period, — i.  e.,  the  time  of  the  formation  of 
shoots.  The  longer  time  the  grain  has  for  the  formation  of  vegetative 
organs  (as  in  damp,  cool  seasons)  the  more  abundant  is  the  grow^th  of 
shoots  and  with  it  the  formation  of  a  greater  number  of  ears  from  the  in- 
dividual seeds. 

H  we  should  carry  into  the  east  varieties  produced  in  the  west,  which 
are  long-lived  and  characterized  by  great  productivity,  we  would  run  the 
risk  of  frosts.  This  is  most  strikingly  true  in  the  English  varieties  of  wheat, 
from  the  squarehead  group,  wdiich  to\\'ard  the  east  come  less  and  less  true 
to  seed,  because  they  winter  kill.  Experience  shows  in  regard  to  frost-resis- 
tance, that  seeds  from  northern  regions  give  plants  in  southern  latitudes 
which  at  times  not  only  ripen  earlier,  in  spite  of  an  initial  retardation,  but 
also  better  withstand  frost. 

From  the  result  of  Schiibeler's^  observations,  it  should  be  emphasized, 
that  the  quick  growth,  which  has  become  habitual  in  northern  or  Alpine 


1  Ueber  vergleichende  Kulturen  mit  nordischem  Getreide,  Von  Dreisch,  Kor- 
riicke,  Kraus,  Vilmorin  and  others,  referred  to  by  Wittmack.  Landwirthsch.  Jahrb. 
1875,  p.  479.  and  1876,  pp.  613  ff. 

-   Schiibeler,  Die  Pflanzenwelt  Norwegens,  1873,  pp.  77  ff. 


12-4 

climates  because  of  a  short  vegetative  period,  is  lost  after  four  or  five  years 
of  cultivation  in  lower  latitudes.  Conversely,  long-lived  varieties  accustom 
themselves  in  a  few  years  to  a  short  vegetative  period.  Yellow  chicken 
maize  from  Hohenheim,  for  example,  which  ripened  in  1852  at  Christiana 
in  120  days  after  repeated  sowings,  shortened  its  growth  period  to  the  extent 
of  30  days  in  1857.  In  Christiana  the  developmental  period  of  barley  is  90 
days,  but  seed  brought  from  Alten  (the  70th  parallel)  needed  only  55  days 
(see  Kowalewski). 

Of  the  chemical  properties  developed  in  a  nortliern  habitat,  which  in 
great  measure  correspond  to  the  changes  in  plants  in  high  elevations,  the 
fact  that  the  sugar  content  of  the  fruits  decreases  toward  the  north  while 
the  aroma  increases  is  of  especial  importance.  Bonnier  and  Flahault  main- 
tain also  that  not  only  the  size  of  the  leaves  increases  in  the  darkness  of  the 
north  but  also  their  green  color^.  Schiibeler's  experiments  in  summary- 
give  the  following  special  examples : — In  wheat  brought  from  Ohio  and 
Bessarabia,  the  grain  became  darker  in  color  each  year  until  it  was  as  yellow 
brown  as  the  native  Norwegian  winter  wheat.  vSimilar  results  were  obtained 
with  maize,  beans,  peas,  celery,  etc.  Celery  taken  from  a  region  extending  from 
the  Caucasus  to  Hindustan,  grows  in  Africa  (Egypt,  Abyssinia  and  Algeria) 
and  may  be  found  in  Europe  from  the  Mediterranean  to  the  Baltic ;  it  now 
extends  even  into  Finland  up  to  the  69th  parallel.  There,  however,  the  root 
stalks  are  poorly  developed ; — the  aroma,  nevertheless,  becoming  more 
pungent^.  The  greater  intensity  of  color  in  the  blossoms,  as  already  men- 
tioned, a  peculiarity  shown  to  correspond  with  an  increasing  elevation  above 
sea-level,  also  appears  in  most  garden  flowers  as  cultivation  advances  to- 
wards the  north.  In  regard  to  the  formation  of  aromatic  substances,  be- 
sides celery,  juniper  may  also  be  cited  as  an  example.  In  Norway  it  is  much 
richer  in  oil  than  in  Central  Europe.  Onions  also  and  garlic  are  uncom- 
monly pungent  in  Norway.  Strawberries  are  sour  but  aromatic,  while, 
according  to  Gotze,  they  are  exceedingly  sweet  in  Coimora,  but  almost  with- 
out any  aroma.  Plums  often  remain  so  sour  that,  compared  with  fruit 
brought  from  more  southerly  regions,  they  still  seem  immature.  A  similar 
condition  exists  with  grapes  as  shown  by  comparing  the  sweet  Portugese 
grape  with  the  less  sweet  but  aromatic  Rhenish  grape. 

In  considering  the  horizontal  differences,  expressed  in  the  decrease  of 
rainfall  and  increase  of  clearness  of  the  air,  from  the  west  towards  the  east, 
in  the  conditions  of  light  between  southern  and  northern  regions  etc.,  we 
should  not  forget  one  circumstance,  to  which  de  Candolle*  has  already 
called  attention.    This,  to  be  sure,  has  not  been  sufficiently  verified  experi- 


1  Bonnier  et  Flahault,  Observations  sur  les  modifications  des  vegetaux  suivant 
les  conditions  physiques  du  milieu.  Annal.  d.  sc.  nat.  Botanique,  t.  VII,  Paris  1879, 
p.  93. 

2  The  effects  of  Uninterrupted  Sunlight  on  Plants.  Gard.  Chron.  1880,  I.  p.  272. 

3  Hansen,  C,  Der  Sellerie.     Gartenflora,  1902,  p.  18. 

4  de  CandoUe,  A.,  Sur  la  methode  des  sommes  de  temperature  appliquee  aux 
ph€nom&nes  de  la  v4g6tation.  Archiv.  des  sc.  physiques,  etc.  Nouv.  ser.  LIU.  L.IV. 
Genf  1875,  cit.  Bot.  Jahresber.    1875,  p.  585. 


125 

mentally,  but  finds  repeated  substantiation  in  practical  experience.  It  is 
namely  the  greater,  more  complete  dormant  period  of  plants.  According  to 
Ihne\  trees  which  thrive  normally  in  Central  Europe  and  in  Coimbra  put 
out  their  leaves  possibly  a  month  earlier  in  Coimbra  and  their  autumnal 
change  of  color  occurs  about  a  week  and  a  half  later  than  with  us.  Thus 
their  dormant  period  is  about  six  weeks  shorter  there.  The  length  and  com- 
pleteness of  this  dormant  period,  however,  must  influence  greatly  the  rate 
of  subsequent  development.  It  may  indeed  be  assumed  that,  with  the  con- 
tinuation of  a  temperature  which  does  not  stop  the  functions  entirely,  a 
number  of  vegetative  processes  continue  with  a  slow  but  steady  consumption 
of  materials  (process  of  oxidation)  and  without  any  compensation  to  the 
plant  through  newly  assimilated  substances.  Besides  this,  it  seems  that 
many  enzymes,  which  affect  the  energy  of  metabolism,  either  succeed  in  de- 
veloping to  the  necessary  amount  only  during  a  complete  dormant  period, 
or  are  made  ready  for  it.  If  no  complete  rest  takes  place  it  may  be  observed 
especially  in  the  two  or  three  year  old  bushes  and  in  the  buds  on  branches 
of  woody  plants.  These  are  forced  earlier  and  produce  weaker  organs 
(smaller  leaves,  a  greater  number  of  sterile  blossoms). 

The  increased  weight  of  the  seeds  in  northern  latitudes  has  already 
been  considered.  There  are,  however,  some  experiments  by  Petermann"- 
which  prove  a  higher  germinating  pozver  of  Swedish  seeds  of  clover  varie- 
ties, timothy  (Phleiim  prafense  L.j,  and  of  spruces  and  pines  as  compared 
with  German,  French  and  Belgian  seeds.  The  Swedish  seeds,  which 
actually,  on  an  average,  possess  a  greater  weight,  show  greater  power  of 
germination,  not  only  in  the  number  of  fertile  seeds  which  can  germinate, 
but  also  in  the  energy  with  which  germination  takes  place.  These  results 
may  be  explained  very  well  by  a  greater  developmental  energy  in  the  plants, 
due  to  a  more  complete  winter  rest. 

These  observations  have  a  very  noteworthy  practical  bearing  in  so  far  as 
they  affect  the  culture  of  seeds  obtained  in  exchange.  It  is  not  enough 
merely  to  introduce  seed  from  other  regions,  but  it  will  seem  necessary  to 
ask  above  all,  what  characteristics  it  is  desired  to  improve  in  the  cultivated 
plant  and  in  what  climates  these  characteristics  attain  a  higher  development. 
Taken  from  such  localities  the  seed  will  then  give  the  desired  results. 

The  cultural  results,  obtained  by  using  plants  of  other  climates,  hold 
good  as  a  rule,  however,  only  for  a  very  few  growth  periods.  Often  the  in- 
fluence of  the  present  habitat  is  felt  in  the  second  generation  when  the  plants 
of  foreign  importation  have  assumed  the  habits  of  the  native  varieties. 
Fruit  trees  taken  from  Angers  grew  and  bloomed  on  Malorka  even  at  the 
end  of  February,  while  the  native  ones  did  not  blossom  until  a  month  later^. 
A  shipment  made  two  years  later  from  Angers  showed  the  same  phenom- 


1  Ihne,   Phanolog-ische  Mitteilungen.    Cit.   Bot.  Jahresb.  1898,  II,  p.  409. 

-  Petermann,  Recherches  sur  les  gi'aines  ori^naires  des  hautes  latitudes. 
Extrait  du  t.  XXVIU.  des  Memoires  couronnes  et  autres  Memoires  publics  pai- 
I'Acad.  Royale  de  Belgique,  Bruxelles,  1877. 

3  Gartenzeitung  von  Wittmack,  1882,  p.  374. 


enon.  The  fruit  trees  of  the  first  shipment  were  now,  however,  blossoming 
later,  i.  e.,  simultaneously  with  the  native  ones.  The  transition  from  the 
hereditary  form  of  growth  to  the  new  one  determined  by  the  climatic  con- 
ditions is  rarely  effected  as  rapidly  as  it  is  lost  when  returned  to  its  former 
habitat.  Yet.  in  our  vegetables,  we  have  examples  of  a  rapid  change  in 
pecularities.  In  a  tropical  climate  these  keep  approximately  their  own  char- 
acter only  in  the  first  year.  Already  in  the  second  year  the  seeds  of  these 
imported  plants  produce  elongated,  lignified  specimens'.  These  are  our  cul- 
tivated forms  which  are  beginning  to  vary  from  the  normal.  No  rapid 
changes  are  noticeable  in  species  growing  wild,  as  has  been  shown  by  Hoff- 
mann's experiments  with  parallel  seeding  of  certain  forms  of  Phaseolus 
and  Triticum  in  Giessen,  Genoa,  Montpelier,  Portici  and  Palermo-.  On 
the  other  hand,  Hoffmann  mentions  slow  changes,  first  taking  place  in  the 
course  of  many  generations.  Thus  Ricinus  communis  becomes  tree-like  and 
perennial  in  the  tropics,  in  the  same  way  Reseda  odorafa  becomes  more  or 
less  persistent  in  New  Zealand  and,  conversely,  Bellis  percnnis  becomes  an 
annual  in  St.  Petersburg. 

Among  the  changes  in  mode  of  growth,  which  are  onl\-  slowly  com- 
pleted, belongs  the  formation  of  the  annual  rings  in  our  trees.  At  any  rate 
the  distribution  of  vascular  spring  wood  and  the  slightly  vascular  summer 
wood  within  the  same  degree  of  latitude  fluctuates  in  each  year  according 
to  the  amount  and  distribution  of  precipitation.  But  in  the  changes 
of  the  average  weather,  due  to  changes  in  latitude,  the  same  dif- 
ferences become  constant  and  form  therel)y  ecolf)gical  varieties.  Bonnier'* 
treats  thoroughly  such  anatomical  differences  in  the  development  of  the 
same  species  in  northern  and  southern  positions.  He  compares  examples 
of  the  linden,  red  beech,  acacia  and  others  from  the  region  of  Toulon  (with 
its  260  days  of  active  growth)  with  those  at  Fontainebleau  (growth  period 
178  days)  and  found  that  the  spring  wood  develops  better  in  the  south, 
hiaving  more  abundant,  often  wider  ducts.  In  this  the  abundance  of  precipi- 
tation in  the  spring  in  the  Mediterranean  district  surely  has  a  definite  bear- 
ing. The  summer  wood  of  the  south,  however,  is  richer  in  libriform  fibres 
and  often  consists  only  of  these,  while  at  Fontainebleau  numerous  ducts  are 
formed.  e\en  in  summer.  Tlie  lea\es  of  the  Toulon  plants  were  shown  to 
be  one-third  to  one-half  thicker  and  pr(j\ided  with  more  layers  of  palisade 
parenchyma  in  comparison  with  the  plants  grown  in  the  north.  The  stomata 
are  more  numerous,  the  sclerenchyma  is  greater  and  the  cuticle  strength- 
ened. The  Toulon  plants  exhibit  the  character  of  Mediterranean  flora  in 
general. 

Tlie  greater  intensity  of  the  color  of  the  blossoms,  as  the  plants  advance 
from  the  plains  to  the  mountains  and    from    lower    latitudes    to    northern 


1  Deutsche  Gartnerzeitung,  1883,  No.  17. 

-  Hoffman,  H.,  Riickblick  auf  meine  Variaiionsversuche  von  1855  bis  1880.  Bot. 
Z.,  1881,  p.  430. 

3  Bonnier,  Cultures  experimentales  dans  la  legion  mediterraneenne,  etc.  Cit. 
Bot.  Jahresb.  1902,  II.  p.  299. 


127 

regions,  has  already  been  considered.  Recently  attention  has  also  been  di- 
rected to  the  increased  change  of  color  in  foliage  leaves  and  its  peculiar 
significance  as  a  protecti\e  adaptation  has  been  suggested.  MacMillan^ 
treats  of  these  conditions  very  fully.  lie  speaks  of  "ivarming-up  colors" 
meaning  especially  the  red  coloring  substances  which  are  more  abundantly 
represented  in  colder  regions.  Alpine  and  arctic  plants  are  more  often 
found  with  blue  or  violet  blossoms  than  with  yellow  ;  the  ends  of  the  twigs 
are  often  reddened.  The  temperature  is  somewhat  raised  by  the  red  coloring 
matter  and  the  influence  of  cold  somewhat  weakened.  If  one  thermometer 
be  covered  with  a  green  leaf  and  another  with  a  purple  one,  while  both  are 
exposed  to  the  sun,  in  a  short  time  the  thermometer  protected  by  the  purple 
leaf  shows  a  rise  of  6°  to  io°  of  temperature.  In  the  same  way  he  found 
that  a  thermometer,  stuck  in  a  bunch  of  violets,  shows  a  higher  temperature 
than  one  in  a  bunch  of  cowslips,  after  an  equal  ex])osure  to  the  sun. 

The  autumnal  coloring  may  be  conceived  as  a  definite  reaction  of  the 
plant  to  the  lowered  temperature.  The  plant  provides  warmth  for  itself  in 
its  red  coloring  matter.  On  this  account  so  many  spring  flowers  are  red 
and  violet  and  autumn  flowers  blue  or  red. 

In  warm  climates  plants  often  assume  peculiarities  directly  opposite  to 
those  of  arctic  or  alpine  plants.  In  tropical  plants  the  storage  cells  are  less 
strongly  developed  than  in  related  species  from  colder  regions.  The  buds 
are  less  protected,  pubescent  coverings  more  rare  on  leaves  and  twigs  (with 
the  exception  of  desert  plants).  Many  winter  habits  disappear.  There  are 
fewer  biennials.  The  warming-up  colors  recede  more  and  more,  while 
\^hite,  yellow  and  spotted  blossoms  (Orchids)  predominate. 

Nature  would  develop  red  coloring  matter  to  prevent  loss  of  the  super- 
fluous light  and  to  transform  it  into  warmth  and  to  use  it  as  a  stimulus  to 
growth. 

Wit  cannot  support  this  theory  of  the  premeditated  utility  of  the  red 
coloring  matter  as  an  apparatus,  producing  warmth  and  weakening  the 
light,  even  if  we  had  such  an  inclination.  If  the  red  coloring  matter  has 
once  been  produced,  it  wdll  be  effective  in  the  way  given.  The  idea  that  the 
plant  can  produce  it  as  a  protection  against  cold,  when  the  temperature  be- 
comes lower,  is  not  plausible,  because  in  the  hottest  summer  temperature 
leaves  can  be  reddened.  In  the  Rosaceae  which  are  rich  in  tannin  (Crataegus, 
for  example),  I  have  been  able  to  produce  the  red  autumnal  coloring  after 
a  few  weeks  in  the  middle  of  summer  by  girdling  the  twigs.  The  fact  that 
in  summer  the  underside  of  many  leaves,  when  reversed,  becomes  red  within 
a  few  days  is  universally  known.  Parasites  furnish  further  instances.  On 
the  same  cherry  tree.,  for  example,  the  leaves  of  branches  attacked  by 
Exoacus  Cerasi  turn  glowing  red,  while  the  healthy  ones  remain  green.  In 
many  spot  diseases  the  circular  fungus  centre  appears  surrounded  by  red. 
Amaryllidaceae,  whose  leaves  die  down  in  summer  (Hippeastrum  etc.), 
develop  carmine  spots  and  stripes. 

1  MacMillan,  Conway,  Minnesota  Plant  Life    Saint  I'aul,  Minnesota,  1899,  p.  417. 


128 

Thus  we  believe  that  the  red  coloring  matter  may  be  looked  upon  as  a 
necessary  reaction  of  the  cell  to  the  influence  of  different  factors  connected 
with  a  relatively  over-abundant  supply  of  light.  One  of  these  factors  may 
be  the  lowering  of  the  temperature  due  to  a  change  in  the  latitude  or  longi- 
tude of  the  place  of  growth. 

If  we  look  back  to  the  many  changes  undergone  by  the  plants  in  their 
morphological  and  chemical  structure  because  of  any  change  in  latitude  of 
the  place  of  growth,  we  cannot  shut  our  eyes  to  the  conviction,  that  not  in- 
frequently in  these  changes  of  place  may  be  sought  the  reason  for  a  predis- 
position toward  disease  or,  on  the  other  hand,  toward  greater  immunity. 

We  have  mentioned  that  the  western  squarehead  wheat  grown  in 
eastern  regions  has  greater  susceptibility  to  frost  and  now  remind  the 
reader  that  parasitic  diseases  may  also  be  dependent  on  the  different  mode 
of  development  of  the  host  plant  inherited  in  the  seed.  One  should  con- 
sider, for  example,  the  fact  that  many  parasitic  fungi  appear  or  are  especial- 
ly abundant  at  definite  periods.  In  case  such  fungi  only  attack  young  leaves, 
the  presence  of  young  leaves  when  the  spores  are  ripening  will  determine  an 
epidemic.  The  rapidity  with  which  a  plant  passes  through  its  develop- 
mental cycle  in  any  given  climate  is  a  determining  factor  in  this  question. 
If  it  develops  slowly,  its  leaves  are  young  and  remain  susceptible  for  a  longer 
time,  giving  a  greater  danger  of  fungus  infection.  If  a  variety  matures 
quickly  (for  example,  one  introduced  from  more  northern  or  eastern 
regions)  then  the  leaf  may  be  fully  matured  at  the  time  of  the  actual  distri- 
bution of  the  spores  and  therefore  be  resistent  to  many  parasites. 

Such  circumstances  deserve  greater  consideration  than  has  been  given 
them  as  yet.  They  will  also  be  a  factor  in  the  discussion  of  the  "biological 
races"  of  individual  parasites,  for  it  is  most  probable  that  often  infections 
of  the  most  closely  related  host  species  fail  because  the  host  plant  at  the 
time  of  infection  is  already  in  an  advanced  developmental  stage,  in  wliich 
the  leaf  is  more  mature,  i.  e.,  has  thicker  walls  and  less  cell-content.  The 
fact  that  the  fungus  infection  is  connected  with  a  definite  developmental 
stage  of  the  host  plant  is  shown,  for  example,  in  the  rust  fungi  of  grains. 
Eriksson^  states  that  the  rust  occurs  earlier  in  the  varieties  ripening  early 
and  recent  observations  show  that  the  different  forms  of  Puccinia  have  defi- 
nite periods  for  attacking  grain.  Thus  it  was  shown  in  1904-  that  Puccinia 
gluiiuirmn  a[)i)eared  first  and  foremost  in  wheat,  then  followed  P.  dispersa 
which,  however,  attacked  only  those  organs  and  varieties  which  were  still 
immature.  Later,  slowly  ripening  varieties  of  wheat  were  found  badly  at- 
tacked by  P.  dispera  and  slightly  by  P.  glumarum,  wdiile  the  converse  is 
true  for  varieties  maturing  early.     P.  graminis  was  found  in  stored  grain. 


semence 

2  Jahre 
Getroiderost 


sson,  J.,  Sur  I'origine  et  la  propagation  de  la  rouille  des   cereales  par  la 
Ann.   .scienc.   nat.    Bet.   VITT.    ser.   VoLs.   XIV.   and  XV.    Paris   1902. 
•esb.  d.  Sonderausschussos  f.  Pflanzen.schutz.     Deutsche  Landw.  Ges.  1905 


129 

Glassy  Grain  Kernels. 

These  must  also  be  considered  as  the  result  of  climate  influences. 

Grains  are  called  glassy  when  their  endosperm  is  hard,  almost  trans- 
lucent and  grey  or  reddish  in  cross-section,  while  in  the  normal  mealy 
kernel  the  endosperm  appears  soft,  white,  porose  and  easily  friable. 

This  glassiness  of  the  kernels  occurs  usually  more  abundantly  in  the 
north  and  east  of  Europe  than  in  the  west,  which  fact  points  to  the  influence 
of  atmospheric  dryness  with  a  higher  light  intensity.  In  damper,  western 
regions  the  vegetative  organs  obtain  a  greater  ascendancy.  Thus  Lieben- 
berg^  states,  for  example,  that  the  otherwise  excellent  northern  barley  has 
two  disadvantages ; — viz.,  too  large  a  percentage  of  glassy  grains  and  too 
dark  a  color  which  is  caused  by  rain  falling  on  the  grain  when  ready  for 
harvesting.  These  gusts  of  rain  at  harvest  time  naturally  play  no  part  in 
the  development  of  grains  which  mature  during  the  dry  season.  With  the 
lengthened  light  action,  varieties  of  rye  also  become  intensively  colored. 
The  same  author  reports  that  at  the  grain  exhibition  in  Sweden,  the  oat 
samples,  on  an  average,  possessed  only  22.66  to  32.04  per  cent,  of  chaff  by 
weight,  while  in  the  Austrian  and  French  varieties  it  fluctuated  between 
25.23  and  38.37  per  cent.  In  general  there  is  truth  in  Haberlandt's"  state- 
ment, that  a  continental  climate  produces  glassy  grains,  but  that,  on  the 
other  hand,  cool,  wet  summers  or  an  artificial  abundance  of  nutritive  sub- 
stances and  water  produce  mealy,  specifically  lighter  grain  kernels,  poorer 
in  nitrogen. 

The  glassy  condition  of  the  grain,  according  to  Gronlund's^  investiga- 
tions on  mealy  and  glassy  barley,  exists  in  the  fact  that  the  cells  of  the  albu- 
men in  the  mealy  grain  which  contain  the  starch  show  that  the  spaces 
between  the  starch  cells  are  filled  with  cell-sap,  while  in  the  glassy  grains 
these  spaces  are  filled  with  protoplasm.  Johannsen's*  work  assumes  a 
greater  air  content  not  only  between  the  walls  of  the  mealy  grains,  but  in 
their  whole  mass.  In  germination,  the  glassy  grains  become  mealy.  Ac- 
cording to  Gronlund,  who,  moreover,  acknowledges  no  relation  between 
weather  and  the  production  of  the  glassy  conditions,  glassy  kernels  germi- 
nate more  easily  and  better  and  give  stronger  plants.  Although  he  assumes  as 
mcontestible  that  glassy  kernels  may  be  produced  from  soil  containing  much 
nitrogen,  yet  he  believes  that  poorer,  sandier  soil,  poorly  cultivated,  pro- 
duces this  peculiar  formation  much  more  certainly.  He  found  that  mealy 
grain  was  produced  by  pure  potassium  fertilisation.  Moreover,  both  forms 
occur  at  times  in  different  stages  in  the  same  head.  I  would  like  to  assume 
for  the  production  of  glassy  kernels  that  the  process  of  starch  formation  is 


1  V.  Liebenberg-,  Bericht  uber  die  allgemeine  nordische  Samenausstellung  etc., 
1882,  cit.  Bot.  Centralbl..  1882.  No.  43,  p.  115. 

^  Haberlandt,  Die  Abhangigkeit  der  Ernten  von  der  Grofse  und  Verteilung  der 
Niederschlage.     Oesterr.  landw.    WochenbL,  1875,  p.  352. 

3  Nach  einer  Preisscheift  des  A^erf.  cit.  im  Jahresbericht  f.  Agriculturchemie 
XXIII  (1880),  p.  214. 

*  Allg-.  Brauer-  und  Hopfenzeitung-,  1884,  Nos.  78  and  79. 


130 

shortened  in  sandy  soil,  which  dries  quickly,  and,  since  potassium  makes  the 
corn  mealy,  I  would  much  sooner  believe  that  the  action  of  the  potassium  is 
stopped  too  soon  and  indeed  because  other  processes,  viz.,  those  of  ripening, 
take  place  too  early  and  too  intensively.  This  will  happen  much  more 
quickly  with  strong  action  of  light  and  warmth  and  when  the  water  con- 
tent is  less.  Sanio's'  statement  that  in  East  Prussia  the  glassiness  of 
wheat  is  due  to  its  becoming  overripe  on  the  stalk  supports  the  theory  of 
the  predominance  of  the  ripening  process  at  a  time  when  starch  formation 
should  be  taking  place.  This  opinion  is  analytically  supported  by  R.  Pott's 
investigations-  who  found  on  an  average  a  higher  percentage  of  ash  in 
glassy  varieties  of  wheat  than  in  mealy  kernels.  The  kernels,  in  the  too 
rapid  ripening,  had  not  completely  consumed  the  mineral  substances  in 
forming  organic  substances.  Compare  here  the  high  percentage  of  nitrogen 
in  the  grains  of  oats  plants,  which  suffered  from  a  scarcity  of  water  or 
from  its  excess  (see  chapter,  "Excess  of  Water"). 

Petri  and  Johannsen'  have  made  investigations  which  throw  much 
light  on  the  nature  of  glassy  kernels.  The  former,  as  early  as  1870,  stated 
that  glassy  kernels,  when  softened  by  water,  become  mealy  and  the  latter 
substantiated  this  observation.  Two  hundred  kilos  of  barley  were  moistened 
with  half  that  amount  of  water,  until  they  had  taken  up  15  per  cent.  They 
were  then  dried  immediately,  spread  and  turned  until  the  original  weight 
was  again  obtained.  The  percentage  of  mealy  kernels  now  was  50  per  cent., 
while  in  the  original  material  it  amounted  to  only  19  per  cent.  In  cultural 
experiments  it  was  found  that,  in  early  seeding,  a  mealier  barley,  poorer  in 
nitrogen,  had  been  formed,  while  in  later  sowing  the  harvested  product  was 
richer  in  nitrogen.  This  discovery  indicates  that  in  this  glassiness  of  the 
kernels  there  is  only  a  mechanical  difference,  which  develops  if  ripening  is 
very  much  hastened  by  a  scarcity  of  water  with  an  excess  of  light  and 
\varmth.  A  gradual  ripening  process  gives  a  longer  time  for  developing  an 
increased  starch  content  with  the  retention  of  a  larger  water  content  in  the 
substance  which  is  later  partially  replaced  by  air.  This  refers  especially  to 
the  protoplasm  in  the  endosperm  cells.  The  starch  grains  lie  embedded  in 
this.  With  quick  ripening,  the  cytoplasm  sticks  close  to  the  starch  grains, 
making  the  kernels  appear  glassy.  With  slower  ripening  and  greater  water 
content  the  cell  is  more  loosely  constructed,  while  between  the  starch  grains 
more  cell  sap  and  later  more  air  are  present,  and  then,  because  of  the  larger 
intercellular  air  spaces,  the  grain  is  opaque  and  mealy.  As  the  protoplasm 
predominates,  the  tendency  is  toward  glassiness,  and  on  this  account,  even 
normally,  the  outer  layers  of  the  seed,  as,  for  example,  in  maize,  are  glassy, 
the  inner  ones  mealy.  These  conditions  explain  .Schindler's  observations* 
that,  in  wheat  grains,  mealy  and  glassy  portions  can  alternate. 

1  Botanisches  Centralbl.,  1880,  p.  310. 

-  Jahresbericht  f.  Agriculturchemie  1870-72,  II,  p.  5. 

3  Johannsen,    Bemerkungen    tiber   mehlige    undglasige    Gerste    (Ugeskrift    for 
Landsmaend),  1887,  cit.  Biederm,  Centralbl.,  1888,  p.  551. 

4  Schindler,  Lehre  vom  Pflanzenbau  auf  physiologischer  Grundlage.     Wien  1896. 


131 

The  above  explanation  of  the  production  of  glassiness  is  substantiated 
by  the  experimental  results,  which  have  been  obtained  by  the  Deutsche 
Landwirtschafts-Gesellschaft\  The  report  states: — The  glassiness  of  the 
kernels  depends  more  on  the  conditions  of  growth  than  on  the  variety. 
Varieties  with  a  shorter  vegetative  period  are  glassier — such  as  Lupitzer, 
Strube's  bearded  and  Galician  club  wheat  in  comparison  to  Schlanstedter 
and  Noe  wheat.  The  productive  power  of  the  varieties  in  general  stands 
in  inverse  relaton  to  the  glassiness  of  the  grains. 

4.     Continental  and  Marine  Climates. 

The  characteristic  distinction  of  regions  influenced  by  the  ocean  con- 
sists in  the  lesser  fluctuation  between  summer  and  winter  temperatures, — 
since  the  summers  are  longer  and  cooler,  the  winters  warmer.  We  find  that, 
under  the  influence  of  the  Atlantic  Ocean,  spring  comes  earlier,  while  au- 
tumn is  delayed  longer  than  in  regions  with  a  continental  climate.  Yet  the 
effect  on  vegetation  is  not  the  one  expected,  in  spite  of  the  earlier  spring, 
for  the  blossoming  time  of  wooded  plants  is  at  most  only  a  few  weeks 
earlier,  because  of  a  cooler  spring  temperature  and  the  ripening  of  the  fruit 
is  scarcely  earlier,  indeed,  it  is  often  delayed  and  occasionally  does  not  take 
place  at  all.  Consider,  for  example,  grapes  which  do  not  ripen  out  of  doors 
in  England.  Throughout  the  year,  the  air  is  more  moist  and  in  the  change 
of  season  extensive  heavy  mists  often  prevail. 

Haberlandt's  opinion  has  already  been  mentioned,  according  to  which 
early  maturity  of  plants  may  appear  with  the  same  ease  in  northern  latitudes 
as  in  southern  ones,  and  thus  lead  to  the  production  of  corresponding  varie- 
ties. Conditions  of  humidity  also  act  determinatively  in  this  and  all  become 
evident  in  the  great  fluctuations  in  a  continental  climate  in  contrast  to  an 
uniformly  damp  coast  climate.  Haberlandt's  culture  experiments"  gave 
results  as  follows.  Seed  brought  from  damp  climates  gives  proportionately 
more  straw,  but  less  grain, — the  grain  is  also  more  easily  subject  to  lodging. 
On  the  other  hand,  in  seed  from  dry  regions,  with  a  short  spring  and  hot, 
dry  summer,  there  is  a  production  of  less  straw  and  greater  grain  crops, 
and  plants  from  such  seed  better  withstand  drought.  When  exchanging 
seed  it  is  more  advantageous  to  take  it  from  countries  with  a  continental 
climate.  The  hard  winters  influence  the  grain  product  in  such  a  way  that 
the  plants  produced  are  less  apt  to  winter  kill  than  those  which  have  been 
transplanted  to  the  East  from  the  moister  west  with  its  milder  climate. 

The  continental  climate  produces  smaller  but  specifically  heavier  grain, 
while  a  cool  and  damp  summer  or  an  artificial  abundant  supply  of  water 
and  food  substances  increases  the  size  of  the  grain,  to  be  sure,  but  at  the 
same  time  causes  more  porous  contents,  since,  instead  of  the  glassy  con- 


1  Mitteilungen  der  Saatzuchtstelle  iiber  wichtige  Sortenversuche.  Saatliste 
vom  6.  Dez,  1914.     Deutsche  Landwirtsch.-Ges. 

-  Haberlandt,  Fr.,  Ueber  die  Akklimatisation  und  den  Samenwechsel.  Oesterr. 
landw.  Wochenbl.,  1875.     No.  1. 


132 

dition,  a  mealy  one  appears,  together  with  a  decreasing  specific  weight  and 
decreasing  nitrogen  content. 

Finally  an  important  observation  bearing  on  the  exchange  of  seed  is 
the  fact  that  w^inter  grain  coming  from  regions  above  the  45th  parallel 
of  latitude  and  cultivated  by  us  in  the  spring,  does  not  produce  shoots,  while 
on  the  other  hand,  that  taken  from  lower  latitudes  behaved  with  us  like 
summer  grain. 

Because  of  the  great  interest  on  all  sides  in  the  colonies,  it  is  necessary 
to  take  tropical  conditions  into  consideration.  Here  the  differences  of  tem- 
perature on  the  land  and  between  land  and  sea  attain  a  greater  significance. 
Thus,  for  example,  Fesca^  reports,  in  regard  to  the  great  warming  of  the 
land  in  direct  sunlight  as  compared  with  that  of  the  sea,  that  the  tempera- 
ture of  the  tropical  ocean  rarely  exceeds  30°C.  w^hile  the  rock  is  heated  up 
to  60°  to  70°C.  Pechuel-Loesche  observed  a  soil  temperature  above  75°C. 
on  the  west  coast  of  Africa  in  the  5th  parallel  of  south  latitude,  not  less 
than  36  times  between  January  ist  and  March  4th.  In  contrast  to  this, 
however,  stands  the  nightly  cooling  down  to  I5°C.  and  less.  Daily  fluctua- 
tions of  the  soil  temperature  from  30°  to  40°C.  are  very  frequent  in  the 
tropics  while,  on  the  other  hand,  the  daily  fluctuations  of  the  sea  might  at 
most  reach  i°C. 

As  a  result  of  the  differences  in  the  morning  quality  of  land  and  sea, 
a  low  barometric  pressure  must  be  produced  on  land  in  the  day  with  the  in- 
tensive sunhght,  so  that  the  air  from  the  sea  streams  in  that  direction  and, 
conversely  at  night.  These  sea  and  land  breezes  are  considerably  more  in- 
tensive in  the  tropics  and  sub-tropics  with  the  stronger  contrasts  in  warm- 
ing land  and  water  and  form  a  factor  to  be  reckoned  with.  According  to 
Saito^  the  air  above  the  sea  is  almost  free  from  mould  fungi,  bacteria  and 
yeast  germs,  while  the  air  above  the  land  (street  and  garden  air  in  Tokyo 
was  investigated)  was  especially  rich  in  germs  in  wet  and  warm  periods. 
Thus  the  sea  breezes  act  as  purifiers  of  the  air.  The  sea  breezes  decrease 
towards  the  poles,  since  the  sea  gradually  assumes  a  higher  mean  heat  than 
the  land  and  also  because  the  daily  fluctuations  of  the  soil  are  less. 

For  the  same  reason  the  changing  annual  wdnds,  the  monsoons,  corres- 
pond to  the  periodic  daily  winds  in  the  strong  warming  of  the  great  conti- 
nents to  which  vegetation  must  adapt  itself. 

The  amount  of  precipitation  occurring  as  rain  depends  also  on  the  re- 
lation to  the  sea  and  the  temperature  and,  accordingly,  it  is  most  abundant 
in  a  warm  sea  climate,  scantiest  in  a  continental  one.  An  annual  mean  of 
9°C.  approximately  holds  for  all  the  German  North  Sea  coasts.  With  an 
80  per  cent,  saturation,  the  air  would  contain  7.26  g.  water  vapor  in  a  cubic 
meter.  If  the  air  cools  down  to  4°C.  it  can  hold  only  6.9  g.  water  vapor  per 
cubic  meter  and  the  difference  must  therefore  be  eliminated  as  precipitation. 

1  Pflanzenbau  in  den  Tropen  und  Subtropen,  p.  23. 

-  Saito,  Untersuchungen  liber  die  Atmospharischen  Pilzkeime.    Journ.  College  of 
Science,  Tokyo.    Vol.  XVIII. 


133 

If  tropic  air  reaches  25°C.  with  the  same  saturation  (80  per  cent.)  it  con- 
tains 18.48  g.  water  vapor  and  ehminates  1.18  g.  water  per  cubic  meter  when 
cooled  down  to  5°C.  This  amount  of  precipitation  therefore  is  more  than 
three  times  that  of  air  at  9°C.  when  influenced  by  the  same  decrease  in  tem- 
perature on  the  North  Sea  coasts.  Thus  are  explained  the  heavy  tropic 
rains  and  especially  the  heavy  fall  of  dezv  which,  in  places,  must  suffice  for 
a  certain  period  in  hot  climates  as  the  only  source  of  water. 

Just  as  in  cultivation  experiments,  soil  analyses  and  mean  temperature 
offer  no  sufficient  insight  into  a  possible  utilization  of  food  substances  on 
the  part  of  cultivated  plants,  just  so  httle  can  the  annual  rain  fall  indicate 
the  moisture  conditions  of  a  region.  For  it  depends  essentially  upon  the  soil 
conditions  and  the  distribution  of  the  precipitation  in  the  different  months. 
Over  a  greater  part  of  the  desert  of  Sahara  (see  Fesca)  the  same  or  a  greater 
amount  of  rain  falls  than  that  sufficient  for  Germany's  agriculture  (60  cm.) 
without  its  having  there  any  essential  effect.  For,  on  a  highly  heated  soil, 
moisture  exaporates  immediately.  The  most  desirable  distribution  of  rain 
in  the  tropics  is  not  the  one  extending  uniformly  throughout  the  whole  year, 
but,  viz.,  at  the  beginning  of  the  vegetative  period  an  abundant  precipitation 
and  then  a  time  of  dryness.  The  abundant  clouds  in  the  rainy  season  con- 
tribute essentially  to  the  production  of  a  cooler  temperature  which  is  es- 
pecially favorable  for  the  development  of  the  vegetative  organs. 

Along  the  coast  the  climate  is  cloudier  than  it  is  inland.  In  regions  of 
great  atmospheric  dryness,  as  in  the  Mediterranean  basin,  often  there  is 
only  20  per  cent,  cloudiness  as  an  annual  average :  in  the  dryest  months  often 
only  10  per  cent., — in  the  moist  tropics  not  infrequently  more  than  80  per 
cent.  Since,  howeven  the  cloudiness  decreases  the  taking  up  and  giving  off 
of  heat,  the  temperature  of  the  lower  latitudes  is  less  and  that  of  the  higher, 
greater.  Many  cultivated  plants  require  these  lower  temperatures  and 
cloudiness.  We  believe,  with  Zimmerman^,  that  many  diseases  in  coffee  plan- 
tations, especially  the  excessive  production  of  fruit,  may  be  due  to  insuf- 
ficient shading.  In  the  same  way  it  may  be  that  the  great  susceptibility  to 
fungous  diseases  which  has  appeared  in  the  last  15  years-  since  tea  has  been 
cultivated  in  the  Caucasus,  has  been  due  in  part  to  the  difference  of  the 
Caucasian  climate  from  that  of  the  regions  from  which  tea  was  introduced. 

The  development  of  the  plant  body  is  of  course  adaptable  to  the  climatic 
conditions  and  factors  of  growth.  The  more  recent  biology  takes  these  cir- 
cumstances into  consideration  as  is  shown  by  the  work  of  Hansgirg".  He 
speaks  of  stenophyllus  wind  leaves  (as  in  the  willow  type)  ;  of  leather 
(coriaceous)  and  wind  leaves  (palm  type)  ;  of  xerophyllus  leather  leaves 
(Myrtus,  Laurus),  of  dew  leaf  types   (BromeHaceae,  Pandaneae)  ;  thick 


1  Zimmermann,    Sonderberichte    iiber   Land-    und   Forstwirtschaft   in   Deutsch- 
Ostafrika.     Vol.  I,  Part  5,  1903. 

2  Speschnew,    Travaux    du   jardin   bot.    de    Tiflis   VII,    1    Verhandl.    d.    Internat. 
landwirtsch.  Congresses  in  Rom  1903. 

3  Hansgirg-,  A.,  Phyllobiologie  nebst  Uebersicht  der  biologischen  Blatttypen  etc. 
Leipzig,   Borntrager,   1903. 


134 

leaves  (Crassula  and  mesembryanthemum  types)  etc.  The  most  conspic- 
uous example  is  the  vegetation  of  the  sea  shore  with  its  halophytic  character. 
Brick^  explains  the  fleshy  and  glassy  constitution  of  the  vegetative  organs  as 
due  to  the  abundance  of  sodium  salts,  which  makes  the  parenchyma  ex- 
tremely turgid. 

The  greater  the  number  of  examples  showing  the  adaptation  of  the 
plant  to  climatic  conditions,  the  more  marked  will  be  the  untt'na])ility  of  the 
theory,  that  the  cliniatic  relations  formed  in  each  place  of  cultivation  can  be 
changed  at  will  without  causing  injury.  If  the  whole  sum  of  the  climatic 
factors  should  correspond  in  two  widely  separated  localities  this  would  be 
no  guarantee  that  the  given  plant  would  thrive  as  well  in  the  new  home 
as  in  the  old,  since  the  distribution  of  light,  heat  and  moisture  can  be  proved 
to  be  very  different  in  the  different  periods  of  growth.  The  diseases  of  the 
New  Holland  and  Cape  plants  which,  adapted  to  a  dry  climate,  must  pass 
their  lives  in  our  sunless,  damp  conservatories,  give  the  most  abundant 
proof.  Decay  of  stem  and  root,  dying  of  the  twigs  caused  by  Botr}'tis  etc.. 
constantly  cause  injuries  to  the  successful  cultivation  of  these  plants.  The 
so-called  damping  off  of  the  shoots  of  Pimelea,  Chorizema,  Pulteneae,  Cor- 
rea,  Boronia,  Agathosma,  and  Borosma,  of  Helichrysum,  Humea  etc.,  is  a 
result  of  the  great  humidity  in  our  conservatories  which  can  not  be  over- 
come. 

5.     Influence  of  Forests. 

The  forestration  of  a  locality  modifies  the  influences  of  the  position  and 
soil  constitution  and  to  this  point  pathology  must  pay  especial  attention. 
The  influence  of  forests  is  like  that  of  surfaces  of  water,  for,  since  organic 
substances  possess  a  higher  specific  warmth  than  do  mineral  substances,  the 
overgrown  soil  will  be  cooler,  with  an  equal  exposure  to  the  sun,  than  the 
naked  rock  or  sand.  The  summer  heat  is  also  moderated  by  forests.  With 
the  abundant  evaporation  of  the  foliage,  the  air  becomes  more  moist,  the 
thicker  the  growth  and  the  less  motion  in  the  air.  Corresponding  to  the 
greater  evaporation,  there  is  a  more  abundant  cloud  formation  over  forests 
which  is  not  so  easily  dispersed.  Since  the  relative  humidity  of  the  air  is 
greater  in  and  above  the  forest,  much  more  dew  is  formed.  The  force  of  the 
rain  gusts  is  decreased.  Since  torrential  rains,  especially  on  slopes,  cannot 
be  taken  up  as  quickly,  the  mass  of  water  runs  off  from  the  naked  earth 
and  at  the  same  time  carries  away  the  fine  humus  from  the  higher  fields  to 
the  lowlands.  The  annual  repetition  of  this  process  so  changes  the  conditions 
of  the  fields  that  the  higher  places  become  impoverished  and  retain  only  a 
slightly  fertile  soil  skeleton,  while  on  the  low  lands  the  humus  layers  keep  on 
growing.  The  power  of  the  soil  to  retain  water  decreases  with  the  loss  of 
humus  and  injuries  due  to  a  scarcity  of  water  show  themselves.  In  heavy 
soils  the  steady  beating  of  the  rain  drops  in  severe  storms  tends  to  form  a 
crust. 


1  Brick,    Beitrage    zur   Biologie    und   verg-leichenden    Anatomie    der    baltischen 
Strandpflanzen.  Cit.  Bot.  Jahresb.  1888,  I,  p.  765. 


135 

All  these  unfavorable  conditions  are  overcome  by  the  forest,  the  tops  of 
the  trees  catching  the  rain  and  partially  retaining  it.  Nevertheless  the  water, 
which  passes  through  and  runs  down  along  the  trunks,  is  retained  by  the 
moss  and  the  dry  leaves  in  deciduous  forests,  forming  the  upper  surface  of 
the  soil  or  the  humus,  thus  becoming  of  benefit  to  the  vegetation.  Furst's^ 
"lUustriertes  Forst-  und  Jagdlexikon"  gives  some  positive  figures  on  these 
theoretical  discussions.  Based  on  the  observations  of  the  forest  meteorologi- 
cal stations,  it  is  stated  that  the  temperature  of  the  air  in  the  annual  average 
is  possibly  o.8°C.  lower  under  the  close  roof  of  tree  crowns  of  the  forests, 
than  in  the  open.  The  difference  is  greatest  in  summer  (up  to  3°C.)  while 
it  approximates  the  annual  average  in  spring  and  autumn  and  almost  dis- 
appears in  winter.  "The  fluctuations  in  temperature  are  less  under  the 
shelter  of  the  tree  crowns  than  in  the  open." 

The  temperature  of  the  forest  soil  is  from  i  to  3°C.  lower  at  all  seasons 
of  the  year  than  that  of  open  land.  The  absolute  moisture  does  not  differ 
in  the  forest  and  in  the  open ;  but,  on  account  of  the  lower  temperature,  the 
relative  moisture  in  the  forest  during  the  winter,  spring  and  autumn  is  from 
4  to  8  per  cent,  higher  than  in  the  open,  and  in  summer  from  12  to  20  per 
cent.  The  evaporation  from  a  free  surface  of  water  in  the  forest  is  from 
50  to  60  per  cent,  less  than  in  the  open;  "the  evaporation  of  the  water  from 
the  soil  is  reduced  from  80  to  90  per  cent."  Of  the  precipitated  moisture, 
10  to  50  per  cent,  will  be  retained  by  the  crowns  of  the  trees,  according  to 
the  species,  the  age  and  dimensions  of  the  forests  as  well  as  the  amount  of 
precipitation,  and  in  light  rains  it  often  amounts  to  100  per  cent.  In  general 
60  to  80  per  cent,  reaches  the  soil  in  the  forest.  "In  Central  Europe 
the  annual  and  the  summer  temperature  will  be  lowered  1°  and  2°  to  3°C. 
by  the  dimensions  of  the  forest  and  the  relative  moisture  raised  ca.  5  per 
cent,  and  15  per  cent." 

Since  the  amount  of  the  distant  action  from  extended  forestration  has 
not  yet  been  determined,  the  question  as  to  the  influence  of  the  forest  on 
chmate  must  remain  open.  But  one  effect  of  the  forest  on  the  immediate 
vicinity  cannot  be  denied  and  this  phytopathologists  must  consider. 

Differences  in  insolation  are  felt  slightly  in  the  forest,  but  very 
quickly  and  strongly  in  the  open  field.  The  soil  is  warmer;  the  layers  of  the 
air  lying  above  it  must  necessarily  produce  an  equalizing  air  current  which 
is  most  significant  in  spring  when  vegetation  awakens. 

Hesselmann's-  investigations  give  an  insight  into  forest  vegetation. 
He  observed  the  regular  dying  of  the  twigs  which  takes  place  within  the 
crowns  of  the  trees  and  found  that  in  birch  and  mountain  ash  the  leaves 
were  still  strongly  active  in  assimilation ;  but  in  the  hazle-nut  markedly  less 
so.  If  well-lighted  branches  die,  phenomena  of  correlation  are  at  fault. 
Trees  which  can  live  in  shade   develop  distinct  sun  and  shade  leaves;  trees 


1  Illustriertes  Forst-und  Jagdlexikon,   2nd.  Ed.,  revised  by  Dr.  Hermann  Fiirst, 
Berlin  1904,  Paul  Parey,  p.  384. 

2  Hesselmann  Hendrik,  Xur  Kenntnis  des  Pflanzenlebens  scliwedischer  Laub- 
wiesen.    Jena,  Fischer,  1904.     Cit.  Bot.  Centralbl.  v.  Lotsy,  1904.     No.  49. 


136 

which  require  Hght  do  not  show  this  difference.  The  assimilation  activity 
of  the  flora  of  the  forest  floor  is  very  rapid  in  spring  when  the  trees  and 
trunks  are  still  bare  and  decreases  with  the  foliation  more  slowly  in  shade 
trees,  because  of  their  structure,  until  it  finally  ceases  entirely.  The  respira- 
tory intensity  decreases  with  the  decreased  "food  consumption."  Detached 
shade  leaves  of  Convallaria  majalis  etc.,  form  more  starch  in  the  sun  as  well 
as  in  the  shade  than  do  sun  leaves  treated  in  exactly  the  same  way  and  they 
also  fix  carbon  dioxid  more  rapidly  in  the  same  amount  of  light  than  do 
these.  Moreover  in  Convallaria  the  storage  of  starch  was  found  to  be  less, 
the  drier  the  soil.  Equally  large  leaf  surfaces  containing  palisade  cells  tran- 
spire much  more  strongly  than  do  those  leaves  having  the  structure  of  shade 
leaves. 

It  is  evident  from  these  statements  that  changes  of  great  importance 
must  take  place  in  the  economy  of  trees  accustomed  to  shade,  when  suddenly 
exposed  to  light,  viz.,  when  left  standing  by  removing  parts  of  forests.  In 
parks  too  strong  and  sudden  an  exposure  to  light  by  the  removal  of  num- 
erous trees  not  infrequently  results  in  the  partial  or  total  death  of  the 
crowns  of  the  specimens  left  standing. 

We  must  turn  our  attention  to  still  another  point.  If  plantations  of 
fruit  trees  along  streets  on  level  land,  especially  cherries,  be  examined,  many 
cases  will  be  found  wih  trunks  split  open  on  the  south  or  southwest  side, 
with  the  bark  torn  into  tatters  and  often  showing  lumps  of  gum  on  the 
wounded  surfaces.  These  injuries  are  ver}'  evidently  due  to  frost.  The  ex- 
planation lies  in  the  fact  that  the  level,  cleared  lands  are  exposed  in  spring 
to  extreme  temperatures.  The  February  and  March  sun  shining  intensely 
on  the  trunks,  and  strengthened  in  its  action  by  the  reflection  from  the  soil, 
starts  the  reserve  plant  food  prematurely  and  the  tissues,  being  richer  in 
water  and  sugar,  at  once  succumb  to  the  action  of  the  frost.  A  moister 
atmosphere  in  the  neighborhood  of  water  or  wooded  areas  equalizes  the 
temperature  and  senses  as  a  protection  from  frost. 

Naturally  in  regions  with  greater  soil  elevations  and  more  noticeable 
dift'erences  between  valleys  and  mountains  these  factors  co-operate  determi- 
natively  and  often  decisively,  but  on  the  plains  the  forestration  is  a  very 
considerable  factor.  Cutting  considerable  forest  tracts  on  wide  plains  often 
is  a  source  of  injury  avenged  not  only  on  the  owner  but  on  the  whole  neigh- 
borhood, since  it  increases  the  chance  for  damage  from  late  frosts.  In  this 
connection  many  small  forest  tracts,  scattered  over  a  large  plain,  would  be 
of  use  since  no  considerable  distant  action  from  one  single  large  forest  may 
be  reckoned  upon.  There  is  a  further  advantage  to  be  derived  from 
forests, — that  of  protection  against  the  wind  (windbreak)  when  there  are 
no  mountains. 

Just  as  every  bright  side  has  its  shadow,  forests  can  exert  an  injurious 
influence  on  the  adjacent  fields.  The  forest  properly  located  can  withhold 
the  summer  rains,  usually  coming  from  the  west,  from  a  given  field  so  that 
there  will  be  dry,  windless  streaks  across  the  fields  in  its  immediate  prox- 


137 

imity, — or,  on  the  other  hand,  the  forest  may  make  streaks  across  the  field 
accessible  to  rains  and  prevent  the  rapid  drying  off  of  the  seeds.  In  the  first 
case,  the  forest  may  become  a  harboring  place  for  injurious  insects.  It  has 
often  been  observed  in  the  case  of  dwarf  cicades  that  they  begin  their  de- 
vastation of  the  fields  from  the  dry  edges  of  the  forest.  The  more  severe 
attacks  of  Puccinia,  Ophiobolus  and  Leptosphaeria  herpotrichoides  serve  as 
examples  of  the  influence  of  moisture,  near  the  border  of  the  forest,  upon 
fungous  diseases.  Goethe's  discoveries^  as  to  the  influence  of  the  place  of 
growth  upon  the  canker  of  fruit  trees,  caused  by  Nectria  ditissima,  must 
be  considered.  The  tendency  to  disease  from  canker  is  favored  by  an  in- 
creased humidity  as  offered  by  higher  regions  or  also  by  cold  valley  soils. 
"The  trees  show  in  such  places  a  meagre  growth  and  are  covered  with 
mosses  and  lichens.  Similar  conditions  are  observed  also  near  extensive 
forests,  out  of  which  cold,  damp  air  streams  even  in  the  summer." 


Goethe,  Rudolph,  Ueber  den  Krebs  der  Obstbaume.     Berlin  1904.     Paul  Parey. 


CHAPTER  11. 


UNFAVORABLE  PHYSICAL  CONSTITUTION  OF  THE  SOIL. 


I.     LIMITED  SOIL  MASS. 


Root  Curvature. 

For  practical  agricultural  and  forestry  purposes,  the  question  as  to  the 
limitation  of  space  in  the  soil  plays  a  subordinate  role  when  there  is  no 
scarcity  of  food  stuffs,  since  disturbances  in  nutrition,  arising  from  the 
overgrowth  and  rubbing  of  roots  pressed  tightly  against  one  another,  or  by 
their  growth  in  crevices  of  rocks,  have  no  agricultural  significance.  The 
matter  is  quite  different,  however,  in  gardening  and  the  cultivation  of  house- 
plants  by  the  plant  lover. 

In  these  circles,  however,  opinions  as  to  the  influence  of  too  small  soil 
space  on  the  spreading  of  the  roots  are  divided.  Predominant  and  also 
clearly  expressed  on  the  part  of  many  agricultural  chemists  is  the  opinion 
that  the  mechancial  effect  on  roots,  closely  pressed  on  one  another  and 
tangled  by  repeated  curvature,  has  no  influence  on  the  thriving  of  the  plants. 
They  think  that  in  limited  soil  space  only  a  scarcity  of  food  may  ever  be 
involved  which  would  make  itself  felt  very  quickly  and  could  be  corrected 
advantageously  by  fertilizing.  The  best  proof  should  lie  in  the  cultivation 
of  the  so-called  "market  varieties"  by  commercial  grow-ers  in  large  cities, 
who,  conforming  to  public  taste,  grow  very  vigorous  specimens  of  all  blos- 
soming plants  (Fuchsias,  Pelargoniums,  Begonias,  etc.)  in  relatively  very 
small  pots. 

The  fact  is  correct,  the  explanation,  however,  inconclusive. 

The  restriction  of  a  large  root  mass  in  a  small  space  results  first  in  the 
increased  production  of  lateral  roots.  This  may  be  observed  easily  in  water 
cultures.  If  one  of  the  large  roots  reaches  the  bottom  of  the  glass  container 
and  its  tip  is  forced  to  bend  around,  new  lateral  roots  are  produced  im- 
mediately. NolP  has  given  special  study  to  this.  He  found  that  on  the 
bent  portions  of  the  main  root,  the  lateral  roots  were  formed  only  on  the  con- 


1  Noll,  F.,  Ucljer  den  bestimmenden  Einfluss  der  Wurzelkriimmungen  auf 
Enststehung  und  Anordnuiig:  der  Seitenwurzcln.  Landwirtsch,  Jahrbiicher  XXIX 
(1900).  p.  361. 


139 

vex  surface,  the  concave  surface  remained  free.  This  is  true  of  both  main 
and  lateral  roots  and  not  only  under  mechanical  influences,  but  also  as  a 
result  of  geotropic  and  hydrotropic  stimuli.  Pollock^  has  pointed  out,  in 
this  connection,  that  twisted  roots  contain  more  water  in  the  cells  of  the 
convex  side  than  in  those  of  the  concave  side. 

Noll  ascribes  this  growth  of  new  lateral  roots  at  the  point  of  curvature 
to  a  perceptive  power  of  the  plant  to  the  formal  relations  of  its  own  body 
(Morphaesthesia).  This  expression  may  be  accepted  if  by  it  is  understood 
a  mechanical  transfer  of  material  resulting  from  the  stimulus  of  curvature 
on  the  affected  tissues.  The  process  is  similar  to  the  one  occurring  after 
direct  injury  when  the  cytoplasm  has  accumulated  in  the  cells  adjacent  to  the 
wounded  surface.  Of  course  laterals  are  found  also  on  concave  parts  of 
twisted  roots,  but,  in  such  cases,  the  buds  of  the  laterals  were  present  before 
the  twisting  of  the  mother  root  had  taken  place. 

In  trees  grown  in  the  open  the  development  of  lateral  roots  on  the 
convex  side  can  be  of  practical  advantage,  since  the  plant  is  thus  more  firmly 
anchored  and  extends  over  a  greater  area  of  soil  containing  food  stuffs, 
where  otherwise  the  root  branches  might  not  have  penetrated.  But  where 
the  whole  root  ball  has  only  a  definitely  limited  soil  space  at  its  disposal,  as 
in  potted  plants,  disadvantages  arise  w^iich  must  find  expression  in  the  pro- 
duction of  organic  substances.  We  can  perceive  these  disadvantages  at 
once,  if  M-e  observe  more  closely  a  pot  said  to  be  "root  bound."  The  greatest 
number  of  young  roots  have  grown  out  towards  the  periphery  and  been  so 
pressed  against  the  porous  sides  of  the  flower  pot,  that  many  fibres  are 
broken  off  when  the  pot  is  removed.  Part  of  the  root  fibres  have  stuck  fast 
like  bands  or  membranes  and  have  died.  The  latter  circumstance  is 
especially  apparent  in  palms  and  Dracaenae,  in  which  the  dead  roots  consist 
only  of  the  stele  and  the  outer  bark,  which  has  shivelled  up  like  a  papery 
covering. 

The  straining  of  the  roots  toward  the  side  of  the  pot  may  be  attributed 
to  the  need  of  oxygen.  Naturally  this  demand  is  less  easily  satisfied  as  the 
network  of  roots  fills  the  ball  of  earth  more  closely.  To  this  must  be  added 
the  secretions  of  the  root  itself.  Czapek-  determined  that  these  secretions 
may  be  ascertained  in  moist  air  as  well  as  in  water  cultures.  In  air  saturated 
with  vapor  they  are  frequently  observed  as  drops  on  the  root  hairs,  the  re- 
sult of  a  strong  internal  pressure  in  the  cells. 

Minimum  amounts  of  potassium,  calcium,  magnesia,  sulfuric,  hydro- 
chloric and  phosphoric  acids  are  eliminated.  Potassium  phosphate,  causing 
the  well-known  reddening  of  litmus  paper,  is  somewhat  more  abundant. 
In  regard  to  acids,  Czapek  found  that  the  presence  of  lactic  and  acetic  acids 
could  not  be  proved,  but  that, on  the  contrary,  formic  acid  is  found  not  in- 
frequently in  its  potassium  salt  as  a  diffusion  product  of  the  living,  youngest 


1  Pollock,   James,   The  mechanism   of  root   curvature.     Botan.      Gaz.      Chicago, 
XXIX,  1900.    pp.  1  ff. 

2  Czapek,    Fr.    Zur    Lehre    von    den    Wurzelausscheidungen.      Jahrb.    fiir    wiss. 
Bot.  1896.     Vol.  29.     Part  III. 


140 

parts  of  the  roots.  Potassium  oxalate  was  eliminated  by  hyacinth  roots. 
Carbon  dioxid,  however,  must  be  considered  primarily  and  causes  the  rock 
etchings,  as  it  occurs  dissolved  either  in  the  water  of  the  root-hair  cells  or  of 
the  soil  interstices.  Monopotassium  phosphate  and  carbon  dioxid  among 
the  root  secretions  must  be  especially  considered.  In  pot  cultures  the  latter 
is  of  especial  importance.  It  is  retained  in  the  root  balls  in  great  quantities, 
the  more  thickly  matted  they  are  and  the  wetter  they  are  kept  by  the  grower. 
The  production  of  carbon  dioxid  is  greatly  increased  by  the  respiration  of 
the  soil  micro-organisms  which  in  their  metabolism  decompose  the  carbo- 
hydrates and  other  organic  substances.  For  instance  Stocklasa^  found 
alcohol,  acetic  acid  and  formic  acid  in  forest  soil  and  finally  carbon  dioxid 
and  hydrogen.  The  hydrogen  often  unites  with  oxygen  to  form  water. 
Lack  of  oxygen  and  the  excess  of  carbon  dioxid  kill  part  of  the  roots  and 
the  process  is  gradually  evidenced  when  plants  are  grown  in  small  pots, 
even  if  over-abundant  foodstuffs  be  given  them  by  fertilizing.  However,  if 
fertile  earth  alone  is  used,  without  subsequent  additions  of  fertilizers,  the 
roots,  becoming  thickly  matted  on  the  walls  of  the  pot,  do  not  touch  the  ball 
of  earth  actually  as  they  develop  on  top  of  older  roots.  In  such  cases,  they 
cannot  further  draw  from  the  soil  the  food  materials  needed  in  growth. 

Early  investigations  by  Hellriegel'-  prove  that  excessively  limited  soil 
space  in  itself  limits  production.  To  perform  these  experiments  many 
annual  and  perennial  agricultural  plants  (barley,  peas,  buckwheat^  clover, 
etc.)  were  sown  in  glass  containers  of  different  heights  in  as  uniform  gar- 
den soil  as  possible  and  were  grown  with  an  observance  of  all  the  precautions 
used  in  sand  and  water  cultures.  In  order  to  prevent  any  question  as  to  the 
exactness  of  the  results  obtained  due  to  a  different  amount  of  soluble  nutri- 
tive elements  control  experiments  were  made  with  an  abundant  addition  of 
fertilizers,  under  otherwise  similar  conditions.  The  result  was,  that  no 
difference  in  production  whatever  was  shown  in  favor  of  the  fertilized 
plants,  that  those  not  fertilized  must  thus  have  found  in  the  unfertilized 
garden  soil  all  the  nutritive  substances  that  they  needed  for  their  production. 
An  indirect  proof  lay  also  in  the  results  of  the  experiments  given  by  the 
unfertilized  plants  when  compared  with  one  another.  The  yield  showed  in 
fact,  that  clover  in  the  first  year  had  produced  about  as  much  dry  material 
as  the  other  varieties  of  plants.  This  did  not  prevent  the  clover,  however, 
from  producing  in  the  second  year  on  the  same  soil  a  second  crop  and  in 
fact  a  crop  two  or  three  times  as  great,  and  even  in  the  third  year  it  produced 
as  much  as  in  the  first  year.  From  this  it  is  evident  that  the  amount  of 
nutritive  substances  could  not  play  a  role  in  any  of  the  experimental  pots, 
since  they  were  everywhere  present  in  excess. 

If  now,  however,  the  amount  of  dry  substance  increased  with  the  size 
of  the  container,  this  result  could  be  ascribed  only  to  the  influence  of  the 

1  Stocklasa  and  Ernest,  Ueber  den  Ursprung,  die  Menge  und  die  Bedeutung 
des  Kohlendioxj'ds  im  Boden.  Centralbl.  f.  Bakteriologie  etc.  Section  II,  Vol.  XIV. 
1905,  p.  723. 

2  Hellriegel,  Beitrage  zu  den  naturwissenschaftlichen  Grundlagen  des  Acker- 
baues.    Braunschweig.  Vieweg,   1883.  pp.  184-224. 


Height  of  the  CyUnder. 

I. 

II. 

III. 

IV. 

96  to  99      cm. 

65  to  dj      cm. 

34  to  35      cm. 

18.0  cm. 

Earth  content. 

Air  dry. 

Absolutely  dry. 

19,500  g. 
13,000  g. 

6,500  g. 

3.250  g. 

18,600  g. 
12,400  g. 

6,200  g. 

3-100  g. 

141 

volume  of  the  soil.  The  plants  under  experiment  stood  in  glass  cylinders 
of  the  dimensions  and  contents  given  below,  received  steadily  from  30  to 
60  per  cent,  of  the  water  required  by  saturation  of  the  soil  and  resulted 
with  clover,  as  follows : 

Diameter  in  the  Clear. 

14  cm. 
14  cm. 
14  cm. 
14  cm. 

Harvested  dry  substances, 
in  the  years  1872,  1873,  1874. 

417.2  g.  with  6.92  per  cent,  pure  ash 

254.6  g.  "      6.97     "       "  "  " 

173.0  g.  "      8.08     "       "  "  " 

76.8  g.  "      8.45     "       "  "  " 

Since,  in  the  containers  with  a  very  large  soil  volume,  too  great  a  con- 
solidation, therefore  somewhat  abnormal  conditions  for  some  plants,  has 
appeared,  because  of  the  sudden  addition  at  first  of  great  amounts  of  water 
saturating  the  soil  to  60  per  cent,  of  its  water  capacity,  Hellriegel,  in  his 
harvest  tables,  explained  especially  the  results  for  the  sizes  III  and  IV. 
From  this  it  appeared  that,  with  peas,  an  amount  of  soil  of 

3,100  g.  gave  on  the  average,  29.97  in  dry  substances. 

6,200  g.      "       "      "  "         47.94    "     " 

For  peas,  therefore,  the  proportion  of  the  soil  was  i  :2. 

"        "  "  "  "  "     "     harvest  was  i  :i.6. 

For  beans,  therefore,  the  proportion  of  the  soil  was  1.2. 

"     "     harvest  was  i  :i.8. 

In  1872,  exactly  the  same  proportions  in  harvest  results  were  found  for 
barley  as  for  beans.  We  omit  here  the  repetition  of  the  figures,  since  those 
cited  show  clearly  enough  that,  in  two  equally  wide,  but  unequally  tall  ves- 
sels, both  containing  nutritive  substances  in  excess,  and  steadily  receiving 
the  favorable  amount  of  water,  the  harvest  came  out  as  i  :i.6  up  to  1.8,  if 
the  amounts  of  soil  bore  the  proportions  of  i  :2.  Thus  a  strikingly  evident 
influence  of  the  soil  volume  may  be  confirmed  and  the  question  now  is,  how 
this  influence  may  be  explained. 

Hellriegel  found  that  the  height  of  the  yield  stood  in  inverse  ratio  to  the 
amount  of  the  mechanical  resistance,  which  opposes  the  development  of  the 
root-network  of  the  plants  under  experiment. 

If  commercial  growers  get  apparently  opposite  results  and  find  that 
the  growth  in  small  pots  is  great  and  quick,  the  explanation  lies  in  the  fact 
that  they  use  a  very  rich  earth  and  highly  concentrated  solutions  are  present 
in  the  soil.  Comparative  measurements  showed,  however,  that  the  root 
development  in  rich  nutrient  solutions  is  essentially  shorter  than  in  weakly 
concentrated  ones.    Hence  the  demand  of  the  root  fibre  is  actually  smaller. 


142 

However,  in  the  same  length  of  time,  the  root  makes  a  stronger  growth  when 
kept  under  glass,  or  in  hot  beds,  than  where  the  plants  are  in  the  open ; — 
for  these  glass  cases  all  have  bottom  heat.  Finally,  the  aerial  axis  finds  itself 
under  conditions  making  possible  an  especially  rapid  and  abundant  develop- 
ment. The  atmosphere  rich  in  water  vapor  and  carbon  dioxid  develops  the 
largest  individual  cells  possible  with  comparatively  little  transpiration, 
hence,  the  turgid  and  significant  large  size  of  the  foliage.  Therefore,  in 
garden  cultures  in  small  pots,  the  root  is  better  and  earlier  formed  and 
utilized,  so  that  the  injuries  due  to  root  curvature  and  bruising  make  them- 
selves first  felt  at  a  time  when  the  aerial  axis  has  already  made  a  consider- 
able growth.  That  growers,  however,  clearly  recognize  the  disadvantage  of 
small  pots  and,  when  possible,  do  without  them  is  evident  from  the  so-called 
"feeding  cultures"  (forcing).  In  this  the  specimens  are  shifted  into  larger 
pots  as  the  root  branches  penetrate  to  the  sides  of  the  pot. 

Dwarf-growth  (Nanism). 

The  dwarf  conifers  found  in  trade  under  the  name  "Japanese  or 
Chinese  Trees  of  Life"  show  an  interesting  effect  of  the  influence  of  a 
limited  soil  space.  The  figure  on  the  next  page  illustrates  a  living  specimen 
which  has  been  classified  by  the  well-known  firm  J.  C.  Schmidt  (Berlin)  as 
Thuja  obtusa  and  kindly  placed  at  our  disposal.  The  tree,  with  the  pot,  is 
86  cm.  high  in  all, —  and  60  cm.  high  above  the  soil.  At  its  greatest  width 
the  crown  is  80  cm.  across.  The  base  of  the  trunk,  divided  into  several  pro- 
truding ridges,  has  a  diameter  of  19  cm.,  the  trunk  at  the  height  of  the 
crown,  where  the  branches  appear,  one  of  12  cm.  This  healthy  specimen, 
with  a  dense  crown,  whose  age  is  estimated  to  be  100  years,  cost  $87.50. 

In  literature,  notes  may  often  be  found  referring  to  the  skill  of  the 
Japanese  and  Chinese  in  growing  dwarf  specimens  of  trees,  hundreds  of 
years  old  for  table-decoration^ 

Our  examination  of  the  trunk  from  a  dead  tree  destroys  the  halo  of 
the  miraculous,  with  which  these  productions  of  Japanese  and  Chinese  hor- 
ticulture have  been  surrounded.  A  section  8  cm.  long  and  6  cm.  at  its 
widest  diameter  showed  most  excentric  annual  rings.  The  distance  of  the 
pith  from  the  bark  amounted  to  1.5  cm.  at  one  side  of  the  trunk  and  to  6.5 
cm.  at  the  other.  Counting  with  a  magnifying  glass  showed  30  annual  rings 
on  the  wider,  but  only  15  on  the  narrower  side.  On  the  side  favored  in  growth, 
a  great  variation  in  the  breadth  of  the  annual  rings  was  noticeable.     Four 


1  In  an  article  on  "dwarf  growth  in  the  vegetable  kingdom, "*  Griibe  quotes  a 
report  by  Sir  Geo.  Staunton,  from  "des  Grafen  McCartney  Ge.sandtschaftsreise  nach 
China,"  Berlin  1798.  Staunton  saw  in  Tintr-hai,  spruces,  oaks  and  orange  trees 
none  of  which  were  more  than  2  feet  high  and  on  which  fruit  had  set  abundantly. 
At  the  base  of  the  trunk  the  soil  was  covered  with  layers  of  stones  weathered  and 
covered  with  moss  giving  the  pots  the  appearance  of  great  age.  "Throughout 
China,  there  is  a  great  liking  for  these  artificial  plant  dwarfs  for  we  found  them, 
as  a  rule,  in  every  house  of  any  pretention  whatever."  It  is  there  further  related 
that  the  "liliputian"  trees  were  propagated  bv  binding  loam  or  garden  soil  around 
different  branches.  This  was  kept  moist  until  the  branches  developed  new  roots  in 
the  earth  ball;  they  were  then  cut  off.  We  still  use  this  process  in  the  layering  of 
branches  or  top  shoots  and  the  covering  of  the  cut  places  with  moss.     This  plan 


143 

zones  could  be  distinguished.  Each  of  these  ended  with  very  slender  rings, 
the  tracheids  of  which  had  especially  narrow  lumina  and  had  become 
browned  through  resinosis.  Otherwise  the  wood  was  healthy.  In  its  dimen- 
sions the  bark  corresponds  to  the  section, — i.  e.,  on  the  side  of  the  narrower 
rings,  it  was  1.5  mm.  thick,  on  the  other  side  4  mm.  On  the  narrower  side, 
a  depression  was  found,  in  which  a  scantier  development  of  the  wood  had 
been  equalized  by  a  thicker  formation  of  bark,— up  to  5  mm.  There  was 
shown  here  a  tendency  to  loosen  the  individual  bark  scales  between  the  flat 
cork  layers  resembling  full  cork. 


Fig.  15.     Dwarf  specimen  of  Thuja  obtusa,  60  cm.  high  and  80  cm.  wide.     (Orig-.) 

At  the  base   of  the  trunli  may  be  seen  the  division  of  the  aerial  axis 

into  a  number  of  root  branches  projecting-  above  the  pot. 

Thus  the  statements  as  to  the  great  age  of  the  trees  are  seen  to  be 
erroneous.  These  cannot  be  more  than  some  thirty  years  old  and  their  dwarf 
growth,  in  our  opinion,  can  be  obtained  by  keeping  the  plants  in  the  very 


was  followed  in  China,  because  it  had  been  observed  that  an  artificially  produced 
dwarf  character  is  hereditary.  When  the  tendency  has  become  hereditary  it  is 
strengthened  in  the  new  individual  by  turning  down  the  end  bud  of  the  main  shoot 
and  bending  it  with  wire  in  another  direction.  "If  it  is  desired  to  give  the  dwarf 
tree  the  appearance  of  an  old.  already  half  dead  tree,  the  trunk  is  often  covered 
with  syrup  to  attract  ants  and  these,  after  they  have  eaten  the  sweet,  immediately 
injure  the  bark,  giving  it  thereby  a  brownish,  half -weathered  appearance." 

Rein**  describes  the  Japanese  process  which  is  somewhat  different.  They  call 
the  dwarfing  or  "Nanisation"  "Tsukurimono."  This  expression  is  not  used  in  the 
new  book  by  Ideta***.    According  to  Rein,  the  dwarf  growth  is  secured  by  choosing 


144 

smallest  pots  until  they  are  root-bound  ;  then  transplanting  into  a  large  pot,  in 
which  the  root  crown  is  raised  up  above  the  pot  in  order  that  the  root  ball 
may  have  full  benefit  from  the  soil.  After  the  year  of  transplantation,  wide 
annual  rings  are  produced  at  first,  which  become  narrower  as  the  plant  be- 
comes root-bound  until  the  growth  has  become  very  slight  and  the  last 
annual  ring  formed  is  made  up  of  a  few,  browned  autumn-wood  tracheids. 
In  this  way  the  stilt-like  trunk  bases,  borne  on  the  freely  exposed  root 
branches,  are  produced.  The  crown  is  probably  kept  thick  by  a  light  cutting 
back  of  the  tips  of  the  branches,  obtaining  thereby  a  greater  ramification. 
In  the  same  way  the  root  balls  might  have  been  pruned  at  each  transplanting. 
We  conclude  from  the  porous  places  filled  with  full-cork,  which  occur 
scattered  in  the  bark,  that  the  trees  have  been  kept  wet.  At  any  rate  w^e 
would  have  no  difficulty  in  growing  trees  in  such  decorative  dwarf  forms 
from  the  genera  Thuja,  Thujopsis.  r)iota,  Cupressus  and  similar  ones  by 
limiting  the  soil  content. 

A  corresponding  treatment  is  recommended  here  and  there  for  de- 
ciduous trees  and  plants.  In  forcing  w'oody  blossoming  plants  it  is  desirable 
to  have  for  sale  small  specimens  as  full  of  bloom  as  possible.  To  attain 
this  end,  the  bushes  are  planted  in  small  pots,  cut  back  and  kept  until  spring, 
as  long  as  possible,  in  cool  dark  cellars  in  order  to  retard  the  growth  beyond 
the  natural  time  of  awakening.  Ice  cellars  serve  best  in  this  connection. 
When  vegetation  has  advanced  considerably  out  of  doors  the  plants  are 
brought  out.  They  now  find  a  very  dififerent  combination  of  vegetative 
factors  for  the  maturing  of  their  growth.  Instead  of  moist  spring  air,  a 
comparatively  slight  warmth  of  the  sun  and  long,  cool  nights,  the  plant  finds 
dry,  bright,  long  days  with  little  precipitation.  As  a  result  the  branches  re- 
main short  and  the  eyes  easily  develop  blossom  buds. 

It  will  not  be  out  of  place  to  call  attention  to  the  fact,  that  in  keeping 
the  bushes  in  warm  cellars,  an  opposite  result  is  obtained, — namely,  abso- 
lute unfitness  for  forcing.  The  warm,  dark  place  where  they  are  kept  pro- 
duces deformed,  very  premature  shoots,  which,  when  brought  at  last  into 
the  open  air,  either  dry  up  or  gradually  and  slowly  lengthen  to  whip-like, 
blossomless  wands.  The  stored-up  material  has  been  wasted  in  the  cellar 
in  forming  the  deformed  shoots. 


especially  small  seeds  from  under- developed  plants.  These  little  trees  are  pruned 
and  transplanted  frequently  into  as  small  pots  as  possible.  The  cross-.s«ction 
described  above  in  the  text  shows  this.  Further,  the  trunk  and  branches  are 
twisted  and  bent  toward  the  horizontal.  It  is  said  that  the  root  ball  is  cooled. 
Amongr  vari'eties  of  plants  used  especially  in  .Japan  for  the  growth  of  dwarfs  are 
mentioned  the  tov  varieties  of  Acer  palmatum,  which  are  budded,  "greffe  par 
apDroacho."  Further  Pinus  massoniana  and  P.  densiflora,  Podocarpus  Nageia, 
Sciadopytis  verticillata.  Amonir  fruit  trees  the  Kaki  plum.  Diospyros  Kaki,  is 
suitable  for  this,  the  Mume-plum,  Prunus  Mume  and  Sakura,  Prunus  Pseudocerasus, 
ns  well  as  Amygdalus  Persica.  Among  decorative  plants  arc  mentioned  Evonymous 
Japonica  and  the  bamboo. 


♦  "Zwergbilduner  im  Pflanzenreich"   Gartenwelt,    1904,  No.   49. 

**  Rein,  J.  J.,  Japan  nach  Reisen  und  Studien.  Leipzig',  Engelmann.  Vol.  II., 
p.   315. 

***  Ideta  Arata.  Lehrbuch  der  Pflanzenkrankheiten  in  Japan.  3rd  Ed.  Tokio, 
Shokwabo,  1903. 


145 

The  most  frequent  occurrence  is  dwarfing  due  to  scarcity  of  water. 
Like  every  other  organism,  the  plant  has  the  ability  of  adjusting  itself  with- 
in wide  limits  to  different  conditions.  An  individual,  accustomed  from  its 
youth  up,  to  a  very  scanty  amount  of  water,  can  pull  through  with  half  the 
amount  of  water  used  by  a  plant  of  the  same  species  and  variety,  which  had 
developed  with  excessive  water.  Naturally  the  structure  of  the  whole  in- 
dividual is  adapted  to  these  conditions.  More  thorough  investigations  have 
been  made  with  barley^,  which  was  cultivated  with  a  varied  water  content 
in  the  soil  (lO,  40,  and  60  per  cent,  of  the  soil's  capacity  for  absorbing  water). 
The  most  favorable  water  content  for  growth  might  be  found  possibly  be- 
tween 50  and  60  per  cent,  of  saturation. 

In  the  experiment  it  was  shown  that  the  plant  even  with  only  10  per 
cent,  of  water  had  regulated  its  organization.  Little  leaf  and  root  substance 
had  absolutely  been  formed,  but  the  proportion  between  grain  and  straw 
was  normal;  therefore  about  as  much  dry  substance  in  the  form  of  grain 
as  in  the  form  of  straw.  With  the  same  amount  of  food  in  the  soil,  the  dry 
substance  increased  as  the  roots  obtained  additional  water.  With  too 
much  water,  i.  e.,  more  than  60  per  cent,  saturation,  very  little  dry  substance 
was  produced  absolutely  and  this  small  amount  was  worthless  since  the  pro- 
portion between  straw  and  grain  was  changed, — to  the  detriment  of  the 
latter.  Measurement  of  the  leaves  showed  that  the  grains  grew  longer  and 
wider,  when  water  was  supplied  regularly  and  more  abundantly.  These 
larger  leaves,  found  with  a  greater  water  supply,  are  due  partly  to  the  in- 
creased number  of  cells,  partly  to  their  greater  distention.  If  the  individual 
cells  of  the  upper  epidermis  are  larger,  it  may  be  assumed  from  the  ver}' 
beginning,  that  the  respiratory  apparatus  (the  stomatal  cells)  will  share  in 
the  greater  stretching  of  the  upper  epidermal  cells  and  will  also  appear  to  be 
the  more  widely  separated  thereby.  Direct  measurement  confirmed  this 
assumption,  so  that  therefore  for  each  square  centimetre  of  a  leaf  grown 
with  abundant  water,  fewer  but  larger  stomata  will  be  found,,  than  when 
plants  are  growm  with  a  scarcity  of  soil  water.  H.  Moller  has  determined 
by  experiments-  that  plants  dwarfed  by  lack  of  water  (Nanism)  are 
structurally  different  from  plants  whose  dwarfishness  is  due  to  a  scarcity 
of  mineral  substances  in  too  weak  solutions.  In  the  latter  the  narrower 
leaves  are  probably  not  due  to  narrower  cells,  resulting  from  water  scarcity, 
but  to  a  smaller  number  of  cells,  since  measurements  show  the  same  cell 
breadth  and  the  same  size  of  the  stomata  in  plants  from  a  satisfactory  nutri- 
ent solution  and  from  an  insufficiently  concentrated  one.  These  differences 
are  easily  explained.  When  the  mineral  substances  are  insufficient  the  cell 
Increase  will  suffer  only  from  water  scarcity.  The  cells  are  less  distended. 
As  shown  by  some  of  Moller's  experiments  with  Bromus  mollis,  this  nanism 
is  not  hereditary,  since  specimens  of  huge  size  can  be  grown  from  the  seed 


1  Sorauer,  Einfluss  der  Wasserzufuhr  auf  die  Ausbildung  der  Ger.stenpflanze. 
Bot.   Zeitung  1873,  p.    145. 

-  H.  Moller,  Beitrage  zur  Kenntnis  der  Verzwergung-  (Nanismus),  Landwirt- 
schaftliche  Jahrbiicher  von  Thiel.,    1883,  p.  167. 


146 

of  dwarf  plants.  Yet,  with  equal  vegetative  conditions,  seed  from  normal 
plants  produces  more  vigorous  specimens  than  that  from  dwarfed  plants. 

The  case  of  nanism  due  to  scarcity  of  nutritive  substances,  which 
MoUer  studied,  is  not  rare  in  sandy  soils.  The  lack  of  nitrogen  plays  the 
chief  part  here.  This  nanism  is  usually  characterized  by  the  fact  that,  be- 
sides the  general  reduction,  the  relations  of  the  separately  produced  organs 
have  been  changed.  In  proportion  to  the  whole  growth,  the  root  undergoes 
a  greater  distention  ;  but  the  sex  organs  suffer  a  greater  retrogression.  The 
number  of  blossom  eyes  is  ver}^  small.  Instead  of  a  cluster  or  a  head,  there 
is  often  only  a  single  blossom.  Where  a  greater  number  of  blossoms  are 
formed  single  seeds  develop  which  can  germinate.  It  is  easy  to  understand 
that  the  leaf-forms  are  simplified. 

In  discussing  dwarf  growth,  the  phenomena  of  bud  variation  must  be 
considered.  These  have  no  connection  with  soil  conditions  or  other  external 
vegetative  factors.  The  form  of  growth  up  to  this  time  is  so  changed  by 
some  impulse  or  stimulus,  acting  temporarily  or  persistently,  that  the  organic 
substance  is  used  up  in  the  form  of  more  numerous,  shorter,  usually  thicker, 
short-leaved  branches  instead  of  fewer  slender,  large-leaved  ones,  in  this 
way  producing  witches-brooms.  In  many  cases  the  incitement  to  such  a 
changed  direction  of  growth  may  be  found  in  parasitic  attacks.  The  fungus 
genus  Taphrina  (Exoascus)  especially  irritates  the  branches  of  various 
deciduous  trees  resulting  in  the  formation  of  witches-broonis  (see  Volume 
II.  page  179).  In  other  cases  we  find  rust  fungi  or  mites  of  the  genus 
Phytoptus.  Besides  these  forms  due  to  parasites,  however,  some  surely 
exist  in  which  other  organisms  are  not"  active.  We  find  especially  in  her- 
baceous, quickly  growing  plants  (Campanula,  Pelargonium)  the  occurrence 
of  a  bud  disease  (Polycladia)  as  a  correlation-phenomenon. 

In  sickness  or  loss  of  blossoming  branches,  small  fleshy  bunches  are 
formed,  at  times,  at  the  base  of  the  stem,  made  up  of  closely  set  bud-eyes, 
some  of  which  grow  out  into  sickly  branches.  In  diseased  thickets  growth 
is  often  exhausted  by  a  continued  new  formation  of  short  branches,  because 
the  blossoming  axes  no  longer  lengthen,  but  stop  growing  and  turn  yellow. 
In  Calluna  vulgaris,  instead  of  long  blossoming  branches,  we  find  blossomless 
bunches  of  twigs,  pyramidal  in  form,  which  might  also  be  called  witches- 
brooms. 

In  other  cases  polycladia  and  bushy  forms  are  produced  by  the  develop- 
ment of  normally  formed  but  still  dormant  lateral  eyes,  when  the  buds  of 
the  tips  have  been  injured.  This  takes  place  when  wild  growths  choke  out 
cultivated  ones.  In  conifers,  the  heart  buds  grow  out  and  form  bushy 
crowns,  which  are  called  "rosette-groivths."  The  so-called  "cow-bushes" — 
due  to  injury  to  beeches,  alders,  etc..  from  the  grazing  of  cattle,  are  similarly 
explained. 

Pure  bud  variations  are  numerous.  In  them  the  growth  in  length  of 
the  individual  branches  is  restricted  without  any  recognizable  cause,  result- 
ing in  a  greater  and  more  rapid  development  of  lateral  branches.     Among 


147 

the  actual  forms  of  witches-broom,  the  tendency  at  present  is  to  place  under 
this  head  of  bud  variation  the  numerous  spherical  bushes  of  the  spruce 
witches-broom^.  The  greatest  number  of  examples  is  furnished  by  the 
many  cultivated  plants  of  our  gardens  in  the  so-called  globe  forms  of  coni- 
fers and  in  the  dwarf  forms  of  blossoming  bushes.  In  the  short-lived  sum- 
mer plants  (Ageratum.  Zinnia,  Tagetes,  etc.)  we  find  that  the  dwarf  growth 
can  become  an  hereditary  peculiarity,  persistent  in  the  seed. 

Too  Thick  Seeding. 

A  limitation  of  the  soil  space  and  a  struggle  for  water  and  nutritive 
substances  is  always  produced  by  too  thick  seeding.  The  struggle  of  the 
plants  with  one  another  for  their  food  appears  earliest  and  sharpest  in  sandy 
soils.  Besides  the  dwarfing  of  individual  specimens,  the  weakening  of  repro- 
duction deserves  especial  consideration.  This  becomes  evident  not  only  in 
the  decrease  of  the  blossoms,  but  also  in  the  change  in  their  character  and 
becomes  especially  perceptible  in  horticulture,  because  staminate  blossoms 
are  produced  predominantly.  The  unavoidable  scarcity  of  nitrogen  is  also 
a  factor.  The  greater  the  amount  of  nitrogen  supplied,  the  more  abundant 
the  meristem,  rich  in  cytoplasm. 

Hoffmann-  gives  the  results  of  many  cultural  experiments  in  pots  and 
open  ground,  to  determine  the  influence  of  too  thick  seeding  for  different 
plants.  In  this,  for  every  loo  pistillate  blossoms  there  developed  the  follow- 
ing number  of  staminate  ones  : — 

With  a  more  seat- 
In  With  Too  Thick  Seeding,      tered  position  of 

the  plants. 

Lychnis  diiirna 233  125 

200  yy 

"        vespertina 150  73 

Mercurialis  annua   100  90 

Rumex  Acetosella   152  81 

Spinacia  oleracea  (average  of 

several  sowings)    283  y6 

In  Cannabis  his  results  were  contradictory,  which  may  be  explained  by 
a  consideration  of  Fisch's  statement^'  that  the  proportion  of  the  sexes  in 
hemp  is  already  determined  in  the  seed, — that,  therefore,  external  in- 
fluences can  bring  about  no  further  changes.  Belhomme  maintains  that  the 
form  of  the  hemp  seeds  admits  of  conclusions  as  to  the  sex  of  the  future 
plant,  since  the  longer  or  the  more  spherical  form,  as  in  bird's  eggs,  indicates 
a  staminate  or  a  pistillate  individual. 

Since  the  phenomena  appearing  with  too  thick  seeding  may  be  traced 
essentially  to  scarcity  of  food  substances,  further  examples  will  be  cited 
when  the  scarcity  of  nitrogen  is  discussed. 

1  Tubeuf  and  Schroter,  Naturwissensch.  Zeit-schr.  f.  Land-  11  Forstwirtschaft. 
1905,  p.   254. 

2  Hoffmann,  H.,  Ueber  Sexualitat.  Bot.  Zeituns'.  18S5.  No.  16. 

3  Fisch,  Ber.  der  Deutsch.  Bot.  Gesellsch.     1887.    Vol.  5.    Part  3. 


2.  UNSUITABLE  SOIL  STRUCTURE. 


a.     Light  Soils. 
Disadvantages  of  Sandy  Soils. 

The  way  in  which  the  individual  soil  particles  are  related  to  one  another, 
is  termed  the  structural  condition.  If  the  constituents  of  the  soil  are  simply 
laid  one  above  the  other  in  separate  grains  Ave  speak  of  a  separate  granular 
structure.  In  soils  under  cultivation,  however,  the  individual  soil  particles 
are  found  united  into  different  kinds  of  aggregates,  called  a  friable  structure. 
While,  in  the  first  case,  each  soil  grain  has  a  homogenous  constitution,  the 
soil  grains  in  the  second  case  are  porous  and  not  homogenous,  therefore 
can  be  more  easily  transformed.  The  content  in  soluble  salts,  the  activity 
of  the  animal  world  in  the  soil  and  the  action  of  plant  roots  and  their  se- 
cretions, as  well  as  the  physical  processes  of  working  the  soil,  determine  the 
formation  of  a  friable  structure.  The  amount  of  space  between  the  indi- 
vidual grains  will  vary  according  to  their  size  and  arrangement.  Ramann 
calculates  the  porosity  volume  of  equally  large  soil  particles,  according  to 
whether  the  particles  are  arranged  regularly  in  rows  on  top  of  one  another 
or  between  one  another,  as  fluctuating  between  47.64  per  cent,  (greatest 
porosity)  and  25.95  P^r  cent,  of  the  whole  volume  (closest  stratification) ^ 

While  in  the  friable  structure,  because  of  the  different  individual  par- 
ticles, a  continuous  change  in  size  and  arrangement  takes  place,  due  to  me- 
chanical and  chemical  influences,  in  the  separate  granules,  most  distinct  in 
stony  and  gravelly  soils,  the  physical  relation  is  more  regular  and  therefore 
more  significant. 

We  have  already  spoken  of  the  influence  of  actual  sandy  soils  and  the 
changes  which  roots  can  experience  when  growing  in  cracks  in  rocks.  The 
injuries  to  vegetation,  which  are  caused  by  too  loose  a  structure  of  stony 
soil  at  the  disposal  of  the  root,  seem  lessened  when  the  blocks  of  stone  are 
weathered  to  rubble.  Fine,  earthy  particles  are  produced,  especially  when 
the  stones  are  easily  decomposed  (many  granites,  Gneiss,  Syenite,  etc.)  af- 
fording the  roots  more  abundant  food  and  firmer  support.  Next  to  the  great 
possibility  of  being  rapidly  heated  through,  the  factor  acting  most  injuriously 
is  great  dryness,  which  prevents  a  decomposition  of  organic  substances  lead- 
ing to  the  formation  of  humus ;  this,  under  certain  circumstances,  forms 
moors.  Forestry  in  mountains  must  take  such  conditions  into  account.  Sandy 
soils  come  under  consideration  for  field  cultures  on  the  level.  As  soon  as 
these  possess  greater  admixtures  of  clayey  substances  (loamy  sand)  or  of 
humus,  they  form  most  productive  soils  and  therefore  find  in  this  discussion 
no  further  consideration.  Sandy  soil  is  unfavorable  for  cultivation  only 
when  the  sand  is  truly  quartz  sand  and  is  either  pure  or  is  present  in  a  very 
high  per  cent.  (70  to  90  per  cent.) 


Ramann,   Boclenkuntlo,    2ncl.   Ed.,   p.    222.     Berlin,    J.    Springer,   1905. 


149 

In  such  cases,  the  slight  absorptive  capacity  should  be  mentioned  first 
of  all  as  a  hinderance  to  cultivation.  The  diseases  caused  by  scarcity  of 
water  and  food  substances  are  pre-eminently  peculiar  to  sandy  soil.  The 
more  clayey  and  humus  admixtures  present,  the  more  the  danger  disappears, 
in  so  far  as  it  is  not  brought  about  again  in  another  way  by  the  washing 
away  of  considerable  amounts  of  easily  soluble  mineral  substances. 

Such  an  erosion  takes  place  much  the  more  quickly  when  the  decom- 
position of  organic  substances,  which  occurs  easily  under  the  influence  of 
warming  and  aeration,  is  increased  by  other  conditions.  On  this  account 
one  must  be  especially  careful  in  removing  forests  and  litter.  In  deep,  sandy 
soils,  the  removal  of  the  litter  holding  its  moisture  is  disadvantageous  since 
the  organic  substances  present  are  but  very  little  decomposed  by  atmospheric 
influences  and  bacteria,  and  accumulate  as  raw-humus,  which  can  finally 
give  rise  to  the  formation  of  meadow  ore.  According  to  Ramann,  in  lower 
positions  the  deposition  of  raw-humus  gradually  leads  to  complete  marshi- 
ness, as  in  the  large  moors  of  North  Germany,  which  almost  without  excep- 
tion have  originated  from  land  which  at  one  time  was  covered  by  forests. 
The  humus  is  beneficial  only  when  mixed  with  sand,  since  the  friability  of 
the  soil  and  its  water  content  is  increased  and  its  capacity  for  heating  re- 
duced. 

This  capacity  for  heating  and  giving  ofif  heat  of  sandy  soils  is  an 
essentially  harmful  quality.  Pure  sand  possesses  the  greatest  capacity  for 
giving  off  heat  and  consequently  the  greatest  capacity  for  becoming  wet 
with  dew.  The  process  of  taking  up  and  giving  off  heat  decreases  as  the 
sand  is  finer  grained  and  whiter.  Sand  of  the  latter  kind,  for  example,  is 
that  rich  in  calcium,  while,  of  colored  sands,  the  ones  rich  in  iron  hydroxid 
are  very  warm  and  cool  off  slowly,  behaving  therefore  like  sand  mixed  with 
some  clay. 

Associated  with  the  great  fluctuations  in  temperature  peculiar  to  sand 
is  the  poor  capacity  for  conducting  warmth.  As  a  result  of  difficult  equali- 
zation its  subsoil  has  a  more  even  temperature,  since  it  is  warmer  in  winter 
and  cooler  in  summer  than  under  more  binding  soil  coverings.  The  danger 
from  frost  is  increasedly  greater  and  more  injurious.  The  rapid  warming 
in  spring  days  forces  vegetation  prematurely  and  the  great  drop  in  tem- 
perature at  night  is  injurious,  while  the  plant  would  be  uninjured  if  it 
started  later  in  a  soil  containing  water  and  rich  in  clay. 

The  sandy  soils  of  fine  constitution  and  slight  coherence  present  the 
greatest  possibiUties  for  injury  to  crops.  The  injurious  effects  of  drifting 
sand  are  shown  in  the  sand  dunes.  Even  if  the  dunes  reduce  the  severity  of 
the  sharp  sea  winds  for  plants  near  the  coasts,  they  are  nevertheless  injurious 
since  they  advance  further  and  further  inland,  covering  all  plants.  The 
inability  of  the  land  breeze  to  blow  back  during  the  night  the  sand  which 
the  sea  breeze  has  swept  over  the  land  by  day  is  due  to  the  fact  that  the  land 
breeze  is  heavily  laden  with  dew  and  tends  to  compact  the  sand  again.  If 
the  danger  of  being  covered  with  sand  threatens  and  artificial  protection  is 


150 

too  expensive,  one  must  try  to  bind  tlie  movable  sand  hills  by  some  natural 
method.  Sand  grasses  are  here  most  valuable,  since,  by  the  rapid  root  de- 
velopment of  the  nodes  of  the  buried  stolens,  they  constantly  advance  over 
the  upper  surface  and  bind  it  together.  Arundo  arenaria,  L.  and  Elymus 
arenarius  L.  are  most  frequently  used.  Besides  these,  Arundo  baltica 
Schrad,  and  Carex  arenaria  L.  should  be  recommended,  and,  with  sufficient 
moisture,  even  our  quack  grasses  as  well.  Among  the  dicotyledons,  Hip- 
pophac  rhamnoides,  L.  is  ver>^  good.  Depending  upon  the  admixtures  in  sandy 
soil,  experiments  may  be  attempted  with  Salix  arenaria  L.,  Lycium  bar- 
barum,  L.,  Ulex  europaeus  L.  and  the  lime-loving  Genista  species. 

No  matter  whether  w-e  are  concerned  with  sandy  soil  in  the  interior, 
as  in  the  Mark  Brandenburg,  Oldenburg  and  Hanover,  or  with  the  sand  of 
dunes,  the  first  planting  must  always  take  place  with  the  idea  of  binding  the 
sand  with  low,  rapid  growing  vegetation.  Where  nature,  in  the  course  of 
years,  has  spread  out  a  thin  vegetative  covering,  this  should  be  protected  by 
every  possible  means,  since,  in  it,  we  have  a  basis  which  cannot  be  valued 
highly  enough  for  the  ultimate  aim  of  all  cultural  endeavors,  viz.,  to  obtain 
a  protective  forest.  Even  if  the  vegetation  is  ever  so  thin,  it  still  restrains 
the  sand  and  makes  the  planting  with  young  conifers  possible.  With  their 
deeply  growing  roots  they  are  better  satisfied  with  poor  nutritive  conditions. 
In  the  beginning  attention  should  be  paid  to  the  production  of  a  bushy 
growth  and  only  later  extended  inland  to  the  cultivation  of  tree  forms.  At 
the  sea  shore,  on  all  woody  plants,  a  great  many  branches  will  always  be 
found  which  have  been  killed  back  by  the  action  of  the  wind.  The  most 
important  cultural  method  is  to  leave  these  dead  branches  on  the  plants. 
They  break  the  force  of  the  sea  wind  and  form  a  natural  protection,  keeping 
the  foliage  alive. 

LowERiNt;  OF  THE  Ground  \\'ater  Level. 

The  building  of  canals  and  the  regulation  of  rivers  tend  to  lower  the 
water  level  in  sandy  soils  and  act  most  disasterously  on  plant  growth.  In 
contrast  to  the  "soil  moisture"  of  the  upper  masses,  the  ground  water 
trickles  down  in  the  depths,  collecting  on  the  impervious  soil  layers  and 
forming  the  reserve  supply  for  roots  in  times  of  continued  drought. 

In  regions  like  the  Alpine  provinces  and  the  Bavarian  plateau,  which 
have  a  high  absolute  amount  of  precipitation  and  smaller  evaporation,  the 
fluctuations  of  the  ground  water  level  controlled  by  the  annual  precipitation 
are  of  scant  significance  for  vegetation.  In  regions,  however,  with  scanty 
absolute  amounts  of  precipitation,  and  great  evaporation,  where  the  annual 
fluctuations  of  the  ground  water  level  depend  on  the  amount  of  evaporation, 
as,  for  example,  on  the  flat  lands  of  Northern  Germany,  and  where  the  reg- 
ular slope  of  the  ground  water  curve  indicates  a  gradual  flowing  away 
through  springs  and  rivers  (see  Ramann  loc.  cit.  275)  a  lowering  of  the 
water  level  by  canals  and  rivers  will  have  tlie  most  serious  influence.  The 
soil  dries  out  very  greatly  towards  the  autumn  and  vegetation  becomes  de- 


EDGAR  TULuo 


151 


pendent  on  the  water  of  capillarity.  This  becomes  scantier  and  scantier,  the 
sandier  and  coarser  grained  the  soih  ^\'ithout  the  supplemental  ground 
water  tree  growth  cannot  persist. 

If,  in  the  course  of  years,  the  level  of  the  ground  water  fluctuates  a 
half  metre  in  average  height  the  plant  growth  will  adjust  itself  to  the  change 
when  an  equilibrium  has  been  reached.  Both  the  water  content  and  the 
water  requirement  of  plants  are  correlated  with  the  soil  moisture,  as  Hedg- 
cock's^  comparative  cultures  in  quartz  sand,  loam,  salt  soil,  humus,  etc., 
show. 

Root  activity  depends  also  on  the  water  content  of  soil  and  plant  and 
this  activity  is  by  no  means  passive  but,  as  Sachs-  and  more  especially 
Molisch^  have  shown,  is  essentially  active  because  the  secretions  of  the  roots 
decompose  the  inorganic  and  organic  substances  in  the  soil.  The  last  named 
investigator  calls  attention,  in  this  connection,  to  the  circumstance  that  un- 
injured roots,  in  contact  with  a  dilute  solution  of  j^otassium  permanganate, 
become  covered  with  a  precipitate  of  brown  stone,  removing  the  oxygen 
from  the  solution.  The  experiment  is  unsuccessful  with  stems  and  leaves. 
With  easily  oxidizable  bodies,  as,  for  instance,  guaiacum,  pyrogallic  acid  and 
humus,  the  root  secretion  acts  as  an  oxidizer.  A  guaiac  emulsion  is  turned 
blue  by  it.  Molisch  considered  the  root  secretion  to  be  a  self-oxidizer  by 
passive  molecular  oxygen,  thereby  making  the  oxygen  active  and  bringing 
about  the  oxidation  of  substances  which  are  readily  oxidized.  In  the 
presence  of  tannic  substances  (pyrogallic  acid,  gallic  acid,  tannin,)  which 
are  more  easily  oxidized  than  the  guaiacum,  the  blue  color  does  not  appear. 
In  the  same  way  it  is  absent  in  the  presence  of  rapidly  oxidized  humus  sub- 
stances. When  absolutely  uninjured  roots  were  dipped  into  dilute  cane 
sugar  solutions,  a  reducing  sugar  became  evident  after  some  hours — probably 
this  transversion  is  caused  by  a  root-ferment.  Starch  paste,  put  on  the 
growing  roots  of  seedlings,  did  not  give  the  starch  reaction  after  a  few  hours, 
but  was  turned  a  reddish  violet  by  iodine.  The  starch  on  touching  the 
roots  had  been  changed  to  erythro-dextrin  and  was  soluble,  passing  over 
into  the  reducing  sugar. 

The  root  secretions,  perceptible  on  the  tips  of  the  root  hairs,  not  only 
impregnate  the  membranes  of  the  cells  but  can  pass  in  the  form  of  drops 
into  the  deeper  tissue  of  the  roots  when  much  water  is  supplied  and  trans- 
piration reduced.  They  can  erode  minerals  with  their  acids  (they  turn  blue 
litmus  red)  and  decompose  organic  substances.  This  action  of  the  roots 
becomes  less  with  increasing  dryness.  Roots,  accustomed  to  a  wet  place, 
when  brought  into  a  dry  one,  do  not  absorb  as  energetically  even  after  water 
has  been  supplied,  if  the  plant  has  been  wilted,  as  if  it  had  not  been  wilted. 
Hedgocock  thinks  that  the  root  hairs  actually  die. 


1  Hedg-cock,  G.  G.,  The  relation  of  the  Water  Content  of  the  Soil  to  certain 
Plants,  etc.  Botanical  Survey  of  Nebraska.  VI.  Studies  in  the  Vegetation  of  the 
State.     1902. 

2  Experimentalphysiolog-ie  p.   189.  Bot.  Zeit.   1860,   p.   188. 

3  Molisch,  H.,  Ueber  Wurzelausscheidungen  und  deren  Einwirkungen  auf 
organische  Substanzen.     Sitzb.  Kais.  Akad.  d.  Wiss.,  Wien,  Section  I,  October,  1887. 


152 

The  production  of  carbon  dioxid  forms  a  measure  of  the  energy  pro- 
duced by  a  root  in  raising  water,  boring  into  the  soil  and  other  life-functions. 
Kossowitsch  has  furnished  quantitative  determinations  on  this  points  He 
found  that  mustard  plants  in  water  cultures  assimilated  about  three  times 
as  much  carbon  for  the  life  processes  of  their  roots,  as  was  necessary  for 
the  formation  of  the  roots  themselves. 

The  strength  of  the  root  activity,  especially  in  lifting  water,  might  de- 
pend also  on  the  differences  in  temperature  between  the  atmosphere  and 
the  soil.  The  greater  this  difference,  the  more  energetic  the  work  done. 
MacDougal's-  experiments  in  the  New  York  Botanical  Gardens  prove  how 
great  such  differences  may  be.  He  found  in  June,  that  the  soil  temperature 
at  a  depth  of  30  cm,  was  at  times  20°C.  lower  than  that  of  the  air.  Naturally 
the  water  content  of  the  soil  here  becomes  a  decisive  factor  and  the  dift'er- 
ences  decrease  as  the  soil  becomes  drier  and  more  accessible  to  the  air.  The 
moisture  holding  capacity  and,  in  sandy  soils,  the  amount  of  production  will 
depend,  in  the  same  soil,  on  its  granular  structure  and  will  be  the  greater  as 
the  sand  is  finer  grained.  Livingston  and  Jensen^  experimented  on  this 
subject.  They  cultivated  different  plant  species  under  similar  conditions,  in 
soils  which  contained  admixtures  of  different  sized  quartz  grains  in  the 
different  experimental  series.  It  was  shown  that  the  best  growth  always 
occurred  where  the  quartz  sand  was  very  fine. 

By  means  of  the  above  observations  we  get  an  insight  into  the  distur- 
bances which  must  take  place,  in  the  activity  of  the  roots,  if  the  water  supply 
of  a  region  is  less,  because  the  ground  water  level  has  been  lowered.  An 
old  tract  of  trees  survives,  because  part  of  the  deep  growing  roots  reach 
the  ground  water  level  and  are  able  to  compensate  the  loss  by  evaporation 
of  the  tree  crowns,  when  the  soil  water  is  reduced  to  a  minimum  during 
periods  of  extended  dryness.  The  roots  lying  in  the  earth,  permeated  by  the 
ground  water,  are  adapted  to  these  conditions.  When  these  roots  are  per- 
manently exposed  to  drought  they  are  destroyed  or  function  feebly.  Not 
only  the  economy  of  the  tree  suffers  from  the  insufficient  water  and  food 
supply,  but  even  the  soil  itself,  since,  entirely  aside  from  the  paralysis  of 
bacterial  activity,  the  secreting  ability  of  root  hairs  and  tips  affecting  the 
decomposition  of  the  soil  also  ceases.  The  soil  becomes  "lean"  and  the 
trees  begin  to  show  dead  branches  in  the  periphery  of  their  crowns.  Since 
parasites  settle  on  dying  parts  completing  the  destruction  of  the  tissues, 
this  blight  of  the  tree  tops  is  explained  in  the  majority  of  cases  as  a  purely 
parasitic  disease  and  treated  as  such. 


1  Kossowitsch,  P.,  Die  quantitative  Bestimmung  der  Kohlensaure,  die  von 
Pflanzenwurzeln  wahrend  ihrer  Entwicklung  ausgeschieden  wird.  (Russ.  Journal  f. 
experim.  Landwirtschaft,  1904,  Vol.  V,  cit.  Centralbl.  f.  Agrikulturchemie,  1905, 
Part  6,  p.  367). 

2  MacDougal,  D.,  Soil  Temperatures  and  Vegetation.  Repr.  Monthly  Weather 
Review  for  August  1903,  cit.  Just,  Bot.  Jahresb  1903,  II,  p.  557. 

3  Livingston,  B.,  and  Jensen,  G.,  An  Experiment  on  the  Relation  of  Soil  Physics 
to  Plant  Growth.  Bot.  Gaz.  Vol.  XXXVIII,  cit.  Bot.  Centralbl.  1904,  No.  50,  p.  617. 


153 

The  Dying  of  Alders. 

Alders  are  most  sensitive  to  a  lowering  of  the  ground  water  level  and  it 
is  easy  to  find  diseased  tracts  of  alders  near  newly  cut  canals  or  regulated 
river  beds.  In  the  works  of  the  Royal  Biological  Institution  for  Agriculture 
and  Forestry  at  Dahlem,  near  Berlin  (1905),  AppeF  has  published  a  study 
of  the  death  of  alders  well  worth  consideration.  He  found  on  the  dying 
branches  a  species  of  the  genus  Valsa  known  to  attack  diseased  or  dead 
branches, — namely,  Valsa  oxystoma — and  stated  that  the  fungus  is  parasitic 
only  when  the  alders  become  susceptible,  owing  to  abnormal  circumstances. 
Drought  is  the  chief  determinative  factor.  Other  disturbances  in  nutrition 
(injury  to  the  roots,  girdling,  etc.)  can  also  create  a  predisposition  to  fungus 
attacks  but,  if  the  alders  are  enabled  to  make  a  healthy  growth,  the  disease 
disappears.  When  alders  are  found  dying  on  apparently  moist,  imperme- 
able, ferruginous  soils,  drought  may  be  considered  to  be  the  cause.  On  such 
soils,  the  alder  spreads  it  roots  only  very  superficially  and  in  continued  dry 
weather  there  is  a  very  marked  scarcity  of  water  in  the  upper  soil  layers, 
which  at  once  makes  the  alder  foliage  wither  and  dry.  The  beautiful  tracts 
of  trees  in  the  Tiergarten  in  Berlin,  especially  the  oaks,  unfortunately  show 
similar  results  from  surface  drought,  and  to  an  ever  increasing  degree. 

Naturally  canal  and  river  bed  regulations  do  not  always  necessarily 
cause  the  lowering  of  the  ground  water  level.  In  the  old  Botanical  Garden 
in  Berlin,  for  example,  the  building  of  the  subway  dried  up  the  water  in 
the  ponds  and  as  a  further  result  the  tree  crowns  rapidly  became  blighted. 
In  other  instances  we  found  that  the  spread  of  brick-paving  and  clay- 
diggings  near  forest  tracts  accelerated  the  death  of  the  alders  because  the 
deep  clay  pits  had  withdrawn  water  from  the  forests. 

The  dangerous  effects  of  lowering  the  ground  water  level  often  fail  to 
impress  us  sufficiently,  since,  in  some  tracts  of  woodland,  the  same  tree 
species  (suffering  from  blight  of  the  crowns  in  soils  from  which  the  water 
has  been  removed)  thrive  in  very  dry  places.  Under  such  circumstances 
the  fact  that  the  lack  of  water  in  itself  does  not  cause  the  death  of  the  trees, 
but  the  abrupt  transition  from  a  previously  well-watered  condition  to  great 
drought  in  the  deeper  layers  of  soil  is  overlooked.  We  may  plant  all  our 
trees  in  very  dry  soils  and  the  individuals  will  adapt  themselves  to  the 
existing  vegetative  factors  and  the  leaves  will  become  small  and  coarse,  the 
internodes  short.  But  a  sudden  great  change  in  this  condition  will  have 
most  serious  results.  If,  however,  such  changes  are  unavoidable,  our  theory 
gives  only  one  line  of  action  to  preserve  the  plantation,— namely,  to  plant 
young  trees  between  the  old  ones.  These  will  adapt  themselves  to  the 
changed  vegetative  conditions. 

Street  Planting. 

The  preservation  of  trees  along  the  streets  and  small  parks  is  of  the 
greatest  importance  for  the  hygiene  of  cities.     The  greatest  injury  results 

3   Vorlaufig-e  Mitteilung-  in  d.  Naturwiss.  Zeitschr.  f.  Land-   u.   Forstwirtschaft. 
2  Jahrg-.  1904. 


154 

from  the  present  methods  of  street  paving  which  fill  the  spaces  between  the 
stones  with  a  binding  material,  and  even  at  times  the  asphalt  covers  the  soil 
entirely.  The  injury  to  the  trees  is  two-fold;  on  the  one  hand,  the  air  is 
cut  ofif,  on  the  other  hand  watering  is  insuflicient.  This  affects  the  older 
trees  principally.  For  young  trees,  the  circle  of  sod  around  the  tree  is 
sufficient,  especially  if  an  iron  grating  laid  over  it  prevents  passers-by  from 
tramping  the  soil.  We  find  that  old  trees  die  much  more  quickly  when  a 
regulation  of  sidewalks  and  a  lowering  of  the  ground  w^ater  level  is  com- 
bined with  street  paving.  In  large  cities  another  factor  must  be  added,  i.  e., 
laying  pipes  for  gas,  electricity  and  sewers.  In  all  this  work,  the  choi)ping 
off  of  the  larger  root  branches  is  unavoidable. 

Therefore,  the  root  space  is  not  only  limited  by  the  pipes,  and  the  soil 
dried,  but  also  the  trees'  organs  for  the  absorption  of  water  are  decreased. 
To  this  cause  may  be  ascribed  the  gradual  break  up  of  old  trees  as  shown 
by  the  dying  branch  tips. 

Different  varieties  of  trees  suiTer  in  \arying  degrees  and  the  linden, 
a  favorite  and  most  frequently  planted  species,  is  among  the  most  sensitive 
of  varieties.  In  it  the  dryness  of  the  soil,  with  which  is  associated  also 
dryness  of  the  air,  is  expressed  by  a  premature  defoliation.  The  large 
leaved  linden  suffers  more  quickly  than  does  the  smaller  leaved  variety,  and 
it  is  a  well  known  phenomenon,  that,  in  the  summer  months,  when  the  in- 
habitants of  the  city  want  shade  most,  the  linden  and  chestnuts  often  for 
some  time  have  leaves  only  on  the  outermost  tips  of  the  branches.  The 
older  leaves,  covered  with  red  spider,  have  dried  up  and  fallen.  The  city 
adminstration  endeavors  to  overcome  this  condition  by  abundantly  watering 
the  ground  about  the  tree  thereby  favoring  a  second  leafing  out  in  the  late 
summer,  which  is  produced  even  without  artificial  watering  when  the  trees 
have  lost  their  leaves  prematurely.  In  this  buds  are  forced  to  unfold 
which  should  develop  in  the  following  year ;  under  such  conditions  a  second 
time  of  blossoming  is  also  often  produced  (Aesculus,  Robinia). 

Many  of  the  shoots  artificially  produced  by  this  watering  do  not 
mature  sufficiently  and  are  injured  by  frost.  Thus  in  different  years,  in  the 
middle  of  the  favorable  early  summer,  the  twigs  die  ofif  accompanied  by 
fungous  infection.  The  winter,  therefore,  did  not  kill  these  less  mature  twigs, 
but  made  them  susceptible  to  fungous  attack,  thus  giving  the  primary  cause 
for  later  death.  This  theory  also  explains  the  death  of  the  cherry  trees  along 
the  Rhine,  which  has  occupied  the  attention  of  investigators  during  the  last 
few  years^  A  Valsa  (V.  leucostoma)  plays  a  part  here  as  in  the  case  of 
the  alders.    We  will  return  to  this  case  in  the  chapter  on  injuries  due  to  frost. 

Such  bad  conditions  in  street  planting  may  be  avoided  by  a  choice  of 
less  sensitive  varieties.  First  of  all,  the  elm  should  be  recommended  as 
such ;  this  has  the  added  advantage  of  being  very  resistent  to  the  acid  gases 
of  smoke.  Also  oaks  and  plane  trees  are  used  with  advantage  according 
to  the  kind  of  soil  present.     In  broad,  airy  streets  Acer  platanoides  also 


Cf.  Deutsche  Landwirtschaftl.    Presse  1899,  Nos.  83,   86,  and  1900,  No.  18. 


155 

thrives  well,  but  suffers  often  from  honey  dew.  The  Robuiise,  especially 
the  so-called  ball  acacia,  retain  their  foliage  well  even  in  great  drought,  but 
offer  only  a  little  shade  and  put  out  their  leaves  late,  usually  losing  them 
early  in  autumn.  Therefore,  when  Robinia  is  planted,  arrangements  for 
watering  should  be  made,  in  which  drain  pipes  perhaps  ^  metre  below  the 
pavement  are  put  at  the  distance  from  the  trunk  where  the  newer  roots  lie. 
These  pipes  can  be  filled  when  necessary  from  hydrants.  However,  atten- 
tion should  be  called  to  the  fact  that  watering  through  drain  pipes  can  be 
used  only  in  the  hot  summer  months,  because  otherwise  there  would  be  an 
excess  of  water  in  the  soil  with  much  more  disasterous  results  than  those 
due  to  a  scarcity  of  water.  Finally,  we  think  that  a  sprinkling  of  the  tree 
crown  at  night  should  be  recommended  especially  where  watering  may  be 
carried  out  only  through  the  ground  about  the  tree. 

We  must  emphatically  state  that  watering  by  means  of  water  drains 
can  be  recommended  only  for  light  soils  with  a  permeable  subsoil.  By 
constantly  w^atering  heavy  soils  with  a  large  water  content,  the  soil  will  be- 
come baked  and  compacted,  resulting  in  a  scarcity  of  oxygen  and  an  excess 
of  carbon  dioxid  as  elsewhere  described,  which  combination  will  bring  about 
the  decomposition  of  the  roots.  Mangin's^  studies  will  be  cited  here  as  a 
single  warning  example.  He  worked  especially  on  the  meagre  growth  of 
trees  in  city  planting'  and  found  the  soils  choked  to  such  an  extent  that  the 
carbon  dioxid  content  of  the  soil  air  increased  from  i  to  5  and  8  per  cent, 
and  even  to  24  per  cent.,  while  the  oxygen  content  fell  to  15,  10,  6  and  even 
o  per  cent.  As  a  matter  of  course  all  the  trees  with  such  an  environment  will 
die.     (Compare  "Too  deep  planting  of  trees,"  p.  98.) 

Effect  of  Drought  on  Field  Products. 

The  results  of  continued  scarcity  of  water,  felt  most  cjuickly  in  sandy 
soils  during  great  heat,  are  determined  naturally  by  the  time  the  dry  period 
begins.  If  it  sets  in  in  May,  as  in  1904,  i.  e.,  when  growth  is  most  rapid  and 
the  activity  w^hich  should  furnish  the  material  for  maturing  of  fruit  is  re- 
duced, the  effect  is  most  serious. 

In  grain,  sowing  of  summer  seed  suffers  most  under  our  cultural  con- 
ditions, when  planted  at  the  usual  time.  This  is  easily  understood  when  we 
consider  that  winter  seeds  sown  in  the  autumn  can,  during  the  whole 
autumn  and  the  early  spring,  fully  develop  their  roots  and  obtain  a  sufficient 
formation  of  shoots.  They  thus  utilize  the  undisturbed  activity  of  their 
lower  leaves.  In  this  way  the  winter  seed  meets  the  dry  period  in  a  strong 
and  well-prepared  condition,  while  summer  seed,  even  where  it  sprouts 
normally,  enters  upon  the  hot,  dry  period  at  a  much  younger  developmental 
stage.  Accordingly  the  leaves  ripen  prematurely,  their  period  of  work  is 
therefore  more  limited  and  even  if  the  plants  develop  blossoms  and  the 
ovaries,   comparatively  little  organic   matter  is  present   for  filling  out  the 


1  Mangin,   L.,  Vegetation  und   Durchliiftung  des  Bodens.     Annal   scienc.   agro- 
nom.     2  ser.  1896;   cit.  Centralbl.  f.  Agrikulturchemle,  1898,  p.  638. 


156 

grain.  The  endosperm  is  only  scantily  filled  with  starch ;  the  grains  slender 
and  light. 

A  second  injurious  efifect  is  the  shortness  of  the  straw.  This  appears 
especially  in  summer  oats,  which  on  light  soils  have  red  stalks  and  grow- 
scarcely  a  foot  high,  maturing  only  a  few  small  heads  instead  of  the  full 
ones.  Barley  shows  less  injury,  wheat  comes  next  and  finally  rye,  the  most 
resistent.  If  the  dry  period  makes  itself  felt  as  early  as  seeding  time,  the 
plants  come  up  late  and  unequally.  This  leads  to  a  double  growth,  i.  e.,  to 
a  very  irregular  maturing  of  the  grain.  At  the  time  of  harvest  many  green 
blades  are  found  among  the  ripened  ones.  The  former  come  from  the  seeds 
which  were  left  on  top  at  the  time  of  sowing,  and  which  at  first  did  not  start, 
while  those  more  deeply  placed  found  moisture  enough  for  a  speedy  germi- 
nation. 

In  this,  limited  local  conditions  often  become  effective.  Thus,  for  ex- 
ample, one  early  crop  may  have  drawn  more  water  from  the  soil  than  an- 
other, or  a  potassium  fertiliser  is  irregularly  distributed  and  keeps  the  soil 
more  moist  in  the  spots  where  it  has  accumulated.  The  whole  development 
of  the  plant  is  also  changed  by  this.  I  found  under  otherwise  equal  conditions 
that  the  root  shortened  when  the  concentration  of  the  nutrient  solution  in- 
creased and  the  plant's  need  for  water  became  less.  This  is  of  great  signifi- 
cance in  soils  imperilled  by  drought. 

In  the  cultivation  of  sugar  beets  and  all  vegetables,  grown  as  seedlings 
in  small  spaces  and  then  planted  out  in  the  field,  the  dryness  of  the  soil 
makes  itself  felt  most  of  all  by  preventing  the  growth  of  the  seedlings  since 
no  new  roots  can  be  formed  in  dry  soil.  Next  under  consideration  is  the 
drying  of  the  foliage,  which  stops  the  development  of  the  beets.  Experience 
teaches^  that,  as  with  grain,  ivell  fertilised  fields  survive  drought  better. 
Varieties  also  show  differences  in  this  regard.  It  has  been  observed  that 
varieties  of  sugar  beets  with  outspread  leaves  wilt  more  easily  than  do  those 
with  erect  petioles. 

The  influence  of  long  continued  drought  on  potatoes  shows  more  in  its 
effect  on  the  maturing  of  the  tubers  than  upon  their  setting.  The  tubers 
remain  small  and  ripen  prematurely.  As  a  rule,  this  premature  ripening 
of  early  potatoes  is  of  less  consequence  economically  because  they  are 
adapted  by  nature  to  a  shorter  vegetative  period  and  because,  in  the  second 
place,  they  are  rapidly  consumed.  Only  the  premature  ripening  of  the  later 
varieties  is  disasterous,  because  the  tuber  has  a  small  content  of  starch  and 
its  keeping  quality  is  much  impaired. 

Leguminoseae  suffer  greatly  from  continued  drought  when  they  are 
grown  for  fodder.  Clover  and  alfalfa  burn  out  in  spots  or  the  second  crop 
fails.  The  most  frequent  results  with  fruit  trees  are  the  premature  ripening 
and  poor  keeping  quality  of  the  fruit  and  premature  defoliation. 


1  Jahresberichte    d.    Sonderausschusses    fiir   Pflanzenschutz.      Deutsche    Landw. 
Ges,  1904, 


157 

Among  the  special  forms  of  injury  which  can  set  in  during  long  con- 
tinued, intensive  drought,  especially  in  light  soils,  one  especially  deserving 
more  thorough  discussion  is 

The  Effect  of  Drought  Upon  Germination. 

When  the  water  scarcity  occurs  after  the  seed  has  passed  the  first 
stages  of  germination,  the  results  are  less  serious,  if  dry  seed  has  been  sown 
on  open  ground  than  if  seed  previously  soaked  has  been  used.  These  dis- 
advantages affect  the  development  of  the  young  individual  in  varying  de- 
grees dependent  upon  the  kind  of  seed  and  the  age  of  the  seedlings  when  the 
drought  takes  place.  According  to  Will's  repeated  experiments'^  with  seeds 
of  monocotyledons  and  dicotyledons,  the  seeds  of  the  former  seem  in  general 
to  be  somewhat  more  resistent.  The  cereals  without  glumes  (wheat  and 
rye)  are  very  little  sensitive  to  a  period  of  drought,  if  it  occurs  during 
germination.  Barley  and  oats,  however,  are  injured  more  easily,  and  the 
horse-tooth  maize  has  very  little  power  of  resistance.  Saussure-  found 
that  maize,  beans,  poppies  and  garden  campion  are  very  susceptible  to 
drought  during  germination.  Nowoczek^  in  his  experiments  repeatedly  in- 
terrupted the  supply  of  water,  until  the  power  of  germination  of  the  seeds 
was  quite  lost,  and  found  that  the  seeds  of  grains  resist  the  changing  con- 
ditions of  moisture  and  drought  better  than  rape,  flax,  clover  and  peas, 
which  lose  their  germinating  power  earlier,  but  even  after  a  period  of 
drought  these  seeds  can  be  revived.  Experiments  on  the  Gramineae  showed 
that  after  each  drought  period  the  fibrous  roots,  already  formed,  died,  and 
the  outermost  leaves  dried  up,  but  that,  when  water  was  again  supplied, 
new  adventitious  roots  were  formed  from  the  first  node  (see  Vol.  I,  p.  102) 
and  the  last  leaves  developed  further.  This  statement  applies  especially  to 
oats  and  to  a  greater  or  less  extent  to  barley,  wheat  and  maize. 

It  should  be  considered  as  universally  well-established  that  soaked  and 
then  carefully  dried  seeds,  when  put  again  into  water  take  it  up  more  quickly 
than  do  air  dry,  non-soaked  seeds  of  the  same  size.  Such  seeds  in  fact 
germinate  a  few  days  earlier. 

Tautphous*  and  Ehrhardt'^  made  experiments  giving  results  which 
were  expected  at  the  start, — viz.,  that  plants  suffer  so  much  the  more,  the 
further  germination  has  advanced;  i.e.,  the  more  developed  the  plumule  is 
when  the  drought  begins,  the  greater  the  damage.  Will  found  the  seed  of 
peas  in  part  especially  sensitive  to  drying  out.  The  testa  was  broken  by 
many  small  cracks  in  most  cases  reaching  into  the  inner  layers.  With  re- 
peated  soaking,   the   palisade   layer  was   broken   into   unequal   pieces,   the 

1  Will,  Ueber  den  Einfluss  des  Einquellens  und  Wiederaustrocknens  auf  die 
Entwicklung-sfahigkeit  der  Samen,  sowie  iiber  den  Gebrauchswert  "ausgewach- 
sener"  Samen  als  Saatgut.  Landwirtsch.  Versurhsstationen  XXVIII,  Parts  I  and  2 
(1882). 

2  Annales  des  sciences  nat.  Bot.  1S27.  Janv. 

3  Ueber  die  Widerstandsfahlgkeit  junger  Keimlinge.  Wissensch.  prakt.  Unter- 
suchung-en  etc.  von  F.  Haberlandt,  Vol.  I,  p.  122;  cit.  Biedermann's  Centralbl.  I,  p. 
344.    1876. 

4  Freiherr  von  Tautphous.  Die  Keimung-  der  Samen  bei  verschiedener  Be- 
schaffenheit  derselben.     Mtinchen  1876;  cit.  Bot.  Jahresber.  1876,  p.  882, 

5  Deutsche  landw.  Presse,  Jahrg-.  VIII,  No.  76;   cit.  von  Will, 


158 

testa  became  slimy  an(J  shortly  decomposition  set  in,  affecting  the  cotyle- 
dons, which  hindered  the  development  of  the  seedlings.  The  production  of 
these  cracks  is  due  to  the  increase  in  volume  of  the  seeds,  when  soaked,  to 
more  than  loo  per  cent.^  This  produces  a  pressure  on  the  testa  and  dis- 
tends it.  making  it  porous.  This  porosity  can  lead  with  dr\ing  even  to 
rupturing.  Through  these  cracks  in  the  testa,  the  embryo,  when  moistened 
a  second  time,  gets  much  more  oxygen  for  the  food-reserve  already  be- 
ginning to  decompose,  and  also  large  quantities  of  water  are  more  quickly 
absorbed.  Further,  the  dissolved  organic  materials  are  transferred  more 
easily  osmotically.  These  may  act  unfavorably  on  further  development. 
A  testa  slowly  and  equally  distended,  remaining  uninjured,  will  there- 
fore probably  more  completely  utilize  the  reserve  substances  of  the  cotyle- 
dons and  perhaps  indeed  force  the  fluids  into  the  tissue  of  the  cotyledons  and 
the  dissolved  reserves  into  the  embryo  by  the  turgidity  produced  by  soak- 
ing. We  cannot  enter  here  more  closely  into  the  enzymes  occurring  in  ger- 
mination and  their  action,  but  refer  in  this  connection  to  the  works  of 
Newcombe-  and  Griiss''. 

From  these  experimental  results  it  can  be  safely  asserted  that  the  use 
of  seeds,  which  have  been  soaked  until  germination  has  started  and  then 
dried  off,  should  be  avoided.  I  am  also  of  the  opinion  that  soaked  seed  is 
to  be  used  sparingly  every  time  especially  in  dry  regions.  In  the  first  place, 
in  dry  regions,  the  conditions  already  brought  about  artificially  by  drying 
soaked  seeds  can  be  repeated  most  easily  in  nature  by  continued  heat  and 
drought  and  act  much  more  injuriously  than  if  the  seed,  in  such  a  condition, 
lay  ungerminated  in  the  soil.  In  the  second  place  the  plants  become  ac- 
customed from  the  beginning  to  an  excessive  water  supply.  The  tissue  be- 
comes more  porous,  richer  in  water  and,  requiring  more  moisture,  dries  up 
much  earlier  with  the  occurrence  of  great  periods  of  drought  than  if  the 
plants  had  developed  with  a  scanty  sui)ply  of  water.  The  evaporation  in  the 
former  condition  is  greater  than  in  the  latter.  On  this  account,  growers 
often  follow  the  rule  that  for  vegetable  plants  developing  rapidly  (cucum- 
bers, beans  and  cabbages)  watering  must  not  be  discontinued,  if  the  plants 
have  had  abundant  water  when  young.  I  have  often  found  that  i)lants  from 
soaked  seeds  are  less  thrifty  than  plants  grown  from  the  same  seed  which 
had  not  been  soaked,  but  which  depended  upon  the  natural  moisture  of  the 
soil. 

Treatment  of  Tree  Seed.s. 

If  the  germination  of  tree  seeds  is  interrupted  by  drought,  the  results 
are  very  disasterous.  This  is  felt  most  in  planting  trees  whose  seeds  retain 
their  germinative  power  only  a  short  time.     Nobbe*  found  that  the  seeds  of 


1  Nobbe,   Handbiu'li,    d.    122 

-  Newcombe,  F.  C,  Cellulose-Enzymes.  Annals  of  Botany  1899,  No.  49;  oil. 
Bot.   Jahresb.    1899,   II,   p.    179. 

3  Griis^  J.,  Beitrage  zur  Knzymologie.  Berlin  1899.  Festschr.  f.  Schwendener, 
Ueber  Zucker-  und  Stilrkebildunp:  in  Gerste  und  Malz,  III  u.  IV.  Wochenschr.  f. 
Brauerei   1897,   1898. 

*  Dcibner-Nobbe,  Botanik  f.  Forstmanner.  4th.  Ed.,  1882,  p.  382. 


159 

willows  lose  their  power  of  germination  in  5  to  6  days  after  they  have  been 
blown  from  the  parent  tree.  The  seeds  of  poplars  and  elms  are  also  proved 
to  be  very  short  lived.  Acorns  and  beech  nuts,  as  a  rule,  are  capable  of 
germination  only  until  the  following  spring.  On  an  average,  ash,  maple  and 
fir  come  under  the  same  head.  On  the  other  hand,  a  large  percentage  of 
•spruce  and  pine  seeds  germinate  after  3  to  5  years ;  however,  the  seedlings 
are  apt  to  be  less  vigorous.  The  maturing  of  the  seed  and  the  care  of  it 
after  it  has  been  gathered  are  important  factors.  For  example,  Nobbe 
found  that  seeds  of  Pinus  silvestris,  which  had  stood  in  closed  glasses  in  a 
living  room,  germinated  after  5  years  to  about  30  per  cent,  and  after  7  years, 
to  12  per  cent.  In  fact,  even  after  10  to  11  years,  individual  seeds  were 
still  found  capable  of  germinating.  Under  the  same  conditions,  seed  of 
Trifolium  pratense,  after  12  years,  germinated  to  10  per  cent.,  Pisum  sati- 
vum, 47  per  cent,  after  10  years  and  in  one  experiment,  Spergula  arvensis 
25  per  cent.,  another  year  67  per  cent.  It  is  stated  that  cedars  and  Italian 
pines  (Pihon)  have  germinated  after  30  years\  It  is  advisable  to  sow  fine 
seeded  conifers  soon  after  ripening.  The  time  of  planting,  whether  summer, 
autumn  or  spring,  is  a  question  of  practical  importance.  The  summer  is 
the  most  difficult  season  because  the  moisture  fluctuates  to  a  great  extent  in 
the  soil;  therefore,  with  trees  whose  seed  must  be  sowed  immediately,  as 
willows  and  poplars,  propagation  by  cuttings  will  obviate  this  difficulty. 
Autumn  sowing  is  much  better  and  necessary  with  oaks,  chestnuts,  hazel 
nuts,  etc.  It  is  recommended  for  very  hard  shelled  seeds  like  those  of 
Crataegus,  Prunus,  Ilex,  Sorbus,  Rosa,  Cornus,  Berberis,  Ribes,  Carpinus, 
Staphylea,  Clematis,  etc.  The  last  named  kinds  often  do  not  germinate  for 
2  to  3  years,  especially  in  sandy  soils.  Spring  sowing  is  best  because  the 
danger  of  winter  and  all  injuries  due  to  animals  are  eliminated.  In  order 
not  to  lose  the  time  between  the  autumn  and  spring,  the  seeds  are  placed  in 
layers  between  sand,  which  is  kept  damp.  This  process  is  called 
stratification. 

The  importation  of  seeds  of  prized  decorative  trees  from  their  native 
countries  has  become  a  large  business.  It  is  important  to  know  the  loss  of 
germinating  power  during  transportation.  Count  von  Schwerin-  in  the 
German  Dendrological  Society  has  called  attention  to  the  fact  that  maple 
varieties  cannot  withstand  any  long  transportation,  so  that,  for  years,  not 
one  of  the  maple  seeds  brought  from  the  Himalayas  had  germinated.  Also, 
the  seed  bed  should  not  be  broken  up  too  soon,  since  many  seeds  retain  their 
vitality  for  a  long  time  in  the  soil.  Thus,  for  example,  Chamaecyparis  Law- 
soniana  often  lies  4  years  in  the  soil,  especially  in  dry  years.  For  years,  in 
the  trade  in  Magnolia  hypoleuca  from  Japan,  either  no  seeds  germinated  or  so 
few  that  the  costs  of  transportation  were  not  paid.  The  seeds  dried  during 
the  journey.  Very  encouraging  results  have  been  obtained  recently  by  leav- 
ing these  seeds  in  their  fruit  and  packing  them  in  powdered  charcoal. 


J  and  -    Ueber  das  Keimen  von  Gehdlzsamen.     Der  Handelsgartner  1905,  No.  14. 


i6o 

To  the  statement  made  heretofore  that  the  seed  of  Acer  retains  its 
germinating  power  until  the  following  spring,  the  qualifying  'statement  must 
be  added,  that  maple  seeds  of  the  Campestre  group  (Acer  ohtusatum,  A. 
italutn,  etc.),  as  a  rule,  germinate  only  in  the  second  year.  Only  occasional 
seedlings  may  be  found  after  the  first  year.  In  many  botanical  gardens,  how- 
ever, trees  of  the  Campestre  series  are  said  to  furnish  seeds  usually  germinat- 
ing early.  The  explanation  of  this  is  that  in  seeding  in  such  places,  the  first 
seedlings  are  used  for  propagation.  From  this  it  may  be  concluded  that  the 
peculiarity  of  producing  seeds,  which  germinate  promptly,  may  be  made 
constant  by  selection.  This  point  of  growing  the  earliest  germinated  seed- 
lings separately  as  seed  bearers,  when  making  large  seedlings,  might  be 
recommended  for  the  consideration  of  plant  breeders. 

Blasting  in  Grains  and  Legumes. 

Under  these  circumstances  the  seeds  do  not  mature  since  the  plants 
do  not  have  enough  water.  Such  a  condition  of  great  drought  is  most  often 
found  on  soils  of  a  very  porous  structure  where  evaporation  is  very  great 
and  the  capillary  movement  of  water  from  the  subsoil  is  slight. 

Yet  great  scarcity  of  water  will  not  always  produce  a  blasting  of  the 
blossoms.  This  depends  essentially,  as  Hellriegel's  experiments  with  grains 
show,  on  the  development  of  the  plant  when  the  water  scarcity  makes  itself 
felt.  If,  following  the  experiments\  a  grain  plant  has  had  only  a  scanty 
amount  of  water  at  its  disposal,  beginning  at  the  time  of  its  germination, 
it  reaches  maturity  in  a  period  of  the  same  length,  or  perhaps  somewhat 
longer,  yet  the  whole  growth  is  weak.  The  proportion  of  the  harvested 
grains  to  the  dry  substance,  however,  is  always  normal ;  i.e.,  approximately 
half  of  the  dry  substance  is  harvested  in  the  form  of  grain.  As  in  all 
vegetative  conditions,  there  is  here  also  a  minimum;  if  the  water  supply  is 
kept  below  this,  no  product  worth  naming  takes  place. 

If  great  scarcity  of  water  occurs  immediately  after  germination  begins, 
the  grains  remain  alive  for  a  long  time  (in  the  experiment  up  to  six  weeks) 
and  later  develop  vigorously,  when  the  water  is  supplied  in  abundance.  A 
period  of  drought  appears  to  be  still  less  injurious  if  the  grains  are  still  in 
the  milk  stage,  i.  e.,  have  reached  their  normal  size,  but  have  not 
finished  their  inner  development  and  become  hard.  The  work  of  the  plant, 
which  now  forms  no  new  dry  substance,  consists  in  transposing  the  sub- 
stances produced  in  the  leaves  to  the  storage  organs,  the  seeds. 

In  all  periods  of  growtli  between  sowing  and  ripening,  a  longer  scarcity 
of  water  acts  more  injuriously  the  younger  the  plant  is  at  the  beginning  of 
the  drought.  AMien  the  long  drought  sets  in  while  the  seeds  are  sprouting 
vigorously,  the  setback  resulting  therefrom  cannot  be  overcome.  The  results 
of  continued  drought  are  the  more  severe,  the  more  water  the  plant  has  had 
in  its  youth.    If  a  plant  has  grown  luxuriantly  with  abundant  soil,  up  to  the 


1  Hellriegel,   Beitrage  zu  den  naturwissensehaftl.    Grundlugen   des   Ackerbaues. 
Braunschweig.     Vieweg  1883,  pp.  589  to  620. 


i6i 

setting  of  the  bloom,  and  then  receives  a  check  from  a  long  drought,  the 
grain  is  not  set ;  a  greater  or  less  extensive  failure  of  the  harvest  takes  place, 
which  we  may  call  the  blasting  of  the  grain.  Ritzema  Bos'^  experiments 
with  "Maartegerst,"  or  winter  barley  sown  in  March,  are  very  interesting. 
A  sowing  was  made  on  a  field  where  autumn  sown  winter  barley  was  frozen 
out.  Only  a  few  of  the  autumn  sown  plants  came  through  the  winter  and 
produced  stalks  during  the  summer  so  that  the  same  field  produced  autumn 
and  March  sown  barley.  The  plants  from  the  March  seeding  suffered  dur- 
ing the  hot  summer  from  blasting,  while  the  plants  of  the  autumn  sowing, 
scattered  among  them,  bore  a  full  harvest  of  grain.  With  us,  besides  grain, 
peas  suffer  most.  Naturally  in  other  plants  as  well,  a  failure  of  the  seed 
harvest  can  take  place,  due  to  the  blasting  of  the  blossoming  parts. 

Thread  Formation  in  the  Potato  (Filositas). 

In  this  disease  ("mules"- — of  the  French)  the  eyes  are  deformed;  from 
them  grow  slender,  thread-like  stems  as  thick  as  medium  sized  yarn.  Not 
infrequently  the  eyes  of  tubers  comparatively  rich  in  starch  did  not  sprout 
at  all,  or  if  they  did,  the  sprouts  were  weak;  they  are  unable  to  break 
through  even  a  shallow  soil  covering.  The  tubers  decay  usually  with  the 
appearance  of  dry  rot,  yet  the  disease  has  occurred  extensively  only  where 
the  soils,  being  easily  heated,  have  to  withstand  long  droughts. 

Fig.  i6  shows  the  basal  part  of  a  cutting  grown  in  a  water  culture 
from  a  potato  affected  by  Filositas ;  the  proportions  of  the  stem,  leaves  and 
tuber  correspond  to  the  natural  size  and  it  is  seen  that  the  stems  actually 
are  only  as  thick  as  a  strong  thread  of  yarn.  The  stolons  (st.)  are  also 
more  delicate  and  have  formed  tubercles  (k),  some  of  which  have  lengthen- 
ed at  the  tip  and  grown  out  to  green  sprouts  (b)  or  developed  scale-like 
green  leaflets  (d). 

The  cutting  here  reproduced  came  from  an  experimental  culture,  the 
results  of  which  are  given  in  precise  figures  in  the  second  edition  of  this 
manual  and  lead  to  the  conclusion  that  in  the  thread  disease  of  the  potato 
we  have  before  us  conditions  of  premature  ripening  which  had  become 
hereditary.  Reports  from  the  localities  where  the  disease  has  occurred, 
especially  from  the  Marchfeld  near  Vienna",  of  the  cultural  methods  fol- 
lowed there,  substantiate  this  theory.  The  potatoes,  which  were  of  the 
earliest  varieties,  were  forced  artificially  and  planted  as  soon  after  as  possi- 
ble. Sandy  soils  on  the  Marchfeld  near  Vienna,  lime  soil  near  Poitiers'', 
had  a  small  water  capacity  and  heated  rapidly,  consequently  with  the  in- 
creasing summer  temperature  and  the  superficial  position  in  the  upper  soil 
layers  the  growth  of  the  aerial  axes  stopped  at  once.  Tubers  are  formed 
about  this  time,  but  they  do  not  mature,  they  are  filled  with  starch  so  that 
they  can  be  marketed  very  earl)'  and  command  high  prices. 


]    Zeitschr.  f.  Pflanzenkrankh,  1894.  p.  94. 

•-  Altvatter,  Das  Marchfeld  und  seine  Bewasserung-.  Oesterr.  landw.  Wochenbl. 
1875.     No.   51. 

3  Journal  d' Agriculture  pratique;  cit.  Biedermann's  Centralbl.  f.  Agrikultur- 
chemie,   1873,  No.   10   und  Annalen   d.   I^andwirtsch.,   1873,  Wochenbl.,   No.   16. 


1 62 

When  young  tubers  are  checked,  ripen  prematurely  and  are  harvested, 
the  eyes  have  not  developed  normally.  Shoots  developing  from  these  eyes 
must  naturally  be  weak.    If  such  tubers  are  used  the  following  year  as  seed 


Fig.  16. 


The  basal  portion  of  a  cutting-  grown  in  water  from  a  potato  tuber  with 
the  filament  disease  (natural  size).     (Orig-.) 


for  similar  cultivation,  these  phenomena  of  weakness  must  gradually  in- 
crease and  result  finally  in  the  growth  of  thread-like  stems  only.  According- 
ly the  disease  is  the  result  of  a  continued  unwise  cultural  method ;  viz.,  an 


i63 

admissible  shortening  of  the  vegetative  period  of  growth.  To  overcome  this 
difficuhy  the  seed  must  be  changed  since  the  method  of  cultivation  will  not 
permit  the  return  to  normal  seeding. 

DiAPHYSis  (Growing  Out)  of  the  Potato. 
In  summers  with  little  rainfall,  as,  for  example,  in  1904,  one  of  the 
most  frequent  complaints  was  that  the  potatoes  remained  small  or  when  ap- 
proximately normal  size,  showed  an  uncommonly  large  formation  of  sec- 
ondary tubers  (" Kindelhildung" ) .  In  Fig.  17  is  illustrated  one  of  the  most 
bizarre  forms,  which  shows  two  kinds  of  diaphysis  (growing  out),  viz.,  the 
actual  "formation  of  secondary  tubers"  and  "water  ends."  The  stem  end 
of  the  tuber   (at  the  left  side  in  the  drawing)   shows  two  daughter  tubers 


,^ 

# 

#; 

•■■'^'^... 

,e "" 

m 

F 

\ 

M^^ 

P 

t^f^-^ 

Fig'.   17.     Proliflcated  potato;   at  the  left  the  beginning'  of  complete  lateral  tubers; 
at  the  right,  subsequent  elongation  of  the  tip  end  (water  ends).     (Orig.) 

growing  on  either  side  at  about  the  same  relative  position  like  the  arms  of 
an  armchair.  Toward  the  tip  we  find  the  daughter  tubers  becoming  smaller 
and  smaller,  until  near  the  conical  end  of  the  tuber  (right  side  of  the 
picture)  they  are  recognizable  only  as  small  hemispherical  processes. 

This  malformation  is  caused  by  Prolepsis,  i.  e.,  a  premature  or  hurried 
development  of  the  eyes.  The  explanation  of  this  phenomenon  is  easily 
found.  After  prolonged  foliage  development  the  underground  eyes  of  the 
potato  plant  develop  tubers  which  store  the  already  manufactured  starch. 
The  drier  the  summer,  the  more  quickly  the  tuber  ripens,  since,  with  the 
regular  enlargement  and  increase  of  its  cells,  the  starch  grains  enlarge  and 
the  cell  walls  thicken.  The  cells  (except  the  youngest  about  the  eyes)  grad- 
ually lose  the  ability  to  increase  in  size  to  any  extent. 

If  now,  after  prolonged  drought  and  advanced  ripening,  a  considerable 
amount  of  water  is  forced  up  into  the  tuber,  this  abundant  absorption  of 


164 

water  increases  the  cell  pressure,  especially  in  the  young-  eye  cells  with  their 
still  elastic  walls,  so  that  the  eye  begins  to  grow.  Young  shoots  sprout  from 
these  eyes  ultimately  reaching  the  upper  surface  of  the  soil.  This  more  un- 
usual condition  occurs  only  after  continued  wet  weather.  As  a  rule,  only 
passing  periods  of  rain  force  the  water  into  the  tubers,  an  effect  lasting  but 
a  short  time ;  then  the  sprout  remains  short  and  thickens  to  the  secondary 
tuber  (Kindel). 

The  cork  layer  (the  skin,  smooth  in  young  tubers)  shows  very  clearly 
how  the  cells  of  the  ripening  tubers  lose  their  elasticity.  When  the  tubers 
are  very  ripe  the  skin  becomes  rough  in  most  varieties  of  potato,  especially 
red  ones.  At  first  the  cells  of  the  cork  layer  are  closely  connected  with  one 
another  but,  with  the  increasing  pressure  of  the  swelling  parenchyma,  the 
cells  are  forced  apart,  tearing  the  skin.  Under  these  tears  new  cork  cells 
are  formed.  This  splitting  of  the  skin  is  greater  or  less  with  different 
varieties.  The  more  split  a  tuber  of  an  otherwise  smooth-skinned  variety 
is,  the  riper  it  is  and  the  richer  in  starch. 

Diaphysis  of  the  tubers  in  many  cases  has  a  bad  influence  in  that  the 
quantity  of  starch  which  may  be  regarded  as  influenced  by  the  soil,  is  de- 
posited in  a  less  available  form  than  in  normal  development.  Together  with 
the  large  tubers  a  great  many  small  ones  are  formed,  which  are  less  mature 
and  therefore  poorer  in  starch.  According  to  the  investigations  of  Kiihn' 
and  Weidner-,  the  tubers  already  present  do  not  become  poorer  in  starch 
when  the  secondary  tubers  are  formed.  The  starch  of  the  secondary  tubers 
does  not  come  from  the  original  tuber,  but  directly  from  the  leaves.  Only  in 
plants,  whose  foliage  is  dead,  does  a  suddenly  renewed  supply  of  water  pro- 
duce secondary  tubers  at  the  expense  of  the  starch  content  of  the  older  ones. 
Both  old  and  young  tubers  have  only  the  starch  content  of  the  healthy 
tuber,  which  has  not  grown  out. 

.'^o-called  "water  ends"  are  nothing  but  the  result  of  a  renewed  growth 
of  the  apical  jiarts  of  the  tuber  excited  by  a  subsequent  supply  of  water. 
These  are  thereby  lengthened  into  a  conical  form  and  are  filled  with  new 
starch  (see  the  right  side  of  Fig.  17).  The  starch  filling  is  just  as  scanty 
as  in  the  real  sccondar}^  tuber,  "Kindel." 

FoRM,\TION  OF  TuH1:RS  ^^'lTHOUT  FoLTAdE. 

If  tubers,  at  the  time  they  would  sprout  naturally,  are  not  put  in  the 
earth,  l)ut  are  kept  in  a  dry,  poorly  lighted  room  until  the  next  period  of 
harvesting,  a  number  of  small  tubers  will  sometimes  begin  growth.  These 
stand  either  close  against  the  mother  tuber  or  hang  from  short  stolons, 
which  have  developed  from  the  eyes.  AMiile,  with  a  timely  sup[)ly  of  water 
and  light,  these  eyes  would  have  grown  into  leaved,  green  sprouts,  in  the 
dry.  dark  store-room,  the  sprouting  eye  has  developed  into  a  thread-like 
runner  (stolon)  beset  with  scales  instead  of  leaves,  the  tip  of  which  has 
thickened  into  a  tuber. 


1  Zeitschr.  d.  landw.  Centralvcr.  tier  Prov.  Saehsen  1868,  p.  .322. 

2  Annalen  des   Mecklenb.   patriot.  Ver.  1868,  No.   39. 


i65 
Aerial  Potato  Tubers. 

When  tubers  are  not  planted  deeply,  nor  hilled  up,  the  plant  remains 
green,  while  the  root  is  liable  to  be  greatly  injured  by  drought  or  animals. 
If  subsequent  rains  cause  the  weakened  roots  to  function  sufficiently  to  keep 
the  aerial  axes  alive,  small,  colored  tubers  are  developed  on  them  from  the 
lateral  eyes.  This  process  is  possible  also  under  different  conditions,  yet 
the  root  must  be  diseased  and  able  to  convey  only  very  small  amounts  of 
water  from  the  soil  to  the  leafy  stems.  If  cuttings  are  taken  from  the  older 
parts  of  the  stem,  they  can  be  forced  to  form  tubers  in  the  leaf  axils. 

Premature  Ripening  of  Fruits. 

In  years  of  continued  drought,  as,  for  example,  1904,  complaints  be- 
come most  numerous  that  fruit  does  not  keep.  Summer  fruit  indeed  ripens 
more  quickly  and  can  be  brought  to  market  one  to  two  weeks  earlier,  but  the 
flavor  leaves  much  to  be  desired.  A\'inter  fruit  remains  smaller,  as  a  rule, 
is  less  juicy  and  w^ell-flavored  and  decays  more  quickly,  or  it  needs  a  much 
longer  time  in  storage  in  order  to  become  fit  to  sell.  The  former  may  be 
observed  with  light  soils,  the  latter  has  often  been  found^  when,  with  heavy 
soil,  rains  occur  after  a  period  of  drought,  causing  a  further  growth  of  the 
fruit  which,  until  then,  had  been  retarded  by  a  scarcity  of  water. 

The  condition  here  pictured  is  explained  in  the  discussion  of  the  fact 
that  the  quality  and  keeping  qualities  of  the  fruit  depend  upon  two  factors. 
First  of  all,  each  fruit  must  have  sufficient  time  for  the  penetration  of  the 
water  and  food  substances  necessary  for  its  maturity;  this  takes  place  at 
the  time  of  swelling.  Then  the  oxidation  processes  of  ripening  set  in  grad- 
ually, in  which  the  reserve  material,  stored  in  the  form  of  starch,  is  used  up 
in  respiration.  The  longer  time  the  fruit  has  to  store  up  the  material  sup- 
plied by  the  leaves,  the  better  provided  it  is  for  the  process  of  ripening  and 
the  better  are  the  keeping  qualities.  If  this  process  is  interrupted  ahead  of 
time  by  drought,  the  processes  of  ripening,  the  conversion  of  starch  into 
sugar,  find  comparatively  little  material  present.  In  normal  summer 
weather,  i.  e.,  alternate  sunshine  and  rain,  the  fruit  during  the  process  of 
ripening  also  takes  up  mineral  elements  besides  water,  as  Pfeiffer  and  I  have 
proved.  An  absolute  increase  in  mineral  substances  takes  place  shortly 
before  complete  ripening.  This  naturally  appears  relatively  small  in  com- 
parison v'ith  the  greater  increase  in  organic  substances.  With  a  continued 
scarcity  of  water  this  increase  does  not  take  place  and  the  fruits  quickly 
use  up  the  scanty  materials.  The  acid  store  is  scanty,  the  formation  of 
sugar  still  less,  which  accounts  for  the  insipid  taste  and  the  poor  keeping 
qualities. 

In  winter  fruit,  processes  of  ripening  are  completed  only  in  storage. 
But  in  all  other  respects  the  same  point  of  view  holds  good.  If  the  weather 
during  the  summer  is  favorable  for  the  absorbing  of  large  amounts  of  re- 


1   Monatsschrift    fiir   Pomologie    unci    praktischen    Obstbau    von    Oberdieck    unci 
Lukas,  1863,  p.  272. 


i66 

serve  substances,  the  fruit  is  well  prepared  for  storage  and  keeps  sound  a 
long  time.  If  the  reserve  substances  are  scanty,  the  fruit  rapidly  spoils.  In 
seasons  after  a  long  period  of  drought,  which  has  practically  stopped  the 
development  of  the  fruit,  if  a  time  of  continued  cool,  dry  weather  comes, 
the  fruit  may  start  its  growth  again  and  renew  its  life  processes.  If  the 
fruit  must  be  harvested  in  the  autumn,  it  is  put  into  storage  in  a  compara- 
tively immature  condition  and  thus  needs  more  time  to  become  ripe.  These 
are  the  cases  (on  the  whole  less  frequent)  in  which  the  fruit  must  lie  dis- 
proportionately long  in  storage  and  does  not  become  mellow,  but  remains 
tough. 

Rusty  Plums. 

Fox  red  discoloration  of  plums  setting  in  some  weeks  before  the  normal 
time  of  ripening  is  a  phenomenon  of  premature  ripening.  The  fruit  is  still 
absolutely  hard  and,  on  an  average,  about  half  as  large  as  that  normally 
ripened.  As  a  rule,  the  rusty  plums  fall  prematurely.  The  phenomenon 
occurs  only  in  continued  hot,  dry  periods  and  is  found  especially  on  sandy 
soils.  This  discoloration  occurs  at  different  times  for  different  varie- 
ties and  is  similar  to  the  premature  coloration,  which  takes  place  in  wormy 
or  otherwise  injured  fruit.  It  should  be  emphasized  that  the  dry  locality  it- 
self is  not  the  cause  of  the  rustiness  of  the  fruit,  but  it  is  due  to  a  scarcity 
of  soil  water  succeeding  a  period  of  normal  precipitation.  Trees  whose 
water  supply  is  scant,  adjust  themselves  to  conditions  by  dropping  the  fruit, 
which  they  cannot  develop,  shortly  after  blossoming.  The  disease  only  ap- 
pears on  those  trees  which  have  held  their  fruit  until  summer  under  normal 
moisture  conditions,  which  are  then  followed  by  a  long,  dry  period.  An 
abundant  supply  of  water  must  be  provided  to  overcome  this,  and  should 
not  be  too  long  delayed,  else  not  only  the  rusty  fruit  but  often  all  the  fruit, 
will  fall. 

Further  Phenomena  of  Premature  Ripening. 

As  a  matter  of  course,  the  results  of  continued  soil  dryness  after  a  nor- 
mal spring  moisture  are  observable  in  all  kinds  of  fruit.  The  dropping  of 
leaves  and  fruit  is  of  frecjuent  occurrence.  The  scanty  maturing  of  the 
organs  remaining  on  the  plant  is  a  less  common  phenomenon.  This  produces 
also  poor  keeping  qualities  in  stored  fruits  and  potatoes  and  small  grains  in 
the  cereals.  We  will  return  later  to  the  discussion  of  other  cases,  when  we 
consider  the  results  of  unusual  dr}mess  of  air. 

Mealiness  of  Fruit. 

Especially  in  hot  summers  on  sandy  soils  it  has  been  observed  that 
fruit,  especially  early  varieties,  does  not  become  juicy  and  crisp,  but  is 
tought,  poor  in  sap,  insipid  rather  than  aromatic  in  taste,  and  when  put 
under  pressure,  makes  a  mealy  paste.  In  cooler  years  and  in  other  localities 
even  the  same  varieties  do  not  become  mealy,  but  change  at  once  a  firm  con- 
dition to  a  liquid,  winey,  doughy  or  a  decomposed  condition. 


167 

I  know  of  no  special  investigations  of  the  case  at  hand.  On  this  account  it 
can  be  stated  only  hypothetically  that  the  mealiness  of  the  fruit  depends  upon 
a  definite  act  in  the  ripening  process,  which  has  been  directed  into  other  chan- 
nels because  of  the  scarcity  of  water.  This  change  in  direction  might  not  be  as- 
sociated with  the  connection  of  the  fruit  and  the  tree,  but  may  set  in  late  in 
the  development  of  the  fruit,  about  at  the  time  when  the  intercellular  sub- 
stances generally  dissolve.  In  normal  ripening  of  fruit,  after  passing  the 
stage  of  great  sweetness,  in  which  the  fruit  is  already  "mellowing,"  i.  e.,  the 
cells  of  its  flesh  are  easily  separated  from  one  another,  there  occur  at  the 
expense  of  the  sugar  first  an  alcoholic  and  finally  an  acetic  acid  fermen- 
tation. The  fruit  becomes  winey  and  doughy  with  a  constantly  advancing 
oxidation  or  browning.  According  to  Fremy^,  a  part  of  the  alcohol  thus 
formed  is  combined  with  the  fruit  acids  to  form  the  ethers,  which  condition 
the  flavor  of  the  fruit.  A  cool  temperature  prevents  the  rapid  oxidation  of 
the  sugar.  The  supply  of  water  from  the  branch  to  the  fruit,  becoming  less 
with  ripening,  explains  the  fact  that,  in  great  summer  heat,  the  fruit  develops 
with  extraordinary  rapidity  and  in  this  gives  off  carbon  dioxid  and  water 
abundantly.  In  fruit,  however,  the  flesh  is  poorer  in  water  and  is  very 
easily  warmed  through ;  the  reduction  of  the  intercellular  substances,  which 
we  reckon  among  the  pectines,  cannot  take  place  in  the  usual  way.  A. 
Mayer-  considers  the  pectines  as  condensation-products  of  Galactose  and 
the  pentoses,  Arahanose,  and  calls  attention  to  the  peculiar  fact  that  they 
are  jelly-hke  because  of  a  special  enzyme  and  are  hydrolized  by  another  to 
the  pentoses.  It  may  indeed  be  assumed  that  these  processes  are  changed 
quantitatively  and  qualitatively  when  the  fruit  becomes  mealy.  This  is  indi- 
cated by  the  circumstance  that  in  mealy  fruit  a  firm  connection  always  exists 
between  the  outer  skin  and  the  flesh  of  the  fruit,  while  in  the  normal  winey- 
doughy  condition  the  outer  skin  can  be  raised  easily  from  the  flesh,  i.  e.,  the 
intercellular  substance  is  dissolved.  The  insipid  taste  of  mealy  fruit  is  ex- 
plained by  the  scanty  content  of  acid  and  the  quick  destruction  of  the  sugar. 

When  establishing  the  theory  that  an  excess  of  warmth  can  cause  a 
relative  lack  of  organic  acids  in  fruit,  attention  must  be  called  again  to  the 
fact  that  the  acids  formed  in  the  leaves  during  the  night  are  in  great  part 
used  up  again  during  the  following  day.  This  process  of  oxidation  will  also 
take  place  in  green  fruit  and  it  is  indeed  conceivable  that  in  the  long,  hot 
summer  days,  this  is  so  intensive  that  a  large  part  of  the  acids  already  pro- 
duced disappears.  Under  such  circumstances  no  vinous  fermentation  takes 
place. 

The  fact  that  I  was  able  artificially  to  produce  the  mealy  process  in 
apples  favors  the  theory  that  the  mealiness  of  fruit  appears  with  the  scarcity 
of  water  in  the  cells  and  a  pasty  decomposition  of  the  cellular  substance,  if 
the  conditions  necessary  for  a  vinous  fermentation  are  not  present.  Fruit 
of  various  sorts  was  packed  in  layers  in  dry  sand  after  ripening  normally 


1  Compt.  rend.  LVIII,  p.  656. 

~  Agrikulturchemie,  5th.  Ed.    Vol.  I,  p.  141.    Heidelberg  1901. 


i68 

on  the  trees  and  was  kei)t  from  autumn  until  the  next  summer  in  a  cool, 
light  cellar,  in  order  to  let  the  fruit  mature  as  slowly  as  possible.  In  this  it 
was  proved  that  some  fruit  with  an  absolute  uninjured  wax  coating  was  still 
sound  in  August,  but  absolutely  insipid  in  taste  and  of  a  mealy  consistency'. 

BiTTKR  Pit. 

In  the  flesh  of  fruit,  especially  of  apples,  brown,  tough,  scattered  spots 
are  produced,  which  sometimes  taste  bitter.  If  these  are  found  just  beneath 
the  skin  they  become  noticeable  as  somewhat  depressed  tough  places,  which, 
at  first  paler  in  color,  finally  become  brown.  The  phenomenon  is  most  fre- 
quent with  porous  soil  in  dry  years,  such  as  1904.  The  firm  fleshed  varieties 
suffer  less.  Although  a  fungus  Spilocaea  pomi  Fr.  is  given  by  some  in- 
vestigators as  the  cause,  I  still  would  like  to  consider  the  phenomenon  as  the 
result  of  a  too  rapid  maturing  in  individual  cell  groups  in  the  flesh.  In  each 
fruit  the  tissue  of  the  flesh  seems  unequally  filled  with  reserve  substances. 
If  premature  dr}mess  of  the  soil  prevents  the  accumulation  of  the  proper 
amount  of  organic  material  for  the  complete  maturity  of  the  fruit,  dilTerent 
tissues  will  remain  especially  poor  in  contents  and  actually  complete  their  life 


1  In  mealy  fruits,  as  well  as  in  thuse  normally  juicy,  the  state  of  ripeness  is 
characterized  by  the  appearance  of  peculiar  .substance  groups  becoming  visible 
immediately  after  the  sections  have  been  put  in  undiluted  glycerin. 

The  adjacent  figure  shows  a  cell  from  an  apple  (Gloria  mundi)  when  the  section 
had  been  placed  immediately  in  glycerin.  The  delicate  plasmatic  primordial  utricle 
which  had  been  contracted  into  folds  is  partially  omitted  in  the  drawing.  The 
content  is  pushed  together  more  or  less.  Also  the  very  large  vacuole  at  once  notice- 
able in  most  cells,  usually  lying  in  one  corner  (which  I  would  like  to  call  an  acid 
vacuole),  is  omitted  in  the  illustration  so  that  the  substances  appearing  with  the 
glycerin  reaction  may  be  more  clearly  apparent.  Emphasis  should  be  laid  upon 
the  fact  that  all  cells  do  not  show  this  response.  The  outer  flesh  of  ripe  apples, 
pears  and  peaches  reacts  especially  well.  The  investigations  indicate  that  a 
substance  closely  related  to  sugar  is  present  in  the  cells  in  various  transitional 
forms.  This  substance  is  found  between  isolated  larger  vacuoles  or  the  numerous 
very  small  ones;  it  might  be  imbedded  in  the  cytoplasm  or  be  free  in  the  cell  sap, 
either  as  separate  cloudy  drops  or  in  rectilinear  masses  which,  from  their  appear- 
ance, may  be  dough-like  in  consistency.  Often  they  are  found  in  more  strongly 
refractive  and  solid  forms  as  tuberous,  warty,  irregular  growths.  This  most  solid 
state  appears  also  in  the  form  of  very  small,  sandy  grains  imbedded  in  the  cell  wall, 
attention  to  which  is  first  called  when  they  swell  up  to  drops  or  (by  forming 
vacuoles)  to  small  bubbles  in  the  glycerin.  All  three  forms  have  a  capacity  for 
swelling  in  glycerin.  When  observed  under  water,  the  drops  become  indistinct  and 
disappear,  but  in  extracted  apple  juice  they  remain  visible  and  may  be  distinguished 
from  the  different  vacuoles.  The  radiating  middle  structure  of  the  figure  shows  the 
most  marked  results  of  the  swelling,  while  the  doughy  condition  of  the  substance  is 
indicated  by  the  shaded  surface  with  curved  outlines  lying  below  this.  The  sur- 
roundings represent  the  part  of  the  cytoplasmic  sack,  which  lies  in  the  same  plane 
and  which  encloses  the  grains  of  coloring  matter  and  two  vacuoles. 

The  process  of  swelling  is  the  same  in  the  three  masses  described  above,  but 
occurs  in  different  intensities.  It  appears  most  rapidly  and  furthest  developed  in  the 
drop  form  and  decreases  the  firmer  the  substance  becomes.  With  the  addition  of 
water  the  drops  disappear  first,  in  their  place  there  remains  at  times  a  finely  ground 
residue  at  the  edge  of  the  cytoplasm;  somewhat  later  the  doughy  masses  become 
invisible  and  the  dividing  line  formed  through  the  cytoplasm  becomes  circular.  The 
polyp  forms  become  slowly  transpaient;  the  warty  masses  gray  grained  and 
cloudy  without  dissolving  entirely  in  one  day.  If,  at  the  beginning  of  the  entrance 
of  water,  cloudy  balls,  generally  lying  along  the  walls  imbedded  between  the 
vacuoles,  ai^  observed,  there  is  frequently  noticed  a  swelling  of  different  groups  of 
cell  contents  beginning  at  the  inside,  which  increases  up  to  the  formation  of  vac- 
uoles. A  similar  phenomenon  is  found  with  glycerin  where  the  process  sets  in  more 
slowly  and  the  changed  conditions  are  retained  longer.  By  this  process  of  swelling 
of  the  substances  imbedded  in  the  cloudy  drops,  the  inner  part  of  those  appears 
at  times  filled  by  one  or  more  vacuoles  in  such  a  way  that  an  actual  cloudy  mass 
occurs  only  as  a  slender  ring  enclosing  the  vacuoles.     This  becomes  more  and  more 


169 

cycle  so  much  the  more  cjuickly.  The  beginnings  of  the  disease  must  be 
sought  in  a  rather  early  stage  of  the  fruit's  development.  I  often  found  in 
diseased  cell  groups,  recognizable  by  browned  and  corked  membranes,  many 
grains  deposited  on  the  cell  wall.  These  slowly  colored  blue  with  iodine 
and  therefore  must  be  spoken  of  as  starch.  Some  of  them  showed  a  warped 
seam  which  remained  whitish.  Further,  a  splitting  of  the  browned  tissue  is 
observed  often  in  the  tough  fleshed  early  apple,  varieties  which  are  most 
inclined  to  become  specked.    These  splits  are  explained  by  the  fact  that  when 


transparent  in  water  until  it  can  no  longer  be  recognized.  No  actual  dissolving-  of 
the  substance  has  been  observed.  If  fresh  sections  are  laid  first  in  water,  cloudy 
drops  do  not  appear,  from  which  it  may  be  concluded  that  the  substance  is  taken 
up  by  the  water.  Indeed,  in  several  cases,  it  was  observed  (in  Reinettes)  that  if 
the  drops  had  disappeared  after  a  rapid  temporary  action  of  the  water  there  was 
left  a  fine  grained  residue.  With  the  addition  of  glycerin  the  solid  grains  either 
form  drops  or  separate  filament-like  pouches.  Per- 
haps it  is  only  these  grains  which,  imbedded  in  the 
drops  and  the  remaining,  above-mentioned  forms 
claimed  to  be  different  aggregate  conditions  of  some 
ground  substance,  swell  up  to  polyp-like  radiations.  It 
is  seen  especially  in  the  drops  which  are  enlarged  to 
a  thick-walled  vesicle  by  a  vacuole  that  only  some 
places  may  be  elongated  like  pouches  or  chains  of 
beads  which  in  individual  cases  can  reach  the  wall 
layer  and  thus  transverse  the  cell  as  knotted  bands. 
With  the  continued  slow  swelling  in  glycerin  the 
figures  change  constantly  whereby  the  substance, 
which  becomes  more  and  more  doughy,  more  weakly 
refractive  and  stringy,  shows  an  attempt  to  return  to 
the  drop  form.  Either  some  of  the  chief  arms  of  the 
above  represented  polyp-figure  take  up  more  and 
more  substance  and  become  broad  bands  which  finally 
draw  together  into  spherical  drops,  or  separate  beads 
of  the  chain  show  a  stronger  growth  with  a  constant 
increase  in  size  and  decrease  in  refractive  power, 
whereby  the  smaller  spherical  links  of  the  chain  and 
the  thread-Ike  substance  possibly  connecting  them 
becomes  more  slender,  finaUy  tearing-  apart  and  be- 
coming drawn  into  the  larger  drops.  In  most  pro- 
nounced cases  these  drops  were  recognizable  after  96 
hours,  but  later  could  no  longer  be  found  nor  pro- 
duced again  by  reagents. 

The  reason  that  I  place  the  substance  mentioned 
in  the  list  of  sugars,  or  between  sugars  and  ferments, 
is  their  occurrence  in  the  same  cells,  which  contain 
large,  strongly  refractive  drops  capable  of  being 
drawn  together  by  glycerin,  or  separated  by  alcohol  and 
showing  a  copper  reaction  into  which  it  seems  to  me 

pass  over  the  small,  above-mentioned  drop  forms.  The  large  syrup  drops  which 
may  be  drawn  together  in  certain  parts  of  the  cytoplasmic  sac  by  glycerin  and 
which  gradually  disappear  again,  may  be  partially  fixed  by  the  use  of  the  potassium 
bichromat  since  a  persistent  brown -grained  precipitate  is  formed.  In  pears  I  found 
this  phenomenon  after  the  action  of  dilute  sulfuric  acid  on  the  glycerin  preparation 
in  which  the  walls  of  the  stone  cells  became  the  color  of  wine.  Ferric  chlorid  gives 
no  special  color  reaction.  If  a  piece  of  caustic  potash  is  put  in  the  glycerin  prepar- 
ation the  syrup  balls  color  an  intense  yellow  and  the  remaining  cell  content  a 
lighter  yellow.  Chemically  pure  grape  sugar  behaves  similarly  but,  dissolved  in 
pure  water,  it  gives  only  a  weakly  yellow  liquid.  The  addition  of  calcium  chlorid 
or  calcium  nitrate  will  hold  the  drops  in  form  somewhat  longer.  They  then  retain 
their  strong  refractive  power  from  2  to  4  days.  With  the  use  of  silver  nitrate  a 
brown  grained  precipitate  is  produced  in  many  syrup  balls,  which  consists  either  of 
many  very  small  grain  bodies  or  less  numerous  larger  tuber-like  ones.  A  part  of 
the  drops  disappear  without  giving  any  precipitate. 

It  seems  to  me  that  we  are  concerned  here  with  an  extremely  easily  changed 
substance,  easily  soluble  in  water  and  alcohol,  but  less  soluble  in  glycerin,  which 
occurs  in  the  same  cell  in  different  transitional  stages,  thus  bowing  different  re- 
actions Even  exposure  to  the  air  brings  about  a  change,  since  an  apple,  which 
shows  a  quantity  of  drops  on  its  freshly  cut  surface,  does  not  show  any  drops  on 
this  same  cut  surface  after  a  few  hours  when  acted  upon  by  glycerin,  and  these  may 
only  be  found  again  deeper  in  the  tissue. 


Fig.  18.  Parenchyma  cell 
from  the  flesh  of  a  ripe 
apple  after  treatment  with 
undiluted  glycerin.    (Orig.) 


the  fruit  was  attacked  hy  the  disease,  while  the  cork  layers  were  swelling, 
the  specked  tissue  had  already  lost  its  elasticity. 

The  dying  of  single  tissue  groups  of  this  kind  as  the  result  of  an  in- 
sufficient storage  of  reserve  substances  will  take  place  so  much  the  more 
easily  as  the  deposition  of  starch  is  made  more  difficult  by  the  one-sided  in- 
creased nitrogen  fertilization.  In  fact,  practical  fruit  growers  have  also 
observed  that  this  specking  is  especially  abundant,  if  the  trees  have  been 
excessively  fertilized  with  sprouted  malt,  hornshavings,  etc. 

Wortmann^  substantiates  our  theory  in  regard  to  the  non-parasitic 
character  of  the  specks  and  of  their  occurrence  with  a  scarcity  of  water. 
He  ascribes  the  appearance  of  the  dead  cork  cell  groups  to  an  excess  of  acid 
which  is  brought  about  by  the  concentration  of  the  cell  sap  of  the  fruit  as 
a  result  of  unreplaced  water  loss.  The  absolute  acid  content  decreases  with 
the  ripening  of  the  fruit,  but  the  relative  acid  content  becomes  increased 
with,  scarcity  of  water  in  the  cells.  Wortmann  concludes  from  his  investi- 
gations of  the  epidermis  that  the  larger  fruits  evaporate  more  than  the 
smaller  ones  and  the  specked  varieties  (reddish  Reinette,  Goldgunderling, 
King  of  Pippins,  Landsberger,  green  Stettiner,  Danziger)  evaporate  more 
than  do  the  varieties  not  inclined  to  specks.  He  found  a  greater  thickening 
of  the  outer  walls  of  the  epidermis  in  the  non-specked  varieties,  the  peeled 
specimens  of  which  evaporated  more  than  did  peeled  specked  apples.  If 
the  fruit  of  non-specked  varieties  was  pricked  with  a  needle  and  laid  in  acid 
or  alkaline  solutions  (potassium,  tartarate,  limewater)  specks  were  pro- 
duced which  could  not  be  distinguished  from  natural  ones. 

The  phenomenon  of  the  so-called  "fly  specks"  should  not  be  confused 
with  this.  Very  fine  little  black  points  united  into  groups  are  found  on  the 
apple  peel,  which  appear  to  the  naked  eye  like  a  cloudy  bloom  and  under  the 
microscope  look  like  accumulations  of  fly  specks.  Fungi,  especially 
Leptoihyrium  pomi  Mntg.  and  Fr.  and  Phyllachora  Pomigena  (Schw.) 
Sacc.  are  given  as  the  causes.  Often  actual  insect  secretions  are  found  in 
which  fungi  grow.  Since  the  skin  under  the  "fly-specks"  does  not  seem  to 
have  been  injured  in  any  way,  rubbing  with  a  damp  cloth  is  enough  to  make 
the  fruit  again  fit  for  sale.  Another  phenomenon,  often  called  specking,  is 
the  "rusting  of  the  peel."  This  term  comes  from  the  change  in  color  of 
the  outer  skin.  During  the  process  of  sivelling,  the  skin  gets  stellate  or  den- 
tritically-branched  tears,  which  are  closed  by  the  formation  of  cork. 

Stoniness  of  Pears  and  Lithiasis. 

When  pears  are  grown  on  poor  soils,  in  dry  years  the  flesh  is  solid,  but 
grates  between  the  teeth  when  eaten,  in  wet  years  the  flesh  is  tender  and  does 
not  grate  between  the  teeth.  This  grating  is  due  to  the  extraordinarily  large 
amount  of  stone  granules  formed  in  the  years  of  drought.  Practical  workers 
often  maintain  the  theory  that  the  formation  of  stone  cells  in  pears  is  the 
direct  result  of  great  drought. 


1  Wortmann,  Jul.,  Ueber  die  sog.  Stippen  der  Aepfel.  Landwirtsch.  Jahrbiichcr 
1892,  Parts  3  and  4. 


m 


Investigations  of  young  fruit  show,  however,  that  in  each  variety  of 
pear  in  normal  development  aggregations  of  coarse- walled  schlerenchymatous 
cells  are  always  present  unequally  distributed.  These  stone  cells  are  in  fact 
an  anatomical  characteristic  differentiating  pears  and  apples^  Therefore,  it 
is  not  the  occurrence  of  the  stone  cells  but  only  the  greater  thickness  of  the 
walls  already  formed  which  is  the  result  of  the  drought.  In  many  varieties 
they  remain  relatively  thin-walled.  To  this  should  be  added  that  their  con- 
nection with  the  surrounding  tissue  is  tougher  and  closer  in  dry  years. 

In  the  so-called  stoniness  of  pears,  only  the  increased  wall-thickening- 
of  the  normally  deposited  schlerenchy- 
ma  cell  centres  is  concerned  and  there- 
fore no  increase  of  the  elements,  while 
we  find  in  Lithiasis  an  accumulation 
of  stone  cell  elements  produced  subse- 
quently by  cell  increase.  These  finally 
may  also  extend  over  the  surface  of 
the  fruit  and  then  form  light  brown 
circular  specks,  either  equally  distrib- 
uted or  clustered  on  the  sunny  side  or 
even  map-like  etchings  due  to  the  run- 
ning together  of  the  specks  (Fig.  19), 
the  upper  surface  of  w^hich  shows  a 
crumbly  construction.  Not  infrequently 
the  same  varieties  of  pear  suffer 
also  from  Fusicladium  (see  Vol.  II). 
Nevertheless,  the  Lithiasis  specks  may 
be  easily  distinguished  from  the  smooth, 
usually  blackened,  fungous  specks,  be- 
cause of  their  crumbly  constitution  and 
the  raised  edges  of  the  wound. 

So  far  as  observations  have  shown 
as  yet,  only  certain  varieties  suffer 
from  Lithiasis.  Many,  in  fact,  form 
predominantly  roundish  specks,  while 
in  others  usually  zigzag  gapping  cracks 
are  produced.     Stone  masses  are  not 

always  depressed,  often  they  occur  on  the  upper  surface  as  pale  cork-colored 
cushions. 

An  entirely  normal  construction  may  be  found  in  the  healthy  parts  of 
the  pear  attacked  by  the  stone  disease;  i.  e.,  underneath  the  small  celled,  not 


Fig-. 


19.     Pear  diseased  with 
Lithiasis.     (Orig.) 


1  Turpin,  Memoire  sur  la  difference  qu'offrent  les  tissus  cellulaires  de  la  pomme 
et  de  la  poire  etc.     Paris.  Compt.  rend.  1838,  I,  pp.  711  ff. 

-  The  substance,  of  which  the  stratified  thickened  walls  of  the  stone  cells  con- 
sist, has  received  the  name  of  glycodrupose  from  Erdmann*.  He  used  this  name 
because  he  thought  that  the  chemical  composition  of  these  cells  is  the  same  as  that 
of  the  tissue  of  stones  of  plums  and  cherries  (Drupaceae).  The  substance,  decom- 
posed by  moderately  concentrated  hydrochloric  acid,  gives  half  its  weight  in  grape 
sugar  in  solution.     The  half  remaining  undissolved  is  called  drupose;    when  boiled 


17-2 

very  thick-walled,  colorless  epidermis  (Fig.  20  e)  lie  three  or  four  layers  of 
usually  tangential ly  elongated  or  cubical  parenchyma  cells  (/>)  which  are 
richer  in  cytoplasm  than  the  deeper  lying  tissues  and  contain  chlorophyll, 
but  no  starch.  The  starch  is  found  to  appear  gradually  first  in  the  inner 
flesh  and  its  grains  usually  increase  in  size  toward  the  core.  Underneath 
the  outer  cell  layers,  rich  in  chlorophyll,  the  deposition  of  the  stone  cell 
centres  begins  (st).  These  form  groups  of  a  few  cells  in  the  normal  flesh; 
in  the  coarse  fleshed  fruit  they  are  separated  only  by  small  intermediary 
areas  of  delicate  parenchyma  (^/'j.  From  the  periphery  toward  the  in- 
terior of  the  fruit,  the  stone  cell  groups  become  more  scarce  and  the  sur- 
rounding parenchyma  assumes  a  stellate  arrangement. 

In  the  first  stages  of  the  disease,  we  find  in  fruit,  which  is  always  green 
and  hard,  that,  underneath  the  uninjured  and  colorless  epidermis,  individual 
cells  contain  no  chloroplasts,  but  ha\  c  a  brown,  strongly  refractive  cell  con- 
tent, which  is  massed  together  in  lumps.  The  number  of  these  browned 
cells  gradually  increases  and  ruptures  the  outer  skin.  Beneath  the  ruptured 
place  which,  by  the  dr}'ing  and  crumbling  decomposition  of  the  tissues  forms 
a  depression  (yr),  a  brown-walled  dying  tissue  (br)  is  found  in  the 
midst  of  the  flesh,  which  later  may  rupture  and  form  cracks.  Often  in 
these  cracks,  and  always  in  the  open  peripheral  pits  (gr),  may  be  found  a 
colorless  slender  mycelium  which  is  a  subsequent  infection  and  may  hasten 
the  decomposition  of  the  tissues. 

A  most  striking  phenomenon  is  the  fact  that  when  the  pit  has  been 
formed  the  flesh  tissues  no  longer  die  and  closed  masses  of  newly  formed 
schlerenchymatic  tissue  begin  to  push  out  like  cushions  with  a  radial  struc- 
ture (/).  These  cushions  of  stone  cells  force  the  dead  bark  (t)  tissue  out 
and  oflf. 

In  cross-section  the  individual  elements  of  the  stone  cell  cushions  are 
square  or  rhomboid,  and  lie  almost  unbrokenly  upon  one  another.  Even  in 


with  nitric  acid  and  washed  with  water,  ammonia  and  alcohol  this  leaves  behind 
a  yellowish  white  cellv^lose.  Erdmann  concludes  from  his  investigations  that  the 
substance  of  the  stone  cells  may  be  produced  from  a  carbohydrate  by  the  loss  of 
water  and  nitrogen  from  starch  or  gum,  while  in  the  normal  process  of  ripening, 
water  must  be  taken  up  for     the  formation  of  the  sugar. 

The  theory  that  the  formation  of  sugar  and  of  cellulose  are  most  closely  connected 
is  given  expression  by  DeVries**.  He  says  that  usually  an  accumulation  of  grape 
sugar  is  found  in  those  young  cells  which  later  strongly  thicken  their  walls.  For 
example,  the  bast  fibres  of  clover  as  well  as  fibres  of  the  inner  fibrous  sheath  of  the 
vascular  bundles,  which  appear  to  be  very  thick  walled  in  a  mature  condition,  are 
rich  in  grape  sugar  in  their  younger,  still  thin  walled  stage,  while  the  surrounding 
tissue  is  poor  in  sugar  or  lacks  it  entirely.  DeVries  found  the  same  conditions  in 
the  young  bast  fibres  of  potato  and  maize.  Even  in  the  hairs,  which  are  thick- 
walled  later,  an  accumulation  of  sugar  takes  place  before  the  thickening  of  the 
walls,  thus,  for  example,  in  the  hairs  of  young  clover  leaves,  in  who.se  parenchyma, 
however,  no  sugar  could  be  proved.  In  the  same  way,  according  to  DeVries,  sugar 
can  not  l>e  found  in  the  root  parenchyma  of  this  same  plant,  while  in  the  young  root 
hairs  it  occurs  abundantly.  The  possible  transversion  of  cellulose  to  dextrin  and 
sugar  by  the  action  of  dilute  sulfuric  acid  after  heating  is  well-known.  With  this 
the  recent  investigations  on  the  Hemicelluloses;  mannen,  galactan  and  araban, 
should  be  compared. 


*  Liebig's  Annalen,  Vol.   138,  p.   101;    cit.   im  Jahresbericht  f.  Agrikulturchemie 
1866,  p.  99. 

**  Wachstumsgeschichte    der    Zuckerriibe,  in  den  Landw.  .Tahrb.  1879,  p.  438. 


173 

early  stages  they  color  a  bright  yellow  with  AniUn  sulph.  and  when  oldest 
will  dissolve  easily  in  sulfuric  acid  without  any  observable  precipitation 
of  gypsum  crystals.     While  the  normal  stone  cells  usually  remain  yellow 


Cross-section  of  a  stone  cell  cushion  from  a  pear  diseased  with  Lithiasis.      (Orig.) 
Explanation  in  text. 


174 

from  the  effect  of  cine  iodid  of  chlorid,  the  elements  of  the  schlerenchyma 
cushions,  which  were  formed  later,  turn  blue  after  some  time,  either 
throughout  or  in  the  innermost  lamellae  of  the  walls. 

The  growth  of  these  schlerenchyma  cushions  takes  place  in  a  meriste- 
matic  layer  (w?)  formed  underneath  the  dead  bark  and  appears  at  first  as  if 
it  would  develop  into  a  flat  cork  layer,  cutting  off  the  centre  of  the  diseased 
tissue,  as  may  be  observed  in  the  Fiisicladium  cushions.  This,  however,  is 
not  the  case.  The  meristematic  layer  is  active  as  long  as  the  fruit  is  green 
and  growing.  Toward  the  periphery  it  forms  new  thin-walled  bark  cells 
(usually  in  small  numbers)  which  again  are  gradually  attacked  by  bacteria 
and  fungi,  while  on  its  inner  side,  toward  the  (usually  seedless)  core,  the 
thick-walled  elements  of  the  stone  cell  cushions  are  increased. 

The  radial  arrangement  of  the  cell  rows  in  these  is  explained  by  the 
tension  of  the  tissues  which  the  swelling  of  the  unripe  fruit  causes.  If,  in 
this,  the  new  formation  of  stone  cells  is  greater  than  the  distension  of  the 
parenchymatous  tissue  of  the  fruit  flesh,  the  stone  cells  are  pushed  out  like 
cushions.  As  a  rule,  however,  both  processes  keep  step  and  finally,  by  the 
death  of  the  pathogenic  meristem  itself  and  the  breaking  of  the  connection 
between  the  outermost  stone  cells,  is  produced  the  crumbly  constitution  of 
the  stone  spots. 

It  is  a  matter  of  course  that  fruit  attacked  by  Lithiasis  is  unfit  for 
consumption. 

Since  this  phenomenon  is  not  found  in  all  varieties,  and  not  every  year 
even  in  the  same  varieties,  but  is  a  destructive  factor  only  on  dry  soil  in  dn' 
years,  the  supposition,  that  the  stock  used  in  grafting  influences  the  problem, 
seems  probable.  Weakly  growing  stock  which  cannot  take  up  sufficient 
amounts  of  water  from  a  dry  soil  for  a  rapidly  growing  top,  because  of  its 
small  root  area,  will  favor  this  stony  condition.  If,  on  this  account,  the  dis- 
ease should  occur  repeatedly  in  the  case  of  dwarf  trees  on  light  ground,  an 
attempt  should  be  made  to  graft  pears  on  the  most  rapidly  growing  varieties 
of  quince.  When  standard  trees  are  in  question,  an  attempt  to  overcome  the 
difficulty  should  be  made  by  renewing  the  soil,  fertilizing  the  sub-soil  and 
watering  abundantly ;  in  obstinate  cases,  by  means  of  renewal  of  the  top  by 
pruning  after  fertilization.  Some  method  of  forcing  the  fruit  to  swell  as 
rapidly  as  possible  might  best  protect  it  from  an  excessive  formation  of 
stone  cells. 

Varieties  of  Fruit  .Suitable  for  Dry  .Soils. 

The  guiding  idea  of  our  manual  is  that  many  diseases  of  cultivated 
plants  may  be  prevented  by  a  more  careful  consideration  of  the  relation 
between  the  character  and  habits  of  the  plant  and  its  environment.  In 
accordance  with  this  plan  in  treating  diseases  favored  by  drought,  w^e  men- 
tion a  number  of  w^ell-known  varieties  suitable  for  dry  soils^. 


1  Oberdieck,  Deut.schland.s  be.ste  Olistsorten.  Leipzig-,  VoiRt.  ISSl.  L.  indicates 
that  the  variety  is  recommended  to  the  agriculturist.  Str.  suitable  for  planting 
along  streets.  The  name  of  the  month  aftei'  that  of  the  variety  indicates  the  time  of 
complete   ripening. 


175 

Apples:  Summer  Rose,  End  of  July.  L.  Str.,  Scarlet  Pearmain,  Au- 
tumn. L.  Str.,  Landsberg,  Autumn.  L.  Str.,  Dantziger,  Autumn.  L.,  King 
of  Pippins,  \A' inter.  L.  Str.,  Orleans,  Winter.  Str.  (For  the  agriculturalist 
where  the  soil  is  better).  Yellow  Bell  flower,  Winter.  L.  Str.,  Alant,  L., 
Deutscher  Gold  Pepping*,  Winter.  L.  (must  be  left  on  the  tree  until  the 
middle  or  end  of  October),  Kassler,  keeps  from  winter  until  summer.  L. 
Str.,  Purpurroter  Cousinet*,  winter  till  summer. 

Pears  for  dry  soils :  Hannoversche  Jakobsbirne*,  end  of  July.  L.  Str., 
Clapp  Favorite.  August.  L.,  Archduke,  August.  L.,  Yat,  beginning  of  Sep- 
tember. L.  Str.,  Kuhfuss*.  beginning  of  September.  L.  Str.,  Treyve,  Sep- 
tember. Autumn  Melting  (Downing),  end  of  September.  L.  Str.,  Bosc,  end 
of  October.  L.,  Marie  Louise,  beginning  of  November.  L.  Str.,  Mecheln, 
December.  Madam  Korte*,  January.  Kemper,  cooking  pear  for  the  whole 
winter.  L.  Str. 

Cherris,  as  is  well-known,  prefer  a  well  drained,  dry  soil;  on  the  other 
hand,  plums,  on  the  average,  flourish  best  in  a  moist,  heavy  soil  and  also 
they  bear  sweeter  fruit.  It  is  desirable  to  know  a  number  of  varieties  re- 
quiring less  water.  Biondeck,  beginning  of  August;  early  Apricot,  middle 
of  August;  Lawson,  end  of  August;  Bunter  Perdrigon,  end  of  August; 
Berlepsch,  beginning  of  September;  Altham,  beginning  of  September;  Jerus- 
alem, beginning  of  Septembr ;  Anna  Spath,  middle  of  September;  German 
prune,  end  of  September.  As  a  street  tree,  the  plum  is  not  very  desirable 
because  of  its  habit  of  growth. 

As  varieties  which  grow  well  on  dry,  light  soils  in  the  climate  along 
the  coast,  should  be  mentioned^:  i.  Apples:  Landsberg,  Purpurroter  Cousi- 
net*, Oldenburg,  Geflammter  Kardinal*,  Bauman ;  the  Prinz  (Downing) 
is  especially  suitable  for  the  provinces  along  the  Baltic  and  the  North  Sea. 
2.  P^ari-:*  Yat  Bosc,  Red  Bergamot,  Summer  Doyenne.  3.  Plums:  House 
Plum.    4.   Cherries:  The  common  sour  cherry. 

Stunting. 

Since  almost  everywhere  in  nature  similar  effects  are  obtained  by 
different  means,  a  limited  soil  space  may  be  only  one  cause  of  dwarf  growth ; 
another  is  the  lack  of  available  nutriment  due  to  either  a  scanty  supplying  of 
raw  soil  solution  to  the  roots  or  to  the  decrease  of  organic  reserve  nutriment. 
This  latter  case  we  will  have  to  consider  again  later  in  the  "Pincement  Grin," 
i.  e.,  in  the  pruning"  of  leaves  to  prevent  the  sprouting  of  the  buds  found  in 
their  axils  and  in  the  production  of  dwarf  seedlings  by  cutting  off  the 
cotyledons  which  are  rich  in  nutrition. 

In  nanism,  however,  caused  by  soil  physically  unfit  because  of  too  great 
porosity,  water  scarcity  alone  must  be  considered.  Given  a  soil  rich  in  mineral 
or  organic  food  substances,  the  size  of  the  plant  depends  upon  the  distension 


*  Name  of  variety  given  in  the  German  original,  not  reported  in  the  United 
States  of  America. 

1  From  a  written  communication  of  Mr.  Klitzing-  (owner  of  a  nursery)  in 
Ludwigslust. 


176 

of  the  individual  cells,  due  to  the  turgor  produced  by  the  water  from  the 
roots,  and  the  conclusion  is  at  once  reached,  that  a  scanty  supply  of  water 
during  the  time  of  growth  must  produce  small  dwarf  specimens.  ICach 
excursion  through  sandy  regions,  in  which  a  damp  subsoil  is  cither  lacking 
or  lies  very  deep,  furnishes  examples  enough  for  this  fact.  I  have  published 
detailed  measurements  concerning  the  shortening  of  cells  due  to  a  scarcity 
of  water'.  Moller-  furnished  experimental  proof  of  dwarfing  due  to  scar- 
city of  other  food  substances  with  an  excess  of  water  and  also  confirms  the 
principle  that  in  slightly  concentrated  nutrient  solutions  the  root  increases 
relatively  in  size.  Mobius''  has  arrived  at  the  same  result  in  his  comparative 
cultures  with  Xanthium  in  sand  and  loamy  soil.  He  found  the  roots  and 
stalks  of  plants  grown  in  sand  branched  more  than  those  of  plants  grown  in 
loamy  soil,  while  the  leaves  were  more  slender  and  the  glandular  hairs 
fewer  in  number.  On  the  other  hand,  in  plants  grown  on  loam  the  content 
of  calcium  oxalate  cr}'stals  seemed  smaller.  The  thorns  were  smaller  on 
sandy  soil,  but  the  walls  of  the  lignified  cells  seemed  considerably  thicker. 

Comparative  studies  of  the  influence  of  dr)-  or  wet  localities  were  made 
by  Duval-Jouve'.  These  proved  that  in  dry,  hot  i)laces,  a  formation  of  the 
hard,  bast  bundles  is  especially  favored,  but  is  retarded  in  shady,  wet  posi- 
tions. Volken's  observations''  on  Polygonum  amphih'mm  in  the  forms  grown 
in  sand,  heath  and  water,  are  very  thorough.  In  the  sand  form  the  circum- 
ference of  the  stem  is  smaller,  at  the  expense  of  the  central  air  canal;  the 
bark  cells  are  more  heavily  thickened,  while  between  the  bark  and  the 
phloem,  a  rather  broad  ring  of  uncommonly  thick  mechanical  cells  is  en- 
closed. A  closed  wood  cylinder  is  formed,  the  vascular  system  in  which  is 
almost  2  to  3  times  as  strongly  developed  as  in  the  water-grown  stem ;  in 
the  latter,  the  absence  of  thick-walled  elements  and  the  occurrence  of  large 
air  holes  facilitate  floating.  The  petioles  of  the  water  form,  which  have  no 
mechanical  reinforcement,  may  become  six  times  as  long  as  in  the  land  form, 
the  midribs  of  which  are  strengthened  by  strong  collenchyma  cords.  The 
palisade  cells  arc  more  strongly  developed  in  tlie  water  plants,  but  these 
lack,  on  the  other  hand,  the  strongly  developed  bristles  on  the  upper  sur- 
face and  here  also  the  somewhat  larger  epidermal  cells  which  in  the  land 
form  contain  a  slimy  content,  explained  by  Volkens  as  a  water  reservoir  in 
times  of  great  drought.  In  the  well-known  Rose  of  Jericho  (Anastatica 
hierochuntica),  that  plant  of  the  desert  which  closes  together  like  a  head 
when  dry,  the  inclination  of  the  branches  toward  each  other  arises  from  the 
fact  that  the  wood  cells  on  the  different  sides  of  each  branch  possess  a 
different  capacity  f(jr  swelling  longitudinally,  which  goes  hand  in  hand  with 
an  unequal  lignification. 

1    Sorauer,  Bot.  Zeit.  1873. 

-   IM(illcr,  Beitrage  zur  Kenntnis  d.  Verzwergung.  T^andw.  Jahrb.  1893,  p.  167. 

•  iMii))ius,  M.,  Ueber  den  Kinfluss  des  Uodens  auf  die  Struktur  von  Xanthium 
spinosum  usw.  Ber.  d.  Deutsoli.  Bot.  Ges.  1905,  Vol.  XXII,  Part  10. 

^  Duval-Jouve,  Anordnung  der  Gewebe  im  Blattc  der  Griiser.  Bot.  Jahresb.  v. 
Just  1875,  p.  432. 

•'■>  Volkens,  Beziehungen  zwischen  Standort  und  anatomlschem  Bau  der  Vegeta- 
tionsorgane.  .Tahrb.  d.  Kgl.  Bot.  Gartens  zu  Berlin.  Vol.  Ill,  1S84,  p.  46;  cit.  Bot. 
Centralbl.  1884,  No.  46. 


177 

From  the  beginning  one  must  note  that  every  limited  supply  of  nutri- 
ment which  leads  to  nanism  must  express  itself  mostly  in  the  amount  of 
additional  growth,  i.  e.,  in  the  formation  of  the  secondary  tissues.  An  ana- 
tomical proof  of  this  has  been  furnished  by  Gauchery",  who  cites  cases 
when  the  cambium  has  formed  anew  only  a  few  rows  of  cells.  Often  he 
could  no  longer  determine  any  meristematic  zone  whatever  between  phloem 
and  xylem ;  therefore,  the  original  cambium  must  have  passed  over  at  once 
into  permanent  tissue  as  the  result  of  deficient  nutrition. 

In  the  plants  which  are  forced  to  grow  in  sandy  or  stony  soil,  often 
with  a  lack  of  water,  a  form  of  hyperplasia^  (arrested  developments) 
appears.  It  is  not  so  much  the  number  of  the  cell  elements  which  seems 
to  be  decreased,  as  their  size.  Thus  specimens  are  formed  which  we  would 
like  to  call  "stunted  plants."  By  this  is  understood  woody  plants,  the  growth 
of  which  is  not  retarded  to  dwarfing  but  which,  by  the  striking  shortening 
of  their  axial  organs,  show  a  repressed,  knarly  habit  of  growth. 

In  this  habit  of  growth  the  very  evident,  increased  spiral  twisting  of  the 
woody  elements  of  the  trunk  counts  as  a  typical  characteristic.  The  finest 
examples  are  seen  in  Syringa  and  Crataegus.  We  can  explain  the  production 
of  the  increased  spiral  twisting  if  we  think  of  the  direction  of  the  woody 
cells  as  the  diagonal  of  the  parallelogram  of  two  forces. 

At  the  apex  of  each  elongating  axis  there  is,  on  the  one  hand,  an  effec- 
tive striving  toward  growth  in  length  in  which  the  elongation  of  the  pith 
body  becomes  a  decisive  factor  of  swelling;  on  the  other  hand,  the  general 
enlargement  of  the  young  cells  acts  also  as  the  cause  of  the  radial  enlarge- 
ment of  the  trunk.  In  considering  a  very  young  wood  cell  in  the  cambial 
layer,  stretching  longitudinally,  w^e  see  that,  as  the  growth  in  length  predomi- 
nates over  the  growth  in  thickness,  it  is  relatively  difficult  to  divert  the  cell 
from  its  longitudinal  growth.  However,  as  the  abundantly  formed  young 
wood  cells,  during  elongation,  are  pressed  outward  by  the  growth  in  thick- 
ness of  the  medullary  cylinder  in  the  direction  of  the  radius  of  the  trunk, 
proportionately  just  so  much  the  sharper  will  be  their  spiral  twisting.  On 
this  account  we  find  long  slender  shoots  with  a  slight  spiral  twisting  in 
plants  on  moist  nutrient  soil,  and  on  sandy  soils  poor  in  water,  or  with  other 
checks  to  growth  in  length,  plants  having  short  axes  with  strong  twistings. 

Confirmation  of  the  hypothesis  is  found  in  the  "enforced  twisting"  to 
be  mentioned  later.  The  more  the  stems  are  distended  like  barrels,  the 
sharper  is  the  spiral  twisting  of  the  cords  of  the  leaf  spur. 

We  mention  this  point  because  the  occurrence  of  such  strongly  twisted 
stunted  plants  is  valuable  as  a  symptom  in  judging  the  soil  conditions. 

Pilosis. 

Plants  grown  on  dry  soil  soon  have  a  hairy  appearance,  even  if  no  more 
hairs  are  formed  than  on  specimens  of  the  same  variety  growing  in  damp 

6  Gauchery,  Recherches  sur  le  nanisme  veg-etal.  Ann.  sc.  nat.  Bot.  1899.  VIII. 
ser.,  t.  IX. 

1  Kuster,  E.,  Pathologische  Pflanzenanatomie,  .lena  1903,  p.  21.  Here  abundant 
bibliographical  citations. 


places.  If  a  definite  number  of  hairs  are  formed  on  a  leaf,  these  are  closer 
together  in  a  given  small  area,  because  the  epidermal  cells  separating  them 
are  shorter.  This  partially  explains  why  alpine  plants  appear  to  be  less 
pubescent  when  grown  on  plains.  These  plants  grow  more  luxuriantly,  the 
dimensions  of  their  organs  become  larger  and  the  hairs  are  separated  further 
from  one  another.  But.  in  fact,  even  in  dry  localities,  an  increased  hair  for- 
mation takes  place.  Thus  Moquin-Tandon'  cites  observations  by  Linneus. 
that  the  Lady's  Thumb  (Polygonum  Persicaria  L.)  seems  very  smooth  at 
the  cc\gG  of  bodies  of  water,  but  beset  with  hairs  in  dr>'  places.  Our  field 
thyme  (Thymus  Serpyllum  L.y  loses  its  glaucous  surface  at  the  sea  shore 
and  acquires  a  short,  \\2i\vy  covering.  Our  Turk's  cap  lily  (Lilium  Marta- 
(/on  L.)  when  cultivated  for  some  time  in  gardens  is  glaucous,  but  becomes 
pubescent  again,  like  the  wild  plant,  when  grown  on  poorer  soil,  etc.  Such 
phenomena  may  be  observed  also  in  garden  i)lants  which,  self-sown,  grow 
on  sandy  places  in  the  fields. 

An  unusual  hair  growth  takes  place,  further,  in  many  parts  of  plants 
when  they  no  longer  develop  normally.  According  to  Moquin-Tandon.  the 
stamens  of  the  triandrous  bindweed  are  covered  with  thick  wooly  hairs. 
The  stamens  of  several  kinds  of  Mullen  (X'erhascum  )  heha\e  similarly  if 
the  anthers  become  deformed.  The  peduncles  of  tlu-  smoke  tree  ( k'lnts 
Cotinus)  are  almost  without  hairs  before  blossoming  and  it  they  bear  seed. 
If,  on  the  other  hand,  the  fruit  does  not  mature,  the  stems  of  the  sterile 
blossoms  grow  longer  and  numerous,  long,  \  iolet  colored  hairs  appear  on 
them.  The  last-mentioned  formation  of  hair  does  not  belong  among  the 
phenomena  connected  with  drought,  but  should  be  considered  as  a  process 
of  correlation.  The  water  and  nutritive  substances,  which  should  be  utilized 
in  the  maturing  of  the  anthers  or  seeds,  are  used  in  a  greater  measure  for 
the  benefit  of  other  parts  of  organs,  when  the  sexual  organs  are  destroyed. 
Possibly  the  phenomena  recently  observed  in  parthenogenesis  belong  in  part 
here,  where  the  micropyle  is  stopped  up  as  the  result  of  the  hair-like  elon- 
gated cells  of  the  style  tissue  or  of  the  integuments'-. 

Als(\  we  find  in  the  root  system  that  pubescence  varies  according  to 
the  place  where  the  root  is  kei)t.  In  the  same  varieties,  the  whole  system 
can  develop  into  the  form  of  long,  slender,  whip-like,  scantily  branched, 
bare,  or  almost  bare  roots,  if  the  root  axis  dips  into  water  or  into  porous 
sand  saturated  with  water.  The  root  branches  become  shorter,  more 
knarled,  branched  and  pubescent,  the  drier  the  soil  is  in  general ; — the  more, 
therefore,  that  the  root  is  obliged  to  depend  only  on  the  moist  air  of  the  soil 
interstices.  In  air  which  is  absolutely  dry,  the  roots  (according  to  Per- 
secke'*),  do  not  develop  any  more  hairs.  If  the  roots  are  exposed  to  moist 
air,  the  young  tips,  just  behind  the  growing  apex,  become  very  hairy,  be- 
cause almost  every  epidermal  cell  has  pushed  f)ut  into  a  hair. 

1   Pflanzen-Teratologie,   translated  by   Schauer,   1842,  p.   61. 

-  Winkler,  H.,  LTeber  Parthenogenesis  bei  Wikstroemia.  I'.ei-.  d,  D.  Bot.  Ges., 
.Tahrpr.  1904,  Vol.  XXII,  p.  573. 

'•'•  Persecke,  Ueber  die  Formveranderuiig-  der  Wurzel  in  Krde  und  Wasser. 
Inauguraldissertation,  Leipzig  1877. 


1/9 

In  the  aerial  parts  of  plants,  which  are  accustomed  to  dry  air,  the  de- 
gree of  humidity  must  be  strikingly  low  if  the  formation  of  hair  is  to  be 
greatly  stimulated  as  C.  Kraus^  states  when  writing  of  potato  sprouts.  In 
very  moist  air  potato  sprouts  from  the  same  variety  are  hairless,  or  have 
only  a  few  shortish  hairs.  Therefore,  in  aerial  organs,  it  is  the  influence  of 
moist  air  in  contrast  to  dry  air  which  prevents  pubescence.  In  roots,  de- 
pending mostly  on  water,  the  same  effect  is  obtained  by  a  continued  supply 
of  water  just  as  the  influence  of  moist  air  favors  pubescence. 

An  extreme  formation  of  hair  on  aerial  and  subterranean  axes  is  there- 
fore the  result  of  causes  acting  in  the  same  way ;  the  usual  necessary  amount 
of  water  is  withheld  from  the  plants  at  the  stage  in  which  they  are  develop- 
ing. 

In  explaining  the  fact  that  greater  dryness  of  the  environment  favors 
the  formation  of  hairs,  Kraus  and  Mer-  have  cited  the  phenomenon  that  the 
organ's  growth  in  length  is  modified  or  arrested  with  the  formation  of 
hairs.  Both  investigators  are  of  the  opinion  that  the  material  saved  by  the 
arrested  elongation  of  the  cells  of  the  axis,  is  utilized  for  the  formation  of 
hairs.  Besides  the  examples  of  Rhus,  etc..  cited  above,  Heckel's^  observa- 
tions support  the  theory  that  a  scanty  formation  of  other  organs  goes  hand 
in  hand  with  a  \  ery  abundant  development  of  hairs.  Heckel  found  speci- 
mens of  Liliuui  Martaijon  L.  and  Genista  aspalathoides  Lam.  with  an  un- 
usual hair  covering  together  with  a  reduction  of  the  blossoming  parts. 
Kraus  emphasizes  the  fact  that,  with  the  decrease  of  growth  in  length,  an 
increase  in  turgor  takes  place  transversely  in  the  whole  organ  (as  we  have 
assumed  in  the  development  of  the  pith  of  stunted  plants)  whicli  extends  to 
the  epidermal  cells  and  excites  these  to  the  pushing  out  of  hairs.  Vesque^ 
like  Mer  and  Kraus,  states  that  increased  transpiration  favors  hair  for- 
mation. 

Attacks  of  parasitic  animals  often  excite  the  epidermal  cells  to  an 
enormous,  fine  growth  of  hair,  for  example,  such  as  mites  which  injure  the 
young  leaves  with  their  mandibles  and  thus  produce  the  so-called  felty  dis- 
ease. These  hair  formations  are  described  under  galls.  In  the  older  my- 
cology, such  hair  felts,  produced  by  the  sucking  stimulus  of  mites,  are  de- 
scribed as   fungi   (Erineum  Pers.  Taphrina  Fr.,  Phyllerium  Fr.). 

LiGNIFICATION  OF  RoOTS. 

The  lignification  of  tuberous  roots  is  due  to  the  return  to  the  original 
prosenchymatous  woody  condition  of  cells  in  the  vascular  bundles  which, 
under  cultivation,  have  become  parenchymatous.  The  carrot,  for  example, 
which  serves  us  as  food,  descends  from  a  plant  whose  root  consists  of  a 


1  Kraus,  Beobachtungen  iiber  Haarbildungen,  zuniichst  an  Kartoffelkeimen. 
Flora  1876,  p.  153. 

-  Mer,  Recherches  experimentales  sur  les  conditions  de  developpement  des  poil.s 
radicaux.  Compt.  rend.  LXXXVIII   (1879),  p.  665. 

"■  Heckel,  Du  pilosisme  deformant  drms  quelques  vegetaux.  Compt.  rend.  t.  XCI, 
1880.   p.  348. 

■*  Sur  les  cause.s  et  sur  les  limites  des  variations  de  structure  des  vegetaux. 
Cit.  Bot.  Centralljl.  1884,  No.  22,  p.  259. 


i8o 

strong,  hard,  wood  body  with  a  thin,  tender  bark.  The  cells  of  the  wood 
tissue,  like  all  the  other  wood  cells,  are  thick-walled,  spindle-shaped  and 
wedged  between  one  another.  In  the  cultivated  root,  instead  of  these  wood 
cells,  thin-walled,  short  cells  are  present,  ending  almost  bluntly  against  one 
another  and  even  the  ducts  which  lie  in  scattered  groups  between  the  par- 
enchymatous cells  are  but  little  lignified.  The  latex  tubes  already  formed  in 
the  bark,  when  spiral  porous  ducts  are  produced  in  the  wood  body,  have 
broadened  like  all  the  cells  of  the  bark.  Instead  of  the  starch  which,  in  the 
wild  carrot,  fills  out  the  whole  bark  tissue,  occurring  here  and  there  in  the 
wood  body  also  and  increasing  to  70  per  cent,  of  the  dry  weight,  sugar  has 
been  formed  usually  in  good  table  carrots  so  that  only  traces  of  starch  may 
be  found.  The  better  the  variety,  the  less  the  starch  content  as  in  the 
Dutch  pale  yellow  and  the  Duwicker  carrot.  Gradual  transitions  are  found 
back  toward  the  wild  plant  in  other  cultural  varieties  used  as  fodder,  such 
as  the  Altringham  carrot  and  the  white  horse  carrot.  Specimens  of  all 
varieties  found  on  poor  soil  go  to  seed  as  a  rule  in  the  autumn  and  are  dis- 
tinguished by  a  thin,  often  divided,  root  which,  because  of  its  lignification, 
recalls  clearly  the  ancestral  wild  carrot.  The  same  behavior  is  character- 
istic of  the  turnip-rooted  cabbage,  Swedish  turnip,  radishes,  Kohlrabi,  etc. 

These  differences  are  best  made  clear  by  comparing  the  anatomical 
structures.  In  Fig.  21  is  shown  a  longitudinal  section  through  a  two-year 
old  wild  carrot.  In  this  figure  a  is  the  vertically  elongated  parenchyma  of  the 
pith-like  central  part  with  scattered  spiral,  porous  ducts ;  b  the  xylem,  made 
up  of  spindle-like  wood  cells  together  with  ducts  and  the  part  of  the  medul- 
lary ray  which  extends  toward  the  secondary  cortex ;  c  the  cambium  which 
has  become  an  elongated,  thin-walled  parenchyma ;  d  the  secondary  cortex 
with  its  resorption  spots  which  follow  the  course  of  the  latex  ducts;  e  the 
primary  cortex ;  /  cork. 

Fig.  22  is  a  corresponding  section  from  a  two-year  old  cultivated  carrot. 
The  letters  in  both  figures  indicate  the  same  parts  and  a  comparison  of  the 
similarly  designated  tissues  makes  very  clear  the  change  in  the  wood  tissue 
and  the  increase  in  the  dimensions  of  the  secondary  cortex  in  the  cultivated 
carrot. 

In  all  tuberous  vegetables  lignification  also  occurs  normally  when  they 
grow  too  old  and  then  this  process,  as  in  individuals  lignifying  prematurely, 
is  accompanied  by  a  partial  disappearance  of  the  sugar. 

It  is  well-known,  from  experience,  that  many  of  our  vegetable  plants 
lignify  in  hot  climates.  Precautions  against  this  latter  condition  will  be  hard 
to  find  since  the  tropical  warmth  and  excess  of  light  favor  rapid  lignification. 
In  cultivation  in  temperate  climates,  lignification  can  certainly  be  avoided  by 
abundant  watering  and  fertilizing; — only  care  should  be  taken  in  this  that 
the  land  is  deep  and  the  seed  good.  Special  attention  should  be  given  to 
the  choice  of  seed,  because  seeds  from  dry  localities  carry  with  them  a  great- 
er tendency  to  lignification  and  to  a  repeated  division  of  the  root. 


iSi 
Ball  Dryness  of  the  Ericaceae. 

The  peculiar  sensitiveness  of  the  roots  to  drought  must  be  taken  into 
consideration  when  growing  the  numerous  species  and  varieties  of  the 
Ericaceae  as  Erica,  Azalea,  Rhododendron,  etc.    These  plants  cannot  endure 


a  complete  drying  out  of  the  roots.  While  other  plants  can  survive  lack  of 
moisture,  even  repeated  wilting,  without  showing  any  noticeable  injury,  and 
even  continue  growth  after  being  again  supplied  with  water,  the  fine  root 
branches  of  the  Ericaceae  do  not  seem  able  to  resume  their  functioning 
when  once  entirely  diy.     In  one  case  I  investigated  the  roots  of  an  Erica 


lM2 

iinicUls  which,  at'lcr  tlu'v  ha'l  dried  out,  had  hccn  subse(iiiently  soaked  24 
hours  in  water,  and  found  that  the  tine  root  ends  were  still  shrivelled 
despite  the  soaking.  The  character  of  most  Ericaceae,  as  moor  and  heath 
plants,  is  shown  by  the  fact  that  (with  the  exception  of  a  few  varieties) 
they  thrive  best  in  a  freely  watered,  easily  drained,  aerated  soil.  In  growing 
plants  in  small  pots  the  need  of  roots  for  air  must  be  given  the  greatest 
possible  consideration.  The  Ericas  soon  become  root  bound.  The  plants 
easily  become  sour  in  large  pots.  The  Erica  and  Azalea  drop  their  leaves 
when  dried  out.  It  is  wrong,  however,  to  try  to  repair  the  previous  mis- 
take by  setting  the  pot  in  water  and.  after  soaking  up  the  earth,  to  place 
the  plants  in  closed  cases  in  order  to  reduce  evaporation  as  far  as  possible 
and  to  cause  turgidity.  The  plants  should  be  left,  on  the  contrary,  in  their 
customary  place,  but  strongly  shaded  during  the  middle  of  the  day. 

AIkans  of  Ovi:kcomixg  Lack  of  Moisture  in  thf.  .^oii.. 

If  a  lack  of  soil  moisture  is  manifested  by  the  failure  of  vegetation  or 
by  its  degeneration,  as  usually  occurs  more  frequently  in  sandy  soils,  one 
naturally  seeks  relief  in  irrigation  when  possible.  This  artificial  supply  of 
water  not  only  refreshes  the  tissues,  but  also,  by  dissolving  the  nutritive 
substances  in  the  soil,  it  is  possible  for  the  plant  to  utilize  and  distribute 
these. 

Irrigatiox. 

W  ith  the  fre(|uent  lowering  of  the  ground  water  le\el,  irrigation  be- 
comes a  vital  question  and  an  acquaintance  with  the  results  of  Konig's' 
investigations  on  the  effects  of  irrigation  water  is  interesting.  One  learns 
accordingly  that  when  a  meadow  is  being  irrigated  the  water  loses  much  of 
its  nutritive  material  and  appreciably  more  during  the  warmer  seasons,  than 
in  the  colder  ones.  This  loss,  however,  is  not  true  of  all  nutritive  substances. 
If  the  carbon  dioxid  content  of  the  irrigation  water  rises,  the  calcium  and 
magnesium  nearly  always  increase  instead  of  decreasing.  As  in  the  case 
of  carbon  dioxid,  this  quantity  seems  to  rise  and  to  fall  with  the  intensity 
of  the  oxidation  in  the  soil.  In  contrast  to  the  above-named  nutritive  sub- 
stances, potassium  appears  to  be  absorbed  at  any  time  by  the  soil  since,  with 
irrigation,  even  in  the  winter,  a  slight  reduction  of  this  important  mineral 
can  be  proved  in  the  water.  Sodium,  or  rather  sodium  chlorid,  just  like 
nitric  and  sulfuric  acids  almost  always  showed  a  slight  increase  during 
winter  irrigation,  while  during  the  growing  season  they  decrease,  i.  e.,  they 
are  taken  up  directly  by  the  plants. 

Konig  concludes  that  the  oxygen  of  the  water  acts  as  a  purifier  of  the 
soil  by  oxidizing  the  organic  soil  contents.  This  oxygen  content  varies 
according  to  the  kind  of  w^ater  used  in  irrigation  and  the  season.  Konig 
found  it  greate;st  in  spring,  smallest  in  summer,  increasing  again  in  the 
autumn.  Spring  w-ater  is  much  richer  in  oxygen  than  river  water  w'hich 
has  passed  through  inhabited  places.    The  opposite  is  true  of  the  suspended 


1   Journal  fiir  Landwirtsehaft.     .TahrR.  ISSO.     A'ol.  28.     Part 


i83 

organic  substances  which  are  taken  up  from  the  soil  by  impoverished 
spring  water,  which  has  a  small  oxygen  content,  but  are  deposited,  on  the 
other  hand,  by  the  richly  saturated  river  water. 

At  a  depth  of  40  cm.  during  the  colder  seasons  temperature  observations 
show  that  irrigated  land  is  warmer  by  varying  amounts,  even  up  to  2.8°C. 
To  this  increase  in  temperature  may  be  ascribed  the  fact  that  in  irrigated 
meadows,  growth  begins  earlier  in  the  spring  and  continues  later  in  the 
autumn. 

Konig  showed  by  an  experiment  in  which  he  artificiallv  mixed  sewage 
with  the  irrigation  water,  how  quickly  the  subsoil  shows  its  absorption 
qualities,  if  the  soil  is  not  saturated  and  the  irrigation  water  is  heavily 
charged  with  fertilizing  matter.  x\fter  the  water  had  been  used  once,  it 
could  be  proved  that  the  soil  had  taken  up  84.5  per  cent,  of  the  organic 
substances;  74.2  per  cent,  of  the  ammonia;  81.6  per  cent,  of  the  potassium 
and  86.8  per  cent,  of  the  phosphoric  acid.  After  the  same  water  had  been 
used  twice  again  the  presence  of  these  substances  in  it  could  not  be  proved 
at  all.  Of  course  these  figures  hold  good  only  for  this  experiment  and  vary 
according  to  the  saturation  of  the  soil  and  water;  they  have  therefore,  for 
example,  no  value  in  irrigation  with  liquid  manure,  in  which  the  soils  must 
become  surcharged  with  nutritive  substances  in  a  comparatively  short  time. 
Nevertheless,  experiments  show  what  varied  advantages  can  be  obtained 
•with  the  right  use  of  irrigation.  The  importance  of  watering  the  soil  arti- 
ficially is  becoming  more  and  more  acknowledged.  The  best  proof  is  found 
in  the  transactions  of  the  land  cultivation  division  of  the  German  Agricul- 
tural Society'  in  which  questions  referring  to  the  direct  supplying  of  water, 
raising  of  the  ground  water  lez'el,  have  already  been  brought  up.  The  sys- 
tems known  at  present  have  been  partially  explained  by  means  of  illustra- 
tions. The  transactions  have  led  to  a  direct  commission  from  the  Directors 
of  the  society,  "that  they  should  take  up  the  question  of  the  watering  of 
land  with  the  greatest  possible  energy." 

Cultivation  of  the  Soil. 

At  present,  in  large  plots  of  land,  it  is  possible  only  in  the  rarest  cases 
to  provide  for  irrigation  without  considerable  expense  and  therefore  cheaper, 
if  less  effective,  means  are  more  often  utilized.  Such  resources  are  found 
in  working  the  soil.  The  breaking  up  of  the  soil  is  most  advisable.  Some 
practical  workers  maintain  that  cultivating  the  field  soil  cannot  possibly  aid 
in  the  retention  of  soil  moisture,  but  that  this  manipulation  must  rather  be 
considered  as  the  quicket  way  to  remove  more  water  from  the  soil.  This 
point  of  view  is  erroneous,  as  is  shown  by  many  experiments.  The  most 
thorough  are  Wollny's",  who  has  worked  with  control  experiments  and  has 
found  that  if  the  uppermost  layers  of  the  soil  are  broken  up,  they  dry  more 


1  Die  Moglichkeit  der  Ackerbewasserung  in  Deutschland.     Arbeiten   d.  Deutsch. 
Liandwirtsch.-Ges.,  Part  97,  1904,  p.  75. 

2  WoUny,  Einfluss  der  Bearbeitung  und   Diingung   auf  die  Wasserverdunstung 
aus  dem  Boden.     Oesterr.  landw.  Woclienbl.  1880,  p.  151. 


i84 

quickly,  to  be  sure,  but,  by  this  means,  save  to  a  greater  extent  the  water 
supply  in  the  lower  layers  of  the  soil. 

The  warming  of  field  soil  by  insolation,  its  aeration  when  winds  blow 
over  its  surface  and  all  such  influences,  remove  the  water  from  the  upper 
layers  of  the  soil  to  a  greater  extent  than  can  be  restored  by  capillary  at- 
traction for  water  from  the  lower  layers.  If  now,  by  breaking  up  the  sur- 
face, the  interstices  between  its  particles  become  considerably  enlarged,  the 
capillarity  is  decreased  and  the  water  no  longer  rises  into  the  larger  in- 
terstices of  the  now  crumbly  soil.  The  more  c]uickly  the  soil  is  broken  into 
coarsely  friable  pieces  by  chopping,  hoeing  and  removing  the  turf,  the  more 
the  dr}'ing  out  of  the  lower  layers,  where  the  roots  are  found,  is  delayed. 

The  opposite  result  is  obtained  by  rolling  the  field  land.  In  this  case^ 
most  of  the  spaces,  where  capillarity  did  not  act,  are  rolled  close  together. 
Capillarity  at  once  becomes  active  and  the  upper  surface  remains  moist  for 
a  longer  time.  Under  certain  circumstances,  however,  rolling  may  also  be 
recommended  as  a  means  of  retaining  moisture  in  the  soil.  This  w-ill  be 
expressly  suitable  for  all  very  porous  soils  with  a  scanty  water  capacity  and 
an  abundant  subsoil  moisture,  since,  by  hardening  the  surface,  its  evaporation 
is  reduced,  while  the  conducting  of  water  from  below  is  increased.  In 
heavy  soils,  with  a  high  saturation  capacity,  rolling  would  naturally  be  di- 
rectly injurious. 

Mulching  of  the  Soil. 

Instead  of  breaking  up  the  soil,  its  surface  may  be  covered  with  a  more 
porous  material.  In  this  connection  advantageous  results  can  be  obtained 
even  by  covering  the  surface  with  sand.  This  changes  favorably  the  con- 
ditions of  moisture  and  of  warmth  at  the  same  time,  for,  according  to 
W'ollny's  investigations",  the  temperature  of  the  soil  is  considerably  re- 
duced by  breaking  it  up,  since  the  conducting  of  heat  in  the  friable  layer  is 
decreased  by  the  considerable  amounts  of  enclosed  air.  In  the  same  way 
soil  provided  with  a  sandy  covering  is  colder  in  the  warm  seasons  than  un- 
covered soil,  because  the  light  color  of  the  surface  decreases  the  absorption 
of  the  heat  rays,  and  the  considerable  amount  of  water  held  back  under  the 
sand  is  warmed  with  greater  difficulty.  If  the  upper  surface  of  the  soil 
itself  dries  up,  its  temperature  must  increase  because  the  evaporation  which 
uses  up  heat  is  at  once  prevented. 

Breaking  up  the  soil  and  covering  it,  therefore,  modify  the  extremes  of 
temperature,  but  are  also  valuable  in  still  another  way.  According  to 
WoUny  (loc.  cit.  p.  337),  it  is  shown  that  during  the  warm  seasons  con- 
siderably more  water  from  the  same  amount  of  precipitation  can  filter 
through  the  soil  when  covered  with  sand  than  through  uncovered  soil.  This 
takes  place  because  the  soil  covered  with  a  layer  of  sand   (even  if  only  one 


1  Wollny  in  Ocsterr.  landw.  WochenbL  1880.  p.  214.-  Nessler,  Bad.  Landw.  Corres- 
pondenzblatt  1860,  p.  230.-  Wagner,  P.,  Versuche  iiber  das  Au.strocknen  des  Bodens 
bei  verschiedenen  DichtiKkeitsverhaltnissen  der  Ackerkrume.  Bericht  der  Ver- 
suchsstation  Darmstadt  1874,  pp.  87  ff.-  v.  Klenze,  Landw.  Jahrb.  1877. 

2  Einfluss  der  Abtrocknung-  des  Bodens  auf  dessen  Temperatur-und  Feuch- 
tigkeitsverhaltnisse.     Forschungen  a.  d.  Geb.  d.  Agrikulturphysik,  1880,  p.  343. 


1% 

centimetre  thick)  remains  richer  in  water,  i.  e.  becomes  saturated  more 
quickly  and  therefore  lets  more  water  flow  into  the  deeper  layers  of  the  sub- 
soil. The  same  result  is  shown  by  covering  with  ochre,  such  materials 
as  stable  manure,  straw,  tan  bark,  and  even  with  stones.  Soil  covered  with 
growing  plants  is  even  less  per\'ious  than  the  naked  earth. 

Some  practical  workers  recommend  the  use  of  peaty  earth  on  sandy 
soils.  Thus  Walz^  made  use  of  the  upper  layers  of  a  peaty  deposit  which 
were  6  to  8  cm.  deep  and  useless  for  fuel,  in  order  to  cover  a  field  of  poor 
sandy  soil  2  cm.  deep,  in  February.  Later  this  surface  which  had  been 
covered  with  peat  and  one  adjoining  it,  but  not  so  covered,  were  richly 
fertihzed  with  stable  manure.  In  the  heat  and  drought  of  summer, 
maize  planted  on  the  field  mulched  with  peat  showed  a  better  growth  and 
furnished  a  higher  percentage  of  yield.  In  the  same  way,  later  crops  were 
found  to  be  more  luxuriant  on  the  plat  of  ground  mulched  with  peat. 

The  value  of  the  peat,  which  Nerlinger-  has  demonstrated  in  exact  har- 
vest results,  arises  from  its  ability  to  soak  up  and  retain  the  fertilizing 
substances  which  otherwise,  in  sandy  soil,  would  be  washed  away.  I  have 
determined  experimentally^  that  fertilizing  makes  it  possible  for  the  plants  to 
give  a  better  yield  with  less  water,  which  explains  the  more  favorable  be- 
havior in  time  of  drought. 

Soils  With  a  Plant  Cover. 

It  has  already  been  said  that  soils  with  a  cover  of  living  plants  allow 
the  least  water  to  drain  through.  This  is  explained  by  the  fact  that  plant 
roots  absorb  the  water.  Comparative  experiments'*  prove  that  the  water  in 
the  soil  is  more  quickly  exhausted  with  a  thick  stand  of  plants,  even  if  this 
exhaustion  does  not  increase  proportionately  to  the  density  of  the  plant 
growth. 

From  these  results,  the  difl^erence  between  a  bare,  broken  soil  and  one 
covered  with  a  dense  turf  during  hot,  continued  dry  weather,  can  be  ascer- 
tained. Therefore,  in  nurseries  on  porous  soil,  it  is  by  no  means  a  matter 
of  indifl:'erence  whether  it  is  often  hoed  or  whether  turf  and  weeds  are  al- 
lowed to  form  a  dense  covering.  It  is  not  a  theoretical  conclusion  but  an 
often  demonstrated  fact  that  occasionally  premature  ripening  and  sterility 
are  produced  in  fruit  trees,  because  the  weeds  and  turf  have  taken  up  the 
scanty  supply  of  water. 

In  forestry  and  trees  in  beds,  if  the  seedlings  do  not  make  a  dense 
growth,  their  development  is  threatened.  Gravelly  soils  without  sufficient 
humus  content  are  also  a  menace  for  older  plants  from  lo  to  15  years  of 
age,  especially  if  protection  is  not  given  on  any  side  by  larger  plantations. 

1  Zeitschrift    d.    Landw.    Yer.    in    Bavern    1S82;    cit.    in    Biedermann's    Centralbl. 
1883,  p.  136. 

2  Flihling-'s  landw.  Zeit.  1878,  Part  S. 

3  Sorauer,  Nachtrag-  zu  den  Studien  liber  Yerdunstung-.  Forsch.  auf  d.  Geb.  d. 
Agrikulturphysik,  Yol.  YI,  Parts   1  and  2. 

4  Wollny,  Der  Einfluss  der  Pflanzendecke  und  Beschattung  auf  die  physikalis- 
chen  Eig-enschaften  und  die  Fruchtbarkeit  des  Bodens.     Berlin,  Parey,  1877,  p.  128. 


1,% 

11h-  forester  considers  turfed  land  as  a  faxorin^  factor,  since  it  retains  the 
water  of  precipitation  and  by  the  quick  evaporation  withdraws  the  water  of 
the  subsoil.  Places  almost  circular  are  sometimes  found  in  forests  about  the 
base  of  the  trunks  where  no  second  growth  lives.  This  circumstance  is 
ascribed  to  the  reflection  of  the  sun's  rays  from  the  smooth  barked,  branch- 
less trunks  (beeches,  birches,  firs).  The  sun  rays  flashed  from  the  mirror- 
like bark  dry  the  soil  to  a  great  extent.  This  condition  can  be  overcome  by 
various  means,  among  which  growing  plants  by  natural  seeding  is  recom- 
mended, since  the  plants  so  produced  will  adapt  themselves  to  the  locality.  In 
places,  which  must  be  i)lante(l,  material  should  be  used  which  has  been 
transplanted  once  in  the  nursery  and,  after  the  plants  are  set  out,  the  soil 
should  be  shaded  most  carefully.  Besides  this,  all  conditions  should  be  con- 
sidered which  in  general  may  be  recommended  for  overcoming  the  lack 
of  moisture,  such  as  the  protection  of  seed  beds  by  walls,  fences,  rows  of 
trees,  or  by  closely  set  brush,  hilling  and  especially  breaking  up  the  soil,  or 
even  fertilizing,  since  this  means  a  saving  of  water.  Sprinkling  with  water 
is  advisable  only  in  the  most  extreme  cases  of  necessity.  In  brushing  the 
edges  of  the  beds  the  use  of  conifers,  especially  the  Weymouth  Pine,  is 
most  to  be  recommended,  for  spruce  brush  sheds  its  needles  too  c]uickly 
and  makes  a  warmer  cover.  Fir  may  easily  be  set  too  densely  and  the 
leaves  on  branches  of  deciduous  trees  wilt  too  cjuickly.  hence  they  do  not 
afford  shade  to  the  soil  which  dries  out  too  rapidly. 

W'ollny  has  shown  by  experiments  that  seed  and  turf  burn  out  if  sown 
too  tliick,  while  vegetation  on  the  same  plot  of  land  remains  uninjured 
if  the  growth  is  more  broken. 

He  found  that  when  the  seed  had  been  sown  with  a  drill  the  soil  be- 
tween the  rows  lost  less  water  than  that  in  the  rows  themselves  and  the 
further  the  plants  stood  from  one  another,  the  more  water  w'as  retained  in 
the  rows  as  well  as  between  them.  Therefore,  the  proper  adjustment  of  the 
quantity  of  seed  to  be  sown  on  soils  poor  in  water,  will  also  assist  in  correct- 
ing injury  due  to  drought\ 

Only  in  very  definite  cases  can  an  overplanted  soil  be  proved  more  ad- 
vantageous than  bare  soil.  By  an  open  growth  of  short-lived  plants  as  a 
cover  crop,  w^ater  can  be  retained  on  sandy  soils  for  later  seeds.  If  seeding 
of  the  quick  growing  plants  takes  place  in  the  autumn  or  early  spring,  the 
time  these  plants  most  need  water  will  come  during  the  autumnal  or  spring 
wet  season,  so  that  when  the  dry  season  comes,  they  are  ready  to  set  fruit 
and  require  relatively  little  water; — rather,  by  shading  the  soil  and  by  the 
forming  of  dew.  they  retain  for  the  more  superficial  layers  a  pretty  even 
moisture  in  which  seeds  sown  later,  and  also  delicate  seedlings,  can  be 
developed  which  otherwise  would  have  dried  u]i  on  bare  soil. 

Forest  Litter. 
It  should  not  be   forgotten  that  any  covering  of  the  soil  retards  the 
aeration  of  the  land  and  therefore,   for  the  maintenance   of   fertilitv,   the 


1   Oesterr.  landw.  Woehenblatt.    ISSO,  p.  233. 


i87 

supply  (it  carbon  dioxid  in  the  soil  must  he  (lepended  upon  to  disintegrate 
and  dissolve  the  fragments  of  rock  ;  hence  great  care  must  he  used  in  the 
choice  of  the  soil  covering.  How  much  the  mulching  disturbs  the  circu- 
lation of  the  air  is  shown  by  Amnion's  experiments\  A\'ith  40  mm.  of  water 
pressure  in  an  hour  there  passed  through  a  layer  of  earth  19.6  sq.  cm.  in 
cross-section  and  0.5  m.  deep,  the  following  amounts  of  air: — 

With  a  Grass  Co\'ering.     Straw  Covering.  Uncovered. 

1.60  1.  6.30  1.  7.32  1. 

In  better  aerated  soils  more  carbon  dioxid  will  also  be  produced  and 
this,  in  spite  of  its  increased  elimination  into  the  air,  will  make  itself  felt  in 
an  increased  amount  in  the  soil.  The  result  of  letting  the  soil  lie  fallow  con- 
sists directly  in  the  greater  production  of  carbon  dioxid  due  to  the  action  of 
micro-organisms  and  to  the  greater  decomposition  of  the  rock  debris. 

Another  disadvantage  of  mulching  is  the  lessened  availability  of  the 
precipitation  for  such  covered  soil.  The  amount  of  this  disadvantage  will 
vary  according  to  the  kind  of  covering.  It  will  increase  with  the  increased 
sponge-like  substance  of  the  covering.  Riegler's-  statement  may  serve  as 
an  example  of  this  diversity.  He  tested  various  forest  litter  and  peat  moss 
(Sphagnum)  as  to  permeability.  Of  the  500  g.  of  water,  sprinkled  daily  in 
a  fine  stream  on  the  air-dry  litter,  the  following  amounts  were  absorbed  or 
ran  throught : — 

Beech  Litter  Hemlock  Litter  Sphagnum  Turf 

Ran  through-absorbed.  Ran  throtigh-absorbed.  Ran  through-absorbed. 
1st  day..  .400.3  99.7  441.3  587  216.0  284.0  g. 

8th  day..  .487.6  12.4  499.6  0.4  493.5  6.5  g. 

This  sprinkling  corresponded  to  10  mm.  of  rain  and  accordingly  possi- 
bly 20  per  cent,  of  the  falling  water  was  retained  by  beech  litter,  12  per 
cent,  by  fir  and  57  per  cent,  by  moss.  The  mulch  was  8  cm.  deep  all  over. 
From  Riegler's  other  tables  it  is  found  that,  in  the  next  3  or  4  days,  still 
greater  amounts  were  absorbed  daily,  gradually  up  to  the  9th  day  the  litter 
became  so  saturated  with  moisture  that  almost  all  the  water  which  fell  upon 
it  ran  off.  Ten  mm.  of  rain  setting  in  after  hot,  continued  dry  weather,  wet 
the  earth  under  the  beech  mulch  only  to  a  depth  of  8  mm. ;  under  the  fir 
mulch,  8.8  mm. ;  and  under  the  moss,  4.3  mm.  Besides  this,  the  conditions 
vary  according  to  the  strength  with  which  the  water  falls  on  tlie  mulch.  If 
the  water,  finely  distributed,  was  sprayed  on  the  moss  cushion,  70  per  cent, 
of  the  given  moisture  was  soaked  up,  while  of  the  same  amount  of  water, 
supplied  in  the  form  of  a  fine  running  stream,  only  14  per  cent,  was  retained. 

Forests. 

The  proximity  of  larger  tracts  of  trees,  viz.,  forests,  must  be  considered 
as  a  means  of  saving  the  moisture  in  the  soil  of  culti\'ated  land.     According 


1  Biedermann's  Centralbl.  1S.S0.   p.  405. 

2  Forseh.  auf.  d.  Geb.  d.  ■Agrikultuii)liy.sik,   ISSO, 


to  Matthieu's^  observations,  extending  over  ii  years,  the  air  in  forests, 
1.5  m.  above  the  soil,  is  on  an  average  colder  than  above  bare  ground,  the 
difference  being  the  greatest  in  summer.  The  forests  exert  the  same  de- 
pressing influence  on  the  mean  air  temperature  as  they  do  on  the  temperature 
extremes,  which  are  less  in  forests.  When  the  temperature  differences 
amount  perhaps  to  only  o.5°C.,  they  are  perceptible  when  a  rain  cloud  passes 
over  the  region.  Air  will  become  saturated  above  the  forest  sooner  than 
above  uncovered  land.  Thereby  the  rain  will  begin  sooner  and  be  more 
abundant  than  on  the  land  which  is  not  forested.  In  fact  measurements  of 
Matthieu  and  Fautrat-  prove  greater  amounts  of  rain  above  forests.  Hygro- 
metric  determinations  have  shown  that  the  weight  of  water  vapor  in  one 
cubic  meter  of  air  above  a  spruce  forest  amounted,  on  an  average,  to  8.66  g., 
while  above  forests  of  deciduous  trees  it  amounted  to  8.46  g. ;  above  un- 
covered soil  at  the  same  height  (104  to  122  m.  high),  at  a  horizontal  distance 
of  100  m.  from  the  conifer  forest,  to  7.39  g. ;  at  the  same  horizontal  distance 
from  the  deciduous  trees,  to  8.04  g.  Thus  the  proximity  of  the  forest  in- 
fluences the  moisture  vertically  and  may  also  exert  the  same  influence 
horizontally. 

Fallow  Land. 

"Fallow  Land"  has  less  effect  on  the  retention  or  increase  of  the  water 
supply  in  the  soil  than  on  the  accumulation  of  nutritive  substances.  Accord- 
ing to  Wollny's^  statements,  the  peculiarities  of  fallow  land  may  be  sum- 
marized as  follows : — Soil  lying  fallow  is  warmer  in  summer  and  colder  in 
winter.  Fluctuations  of  temperature  are  greater  ever}'where  in  fallow  land 
than  in  soil  overgrown  with  plants.  During  the  time  of  growth  the  soil 
covered  by  plants  has  always  a  lesser  water  content  than  when  lying  fallow. 
This  greater  moisture  content  is  retained  in  bare  soil  even  when  worked 
more  frequently.  Bare  soil  also  gains  more  from  atmospheric  precipitation 
since,  during  the  time  of  growth,  considerably  larger  amounts  of  water  per- 
colate through  soil  lying  fallow,  than  in  fields  provided  with  a  growing 
plant  covering.  From  the  standpoint  of  nutrition  the  carbon  dioxid  con- 
tent of  fallow  land  is  most  noteworthy.  WoUny's  researches  show  that  the 
air  in  fallow  soil  contains  approximately  4  times  as  much  carbon  dioxid  as 
in  grass  land.  Therefore,  the  means  for  the  solution  of  mineral  elements  in  the 
soil  are  present  much  more  abundantly ;  which  explains  in  part  the  greater 
accumulation  of  nutritive  substances  in  fallow  land.  This  greater  enrich- 
ment also  depends  partially  on  the  quicker  decomposition  of  the  organic 
substances  because  of  the  greater  temperature  fluctuations,  the  increased 
moisture  and  the  more  vigorous  activity  of  the  micro-organisms.  It  should, 
however,  be  pointed  out  finally  that  soils  with  less  power  for  holding  water 
and  in  greater  depths    (sandy  soils)    with  their  greater  permeability  lose 


1  Matthieu,  Met^orologie  comparec  agricole  ct  forestigre.  Paris  1878;  cit.  in 
Forschungen  auf  d.  Gob.  d.  Agrikulturphysik  1879,  pp.  422-429. 

-  Fautrat.  Ueber  den  Einfluss  der  Walder,  den  sie  beriihrenden  Regenfall 
und  die  Anziehung  der  Wasserdampfe  durch  die  Fichten.  Aus  Compt.  rend.  1879, 
Vol.  89,  No.  24;   cit.  Biedermann's  Centralbl.  f.  Agrikulturchemie.    1880,  p.  241. 

3  WoUny,  Die  Wirkung-  der  Brache.    Allgem.  Hopfenzeitung  1879,  Nos.  55,  56. 


1 89 

considerable  part  of  the  plant  nutritive  substances  which  are  washed  away 
into  the  subsoil.  Such  soils  therefore,  conversely,  must  be  kept  under  a 
covering  of  plants. 

Local  conditions  must  show  which  one  of  these  means  can  best  be  used 
to  prevent  a  lack  of  moisture.  In  any  case  it  is  evident  that  we  do  not  stand 
powerless  in  the  face  of  drought. 

b.     Loamy  Soils. 
General  Characteristics. 

In  considering  physical  influences  injurious  to  vegetation,  we  need  not 
distinguish  between  loam  and  clay  soils.  We  are  concerned  always  with 
mixtures  of  clay  and  sand  and  only  the  proportions  of  these  two  elements 
differ.  The  sand  content  decreases  more  and  more  from  sandy  or  "mild" 
loam  to  strictly  loamy  soil  and  to  clay  soils,  which  are  plastic  in  a  damp  con- 
dition ;  in  them  predominate  the  fine  particles  so  easily  washed  away.  In 
our  agricultural  land,  mixtures  of  lime  and  humus  will  also  be  of  importance 
as  modifiers.  Lime  will  make  heavy  soils  more  open  by  increasing  their 
friability. 

Fertility  is  directly  dependent  upon  friability,  hence  plastic  clays  are 
sterile.  Non-friable  clay  soils  are  impervious  to  water,  and,  in  level  places, 
easily  give  rise  to  the  formation  of  swamps.  The  smaller  the  size  of  the 
soil  particles,  the  greater  will  be  their  water  absorptive  power  so  that  very 
significant  changes  in  volume  occur  with  extensive,  rapidly  successive  differ- 
ences in  the  supply  of  water.  Upon  this  depends  the  characteristic  cracking 
of  clayey  soils  when  drying  out.  Soluble  salts  can  be  washed  out  of  clay 
soils  only  with  difificulty. 

This  drying  out  is  much  more  dangerous  as  the  soil  approaches  pure 
cla}^  When  once  dr}^,  clay  takes  water  up  again  very  slowly  since  it 
can  penetrate  only  with  difficulty  between  the  closely  packed  soil  particles. 
These  peculiarities  decrease  proportionately  as  the  admixture  of  sand  in- 
creases. Drying  out  in  summer  becomes  at  times  more  dangerous  in  heavy 
soils  than  in  sandy,  especially  if  a  vigorous  growth  of  trees  has  developed 
in  regions  which  at  best  are  poor  in  precipitation.  The  summer  rains  do 
not  then  suffice  to  make  good  the  loss  of  water.  These  soils  are  dependent 
on  the  winter  moisture.  Hence  the  plant  growth  suffers  here  much  more  in 
dry  springs,  in  years  when  the  winter  moisture  has  been  less  and  the  snow 
covering  has  failed,  than  on  sand.  This  explains  the  fact  that,  after  hot, 
dry  summers  and  winters,  poor  in  precipitation,  a  blighting  of  the  fops  of 
old  trees  (i.  e.,  a  drying  of  the  branches)  sets  in  because  of  the  lack  of 
moisture,  even  if  the  spring  has  abundant  rain.  .Sandy  soils  with  moderate 
spring  rains  are  saturated  more  cjuickly  and  the  water  is  at  the  disposal  of 
the  roots. 

Heavy  soils  remain  "cold."  This  is  explained  by  their  high  water  con- 
tent which  increases  with  the  fine  granular  structure.  In  many  regions  im- 
ported conifers   (Abies  Finsapo,  Biota  orientalis  anrea,   Taxus  hibernica, 


190 

Picea  orientalisj  die  (|uickly.  This  is  ascribed  to  winter  fro^t  hut  u\Hm 
closer  observation  it  is  discoxered  that  low  temperatures  become  harmful 
onl\-  when  the  soil  is  very  wet'. 

A  dehciency  of  s(jil  aerati(;n  is  the  most  harmful  factf)r  since  upon  the 
aeration  depend  the  phenomena  of  decay  in  the  decomposition  of  organic 
masses.  Thus  in  judging  loamy  soils  as  to  their  fertility  not  only  the  de- 
gree of  friability,  but  also  the  depth  to  which  this  extends,  becomes  decisive. 
Since  the  firm  loam  layers  of  the  subsoil  are  aerated  only  with  difficulty, 
the  spreading  out  of  the  root  system  takes  place  only  in  the  friable  layers. 
Therefore  a  special  value  should  be  laid  on  the  maintenance  of  this  friabil- 
ity. This  must  be  taken  especially  into  consideration  in  forests,  where  the 
lifter  is  cDnstcintly  raked  away.  Ramann's  investigations-  sliow  that,  in  re- 
moving litter,  the  soil  becomes  densely  packed  and  works  harm  to  the 
forest  tract. 

The  packing  of  soil  and  the  necessity  for  loosening  it  should  especially 
be  considered  in  growing  all  tropical  plants,  as  Vosseler^  has  proved. 
He  describes  the  soils  characterized  by  Koerts  as  "older  red  loam."  and 
especially  the  primeval  forest  soil  of  East  Usambara  thus; — "The  red 
soil  consists  mainly  of  fine  loam  and  clay  which  is  pervious  but  too  finely 
porous  to  take  up  small  humus  particles ;  besides,  chemical  action 
takes  place  possibly  in  the  upper  surfaces  alone  and  thus  prevents 
their  penetration  into  the  lower  soil.  .Since  the  soil  itself  is  the  final  pro- 
duct of  decomposition,  it  lacks  the  ad\antage  of  processes  of  loosening  up 
which  i)ossibly  take  i)lace  during  such  action."  Mere  also,  therefore,  the 
loosening  of  the  soil  is  given  as  the  first  re(|uirement  for  successful  culti- 
\ation. 

The  more  cla}e\-  the  soil  is,  llie  more  slowly  the  \  egetable  refuse  will 
be  decomposed  because  of  the  lower  temperature.  While  in  sufficiently 
friable  soils,  a  normal  decomposition  takes  place,  masses  of  raiv  humus 
collect  on  thick  clay  soils,  i.  e.,  particles  of  plants,  which  are  only  slightly 
decomposable,  remain  deposited  on  the  soil  because  the  conditions  are  un- 
favorable for  decomposition.  If  very  fine  grained  soils  with  a  greater 
moisture  holdintj  capacity,  \.  e.,  ability  to  retain  large  amounts  of  water 
without  iii\ing  it  olT  in  the  form  of  (Irojjs.  accjuire  so  much  water  that  it 
oNcrcomes  the  continuit}-  of  the  substance  particles  by  penetrating  between 
them,  thus  forcing  them  apart,  the  soil  Ijecomes  softer.  This  condition  is 
especiall\-  peculiar  to  strong  clay  and  red  soil ;  such  a  disinteijration  occurs 
less   fre(|uentl\-  in  loam}-  soil. 

.Such  reduction  of  the  soil  is  doubly  dangerous,  if  it  takes  place  in  the 
autumn  or  s])ring.  On  the  one  hand,  the  soil  washes  away  at  once  and  the 
seeds  are  soon  exposed  to  drying  or  to  freezing  as  the  case  may  be.     On  the 


1  Cordcs,  VV.,  IlfitniH:  zuni  X't-ihalten  der  Conift're]!  f^egt-n  Witt I'luns.^^einflu.s.sc. 
H;im))ur,a:  U'97. 

-  Ramunn,  10.,  rntoisiicViiing'  .streiiberecliter  ISi'iden.  Sond.  Z.  f.  P'oist-  11.  .lagd- 
wesen,  XXX  .Jahrg-;   cit.  Hot.  .Jahresb.  1900,  II.  p.  4iri. 

•'  Vosseler,  Ueber  einige  Eisentumlichkeiten  der  I'rwaldl^i'idon  O.slusambaias. 
Mitteil.  a.  d.  Biol.  I-,andwirtsch.  Institut  Amani,  1904.     No.  33. 


other  hand,  this  condition  also  retards  working  the  soil  and  planting  the  fields, 
thus  becoming  a  cause  of  poor  harvests.  Especial  consideration  should  be 
given  to  the  fact  that,  for  all  our  cultivated  plants,  the  usual  planting  time 
has  been  determined  by  observing  the  behavior  of  the  plants  in  our  climate. 
It  can  be  shown  at  any  time  that  variation  in  the  periods  of  cultivation  pro- 
duces changes  in  the  character  of  the  plants  (the  change  from  winter  to 
summer  grain).  Such  a  delay  of  the  seeding  time  often  acts  injuriously, 
as,  for  example,  in  peas.  The  same  seed  that  furnishes  a  fine  crop  of  healthy 
plants,  when  sown  early  in  spring,  very  often  produces  low  plants  with 
small  pods,  greatly  injured  by  mildew,  if  sown  in  summer.  Kohlrabi,  planted 
too  late  in  spring,  easily  become  woody,  etc. 

Similar  phenomena  may  be  observed  in  fine  sandy  heath  soils  (loose 
loam).  Grabner^  characterizes  this  form  of  soil  as  consisting  of  sand  grains 
almost  as  fine  as  flour  with  only  small  clay  admixtures.  The  whole  mass 
when  wet  looks  like  loam.  In  a  dr}^  condition,  however,  it  may  be  dis- 
tinguished from  loam  proper  by  its  porosity.  Thus,  as  a  result  of  its  very 
fine  granular  structure,  it  can  become  as  hard  as  stone.  In  places  which 
are  cultivated  constantly  and  kept  loose  by  means  of  animal  manure,  such 
soil  is  often  valuable  but  in  forestry  it  is  not,  for,  after  the  usual  single 
loosening,  the  fine  sand  is  at  once  packed  together  by  rain  and  too  little 
oxygen  from  the  air  can  get  to  the  roots  of  the  trees. 

The  Covering  of  Soil  with  Silt. 

In  heavy  rain  storms  and  floods  soils  with  a  large  content  of  very  finely 
broken  particles  are  washed  together  and,  after  the  evaporation  of  the  water, 
are  left  in  the  form  of  a  thick,  close  crust.  The  moisture  holding  capacity 
of  a  soil  increases  with  the  fineness  of  its  pulverization,  as  has  been  men- 
tioned above.  Increased  pulverization  of  the  particles  deepens  the  upper 
surface  and  the  power  for  retaining  water  depends  on  surface  attraction. 
By  pulverizing  a  soil  mass,  consisting  of  coarse  pieces  of  quartz  from  i  to 
27  mm.  in  size,  which  had  an  absolute  saturation  capacity  of  7  per  cent.,  the 
capillary  absorptive  power  was  so  increased  that  a  fine  sand  produced  from 
the  quartz,  the  size  of  its  grains  being  0.3  mm.,  held  back  more  than  6  times 
as  much  water.  One  sees  that  under  certain  circumstances  the  kind  of 
mineral  may  be  unimportant  and  only  the  mechanical  constitution  of  value  ; 
that,  therefore,  even  quartz  dust  can  assume  the  role  of  clay.  Naturally 
this  dustlike  sand  has  no  coherance  whatever,  and  can  therefore  never  in 
itself  take  over  the  role  of  a  binding  substance  such  as  clay.  Principally, 
however,  it  is  clay  soils  which  sufifer  from  erosion  in  the  form  of  silt  and. 
by  making  air  tight  layers,  cause  the  decay  of  seeds  and  plant  roots.  At 
times  the  roots  form  accessory  organs  in  order  to  find  the  necessary  air  in 
marshy  soils.  In  this  connection,  attention  should  be  called  to  the  knee-like 
outgrowths  of  roots  which  struggle  to  the  upper  surface  of  the  soil,  as  those 


1  Grabner,  Handbuch  der  Heidekultui',  1904,  p.  200. 


192 

of  Taxodium  distichum  and  of  Finns  serotina  which  arc  not  formed  on  dry 
soils,  and  are  described  by  Wilson'  as  aerating  organs. 

An  example  of  the  injury  to  vegetation,  due  to  a  direct  deposition  of 
silt,  is  furnished  by  Robinet-  of  Toulouse,  where  the  nurseries  had  stood 
for  only  two  days  under  water.  At  the  base  of  some  plants  very  little  mud 
was  deposited.  These  remained  healthy.  But  when  the  mud  covered  the  base 
of  their  trunks,  possibly  10  to  12  cm.  deep,  the  damage  was  great.  Almond, 
acacia,  cherry  (even  the  mahaleb  cherry)  mountain  ash,  Tigustrum,  Ma- 
honia,  Evonymous  and  most  conifers  were  killed.  Individual  specimens  of 
Crataegus,  Pirus  Communis  (of  which  those  grafted  on  the  quince  suffer 
less)  Pirus  Mains,  Castanea,  Mespilus,  Catalpa,  etc.,  which  had  stood  8  to 
10  days  under  water,  blackened  at  the  base  and  died  when  the  silt  was  not 
removed.  Platanus.  Alnus,  Ulmus  did  not  suffer,  and  Populus,  as  well  as 
Salix  (weeping  willow) .  developed  many  roots  from  the  base  of  the  trunk  out 
into  the  silt.  All  the  specimens  of  Sophora,  Fraxinus,  Carpinus,  Fagus, 
Betula  and  Robinia  did  not  die ;  the  leaves  of  the  survivors,  however,  turned 
yelloiv.  The  linden  and  chestnut  lost  all  their  leaves.  Evergreen  plants, 
and  even  a  part  of  the  conifers,  lost  their  leaves  wh^n  they  had  been  covered 
by  water. 

Of  double  importance  is  this  change  in  the  physical  constitution  of  the 
soil  in  regions  exposed  to  frequent  inundations  and,  among  them,  the  soils 
suffer  most  which  are  flooded  by  sea  water.  Aside  from  the  injury  to  vege- 
tation from  the  large  salt  content  of  the  soil,  there  is  found,  according  to 
A.  Maycr\  as  a  resulting  phenomenon  of  a  dense  covering,  noticeable  at 
times  only  in  the  second  year,  a  formation  of  a  black  layer,  strongly  im- 
pregnated with  iron  sulfate,  which  may  further  injure  vegetation. 

Von  Gohren*  also  emphasizes  the  formation  of  such  kinds  of  ferrugi- 
nous layers  called  "Knick"  in  West  Friesland  in  very  humus,  loamy  and 
clayey  mud  deposits  of  sea  and  river  marshes  and  explains  their  production 
by  the  fact  that  the  ferric  oxid  in  the  loam  is  reduced  to  ferrous  oxid  by 
the  organic  substances  in  the  absence  of  air.  This  ferrous  oxid  combines 
with  the  crenate  acid  to  form  crenic  ferrous  oxid.  Crenic  ferrous  oxid, 
distributed  in  ever\'^  direction,  is  gradually  oxidized  again,  cements  together 
all  parts  of  the  soil  as  ferric  hydroxid  and  co-operates  in  the  formation  of 
meadow  ore  of  such  ill-repute.  We  will  finish  considering  the  formation  of 
meadow  ore  when  discussing  the  peculiarities  of  swamp  soil  and  now  turn 
first  to  the  phenomena  of  silt  covering  under  the  influence  of  salt  solutions 
found  in  the  use  of  fcriUizinij  salts. 

Mayer's  experiments  show  that  particles  of  clay  suspended  in  water 
are  precipitated  dift'erently  when  they  are  in  suspension  in  pure  water  or  in 
water   containing   sodium   chlorid   and   other  admixtures.     In   pure   water 


1  Wilson,  W.  P.  The  ])roductioii  of  aerating  organs  on  the  roots  of  swamp  and 
other  plants;  cit.  Bot.  Jahre.sber.  1889,  I,  p.  682. 

-  Revue  horticole;    cit.  Wiener  Obst-   u.     Gartenzeitung  1876,  p.   37. 

3  Mayer,  A.,  Ueber  die  Einwirkung  von  Salzlosungen  auf  die  Absetzungsver- 
haltnisse  toniger  Erden.     (Forsch.  auf  dem  Gebicte  d.  Agrik.-  Physik.  1879,  p.  251.) 

*  von  Gohren;    Boden   und  Atmosphiire.     Leipzig  1877,  p.   56. 


193  ■ 

the  particles  are  deposited  according  to  size  (more  exactly,  according  to  the 
proportion  of  their  surface  to  their  mass).  The  finest  particles  remain  un- 
commonly long"  in  suspension  since  they  are  held  by  the  attractive  power 
of  the  water,  which  is  almost  comparable  to  a  chemical  solution.  The  at- 
traction of  gravity  for  these  particles  is  powerless  in  opposition  to  this 
attraction.  After  the  clay,  which  has  been  dissolved  in  a  glass  cylinder  for 
the  experiment,  precipitates  from  a  salt  solution,  it  is  noticeable  that  a  layer 
consisting  of  close,  fine  clay  particles  has  formed  with  a  comparatively  very 
clear  fluid  above  it.  Because  of  the  presence  of  sodium  chlorid,  all  fine 
clay  particles  are  precipitated  more  as  a  whole  (coagulated,  according  to 
Schlosing).  "Flocculency"  is  thus  produced.  The  fall  of  the  somewhat 
coarser  particles  among  these  appears  to  have  been  held  back,  while  that  of 
finer  ones  has  been  somewhat  hastened.  It  has  been  assumed  that  probably  the 
presence  of  the  salt  has  decreased  the  attraction  between  clay  and  water, 
since  the  water  then  lets  the  clay  fall  more  completely.  On  the  other  hand 
the  attraction  of  clay  to  clay  must  have  been  increased,  and  it  is  therefore 
more  compact.  Durham-  explains  the  process  by  the  fact  that  every  bit  of 
the  attraction  of  the  water  otherwise  required  entirely  for  the  suspension  of 
the  clay  is  satisfied  by  the  salt  of  the  solution.  According  to  him,  sulfuric 
acid  acts  like  the  solution  of  sodium  chlorid,  and,  according  to  Mayer,  all 
mineral  acids  behave  in  the  same  way.  The  same  is  true  of  mineral  salts 
even  in  an  excess  of  fixed  alkali  or  ammonia. 

According  to  the  theories  now  prevailing,  electrolytes  act  flocculently. 
i.  e.  all  bodies  which  in  an  aqueous  solution  are  partially  split  up  into  "Ions." 
Non-electrolytes  have  no  action.  At  any  rate,  an  electric  current  precipi- 
tates the  flakes.  It  should  therefore  be  assumed  that  the  particles  distributed 
in  the  water  are  charged  with  electricity  and  the  cause  of  the  oscillation  may 
be  sought  in  this  electric  charge^. 

The  chief  point,  worth  considering  for  all  cultivated  clay  soils,  lies  in 
the  fact  that  the  nitrates,  so  far  as  deposition  of  the  clay  is  concerned,  ap- 
proximate the  chlorates  and,  on  account  of  the  ease  with  which  they  are 
washed  away,  rapidly  cause  the  packing  of  the  soil.  By  this  is  explained  the 
mechanical  destruction  of  soils  rich  in  clay,  when  repeatedly  fertilised  ex- 
clusively zvith  nitrates.  At  first  fine  crops  are  obtained  but  later  retrogres- 
sion takes  place.  Sodium  chloride  fertilising  used  for  certain  plants  has 
naturally  the  same  destructive  effect. 

Behrens*  calls  attention  to  the  real  disadvantage  of  an  excessive  use  of 
fertilizing  salts.  Their  osmotic  action  comes  especially  under  consideration. 
Because  of  this  osmotic  action  of  the  soluble  salts  in  the  soil,  it  is  more 
difficult  to  supply  the  water  needed  by  the  plant  and  the  plant  responds  by 
a  suitable  modification  of  its  organs.  In  correspondence  with  the  physiolog- 
ical lack  of  moisture,  the  plant  reduces  its  evaporation  by  forming  fleshier 

1  Biedermann's  Centralbl.   1883,  Nov.,  p.  7S6. 
-   Chem.  News:    cit.   "Naturforscher"   1878.   p.   112. 

3  Ramann,  E.,  Bodenkunde,  2nd.  Ed..  Berlin.  .1.   Springer,  1905.  p.  225. 
*  Behrens,   J.,  Ueber  Diing-ungsversuche.  .Jahresb.   d.  Vertreter  d.  angewandten 
Botanik,  II  Jahrg.  Berlin,  Gebr.  Borntrager,  1905,  p.  28. 


194 

leaves  with  smaller  intercellular  spaces ;  this  may  be  found  in  plants  near 
salt  springs  and  on  the  sea  shore. 

Among  our  cultivated  plants,  tobacco  suffers  most ;  it  reacts  exactly 
as  in  hot,  dry  summers  and  forms  fleshier  leaves  with  a  reduced  burning 
quality.  Hunger^  confers  these  observations,  made  in  Europe,  and  says 
of  the  cultivation  of  the  Dehli-tobacco  on  Sumatra,  that  the  leaf  most 
valued,  most  grown  and  most  carefully  selected,  is  large,  thin,  poor  in  oils, 
and  develops  only  in  the  presence  of  abundant  water  as  in  continued  rainy 
weather,  while  in  dr}^  weather  small,  thick,  less  valuable  leaves,  covered  with 
many  glandular  hairs,  are  formed. 

The  Improvement  of  Soils  Which  Are  Becoming  Compact. 

The  improvement  of  the  easily  packed  clay  soils  will  have  to  lie  in  the 
increase  of  their  ability  to  be  worked.  Heavy  soils  are  unyielding,  i.  e.,  they 
offer  great  difficulty  by  sticking  to  the  farm  implements,  when  damp,  and  by 
hardness,  when  dry.  Great  clods  are  produced  which  generally  do  not  fall 
apart  easily  if  the  clay  or  red  clay  soil  is  poor  in  humus.  It  is  well-known 
that  the  best  plan  for  working  soil  for  spring  planting  is  to  break  it  up  in 
the  fall  and  let  it  lie  in  rough  furrows.  The  freezing  of  tlie  water  in  the 
interstices  during  the  winter  months  reduces  the  tough  clods  to  a  mellow 
crumbling  mass. 

These  advantages  are  availalilc  only  tor  spring  i)lanting  and  disappear 
after  the  heavy  rain  storms  of  the  summer.  Therefore  care  must  be  taken  to 
prevent  caking  by  supplying  humus  or  marshy  earth ;  fertilizing  with  long 
strawy  manure  is  very  greatly  used.  However,  Uming  and  marling  the  soil 
have  given  very  efifective  results.  Practical  experience  has  shown  that  the 
addition  of  calcium,  which  is  in  solution  in  the  soil  as  the  bi-carlionate,  will 
hinder  its  caking. 

A  definite  amount  of  all  salts,  even  of  tlie  most  effective,  calcium  and 
magnesium,  must  be  kept  in  solution  in  excess  of  the  amount  necessary  to 
start  action  if  any  deposition  of  the  clay  particles  is  to  take  place.  Even  in 
rivers  the  flocculent  action  of  dissolved  salts  makes  itself  felt  since,  for 
example,  the  sediment  in  rivers  flowing  from  lime  regions  is  more  quickly 
deposited  than  in  those  from  regions  poor  in  lime-.  For  agriculture,  fria- 
bility becomes  directly  important  since  upon  this  depends  the  proper  state  of 
tillage.  The  small  bits  of  the  soil  behave  similarly  to  the  clay  flakes.  Hil- 
gard  proved  the  action  of  lime  by  tempering  solid  clay  soils  with  i  per  cent, 
quicklime.  While  the  original  clay  soil  became  as  hard  as  stone  after  drying, 
that  mixed  with  lime  was  found  to  be  crumbly  and  mellow.  Since,  besides 
a  continuous  mechanical  working  of  the  soil,  the  salts  also  condition  its 
looseness,  this  must  be  the  case,  to  an  equal  extent,  in  forest  soil  also.  If 
the  soluble  salts,  determining  the  friable  structure,  are  decreased,  as  by 
excessive  use  of  litter,  covering  with  raw  humus,  the  leaching  of  the  upper 
layers,  etc.,  a  packing  of  the  soil  must  take  place. 

1  Hungrer,  F.  W.  T.,  Untersuchungen  und  Betrachtungen  iiber  die  Mosaikkrank- 
heit  der  Tabakpflanze.     Zeitschr.  f.  Pflanzenkrankh,  1905,  Part  V. 
-   Ramann  loc.  cit.  p.  226. 


195 

A  top  dressing  of  waste  lime  from  sugar  factories  is  often  made  use  of 
in  the  cultivation  of  beets.  The  mechanical  efifect  makes  itself  felt  not  in- 
frequently by  the  fact  that,  as  a  result  of  increased  capacity  for  being  heated 
and  the  scanty  supply  of  water,  these  soils  later  cause  heart  rot  and  dry  rot. 

Hilgard's  statements^  on  the  "alkali  soils"  of  California  are  of  great 
interest.  The  alkali  places  often  found  between  excellent  cultural  lands  con- 
tain so  much  salt  that  they  become  noticeable  by  efflorescence  on  the  surface. 
Those  which  contain  alkaline  carbonates  (and  partially  also  borates)  are  dis- 
tinguished by  the  difficulty  or  almost  impossibility  of  producing  a  really 
friable  soil.  After  each  rain,  a  coffee  brown,  clay  water,  colored  by  dis- 
solved humus,  stands  at  times  for  weeks  on  those  places,  recognizable  be- 
cause of  their  lower  position.  The  same  working  of  the  soil  which  gives 
good  soil  the  consistency  of  loose  ashes  makes  the  alkaline  land  a  mass  of 
rounded  clods  varying  in  size  from  a  pea  to  that  of  a  billard  ball. 

After  evaporation,  heating  and  saturation  with  carbon  dioxid,  the 
blackish  brown  solution,  leached  from  alkaline  soil,  gives  0.251  per  cent,  in- 
combustible residue.  Of  this  0.158  per  cent,  was  redissolved  in  water  and 
this  soluble  part  consisted  of  52.74  per  cent,  sodium  carbonate,  33.08  per 
cent,  sodium  chlorid,  13.26  per  cent,  sodium  sulfate,  1.83  per  cent,  sodium 
triphosphate. 

The  0.093  per  cent,  insoluble  residue  from  the  heated  water  extract  con- 
tained 14.02  per  cent,  calcium  carbonate,  5.37  per  cent,  calcium  triphosphate, 
5.77  per  cent,  magnesium  triphosphate,  24.37  P^i*  cent,  silica  soluble  in 
NaoCO;;,  50.47  per  cent,  of  ferric  oxid,  aluminium  oxid  and  some  clay. 

In  this  case,  as  well  as  in  many  other  alkaline  soils  in  California,  the  ad- 
dition of  a  sufficient  amount  of  gypsum  (land  plaster)  produces  a  striking 
effect.  The  caustic  action  of  the  alkaline  carbonates  on  seeds  and  plants 
stopped  at  once  so  that  where  previously  only  "alkali  grass"  (Brizopyrum) 
and  Chenopodiaceae  grew,  maize  and  wheat  were  produced  without  difficulty. 
The  g}^psum  naturally  requires  a  longer  time  for  the  mechanical  change  of 
the  soil  surface  and  its  greater  loosening. 

Inundations. 

In  opposition  to  the  frequently  widespread  anxiety  when  volumes  of 
water  break  over  cultivated  land,  it  might  be  emphasized  that,  naturally, 
aside  from  the  washing  away  of  nutritive  substances  and  the  mechanical 
injury  due  to  the  pressure  of  the  waves,  vegetation  is  not  extremely  sensi- 
tive to  a  water  cover  over  the  soil  for  some  time.  Woody  plants  especially, 
as  floods  show,  possess  a  great  power  of  resistance,  which  continues  as  long 
as  the  water  keeps  moving. 

Stagnant  water,  remaining  for  a  long  time  on  the  surface  of  the  soil, 
works  the  greater  harm ;  for  a  shorter  time,  inundations  in  the  form  of 


1  Hilg-ard,  Ueber  die  Flockung-  kleiner  Teilchen  und  die  physikalischen  und 
technischen  Bezichunpen  dieser  Erscheinung.  American  Journal  of  Sciences  and 
Arts.   XVII,  March  1879.    Forsch.  auf  d.  Gebiete  d.  Agrikulturphysik,  1879,  p.  44J. 


196 

dammed  up  zvoter  may  come  under  the  head  of  useful  factors  of  cultivation. 
At  any  rate  inundation  will  always  be  more  dangerous  than  those  methods 
of  irrigation  where  the  soil  always  remains  accessible  to  the  air.  The  oxygen 
content  of  irrigation  water  increases  oxidation  in  the  meadow  soils  since 
water  filtering  off  through  the  soil  shows  a  lesser  amount  of  oxygen  and,  at 
the  same  time,  an  increased  amount  of  carbon  dioxid  and  sulfuric  acid  in 
comparison  with  water  in  use  for  irrigation^  So  long  as  sufficient  oxygen 
is  present  the  slow  phenomena  of  oxidation  of  organic  substances  into 
carbon  dioxid,  ammonia  and  nitric  acid,  which  we  term  decomposition,  are 
accomplished  chiefly  by  the  action  of  micro-organisms.  If  a  scarcity  of 
oxygen  occurs,  however,  due  to  continued  retention  of  the  water,  that 
process  of  decomposition  begins,  partly  of  a  purely  chemical  nature,  partly 
with  the  co-operation  of  bacteria,  which  we  call  decay,  whose  final  products 
are  compounds  which  may  still  be  oxidized. 

If  the  water  accumulates  in  places  where  impervious  layers  of  soil 
entirely  prevent  any  vertical  flowing  away  and  all  horizontal  flowing  away 
is  also  made  difficult,  the  land  becomes  marshy. 

With  the  excessive  wetting  of  the  soil,  the  symptoms  are  again  seen, 
which  usually  appear  gradually  with  root  decay.  In  deciduous  trees, 
especially  fruit  trees,  and  w^ith  grapes  a  premature  yellow  leaf  (chlorotic) 
condition  becomes  noticeable,  wdiich  advances  from  below  upward.  This 
advancing  death  and  falling  of  the  leaves  from  the  base  of  the  branch  to- 
ward its  tip  bear  witness  tu  the  fact  that  the  growing  branches  strip  off  their 
older  leaves  in  order  to  mature  their  younger  ones,  which  happens  also  in  a 
gradual  drying  up.  By  this  means,  yellow  leaves  may  be  distinguished  from 
the  pale  leaves  resulting  from  the  action  of  frost,  in  which  the  young  leaf 
apparatus  is  disturbed  and  its  normal  chlorophyll  action  retarded. 

Conversion  of  Land  Into  Swamps. 

R.  Hartig's-  observations  show  that  stagnant  water  is  most  injurious  in 
forest  plantations  since  the  sensitiveness  of  the  trees  to  frost  is  increased 
and  freezing  and  heaving  occur  in  the  seed  beds.  Hartig^  observed  decay 
of  the  roots  to  a  devastating  extent  in  the  tracts  of  the  young  pines  in 
Northern  Germany.  It  begins  between  the  20th  and  30th  years  when,  after 
a  short  period  of  weak  growth,  the  trees,  still  covered  with  perfectly  green 
needles,  topple  over  as  soon  as  a  weight  of  snow  touches  them  or  a  high 
wind  acts  on  them.  It  is  found  that  the  tap  root  (see  Growth  of  Stilts,  p.  92) 
is  wet  and  rotted  up  to  the  base  of  the  trunk  while  most  of  the  lateral  roots 
appear  to  be  healthy.  vSuch  a  decay  of  the  roots  may  indeed  be  found  in 
spruce  plantations,  but  it  is  less  noticeable  because  the  superficially  extended 


1  Wollny,  E.,  Die  Zei-setzung-  der  organi-schen  Stoffe  und  die  Humusbildungen. 
Heidelberg  1897,  Carl  Winter,  p.  3.=;i. 

-  Hnrtig,  R.,  liehrbuch  der  Pflanzenkrankheiten,  3rd.  Ed.  Berlin,  Springer  1900, 
p.  263. 

3  Die  Wurzelfaule.  Zonsetzungsersnlieiniingen  des  Holzes,  Berlin,  .Tul.  Springer, 
1878,  p.  75. 


197 

root  system  makes  the  tree  less  dependent  on  the  few  roots  growing  down 
deep  into  the  soil. 

It  may  be  obser\'ed,  especially  in  the  province  of  Brandenburg,  that  the 
healthy  condition  of  pines  ceases  if  the  sand  flats  most  suitable  for  this 
growth  have  depressions  in  the  ground  where  the  accumulated  water  forms 
marshy  pools.  Up  to  the  edge  of  these  marshy  places  the  trees  stand  erect 
and  are  comparatively  long  needled.  At  the  point  where  the  black  moor 
begins,  the  growth  becomes  weakened,  the  needles  shorter  and  the  tree 
shows  very  small  annual  rings  which  not  infrequently  cease  entirely. 

In  the  increased  planting  of  the  very  profitable  pine  trees,  carrying 
them  even  on  to  damp  soils,  it  is  not  surprising  that  root  decay  is  found 
there  to  a  very  marked  extent.  It  is  advisable  to  limit  the  culture  of  pines 
to  sandy,  open  positions  and  to  choose  for  heavy,  wet  soils,  such  species  of 
trees  as  are  found  by  experience  to  best  endure  moisture.  In  places  where 
no  definite  agricultural  system  regulates  the  tracts,  the  suitable  kinds  of 
trees  make  a  natural  appearance  in  the  course  of  years,  because  of  their 
greater  power  of  resistance  in  the  struggle  for  existence.  It  is  approximately 
the  same  as  the  gradual  control  of  the  position  in  frost  holes  by  the  kinds  of 
trees  which  resist  frost  (hornbean,  birch,  aspen).  The  red  alder  can  best 
endure  the  strain  of  stagnant  water.  Besides  this,  black  and  silver  poplars, 
as  well  as  most  willows  and  the  sweet  birch,  thrive  on  moist  soils.  The  ash 
is  often  found  also,  but  under  these  conditions  the  trunks  are  entirely 
covered  with  moss  and  canker-like  swollen  spots. 

In  order  to  overcome  the  injury  due  to  turning  land  into  swamps,  its 
cause  must  be  determined  exactly.  At  times  the  condition  is  due  only  to  a 
lack  of  air  circulation,  and  here  the  partial  clearing  of  the  land  of  its  tree 
vegetation  by  the  removal  of  the  undergrowth  and  the  lower  branches  of  the 
trees,  together  with  proper  thinning,  would  be  beneficial.  Even  when  the 
land  only  becomes  shghtly  swampy,  especially  in  mountains,  it  may  be  re- 
stored by  planting  with  conifers  (Spruces).  This  holds  good  for  the  cases 
when  increased  evaporation  of  the  upper  surface  is  sufficient  to  overcome  the 
accumulations  of  water  in  the  soil.  As  the  trees  grow,  and  because  of  their 
close  proximity,  their  evaporating  surface  not  only  increases  but  also  less 
and  less  water  can  fall  to  the  soil,  because  of  the  thick  shelter  of  leaves. 

The  very  radical  means  of  removing  the  water  by  drainage  or  ditches 
should  be  used  in  forest  tracts  only  after  careful  consideration  of  all  local 
conditions  since  this  method  is  often  attended  by  greater  disadvantages  than 
advantages.  This  is  especially  true  in  mountain  forests  where  the  lowering 
of  the  water  level  of  one  district  may  easily  have  wide  spread  effects  on  the 
surrounding  region.  In  some  cases,  areas,  especially  slopes,  with  a  strong 
tree  grow^th,  where  there  is  no  excess  of  water,  become  drier.  Trees  accus- 
tomed to  the  former  amount  of  moisture  deteriorate  and  may  partially  die. 
On  plains  such  sharp  changes  due  to  drainage  are  less  to  be  feared. 

It  would  not  be  necessary  to  further  discuss  the  formation  of  marshes 
if,  aside  from  the  exhalation  of  gases,  injuries  to  cultivated  land  did  not 


I. 

11.75  CO, 

2.48  CH, 

2. 

12.62    " 

5-68    " 

3- 

34-99     " 

29.03    " 

4- 

55-81     " 

42.54    " 

5- 

56.00    " 

42.70    " 

6. 

45-9      " 

54-1       " 

7- 

43-3       " 

56.6       " 

198 

follow  attempts  to  drain  the  marshes  and  bogg}-  places.  The  injury  to 
meadows  should  be  considered  especially  in  this  connection  on  account  of 
the  frequent  use  of  injurious  marsh  and  boggy  water  for  irrigation.  The 
conversion  of  irrigated  meadows  into  marshes  by  overfilling  the  soil  with 
sewage  may  be  considered  only  in  passing. 

The  statements  of  Bischof  and  Popoff'  should  be  cited  in  connection 
with  the  exhalation  of  gases.  The  gases  produced  are  often  rich  in  hydro- 
carbons, especially  methane  or  marsh  gas  (CH^).  Popoff  investigated  the 
gas  developed  in  a  cylinder  which  contained  a  slimey  mass  consisting  of 
kitchen  refuse  and  substances  of  similar  character.  This  slime  was  kept 
3J^  weeks  in  the  cylinder,  at  first  at  17°  C,  later  at  7  to  io°C.,  and  gave 
gas  mixtures  of  the  following  percentages  of  composition  in  the  successive 
investigations  which  took  place  usually  at  intervals  of  2  to  4  days: — - 

4.71  O.  81.06  N. 

81.70 

0.0     O.  35-98  N. 
0.0     "  1.65  " 

0.0     "  1.30  " 

0.0     "  0.0     " 

0.0     "  0.1     " 

These  figures  show  that  at  the  beginning  of  the  experiment  part  of  the 
air  found  in  the  cylinder  was  driven  out,  and  part  used  up,  while  the  oxy- 
gen oxidized  the  organic  fragments  in  the  slime.  So  long  as  free  oxygen 
w'as  present,  the  formation  of  carbon  dioxid  exceeded  that  of  marsh  gas, — 
on  the  other  hand,  this  proportion  was  reversed  as  soon  as  the  oxygen  was 
exhausted. 

Proceeding  with  the  hypothesis  that  it  is  the  cellulose  in  the  slime 
which  is  decomposed,  assisted  by  the  action  of  the  lower  organisms,  Popoff 
put  clean  filter  paper  with  a  small  quantity  of  slime  into  a  flask.  On  investi- 
gating the  gas  formed  after  some  little  time,  he  found  its  composition  to  be 
34.07  per  cent,  carbon  dioxid,  37.12  per  cent,  marsh  gas,  1.06  per  cent,  hy- 
drogen and  27.75  per  cent,  nitrogen. 

Near  marshes,  however,  we  also  frequently  detect  the  odor  of  hydrogen 
sulfid.  This  comes  partly  from  the  decay  of  protein  bodies  which  form 
leucin,  tyrosin  and  other  substances  by  their  decomposition  and  finally  car- 
bon dioxid,  marsh  gas,  ammonia,  etc.  Erismann's-  observations,  cited  by 
Detmer,  make  possible  the  determination  of  the  quantitative  composition  of 
the  gas  given  off  in  24  hours  from  18  cubic  m.  of  excrement  placed  in  a 
poorly  ventilated  cess  pool. 

The  whole  mass  gave  11. 144  kg.  carbon  dioxid,  2.040  kg.  ammonia, 
0.033  ^S-  hydrogen  sulfid  and  7.464  kg.  marsh  gas.  In  this  decomposition 
oxygen  and  nitrogen  were  also  set  free.  13.85  kg.  of  oxygen  are  said  to  have 
been  taken  up  by  the  18  cubic  m.  in  24  hours. 


1  Bischof's    Lehrbuch    der    chemischen    unci    physikalischen    Geologie,    2n(l. 
Popoff  in  Pfliiger's  Archiv  f.  Physiologie,  Vol.  X.,  p.  113. 
-  Zeitschr.  f.  Biolog-ie,  Vol.  XI,  pp.  233  ff. 


199 

Thus  a  comparatively  very  slight  development  of  HoS  is  found  and  it 
must  be  assumed  therefore  that,  if  large  amounts  of  H.S  are  formed  in 
marshes  and  other  places,  they  must  owe  their  origin  to  a  reduction  of  sul- 
fates in  the  soil,  conditioned  by  the  organic  substances  present. 

Pagel^  and  Oswald  summarized  the  results  of  their  investigations  on 
such  reduction  processes  in  the  substances  of  marshes  and  found  that,  in 
the  absence  of  air,  sulfur  metals  occur,  as  well  as  hydrogen  sulfid,  and 
that,  together  with  this  reduction  of  the  sulfates,  ammonia  is  set  free  from 
the  marsh  substances  containing  nitrogen.  The  authors  do  not  state  defi- 
nitely whether  these  substances  are  produced  only  in  the  absence  of  air,  but 
in  their  production  may  lie  the  harmful  quality  of  stagnant  water. 

The  Burning  of  Plants  in  Moist  Soil. 

In  summers,  remarkable  because  of  great  temperature  extremes,  it  has 
been  observed  that  on  hot,  clear  windy  days,  plants  of  rapidly  growing,  large 
leaved  crops,  such  as  hops,  wilt  greatly,  particularly  when  grown  in  damp 
places.  The  lower  and  middle  leaves  of  plants  growing  in  damp  hollows 
are  sometimes  seen  to  turn  yellow  and  brown  at  the  edges  and  partially  to 
dry  up  so  that  they  can  be  rubbed  to  a  powder  in  the  hand.  These  specimens 
have  been  partly  burned  by  the  sun.  The  noticeable  feature  is  that  the 
burning  takes  place  directly  on  those  places  in  the  field,  in  which,  through- 
out the  whole  year,  sufficient  moisture  is  present,  while  in  higher,  drier 
portions,  still  more  exposed  to  the  wind,  the  plants  usually  suffer  less.  My 
comparative  experiments-  throw  sufficient  light  on  such  cases.  They  prove 
that  plants,  which  from  the  beginning  produce  their  roots  in  a  soil  contain- 
ing much  water  or  even  in  water  cultures,  evaporate  much  more  water  per 
square  centimetre  than  do  plants  of  the  same  strain  grown  under  conditions 
exactly  similar  except  with  a  lesser  water  supply.  It  is  an  interesting  but 
not  very  well-known  phenomenon  that  many  of  our  cultivated  plants  from 
very  different  families  grown  under  optimum  conditions,  in  producing  one 
gram  of  mature,  dry  substances,  evaporate  approximately  equal  quantities 
of  water,, — indeed  the  transpired  water  varies  from  300  to  400  g.  in  amount. 
If  the  plants  grow  in  localities  which,  hke  soils  with  an  impervious  subsoil, 
constantly  have  a  great  deal  of  water  at  their  disposal,  a  constant  nutrient 
solution  will  be  present  in  the  interstices  of  the  soil,  more  or  less  highly  con- 
centrated according  to  the  soluble  materials  present.  If  the  concentration 
exceeds  the  amount  favorable  for  the  plant  species,  the  plant  grows  less 
vigorously,  remains  short-limbed,  small-leaved,  but  usually  dark  green.  If 
the  concentration  is  exactly  right,  the  growth  is  very  rich  and  luxuriant 
and  the  absolute  water  requirement  is  very  great,  but  is  small  if  reckoned  per 
gram  of  dry  material  produced.  Under  such  conditions  the  plant  finds  the 
soil  water  of  great  value.  In  excessively  damp  places,  however,  it  often 
happens  that  the  soil  solution  is  poor  in  different  nutritive  substances. 


1  Landwirtsch.  Jahrb.,  VoL  VI,  Supplement,  p.  351. 

-   Sorauer,    Studien    iiber    Verdunstung.      Forschungen    auf    dem    Gebiete    der 
Ag-rikulturphysik,  Vol.  HI,  Parts  4  and  5,  pp.  43  ff. 


The  weather  recjuirement  is  greatest  under  such  conditions  just  as  if 
the  plant  made  the  greatest  struggle  to  produce  as  much  as  possible  from 
the  ver)^  scarce  nutrient  substances  present.  The  leaves,  then  formed,  are 
very  large  and  well  spread,  but  are  very  little  resistent  to  cold  as  well  as  to 
heat.  They  react  unfavorably  to  influences  which  pass  over  other  plants 
without  leaving  any  ill  effect. 

Such  disturbances  occur  earlier  in  plants  in  moist  localities.  On  hot 
and  especially  windy  days,  evaporation  is  enormously  increased,  the  amount 
of  water  transpired  is  then  considerably  greater  than  that  supplied  by  the 
axial  organs.  Consequently  the  leaves  on  many  plants  wilt.  The  smaller  the 
normal  transpiration  per  square  centimeter  surface,  the  longer  the  amount 
of  water  brought  by  the  stem,  even  on  extremely  hot  days,  will  compensate 
for  the  loss  of  transpiration.  The  plants  of  damp  localities  which,  as  ex- 
perimentally determined,  evaporate  much  more  water  in  the  same  unit  of 
time  than  do  plants  from  dry  places,  have  thereby  first  of  all  reached  the 
limit  when  lack  of  moisture  in  the  cell  acts  injuriously.  In  these  plants  the 
leaves  dry  up  first  and  not  the  very  youngest  nor  the  very  oldest  but,  as  a 
rule,  those  working  most  actively  and  in  part  still  elongating.. 

Proper  drainage  to  remove  the  water  from  those  particular  tracts  of 
ground  is  the  surest  method  of  overcoming  the  trouble. 

Delayed  Seeding. 

As  a  result  of  damp  soil  tlie  time  for  planting  is  frequently  delayed. 
The  following  are  the  results  of  experiments  by  Fr.  Haberlandt'  and  H. 
Thiel-.  The  most  detailed  experiments  were  made  by  Haberlandt  in  1876 
with  four  kinds  of  summer  grain  in  which,  on  the  ist  and  15th  of  the  months 
April,  May  and  June,  the  seed  was  sown  on  a  bed  3  sq.  m.  in  size.  The 
results  may  be  summarized  as  follows :  The  amount  of  harvest  in  all  sum- 
mer grains  decreased  more  and  more  as  the  seeding  was  delayed.  This  was 
based  first  of  all  on  the  considerably  weaker  growth  of  the  grain  planted 
late  and  was  most  evident  in  the  smaller  number  of  fertile  stems.  A  de- 
crease not  only  in  the  quantity,  but  also  in  the  quality  was  very  noticeable. 
The  weight  in  straw  increased  with  delayed  sowing.  In  general  the  chaff 
and  roots  of  the  crop  increased  disproportionately  to  the  weight  of  the  grain. 
The  quality  of  the  grain  itself  also  decreased  greatly.  Barley  and  oats  from 
later  sowings  had  a  greater  amount  of  chaff  by  weight ;  the  smaller  the  in- 
dividual grains  were,  the  greater  this  disproportion  became. 

The  later  sowings  -were  attacked  to  a  greater  extent  by  ergot,  mildew, 
rust  and  especially  by  leaf  lice.  Besides  this,  up  to  the  time  of  forming  the 
blades,  as  well  as  blossoming  and  ripening,  they  required  a  greater  amount 
of  heat  than  did  earlier  sowings.  Even  the  germinative  power  of  the  har- 
vested grain  was  affected  and  of  a  lowered  quality  in  seed  from  plants  of 


1  Haberlandt,  Fr.,  Die  Beziehungen  zwi.schen  dem  Zeitpunkt  der  Aussaat  und 
der  Ernte  heim  Sommergetreide.     Oesterr.  landw.   Wochenbl.  1876,  No.  3;  1877,  No.  2. 

-  Thiel,  H.,  Ueber  den  Einfluss  der  Zeit  der  Aussaat  auf  die  Entwicklung-  des 
Getreides.  Ref.  in  Biederm.  Centralbl.   f.  Agrikulturchemie.   1873,  p.  47. 


late  sowings.  In  the  first  place,  the  percentage  of  germination  was  lower; 
in  the  second  place,  the  grain  from  late  sown  and  late  harvested  seed  also 
required  a  longer  time  for  germination.  From  Haberlandt's  earlier  investi- 
gations in  this  line,  showing  a  lesser  development  of  grain  in  bulk  as  well 
as  in  absolute  and  specific  weight,  it  is  further  seen  that  the  amount  of  soil 
moisture  alone  is  not  the  only  cause  of  the  difference  between  late  and  early 
sowing.  In  these  experiments  the  plants  had  a  sufficient  water  supply,  from 
the  beginning,  and  yet  showed  these  different  proportions. 

Thiel's  experiments  with  late  sowings  were  made  at  various  times  in  the 
autumn.  The  time  of  harvesting  for  all  the  plants,  even  of  widely  different 
periods  of  sowing,  was  approximately  the  same,  but  very  late  sown  seed 
had  a  very  small  yield  so  far  as  it  remained  alive  at  all.  Indeed  Thiel  rightly 
calls  attention  here  to  the  fact  that  late  sown  seed  sprouted  simultaneously 
with  that  sown  earlier  with  corresponding  spring  weather,  without,  however, 
having  had  time  to  collect  sufficient  material  for  an  abundant  development 
as  did  the  plants  grown  from  seed  sown  earlier.  Naturally  the  constitution 
of  the  seed  plays  a  considerable  role  here.  The  older  the  seed,  the  more 
slowly  the  reserve  substances  are  mobilized.  With  ripening  and  subsequent 
maturing,  the  amounts  of  sugar  and  amido  nitrogen  compounds  decrease^ 
and  do  not  become  prominent  again  until  germination.  The  more  or  less 
favorable  sprouting  of  the  seed  depends  on  its  age  and  the  soil  constitution. 
At  this  point  we  will  insert  the  warning  that  no  reliance  should  be  placed  on 
the  results  of  other  germinative  tests,  but  one's  own  soil  must  be  tested  di- 
rectly as  to  its  behavior  with  different  seeds.  Seed  which  keeps  well,  accord- 
ing to  common  germinating  tests,  may  give  poor  results,  especially  in  heavy 
soils  and,  conversely,  a  light  soil  may  often  help  seed  to  make  a  good  growth, 
which  developed  only  a  moderate  quality  in  the  germinating  bed.  Hiltner's" 
report,  for  example,  on  newly  harvested  rye,  which  had  suffered  from  a 
thunder  storm,  showed  that  it  grew  well  in  some  fields,  but  absolutely  would 
not  grow  in  heavy  soil.  In  another  case,  rye,  developing  97  per  cent,  seed- 
lings in  a  germinating  test,  molded  almost  entirely  on  one  field,  while  in  an 
adjacent  one  it  gave  normal  growth. 

Souring  of  Seed. 

In  the  section  on  too  deep  sowing  (p.  106)  we  have  already  considered 
the  disadvantages  to  which  seed  is  often  exposed  in  heavy  or  in  incrusted  soils 
with  a  large  water  content.  Even  germinated  seed  has  to  struggle  against 
difficulties  due  to  physical  constitution  of  the  soil;  viz.,  from  an  excess  of 
water  in  heavy  soils.  Here  is  found  also  souring  of  seed,  which,  to  be  sure, 
can  occur  also  in  light  soils,  but  has  been  observed  usually  only  in  heavy, 
tough  soils. 

The  souring  is  due  to  a  decay  of  the  roots  which  have  been  longer 
in  contact  with  standing  water,  charged  with  organic  substances.   Most  roots 


1  Johannsen,  W.,   Studier  over  Planternes  periodiske  Livs  yttringer,  I;   cit.  Bot. 
Jahresb.  1897,  I,  p.  143. 

2  Hiltner,  L.,  in  Prakt.  Blatter  f.  Pflanzenbau  u.  Pflanzenchutz,  1903,  Part  I. 


withstand  \en-  well  a  continued  contact  with  running  or  standing  water, 
which  is  free  from  organic  substances,  as  can  be  seen  in  the  di liferent  water 
cultures.  Here,  however,  all  living  or  dead  vegetable  particles  in  the  culture 
vessels  are  avoided,  for  the  decomposing  organic  substances  take  up  all  the 
oxygen  which  is  present  in  a  small  supply.  The  roots  of  the  growing  plant 
must  be  killed  because  of  a  scarcity  of  oxygen  and  excess  of  carbon  dioxid. 
Also,  under  ordinar}'  conditions,  seeds  can  survive  contact  with  water, 
lasting  for  weeks,  if  the  temperature  is  low.  Thus  Feige^  states  that  wheat 
which  had  stood  for  5  weeks  under  cold  water  at  5°C.  still  lived.  On  the 
other  hand,  wheat  kept  8  weeks  under  water,  the  temperature  of  which  in- 
creased to  y^C  had  disappeared  without  leaving  a  trace.  Corn,  which  had 
previously  been  healthy,  withstood  water  at  3°C.  for  4  or  5  weeks,  but  was 
injured  somewhat  more  than  the  wheat  mentioned  above.  In  the  same  way, 
alfalfa  and  clover  withstood  standing  in  water  better  than  did  com. 

According  to  Kiihn,  rye  suffers  especially  from  souring,  while  under 
the  same  conditions  brome  grass  and  others  develop  very  luxuriantly.  To 
this  circumstance  is  due  the  erroneous  belief,  which  even  now  occasionally 
appears,  that  rye  can  change  into  brome  grass.  According  to  our  view, 
"Arrabbiaticcio"  of  wheat  in  Marengo  and  on  the  Roman  Campagna  be- 
longs under  this  head.  Peglion-  explains  the  disease  as  a  general  deteriora- 
tion of  the  plants  due  to  being  overrun  by  the  luxuriant  growth  of  weeds, 
which  thrive  better  than  the  wheat  on  unsuitable  soil.  In  Southern  Italy  the 
disease  is  called  "calda  fredda"  and  "secca  molla." 

The  souring  of  the  winter  oil  seeds,  especially  rape,  is  the  most  serious 
of  all.  From  standing  continually  in  water  the  roots  decay  from  the  tips 
backward  so  that  in  spring  only  the  crown  of  the  root  and  the  leaf  rosette 
remain.  These  appear  to  be  healthy  as  long  as  the  moist  spring  weather 
prevents  their  drying  out,  yet,  as  the  season  becomes  dry,  the  plants  turn 
brown  very  soon  and  may  be  drawn  from  the  soil  by  one  leaf. 

An  investigation  by  E.  Freiberg  and  A.  Mayer''  serves  to  explain  the 
fact  that  under  continued  wet  conditions  the  character  of  the  vegetation 
changes,  so  that  phenomena  appear  like  the  above  mentioned  predominance 
of  brome  grass  when  rye  had  been  sown.  This  experiment  proved  that  the 
roots  of  marsh  plants  need  much  less  oxygen  than  those  of  cultivated  plants. 
This  proves,  as  might  have  been  supposed  from  the  very  beginning,  that  the 
individual  plant  species  make  different  demands  on  the  oxygen  of  the  soil 
and,  accordingly,  must  adjust  their  habitat  to  existing  conditions.  From  the 
result  of  the  experiments,  however,  another  conclusion  may  be  drawn 
which  may  serve  in  general  when  judging  the  demands  made  by  different 
plants  on  soil;  viz.,  the  amount  of  air  needed  by  their  root  systems.  It 
is  found  that  the  more  oxygen  the  plant  needs  for  respiration,  the  greater  is 
its  nitrogen  content.  Marsh  plants  show  a  strikingly  low  nitrogen  content  and 

1  From  Oesterr.  landw.  Wochenbl.  cit.  in.  Biedermann's  Cemtralbl.  1877,  p.  76. 

-  Peglion,  v.,  Sull'  arrabbiaticcio  e  calda  freddo.  Annuar.  d.  R.  Stazione  di 
Patol.  veget.     Roma.  Vol.  I,  1901,  p.  37. 

'•''  Freiberg-,  K,  und  Mayer,  A.,  Ueber  die  Atmungsgrofse  bei  Sumpf-  und  Wasser- 
pflanzen.  Landwirtsch.  Versuchsstationen  1879,  p.  463. 


203 

have  an  open  inner  structure,  permitting  the  storing  of  larger  quantities  of 
air  within  the  body  and  suggesting  the  facihtation  of  internal  respiration. 
Real  water  plants  respire  with  a  lesser  intensity  than  land  plants,  as  Bohm^ 
found  in  his  experiments,  by  measuring  in  a  hydrogen  atmosphere  the  car- 
bon dioxid  given  ofif  during  internal  combustion.  Since  it  may  be  assumed 
that  the  amount  of  respiration  is  determined  by  the  amount  of  protein 
burned  in  the  plant's  body,  the  oxygen  needed  by  the  root  system  will  be 
greatest  in  cultivated  plants,  rich  in  nitrogen,  and  the  most  suitable  soils 
will  be  those  which  most  completely  satisfy  this  need  together  with  the 
other  demands  of  the  plant,  i.  e.,  rich  field  soil,  which  is  loose  or  has  been 
loosened. 

Those  lands,  therefore,  which  are  repeatedly  subjected  to  an  oxygen 
scarcity,  through  the  formation  of  crusts  from  rain  action  and  the  deposition 
of  silt  by  floods,  will  have  to  be  improved  by  corresponding  changes  in  their 
physical  structure.  In  the  cases  of  souring,  on  the  other  hand,  in  which  the 
air  supply  is  not  necessarily  cut  ofif  by  the  physical  constitution  of  the  soil 
and  in  which  only  an  excessive  supply  of  water  can  fill  the  large  interstices 
in  the  soil,  we  will  have  to  turn  to  the  removal  of  the  water..  Here  deep 
drainage  or  at  least  drainage  canals  120  cm.  deep,  lowering  the  ground 
water  level  by  this  amount,  are  the  most  advisable  precautionary  regulations. 
The  development  of  so  deep  a  pervious  layer  is  necessary  because  many 
Leguminoseae,  like  alfalfa,  and  sainfoin,  with  their  deep  growing  main 
roots  and  fewer  fibrous  roots,  are  apt  to  die  when  they  reach  the  ground 
water. 

Souring  of  Potted  Plants. 

The  souring  of  potted  plants  occurs  chiefly  when  loamy  or  peaty  soils 
are  used.  If  the  drainage  hole  of  the  flower  pot  is  stopped  up  and  excessive 
amounts  of  water  given  by  some  inexperienced  laborer,  the  roots  of  the 
potted  plants  die  completely,  since  they  become  brown  and  soft. 

The  sour  soil  can  be  recognized  at  once  by  its  characteristic  odor.  In 
this  the  process  of  decomposition  of  the  abundantly  present  organic  frag- 
ments, always  contained  in  nutritive  pot  soils,  takes  place  very  differently. 
Probably  acid  compounds  and  also  free  acids  are  produced  from  the  but 
imperfectly  understood  humus  elements.  If  iron  is  present  in  the  soil  the 
uninjurious  ferric  salts  can  be  reduced  to  the  injurious  ferrous  ones,  since, 
when  the  soil  spaces  are  enlarged  with  water,  a  perceptible  scarcity  of 
oxygen  must  occur. 

The  water  is  saturated  with  carbon  dioxid  from  the  secretions  of  the 
roots  and  also  from  the  decomposition  of  the  organic  matters  in  the  soil, 
and,  with  continued  action,  the  carbon  dioxid  is  sufficient  to  kill  the  plants. 
W.  Wolf-  proved  experimentally  that  healthy  plants,  set  in  water  contain- 
ing carbon  dioxid,  at  once  began  to  eliminate  it  in  very  greatly  reduced 
quantities.      The    result    is    a    wilting    of    the    leaves    which    die    later. 

1  Bohm,  Ueber  die  Respiration  von  Wasserpflanzen,  Sitzungsber  d.  Kais.  Akad. 
d.  Wiss.  zu  Wien.  1S75,   May  Number. 

2  Tagebl.  d.  Naturf.  Vers,  zu  Leipzig  1872,  p.  209. 


204 

Even  if  we  cannot  yet  explain  with  certainty  the  meclianics  of  wilting 
which  take  place  here  (the  explanation  given  by  W.  Wolf^  does  not 
seem  to  be  sufficient)  we  will,  however,  scarcely  go  astray  in  assuming 
that,  as  the  result  of  the  excessive  accumulation  of  carbon  dioxid  in  the  soil 
water,  the  normal  elimination  by  the  roots  of  carbon  dioxid,  which  is  con- 
siderable in  vigorously  growing  plants,  is  at  once  arrested.  An  unusually 
high  gas  pressure  must  therefore  be  produced  within  the  plant,  increasing 
to  a  positive  pressure  in  the  ducts  and  reducing  their  ability  to  conduct 
water  to  the  aerial  parts.  The  power  of  the  ducts  to  conduct  water  will  be 
decreased  by  the  amount  taken  up  by  the  negative  pressure  in  the  ducts.  If 
thereby  this  conduction  of  water  is  weakened  without  corresponding  re- 
duction of  the  use  of  water  in  the  leaves,  wilting  results  immediately.  If 
the  plants  are  placed  in  distilled  water,  as  in  Wolf's  experiments,  a  normal 
appearance  and  normal  functions  again  set  in.  The  distilled  water  in  this 
case  is  like  a  sponge,  absorbing  the  carbon  dioxid  and  other  excretory  pro- 
ducts of  the  roots. 

Finally  the  result  is  the  same  for  the  root,  whether  the  carbon  dioxid 
appears  dissolved  in  water,  or  as  a  gas  resulting  fi-om  an  insufficient  soil 
absorption.  For  the  aerial  parts  of  the  plant,  however,  conditions  are  differ- 
ent and  it  is  very  important  whether  they  come  in  contact  with  water  rich 
in  carbon  dioxid  or  in  air  containing  the  gas.  At  least  Bohm's  experiments- 
on  the  leaves  of  green  land  plants  have  emphasized  this.  He  immersed 
leaves  of  different  land  plants  under  water  containing  carbon  dioxid  and 
found  that  the  plant  no  longer  gave  off  oxygen  if  the  part  concerned  was 
prevented  from  surrounding  'itself  with  an  atmosphere  containing  carbon 
dioxid  which  would  cut  it  off  from  direct  contact  with  the  water. 

The  results  of  excessive  watering  in  pots  with  the  drainage  stopped 
and  the  consequent  cessation  of  plant  and  soil  activity  are  best  determined 
by  a  microscopic  comparison  with  the  soil  in  a  pot  containing  a  healthy 
growing  plant.  What  intense  activity  is  found  in  the  soil !  From  the  upper 
surface  down  to  the  bottom  of  the  pot  (in  leaf  and  heath  earth)  are  found 
fragments  of  leaves  and  stems,  on  which  many  kinds  of  the  so-called  mold 
forms  with  sterile  mycelia,  or  with  mature  conidia,  exercise  their  power  of 
decomposition.  According  to  the  nature  of  the  vegetable  matter,  Sepedon- 
ium  (chrysospermumf ) ,  Verticillium  ruherrimum,  or  Penicillium  glaucum, 
Acremonium,  Acrocylindrium,  Cladosporium  penicillioides,  different  kinds 
of  Fusiarium  and  many  others  are  found.  On  the  upper  surface  often  still 
other  genera  occur,  especially  the  aerobic  ones  together  with  living  diatoms 
and  other  forms  of  algae.  The  schizomycetes  go  deepest  of  all.  Starch 
granules  and  bits  of  cytoplasm  are  found  surrounded  by  colonies  of  rod 
bacteria  radially  arranged;  colonies  of  bacteria  have  often  been  established 
also  on  fragments  of  crystals.  All  this  active  life  is  engaged  in  reducing 
the  plant  substance  and  favors  the  processes  requiring  oxygen,  which  we 


Jahresber.  f.  Agrik.-Chemie,  1870-72,  II,  p.  134. 

Anzeigen  der  Wien.  Akad.  d.  Wiss.,  1872,  Nos.  24-25,  p.  163. 


term  decomposition.  All  this  active  life  will  either  be  stopped,  by  closing 
the  soil  interstices  with  water,  or  be  turned  to  those  destructive  phenomena 
of  decay,  decomposition  in  the  absence  of  oxygen.  Every  soil  has  its  my- 
cological  as  well  as  its  bacterial  flora,  which  decomposes  the  organic  sub- 
stances. According  to  Oudemans  and  Koning^,  these  are  approximately 
typical  for  definite  kinds  of  soil. 

In  potted  plants  it  is  safe  to  assume  the  beginning  of  stagnation  when 
the  vipper  surface  of  the  soil  is  covered  with  a  hard  white  or  reddish  colored 
lime  crust,  firmly  attached  to  the  edge  of  the  pot.  From  the  uncommonly 
large  amount  of  carbon  dioxid  developed  by  the  addition  of  acetic  acid, 
it  is  evident  that  the  incrustation  of  the  uppermost  soil  layers  in  the  pot, 
and  at  the  edges,  results  especially  from  calcium  carbonate. 

Magnesium  carbonate  is  met  with  and  also  ferrous  carbonate,  which 
later  through  oxidation,  produces  as  ferric  hydrate  dififerent  colors  in  the 
crust.  According  to  the  microscopic  examination,  the  characteristic 
swallow-tailed  crystals  of  gypsum  and  the  octahedrons  of  calcium  oxalate, 
as  well  as  the  rhombic  forms  of  calcium  phosphate,  soluble  in  acetic  acid, 
occur.  The  presence  of  the  last  named  salt  can  not  always  be  demonstrated 
and  never  in  large  amounts.  On  the  other  hand,  calcium  carbonate  and 
probably  magnesium  carbonate,  together  with  very  fine  particles  of  quartz 
sand,  make  up  the  usual  substances  of  the  crusts,  between  which  is  per- 
ceptible at  first  an  abundant  fungous  growth  with  a  formation  of  conidia  on 
the  humus.  The  production  of  these  crusts  may  be  explained  by  the  fact 
that  the  water,  given  in  large  quantities  in  watering,  becomes  charged  with 
the  carbon  dioxid,  abundantly  produced  by  the  process  of  decomposition 
within  the  soil  interstices.  Hence  water  is  a  splendid  medium  for  dissolving 
the  calcium  carbonate  present  in  the  soil,  the  magnesia,  the  ferric  phosphate, 
the  ferric  silicate,  etc. 

The  more  quickly  the  superfluous  water  is  drawn  away  by  good  drain- 
age in  the  pot,  the  less  will  the  minerals  be  dissolved  and  washed  away.  On 
the  other  hand,  if  the  water  stands  in  the  pot  and  once  becomes  charged 
with  calcium,  which  is  soluble  in  the  form  of  calcium  bi-carbonate,  it  can 
only  be  removed  by  evaporation  from  the  saturated  upper  surface  of  the 
pot  and,  when  the  pores  of  the  pot  are  not  closed  by  a  green,  slimy  algal 
growth,  this  excessive  water  also  evaporates  slowly  through  its  sides ;  it 
leaves  behind  the  dissolved  substances.  The  pots  "become  coated."  The 
calcium  remains  behind  as  calcium  carbonate  just  as  on  the  edge  of  a  kettle 
in  which  water  containing  lime  has  been  boiled. 

Thus  the  usefulness  of  the  two  processes,  the  frequent  washing  of  the 
flower  pots  and  the  breaking  up  of  the  upper  surface  of  the  soil,  is  dem- 
onstrated. 

In  the  increasing  desire  to  attain  our  ends  by  fertilization,  dii¥erent 
fertilizers  are  added  to  water  soaked  plants,  but  the  main  need,- — sufficient 


1  Oudemans,  C.  A.  J.,  et  Koning-,  C.  J.,  Prodrome  d'une  flore  mycolog-ique  obtenue 
de  la  terre  humeuse  du  Spanderswoud  etc.  Extr.  Archiv.  neerland.;  cit.  Z.  f.  Pflan- 
zenkr.  1903,  p.  60. 


206 

aeration  of  the  soil, — is  overlooked.  The  plants  have  not  improved  with  this 
treatment.  The  best  results  are  obtained  by  transplanting  when  growth 
starts  and  the  application  of  heat  to  the  roots  to  stimulate  growth. 

Eichhom's^  investigations  prove  that  fertilizing  may  be  injurious  rather 
than  advantageous  with  acid  soil,  in  the  presence  of  free  humus  acid.  He 
states  that  earths,  rich  in  humus,  which  contained  free  humus  acid,  liberate 
the  acids  from  solutions  of  neutral  salts.  The  acidification  thus  produced 
is  stronger  than  it  would  be  without  these  salts  and,  therefore,  fertilization 
with  neutral  salts  will  increase  the  acid  in  such  soils.  This  happens  with 
calcium  phosphate  or  any  phosphate  where  the  phosphoric  acid,  or  calcium 
l)hosphate,  passes  over  into  solution.  The  addition  of  neutral  potassium 
salts,  especially  alkaline  sulfates,  favors  decomposition.  If  the  humus 
acid  is  combined  with  a  base,  such  acidification  does  not  take  place.  The 
addition  of  manure,  liquid  manure,  etc.,  will  act  only  disadvantageously 
with  such  chemical  decomposition  and  is  to  be  avoided  as  are  marly  earths. 

Ix JUDICIOUS  A\^ati:rixg. 

The  frequent  dying  of  house  plants  makes  necessary  a  reference  to  in- 
judicious watering.  Excessive  watering  may  be  due  to  the  fact  that  in- 
experienced people  assume  a  lack  of  moisture  in  the  soil  as  soon  as  the  plant 
wilts.  The  fact  that  frequently,  after  watering,  the  plant  becomes  turgid 
(luring  the  course  of  the  day  gives  weight  to  this  assumption.  If  wilting 
follows  this  second  turgidity,  water  is  added  until  the  plant  is  permanently 
wilted  and  the  roots  decay.  Such  conditions  arise  especially  in  the  autumn 
when  the  more  tender  plants  are  put  in  conservatories  with  but  little  heat. 
The  coldness  of  the  soil  then  causes  the  wilting.  We  know  from  a  number  of 
cases  cited  by  Sachs-  that  different  plants  require  definite  temperatures  for 
their  roots  to  keep  them  working,  i.  e.,  taking  up  water.  Tobacco  and 
pumpkins  wilt  in  a  soil  at  3°  to  5°C. ;  but  if  the  same  soil  is  warmed  to 
12°  to  i8°C.,  the  root  activity  is  re-established.  In  the  examples  cited  above, 
when  the  previously  watered,  wilted  plants  become  turgid  during  the  day. 
this  result  is  attributed  to  the  influence  of  the  watering.  The  real  cause, 
however,  was  the  diurnal  rise  in  temperature  of  the  air  and  of  the  soil, 
caused  by  the  sun.  whereby  the  roots  were  again  stimulated  to  take  up 
water.  \\'ith  the  coming  of  night  and  the  corresponding  fall  in  temperature 
below  the  limit  at  which  the  roots  are  still  to  take  up  water,  the  wilting  is 
repeated.  The  plant  can  therefore  die  of  thirst  even  when  the  soil  is  very 
moist,  if  the  soil  be  too  cold.  On  the  other  hand,  in  moist  air,  the  plants 
can  remain  alive  a  long  time  with  wholly  decayed  roots,  as  is  shown  by  water 
cultures.  This  is  also  the  reason  why,  in  root  diseases,  symptoms  of  dis- 
turbance are  noticeable  in  the  aerial  organs  only  at  a  late  stage. 

Another  cause  of  the  wilting  becomes  noticeable  in  midsummer.  If 
plants  transpiring  rapidly  are  exposed  for  some  time  to  the  hot  sun  and  to 


1  Landwirtsch,  .lahrbiicher  1877,  p.  5)57. 
-  Lehrbuch  der  Botanik,  1st.  Ed.,  p.  559, 


20/ 

currents  of  air,  they  begin  to  wilt  in  spite  of  sufficient  soil  moisture,  because 
the  quantity  of  water  evaporating  through  the  leaves  cannot  be  replaced 
cjuickly  enough  by  the  root.  To  be  sure,  the  supply  of  water  will  be  in- 
creased as  the  temperature  rises  simultaneously  with  the  increased  sunshine. 
According  to  De  Vries^,  imbibition  of  the  cell  walls  is  increased  and  thereby 
their  ability  to  conduct  water,  but  the  increased  supply,  nevertheless,  cannot 
make  good  the  loss  through  evaporation  and  the  leaves  must  droop.  If  the 
pots  are  then  watered,  without  having  been  tested,  the  earth  will  become 
sour. 

The  same  result  is  found  in  the  so-called  New  Holland  and  Cape  plants 
belonging  to  the  families  of  the  Epacrideae,  Ericaceae,  Papilionaceae, 
Rutaceae,  etc.  The  loose,  fine,  sandy,  but  little  decomposed  earth,  such  as 
heath  mould,  cannot  be  pressed  very  firm  into  the  pots,  because  the  unde- 
composed  pieces  of  roots  and  leaves  form  a  very  loose  consistency ;  with  too 
heavy  watering,  however,  the  fine  grains  of  sand  and  clay  are  first  stirred 
up  and  then  washed  down  so  that  only  the  long,  loose  fibrous  elements  re- 
main at  the  upper  surface  of  the  pot.  These  naturally  retain  but  very  little 
water  and  let  it  run  down  very-  quickly  to  the  bottom  of  the  pot.  On  this 
account  the  upper  surface  of  the  pot  is  always  almost  half  dry.  If  now  the 
gardener  lets  himself  be  led  astray  and  waters  the  pots  under  such  con- 
ditions, and  if  the  pots  have  no  good  drainage,  the  very  fine  roots  will  decay. 
(It  should  be  remarked  in  passing,  that  the  so-called  soured  pots  quite  fre- 
quently show  an  alkaline  reaction.  I  found  with  potted  plants,  whose  roots 
had  decayed,  that  moist  red  litmus  paper  turned  blue  as  far  as  it  lay  upon 
the  surface  of  the  pot). 

As  a  means  of  overcoming  this,  transplanting  into  very  sandy  earth  and 
sinking  the  soured  plants  in  beds  with  warm  soil  has  already  been  recom- 
mended. As  a  matter  of  course  the  roots  must  be  cut  back  to  the  healthy  part 
when  transplanted.  As  a  precautionary  measure,  the  pots  may  be  plunged  into 
the  ground  and  similar  methods  may  be  recommended.  In  doing  this,  how- 
ever, a  stick  or  a  piece  of  wood,  turned  like  a  cone,  should  be  used  to  make  a 
deep,  funnel-like  hole,  whose  upper  edge  is  exactly  the  size  of  the  edge  of 
the  pot.  The  pot  then  hangs  in  the  hole.  Below  the  pot  the  lower  part  of 
the  conical  hole  forms  a  cavity  and  prevents  the  earth  worms  from  crawling 
into  the  drainage  hole  in  the  pot  and  stopping  it  up.  In  flower  pots  stand- 
ing in  a  room,  or  on  flower  racks,  the  soil  will  not  sour  if  only  some  little 
care  Is  taken.  The  water  content  of  the  soil  may  be  judged  easily  and  com- 
paratively accurately  by  tapping  the  pot.  If  the  earth  is  full  of  moisture, 
the  water  lies  between  the  individual  particles  of  soil  and  the  sides  of  the 
pot  and  the  sound  resembles  that  of  a  dense  mass  ;  when  the  amount  of  water 
is  scanty,  however,  the  pot  rings  hollow. 

According  to  the  above,  therefore,  one  should  consider  not  only  how 
much  to  water,  but  in  what  way  potted  plants  should  be  watered.  In  order 
to  avoid  washing  away  the  finest  particles  of  clay  and  sand  and  thereby 


Bot.  Zeitung-.  1872,  p.  781. 


208 

forming  crusts,  or  choking  the  drainage  of  the  pot,  the  water  should  never 
be  poured  quickly  through  the  spout  of  the  watering  pot.  In  plants  set  in 
pots  and  sunken,  a  hose  should  be  used,  or,  in  pots  set  on  forms  in  con- 
servatories, a  slender  and  long  spout,  giving  only  a  gentle  stream  of  water. 
One  should  avoid  holding  the  stream  of  water  at  the  base  of  the  stem, 
which  is  often  entirely  white  as  a  result  of  incrustations  of  lime. 

Use  of  Saucers  Under  Pots. 

In  house  plants  the  use  of  saucers  under  pots  is  general.  This  saucer 
is  necessary  for  preserving  cleanliness  on  the  window  sill  and  on  the  flower 
table,  but  is  usually  injurious  for  the  plants  themselves.  No  matter  whether 
the  pots  be  watered  from  above  or  by  soaking  up  water  from  the  saucers, 
the  soil  will  almost  always  take  up  too  much  water.  Many  plant  lovers  con- 
sider this  condition  advantageous.  The  result,  however,  is  a  choking  of  the 
roots  at  the  bottom  of  the  flower  pot.  The  decay  of  the  roots  continues 
gradually  upward  and  finally  shows  itself  in  the  dying  of  the  edges  of  the 
leaves.  If  these  symptoms  appear,  the  plant  is,  as  a  rule,  lost  to  the  ama- 
teur, but  the  gardener  can  often  cure  it.  For  the  amateur,  who  has  no 
warm  bed  at  his  disposal,  we  would  recommend  setting  the  sick  plant  in  pure 
sand  and  placing  it  in  a  warm,  half  shady  place. 

The  RuNxixG  out  of  Potatoes. 

In  discussing  the  disadvantages  of  heavy  soils,  we  should  consider  the 
point  of  view,  repeatedly  brought  forward  in  practical  circles,  that  our 
potatoes  "run  out,"  i.  e.,  gradually  lose  their  good  qualities  and  degenerate. 
Some  people  would  explain  this  by  holding  that,  in  the  customary  method 
of  propagation  by  planting  tubers,  one  really  propagates  asexually,  without 
interruption,  an  individual  once  produced  from  seed  and  that,  thereby,  an 
organism  so  long  lived  must  at  last  show  the  weakened  condition  of  old 
age.  A  proof  of  this  is  found  in  the  retrogression  in  the  starch  content  of 
our  favorite  older  varieties  as,  for  example,  in  the  Daber  potato. 

According  to  our  point  of  view,  the  cause  of  the  supposed  running  out 
lies  in  the  lack  of  foresight  of  the  agriculturalist  in  growing  varieties  on 
heavy  soil  which  lia\e  been  produced  on  light  soil. 

We  refer  in  this  connection  to  Ehrenberg's  work^  on  the  results  of  15 
years  experiments  at  the  "Deutsche  Kartofifelkulturstation."  The  average 
yield  of  all  the  varieties  grown  seemed  to  increase  constantly  from  1889  to 
1903.  In  regard  to  the  "Daber"  potato,  the  yields  decreased  only  on  heavy 
soil  which  is  easily  explained  since  in  Daber  a  very  light,  dry,  sandy  soil 
predominates.  If  newly  grown  seed  of  this  variety  was  planted  in  heavy 
close  soil,  it  gave  better  results  than  the  form  which  had  been  culti^•ated  there 
for  some  time.  The  same  new  seed,  however,  planted  in  sandy  soil,  usually 
gave  a  poorer  result  when  compared  with  the  naturalized  plant.     \\'e  find 


1   Ehrenberg,  B.,  Der  Abbau  der  Kartoffeln.     Landw.   Jahrb.    Vol.   XXXIII;    cit. 
Centralbl.  f.  Agrikulturchemie,  1905,  p.  235. 


PART  III. 


MANUAL 


OF 


Plant  Diseases 

BY 

PROF,  DR.  PAUL  SORAUER 


Third  Edition-Prof.  Dr.  Sorauer 

In  Collaboration  with 

Prof.  Dr.  G.  Lindau       And       Dr.  L.  Reh 

Private  Decent  at  the  University  Assistant  in  the  Museum  of  Natural  History 

of  Berlin  in  Hamburg 


TRANSLATED  BY  FRANCES  DORRANGE 


Volume  I 
NON-PARASITIC  DISEASES 

BY 

PROF.  DR.  PAUL  SORAUER 

BERLIN 


WITH  208  ILLUSTRATIONS  IN  THE  TEXT 


PART  III. 


MANUAL 


OF 


Plant  Diseases 


BY 


PROF.  DR.  PAUL  SORAUER 


Third  Edition—Prof.  Dr.  Sorauer 

In  Collaboration  with 

Prof.  Dr.  G.  Lindau        And       Dr.  L.  Reh 

Private  Docent  at  the  University  Assistant  in  the  Museum  of  Natural  History 

of  Berlin  in  Hamburg 


TRANSLATED  BY  FRANCES  DORRANGE 


Volume  I 
NON-PARASITIC  DISEASES 

BY 

PROF.  DR.  PAUL  SORAUER 

BERLIN 


WITH  208  ILLUSTRATIONS  IN  THE  TEXT 


Copyrighted,    1915 

By 
FRANCES  DORRANCE 


THE    RECORD    PRESS 
Wilkes-Barre,  Pa. 


209 

proof  in  these  experiments  that  newly  introduced  seed  retains  at  first  the  char- 
acter developed  in  the  place  where  it  has  been  bred.  If,  for  instance,  heavy 
soil  reduces  the  starch  content,  the  reduction  does  not  take  place  in  the  first 
year  with  new  seed  and  therefore  this  seed  contains  more  starch  than  the 
native  seed.  On  sandy  soil,  however,  a  variety  has  been  bred  which  contained 
the  largest  amount  of  starch  possible  under  the  conditions.  The  newly  intro- 
duced varieties  with  the  peculiarities  brought  with  them,  however,  had  not 
as  yet  adjusted  themselves  sufficiently  to  these  conditions  and  therefore  gave 
a  lesser  yield.  Exhaustion  or  degeneration  will  therefore  take  place  only 
where  a  variety  does  not  find  the  cultural  conditions  it  requires.  The  cir- 
cumstances may  be  similar  in  all  phenomena  of  supposed  exhaustion  or 
degeneration.  Our  cultural  varieties  are  the  products  of  breeding  under 
very  definite  conditions  of  position,  soil  and  weather,  and  are  kept  pure  only 
if  they  again  find  conditions  similar  to  those  where  they  are  grown.  If  it  is 
desirable  to  make  use  of  valuable  peculiarities  of  any  definite  species  in 
another  locality,  good  results  are  obtained  only  by  frequently  renewing  with 
seed  from  the  naHve  habitat  or  from  habitats  similarly  situated. 

Sensitiveness  of  the  Sweet  Cherry. 

The  complaint  in  different  places  that  the  sweet  cherry  every  year  suf- 
fers increasing  injury  from  frost,  the  exudation  of  gum,  attacks  of  fungi 
etc.  is  often  due  to  the  failure  to  observe  the  fact  that  the  cherry  does  not 
like  a  heavy  soil.  This  circumstance  has  been  especially  emphasized  recently 
by  Ewert^  and  deserves  to  be  repeatedly  borne  in  mind  by  the  fruit  breeder. 
Naturally  here  also  some  cultural  varieties  are  able  to  adapt  themselves 
better  to  heavier  soils,  but  in  general  the  rule  holds  good  that  the  sweet 
cherry  likes  a  light,  deep  soil  and  flourishes  especially  well  on  alluvial  sand 
and  loose  soils.  The  amount  of  nutrition  in  the  soil  is  a  far  less  decisive 
factor  than  its  physical  constitution,  especially  its  granular  condition. 

Often  a  scarcity  of  lime  is  given  as  the  cause  of  poor  growth,- which 
can  be  overcome  by  supplying  lime.  The  improvement  in  growth,  however, 
may  not  always  be  traced  back  to  the  nutritive  action  of  the  lime  but  to  the 
change  in  the  physical  soil  condition  due  to  it,  viz.,  greater  friability  and 
thereby  increased  aeration.  Ewert's  statements  throw  light  on  lime  as  a  nutri- 
tive substance.  He  states  that  the  sweet  cherry  flourishes  even  when  the  lime 
content  is  from  0.04  to  0.15  per  cent.  Soil  with  possibly  80  per  cent,  of 
easily  washed  away  particles  is  not  suited  to  the  growth  of  cherries  even 
with  40  to  45  per  cent.  CaCOg,  if  this  is  chiefly  present  in  so  fine  a  condition 
that  it  also  can  be  washed  away.  The  cherr)^  is  peculiarly  sensitive  to  stand- 
ing water  and  it  grows  best  in  dry  soil  in  open  places. 

The  Tan  Disease. 
Trees  standing  on  damp  ground  may  show  decreased  growth,  especially 
if  their  early  growth  was  rapid.    The  older  bark  cracks  or,  after  the  outer- 


1  Ewert,  Das  Gedeihen  der  Siifskirschen  auf  einigen  in  Oberschlesien  liauflgen 
Bodenarten.     Landw.  Jahrb.  1902,  Vol.  XXXI,  p.  129. 


210 


most  cork  layers  have  fallen  off,  blister-like  or  flat,  warty  swellings  put  in  an 
appearance  and  later  these  have  a  diseased  wooly  outer  surface.  If  the 
place  becomes  somewhat  dr}-,  a  reddish  yellow  to  a  brownish  yellow  powder 
may  be  brushed  off  which  in  color  resembles  fresh  tan  bark.  This  may  have 
given  rise  to  the  term  "Tan  Disease."  In  introducing  the  subject  of  this  dis- 
ease into  scientific  discussion  I  have  re- 
tained the  name  used  by  practical  growers. 
The  same  process  takes  place  also  in 
roots  and  young  branches.  Young  bran- 
ches with  knotty  tan  pustules  may  be 
found  in  cherries.  Up  to  the  present  this 
disease  of  the  bark  of  the  older  trunk  and 
roots  has  been  observed  most  frequently 
in  apples.  Plums  seldom  suffer.  Similar 
processes,  resulting  in  the  falling  off  of 
larger  pieces  of  bark,  have  been  found  in 
elms  and  will  be  treated  under  growth 
disturbance  due  to  marshy  soils. 

In  figure  23  is  seen  a  piece  from  an 
apple  root,  natural  size.  Its  bark  has  been 
broken  open  by  cross-tears  varying  in  size, 
the  edges  of  which  have  been  forced  back ; 
the  open  places  are  covered  with  an  ochre 
powder  or  (when  first  taken  from  the  soil) 
with  soft,  moist,  brown  masses.  Figure 
24  represents  a  cross-section  through  such 
a  callus  place.  We  find  the  wood  (c  is  the 
cambial  zone)  of  a  practically  normal 
structure  traversed  by  the  medullary  rays 
(m),  most  of  which  show  no  variation 
whatever.  Only  in  some  (m')  it  is  notice- 
able that  in  the  younger  portions  they  be- 
gin to  broaden,  thereby  causing  a  looser 
construction.  This  process  of  loosening, 
however,  finds  its  evident  expression  only 
in  the  bark  where  the  rows  of  medullary 
ray  cells,  beginning  to  separate  from  one 
another,  form  loops.  While  the  younger 
inner  bark,  with  its  hard  bast  cords,  still  shows  no  change  from  a 
normal  structure,  the  older  layers  (at  left  side  of  the  illustration)  display 
an  impoverishment  of  the  cell  contents  and  some  radial  stretching  (k'). 
This  excessive  elongation  of  the  bark  parenchyma  becomes  greater,  the  fur- 
ther toward  the  outside  the  cells  lie,  and  it  increases  within  the  cork  zone  in 
such  a  way  that  the  cells  lying  free  on  the  outer  surface  take  on  a  pouch- 
like form  (s)  and  are  only  very  loosely  united  with  one  another. 


Fig^.  23.     Apple  root  with  ruptured 
tan  spots,  natural  size.    (Orig.) 


If  the  outer  surface  of  the  root  dries  off,  the  cell  pouches  shrink  and, 
in  the  outer  layers,  are  entirely  separated  from  one  another.  Then  a  tan- 
colored,  powdery  mass  forms  which  may  be  wiped  away  wdth  the  finger. 
Even  the  lamellae  of  plate  cork  (t)  which  are  present  at  the  edge  in  thick 
layers  (of  equal  size,  under  normal  conditions)  and,  gradually  dying  back 
from  the  outside,  fall  away  at  the  place  of  the  tan  disease,  are  also  drawn 
into  the  process  of  loosening.  These  split  off  because  some  of  the  middle 
layers  round  off  their  cells  and  show  a  tendency  to  assume  the  structure  of 
cork  as  will  be  described  more  fully  later  under  the  cherr}^ 


Fig-.  24. 


Cross-section  through  a  diseased  spot  in  an  apple  root.    (Tan  disease.) 
(Orig.) 


If  the  outgrowth  of  the  bark  at  the  edge  of  the  tan  canker  and  the  emp- 
tying of  the  cell  have  reached  maturity,  the  well-known  hourglass  arrange- 
ment of  plate  cork  layers  occurs  (f)  which  cut  off  the  hypertrophied  bark 
parenchyma,  finally  becoming  cork,  and  it  becomes  an  element  of  the  bark 
scales.  The  cell  elongation  meantime  advances  laterally  and  further  toward 
the  inside.  Thus  at  w  we  see  the  beginnings  of  this  since  the  bark  cells, 
normally  elongated  tangentially,  are  becoming  square  in  cross-section  and  in- 
crease in  number  by  division  in  order  to  round  off  more  toward  the  diseased 
side,  to  become  more  open  by  enlargement  of  the  intercellular  spaces  (r) 
and  finally  to  pass  over  into  the  radial  elongation  which  increases  to  pouch- 


212 


like  outgrowths.  By  this  advance  of  the  process  of  over-elongation 
into  constantly  younger  bark  parenchyma  layers,  the  activity  of  the  root  is 
finally  exhausted  at  the  place  of  the  tan  disease. 

The  injury  is  not  so  intensive  in  the  aerial  axes  Sometimes  in  larger 
trunks  the  phenomenon  is  not  noticed  until  the  bark  is  closely  examined.  It 
is  then  found  that  some  bark  scales  stand  out  raggedly.  If  these  are  re- 
moved, which  may  be  done  very  easily,  it  is  observed  tliat  the  outermost 
layers  of  the  succulent  bark  tissue  form  irregular  blister-like  swellings  which 
rupture  later  and  decompose  into  dust-like 
masses  which  may  be  wiped  away  in  dry 
weather.  Figure  25  shows  the  fresh  bark  sur- 
face of  an  apple  tree  which  has  been  laid  bare 
by  the  removal  of  the  outer  bark  scales. 

On  this  greenish  brown,  juicy  surface 
hemispherical  or  elongated  warty  excrescences 
(a)  appear  very  clearly.  Figure  26  shows  a 
cross-section  through  such  a  boil-like  swelling, 
in  which,  however,  the  wood,  cambium  and 
M  ^     J    I        \     ^         ^  youngest   inner  bark  have   not  been   drawn. 

I  \      '    ,-  ^   .  We  recognize  at  the  first  glance  the  corres- 

^^  '^  "-■  pondence  in  structure  with  that  of  the  tan  spot 

of  the  root.  At  the  lower  part  of  the  figure 
we  find  the  bark  parenchyma  with  three  hard 
bast  bundles  of  a  normal  arrangement  and 
position,  but  close  above  these  hard  bast  bun- 
dles is  noticeable  a  change  in  position  since 
the  tangentially  elongated  bark  cells,  rich  in 
chlorophyll,  begin  to  increase  in  length  radially 
(r),  to  divide  and  to  be  arranged  in  parallel 
lines  broken  by  large  intercellular  spaces  (i). 
The  fact  that  this  change  in  tissue  must  have 
taken  place  very  early,  at  the  time  of  pushing 
out  from  the  cambium,  is  evident  because  the 
permanent  tissue  of  the  collenchyma  (cl)  has 
developed  only  one  layer  within  the  tissue  of 
the  excrescence.  The  chief  part  of  the  swelling  has  come  from  the  peri- 
pheral layers  which  have  developed  into  cushions  (w)  of  elongated,  finally 
pouched  cells  (s),  which  have  raised  the  plate-cork  cell  layers  and  finally 
spHt  them. 

In  explaining  this  phenomenon  we  must  not  forget  that  these  tan  places 
arise  underneath  the  old  bark  scales,  and,  with  a  formation  of  full  cork, finally 
become  bark  scales  by  suberization.  Thus  we  find  that  the  organization  of  the 
bark  into  constricted  and  constricting  cell  layers,  as  they  alternate  in  the 
bark,  has  taken  place  in  the  young  bark  tissue,  for  we  find  that,  in  young 
fresh  bark  tissue,  cross  bands  of  plate-like  cells,  varying  in  structure  and  the 


Fig.  25.  Piece  of  the  bark 
from  the  trunk  of  an  apple 
tree  with  the  tan  disease. 

a  the  calluses  of  the  tan  disease,  f>  frag- 
ments of  the  dry  bark  scales  covering 
the  whole.     (Grig.) 


^13 

constitution  of  their  walls,  transverse  in  curves  (np)  the  hypertrophied  tis- 
sue, v^hich,  at  the  beginning,  contains  starch. 

This  formal  and  functional  organization  of  the  bark  parenchyma  which 
determines  the  formation  of  the  bark  may  be  found  also  in  other  tree  barks, 
but  first  occurs,  so  far  as  I  have  observed,  in  the  older  axes  in  which  the 
bark  parenchyma  has  been  influenced  by  the  pressure  of  the  bark  scales 
lying  above  it.    On  this  account  I  have  called  these  bands  of  tangential  cells 

S 


Fig.  26.     Spot  on  the  trunk  of  an  apple  tree  with  the  tan  disease.     Explanation  of 
the  letters  in  the  text.     (Orig.) 

(np)   "Pressure  bands,"  which  later  suberize,  often  also  developing  plate 
cork  cells  and  cutting  off  the  bark  scales. 

I  have  had  opportunity  to  study  the  tan  disease  in  young  cherry  branches 
in  a  wet  summer  on  very  vigorous  young  trees  in  a  nursery.  Figure  2y 
shows  that  on  these  cherry  branches  the  outer  bark  had  split  or  been  torn 
open  in  broad,  irregular  stripes  (e).  An  intense  yellow  ochre  colored  mass 
(/)  could  be  recognized  at  the  ruptured  spot,  which,  when  tapped  vigorously, 
gave  off  a  powdery  dust.  The  whole  impression  given  by  these  branches 
was  as  if  they  had  been  very  thickly  covered  with  rust  fungus. 


214 


The  first  indication  of  the  disease  occurred  in  July,  when,  among  nor- 
mally growing  trunks,  the  leaves  of  some  specimens  turned  yellow  and  fell 
off.  Nevertheless  the  terminal  buds  of  the  branches  developed  a  vigorous 
August  growth  which  held  most  of  its  foliage  until  fall.     In  September  the 

outer  bark  covering  split  and  the 
surface  appeared  like  yellow  ochre 
velvet  beginning  at  the  lowest  part 
of  the  branch  and  decreasing  in  in- 
tensity toward  the  tip.  Further, 
the  fact  is  worthy  of  notice  that 
practically  only  the  luxuriantly 
growing  wild  trees  appeared  to  be 
diseased.  The  phenomena  of  the 
tan  were  only  sparsely  noticeable  in 
grafted  trees.  It  was  seen  at  once 
that  branches,  where  they  had  re- 
tained their  leaves,  had  only  a  few 
really  torn  spots  in  the  bark,  indeed 
only  closed,  warty  excrescences,  i.  e. 
the  younger  stages  of  the  disease. 
In  the  axils  of  two  year  and  much 
older  diseased  trees,  ruptured  places 
in  the  bark  (r)  occurred  less  fre- 
quently. Usually  the  individual 
centres  of  disease  appeared  there 
in  the  form  of  very  broad,  very 
liigh  yellow  ochre  cushions  running 
crosswise. 

The  investigation  of  these  cus- 
hions and  of  the  broad,  ruptured, 
discolored  surfaces  on  branches  one 
year  old  showed  at  once  marked 
correspondence  with  those  on  the 
older  ones ;  only  it  could  not  be 
seen  that  the  lenticel  cushions  give 
ofif  any  dust.  The  discolored  mas- 
ses were  found  to  be  light  brown, 
cylindrical,  wrinkled  cork  cells  with 
rounded  corners,  which  were  broken 
off  individually  or  in  small  groups. 
The  branches,  giving  off  this  dust,  seem  with  a  few  exceptions  to  be 
otherwise  healthy,  only  their  primary  bark  is  ver}--  much  broken  by  the 
considerable  separation  of  the  parenchyma  cells.  Places  with  loosened 
structure  are  found  in  the  wood  as  well  as  in  the  bark.  Cross  bands  of  duct- 
less parenchyma  wood  may  be  noticed  in  the  stages  produced  toward  the 


■k-fv   'Pi'^ 


old  clK  1 1 


Onr   year  old  and  two  year 
bianrhes  with  tan  cushions 


between  the  spht  bark  stripes.    (Orig.) 


215 

middle  of  summer.  These  are  filled  full  of  starch,  while  the  normally 
constructed  wood,  excepting  the  medullary  rays,  has  none.  Within  these 
cross  bands  the  medullary  rays  are  broadened  and  have  gummy  spots. 

The  beginnings  of  the  tan  formation  are  found  close  under  the  terminal 
buds  of  the  topmost  branches,  where  the  epidermis  is  still  uninjured,  but  is 
already  underlaid  with  cork,  possibly  five  layers  thick.  In  places,  this  pro- 
tective layer,  consisting  of  comparatively  thick  walled  cells,  corresponding 
to  plate-cork,  shows  a  change  even  in  its  first  stages,  so  that  the  cells  lying 
directly  beneath  the  epidermis  have  developed  into  parallel  rows  of  cylindri- 
cal, radially  elongated;  brovvm-walled,  full-cork  cells.  There  is  present  here, 
therefore,  the  character  of  lenticel  growth  which  Stahl^  has  already  de- 
scribed thoroughly  for  the  cherr}'  and  which  only  differs  from  his  descrip- 
tion in  that  here  the  full  cork  cushions  are  rarely  produced  under  the 
stomata. 

It  is  seen  that  an  extensive  formation  of  full  cork  can  take  place  in- 
dependently of  the  stomata  in  the  development  of  a  plate-cork  layer,  since 
several  layers  of  lenticels  are  produced  in  which  the  cork  formation  ad- 
vances inward  into  the  primary  and,  in  fact,  into  the  secondary  bark. 

As  the  shoot  of  the  current  year  becomes  older,  a  second  layer  of  plate- 
cork  appears  very  normally,  directly  beneath  the  one  first  produced.  It  has 
been  found  just  as  thick  (viz.,  5  to  7  cells)  as  the  first  whose  cells  gradually 
collapse  with  the  apparently  lessened  swelling  and  the  browning  of  the  walls. 
During  this  process  the  normal  cork  covering  of  the  cherry  trunk  appears 
to  be  differentiated  into  two  layers.  The  upper,  older  one  is  very  dense, 
since  the  cells  usually  have  so  collapsed  that  their  cavities  are  recognizable 
only  as  fine  fines ;  this  layer  passes  over  gradually  into  the  second,  later 
formed  cork  layer.  In  the  latter,  the  plate-like  cells  are  very  uniform  and 
their  wide  lumina  are  filled  with  a  watery  content  or  even  with  air.  They 
border  on  a  browned  cell  layer,  with  a  clearly  protoplasmic  wall  lining, 
which,  as  cork  cambium,  assumes  the  continued  formation  of  the  cork  layer 
occurring  in  places.  When  treated  with  sulfuric  acid,  the  composition  of 
the  oldest,  sunken,  collapsed  brown  cork  layer  is  easily  recognizable,  since 
the  cells  are  often  distended  and  show  in  places  their  original  height  and 
width,  at  times  almost  square  in  cross-section,  while  the  full  cork  cells  are 
not  changed.  With  this  treatment  the  layer,  produced  later,  rounds  out  its 
youngest  cork  cells  into  hemispheres  after  the  cork  cambium  has  been 
destroyed. 

In  the  formation  of  the  many  layers  of  lenticels,  the  development  of 
such  elements  is  repeated  in  the  secondary  cork  layer  underneath  the  first 
centres  of  full  cork. 

The  second  case  of  lenticel  formation,  not  connected  with  stomata,  is 
illustrated  in  figure  28.    This  shows  the  cross-section  of  a  new  structure  on 


1   Stahl,    Entwicklungsgeschichte    und    Anatomie    der    Lenticelle.     Bot.    Z.    1873, 
No.  36. 


2l6 

the  barked  cherry  trunk.  We  must  imagine  that  all  the  tissue  here  shown 
in  the  form  of  a  callus  covered  with  bark  rests  upon  the  old  wood  cylinder 
from  which  the  bark  has  been  removed. 

Since  reference  to  the  anatomical  processes,  leading  to  the  formation  of 
this  new  tissue  on  the  exposed  wood,  is  made  in  the  chapter  "Wounds" 
(bark  wounds),  we  will  mention  here  only  the  fact  that,  if  at  any  given  time 
the  bark  is  removed  from  a  tree,  the  newest  cambium,  thus  exposed,  begins 
to  grow  again  and  covers  the  wounded  surface  with  a  parenchymatous  tissue 
layer.  This  parenchymatous  covering  is  increased  by  the  later  appearance 
of  a  constant  meristematic  layer.     The  inner  surface  of  this  layer  forms 


Fig- 


Newly  formed  wood  and  bark  body  on  the  bark  wound  of 
The  bark  shows  a  lenticel  excrescence.     (Orig.) 


cherry  trunk. 


normal  cambium,  which  gives  rise  to  woody  tissues  toward  the  centre  and 
back  towards  the  periphery. 

Figure  28  is  a  new  structure  several  months  old  which,  in  the  form  of  a 
broad  wrinkled  callus,  has  grown  on  the  cambium  of  an  experimentally 
barked  sweet  cherry  trunk.  The  old  wood  of  the  barked  trunk  has  been 
omitted  in  the  drawing;  it  would  join  on  at  hp.  The  cambial  zone  (c) 
has  sharply  differentiated  this  tissue  into  wood  and  bark.  The  wood,  where 
it  rests  on  the  old  trunk,  has  a  parenchymatous  structure  {hp)  ;  which  later 
passes  over  into  a  vascular  new  wood  {nh)  forming  libriform  fibres.  The 
structure  of  the  bark  is  at  first  irregular  and  corresponds  to  the  formation 
of  wood  which  only  gradually  obtains  its  normal  structure,   for  the  hard 


bast  bodies  begin  in  the  form  of  individual,  short  elements  (hb)  with  wide 
lumina  and  only  later  grow  out  from  the  cambium  as  connected  groups  of 
elements  (hb'^)  elongated  like  fibres^^. 

The  bark  of  the  new  structure  has  formed  a  protective  cork  layer  in 
its  peripheral  parenchymatous  layers  which  has  gradually  grown  very  thick. 
At  first  only  plate  cork  was  formed ;  but  later,  in  different  places,  full-cork 
masses  (Ik)  developed  instead  of  the  plate  cork  cells,  splitting  the  covering 
(k)  composed  of  the  latter  cells  and  pressing  the  cork  cambium  inward  (kk) 
by  their  increase  which  extends  further  and  further  backward. 

The  full  cork  began  to  form  when  the  whole  peeled  surface,  for  the 
purpose  of  further  investigation,  was  enclosed  in  a  glass  cylinder,  partly 
filled  with  water.  While  this  lenticel  out-growth,  produced  from  the  phello- 
gen,  was  only  slightly  noticeable  in  those  parts  of  the  bark  which  remained 
in  the  air,  it  had  developed  an  unusual  luxuriance  below  the  surface  of  the 
water. 

The  tan  disease  of  the  cherry  is  therefore  an  abnormal  increase  of  the 
normal  lenticel  formation.  So  many  and  such  extensive  full-cork  cushions 
are  produced  close  to  one  another  that  they  unite,  pushing  off  the  epidermis 
in  large  connected  tatters  and  appearing  as  uniform  velvety  surfaces  cover- 
ing a  large  part  of  the  branch.  The  outermost  layers  of  the  full  cork  cush- 
ions are  so  loose  that  the  connection  between  the  peripheral  cells  is  broken 
by  a  slight  blow  when  the  air  is  dry;  this  explains  the  discoloration  and  the 
dust  flying  from  places  affected  with  the  tan  disease,  if  the  spots  be  touched 
or  shaken  vigorously.  This  scattering  of  the  dust  increases  with  the  num- 
ber of  full  cork  cells  lying  above  one  another  and  cushions  composed  of 
parallel  rows  of  full  cork,  20  cells  deep,  have  been  observed.  In  this  case 
the  process  of  elongation  has  included  the  entire  thickness  of  the  primary 
phelloderm  so  that  the  later  formed,  secondary  full  cork  lies  directly  under- 
neath this,  i.  e.,  no  separating  plate  cork  layer  is  left  between  the  difl:erent 
generations. 

The  appearance  of  the  tan  disease  will  have  to  be  traced  to  the  super- 
ubundance  of  ivater  in  the  bark  body.  This  local  excess  of  water  may  be 
due,  on  the  one  hand,  to  supplying  the  roots  abundantly  with  water,  especially 


1  Reference  should  be  made  in  passing-  to  the  illustration  of  the  beginnings  of 
tuber  gnarls  not  in  any  way  whatever  connected  with  the  tan  disease  but  shown 
in  the  drawing-  at  B.  They  are  produced  by  a  local  accumulation  of  plastic  material 
as,  for  example,  the  isolated  wood  in  the  bark  of  the  new  structures  formed  near 
the  wounds  of  various  trees  (cherry,  apple,  pear  and  pine).  At  the  centre  of  such 
wood  formations  with  a  spherical  wart-like  structure  may  be  recognized  one  or 
more  hard  bast  cells. 

The  case  in  which  hard  bast  cells  (especially  diseased  ones)  are  overgrown  by 
tissue  is  of  very  frequent  occurrence  in  injuries  of  very  different  origin.  This  over- 
growth consists  usually  only  of  a  covering  of  plate-like  cork  cells  several  layers 
thick.  In  some  cases,  however,  instead  of  the  rapidly  transformed  cork  cambium, 
a  persistently  active  cambial  layer  is  formed  which  deposits  wood  elements  toward 
the  inside  and  bark  elements  toward  the  outside.  Such  a  case  is  represented  in  the 
wart-like  tissue  excrescence  (B)  at  (u')  while  at  (u)  in  the  left  part  of  the  figure 
(A)  may  be  seen  only  a  cork  covering  around  one  of  the  isolated  hard  bast  cells 
first  produced.  The  bark  rays  pass  around  these  new  structures  on  both  sides  as  if 
around  some  foreign  body. 


2l8 

those  of  vigorous  individuals ;  on  the  other,  by  the  lessened  transpiration  of 
the  bark  because  of  greater  humidity.  Such  conditions  in  the  cherr}^  lead 
to  lenticel  excrescences  as  is  proved  by  experimentally  producing  an  accum- 
ulation of  full  cork  in  parts  of  the  bark  kept  under  water  and  further  by 
observing  specimens  naturally  diseased.  In  this  way  it  was  discovered  that 
the  cork  excrescences  preferred  the  youngest,  well-leaved  internodes  in 
which  the  bark  formed  folds.  Such  folds  were  produced,  for  example,  in 
places  where  the  vascular  bundles  of  the  leaf  left  the  axial  cylinder  and 
pushed  out  the  bark  when  passing  into  the  petioles. 

Some  other  observations  have  been  made  showing  that  the  decreased 
evaporation  due  to  increased  moisture  favors  lenticel  formation.  Thus 
vStapf^  in  his  studies  on  the  potato,  mentions  that  stomata  develop  into  lenti- 
cels  if  transpiration  is  arrested.  Further,  Haberlandt^  found  that  in  the 
horizontal  branches  of  different  trees  (the  linden,  elm,  honey  locust,  etc.) 
the  lenticels  always  occurred  in  greater  numbers  on  the  under  side  than  on 
the  upper  side,  although  counting  the  stomata  on  both  sides  gave  approxi- 
mately eciual  numbers.  The  under  side  of  the  branch,  inclined  toward  the 
earth,  will  surely  transpire  less  than  the  upper  side,  because  of  the  greater 
proximity  of  the  soil  and  the  lesser  supply  of  air. 

The  tan  cushions  in  plum  trees  are  essentially  similar  to  those  observed 
in  the  cherry.  As  yet  they  have  been  observed  only  on  old  specimens  with 
diseased  roots.  I  have  known  of  only  the  initial  stages  in  apricots.  In  all 
varieties  of  stone  fruits  the  cork  excrescences  were  accompanied  by  marked 
processes  of  bark  loosening  which  in  part  resulted  in  the  shoving  of  the 
bast  cords  towards  the  outside.  In  young  wood  a  weakly  developed  wood 
ring  and  a  reduction  of  hard  bast  bundles  to  isolated  wide  bast  cells,  filled 
with  a  brownish-red  gummy  substance,  was  often  noticed  where  the  tan 
disease  had  not  broken  out.  Traces  of  gummosis  were  present  everywhere, 
and  at  times  rich  gum  centres  were  found.  In  cherries,  the  especial  sus- 
ceptibility of  certain  varieties  to.  the  tan  disease  may  be  recognized  when 
different  varieties  are  planted  close  to  one  another,  as,  for  example,  in  the 
"black  ox  heart"  and  in  "Winkler's  white  ox  heart." 

All  the  cases  which  I  have  known  originated  on  heavy  soils  or  marshy 
meadows.  The  history  of  some  cases  showed  that  the  diseased  trees  had 
been  fertilized  with  stable  manure  or  liquid  manure.  These  statements  in 
connection  with  the  anatomical  conditions  lead  me  to  explain  the  tan  dis- 
ease as  the  result  of  an  excessive  water  supply  from  the  soil.  When  trees 
are  attacked  during  vigorous  growth,  they  undergo  such  a  disturbance  that 
the  evaporation  from  the  top  is  not  sufficient  to  remove  the  excess  of  water. 
The  decreased  leaf  activity,  or  a  partial  loss  of  foliage  due  to  atmospheric 
influences  or  to  pruning,  should  receive  especial  consideration.    These  cork 


1  Stapf,  Beitrage  zur  Kenntnis  des  Einflusses  geanderter  Vegetationsbedingun- 
gen  etc.  Verh.  d.  Zool-Bot.  Ges.  Wien;  cit.  Bot.  Jahresb.,  VI.  Jahrg.,  Section  I,  p.  214. 

2  Haberlandt,   Beitrage   zur  Kenntnis   der   Lenticellen.      Sitzungsber.   d.   Akad. 
d.  Wiss.  in  Wien,  Vol.  LXXII,  Section  I.    July  No.  1875. 


219 

excrescences  and  phenomena  of  loosening  of  bark  and  wood  occur  also  in 
healthy  trees,  with  corresponding  conditions  in  the  place  of  growth,  but  in- 
crease in  the  tan  disease  to  an  extreme  manifestation. 

The  remedies  are  apparent,  and  extensive  aeration  of  the  soil  chiefly 
promises  success. 

The  Girdling  of  the  Red  Beech. 

According  to  the  description  given  by  Th.  Hartig^  the  disease  named 
in  this  heading,  which  I  have  not  known  from  my  own  observation,  should 
be  included  here.  Hartig  found  in  a  beech  grove,  20  years  old,  that  many 
trunks,  beginning  about  one  to  two  metres  above  the  ground  and  extending 
to  the  top  of  the  tree,  were  surrounded  at  intervals  of  30  to  100  cm.  with  an 
almost  circular,  somewhat  spirally  running  roll  as  thick  as  a  quill.  These 
rolls  were  proved  to  be  overgrowth  phenomena  in  wounds  caused  originally 
by  lenticel  excrescences.  The  formation  of  cork  had  extended  further  and 
further  backward  into  the  bark  until  it  reached  the  wood  and  for  a  year  or 
two  years  the  formation  of  wood  was  arrested  at  this  point.  No  appreciable 
injury  due  to  the  disease,  which  occurs  only  in  very  well  grown  sapling 
groups  and  there  especially  on  trunks  of  the  first  or  second  class,  could  be 
confirmed. 

Root  Disease  of  the  True  Chestnut  (Mai  nero). 

This  disease,  very  common  in  France,  manifests  itself,  according  to 
Delacroix-,  most  strikingly  in  damp,  impervious  soil  and  in  grafted  trees. 
The  leaves  lose  their  dark  green  color  and  the  branches  begin  to  dry  up  at 
the  tips.  The  nuts  only  partially  ripen  and  remain  in  the  burrs.  Delacroix 
found  that  the  mycorrhiza  of  the  fine  roots  had  changed,  as  if  diseased,  and 
had  assumed,  as  he  thinks,  a  parasitic  character  because  the  amount  of 
humus  was  deficient.  The  mycelium  then  grows  into  the  larger  roots  up  to 
the  base  of  the  trunk  and  then,  in  the  trunk,  upward  to  the  branches.  A 
secretion  containing  tannic  acid  results  from  the  injuries  to  the  roots  and 
trunk.  In  this  weakened  condition,  the  trees  ofifer  a  suitable  centre  for  in- 
fection by  other  parasites,  as,  for  example,  Polyporns  sulfureus  and  Armil- 
laria  mellea  as  well  as  Sphaerella  maculiformis. 

I  include  this  disease  at  this  point  because  of  the  results  of  a  thorough 
investigation  which  I  had  an  opportunity  to  make  with  material  from  Ren- 
nes.  The  explanatory  letter  sent  by  M.  Crie  stated  that  the  dying  branch- 
wood  had  an  odor  indicating  fermentation  if  broken,  or  the  bark  removed, 
and  he  suspected  a  conversion  of  the  tannin,  whereby  glucose  and  alcoholic 
fermentation  took  place.  The  pieces  of  branches  sent  were  thickly  covered 
with  Hchens  and  the  leaves  showed  a  browning  which  extended  from  the 
edge  deep  into  the  intercostal  fields. 


1  Hartig-,   Th.,   Vollstandig-e  Naturgeschichte  der  forstlichen   Kulturpflanzen,   p. 
211.    Berlin  1852. 

2  Delacroix,   G.,   La  maladie   des  chataigniers   en   France.     Bull   soc.   mycol.   de 
France  XIII,  1897,  p.  242. 


The  roots  decided  the  matter.  They  had  a  rough  appearance  due  to  a 
great  many  black,  hard  cushions,  differing  in  size  and  flattened  into  hemi- 
spheres, which  covered  the  upper  surface.  If  treated  with  a  solution  of  caustic 
potash,  when  the  tannin,  occurring  as  a  flocculent  precipitate,  turned  a  wine 
red  to  brown,  cross-sections  show  that  the  bark  excrescences  were  covered  by 
a  normal  cork  layer.  The  primar}'  bark  had  developed  parenchymatous  ex- 
crescences the  cells  of  which,  arranged  in  radiating  rows,  had  colorless  walls, 
apparently  dissolving  with  difficulty  in  sulfuric  acid,  and  had  a  very  firm 
brown  content.  These  bark  excrescences  were  later  cut  off  by  an  hourglass- 
like, pl&te  cork  lamella,  distending  the  outer  cork  layer,  and  were  forced  out 
over  the  upper  surface  of  the  root  as  calluses  by  the  subsequent  growth  of 
the  inner  bark.     The  healthy  bark  was  filled  with  starch. 

In  the  material  sent  me  the  branches  had  only  very  slightly  raised  bark 
excresences,  possibly  34  to  ^  mm.  broad,  flattened  and  hemispherical.  In 
them  was  found  the  beginning  of  a  many  layered  lenticel  excrescence  such 
as  had  been  obsen'ed  in  great  numbers  in  the  cherry  with  the  tan  disease. 
The  constitution  of  the  leaves,  still  remaining  on  the  branches,  had  already 
indicated  the  diseased  condition  of  the  roots.  They  showed  a  browning  and 
dr)dng  up  of  the  parenchyma  in  the  intercostal  fields,  extending  from  the 
edge  toward  the  mid-rib.  Finally,  the  parenchyma  was  green  only  in  the 
immediate  proximity  of  the  ribs.  The  black,  yellow-edged,  roundish  spots, 
scattered  over  the  sick  leaves  and  containing  various  fungi  colonies,  musr 
be  considered  as  secondary  phenomena.  The  condition  found  in  the 
branches  in  connection  with  the  excrescences  on  the  roots  brings  the  disease, 
which  has  been  termed  "Mai  nero,"  into  the  group  of  the  tan  diseases.  Ac- 
cordingly, the  choice  of  fibrous  or  good  friable  land  which  has  a  constant, 
abundant  soil  ventilation  will  be  the  best  precaution  against  the  disease. 

The  Rootblight  of  Sugar  and  Fodder  Beets. 

As  rootblight  we  designate  a  disease  of  the  tissues  which  can  set  in 
even  when  the  young  seedlings  unfold  their  cotyledons  or  begin  to  open  the 
first  leaflets.  A  black  spot  appears  on  the  stem  below  the  seed  leaves  which 
spreads  further  toward  the  root  end  (less  toward  the  cotyledons)  and  be- 
comes depressed.  Even  if  the  young  seedling  has  not  reached  the  upper 
surace  of  the  soil,  the  first  stages  of  the  disease  can  be  recognized.  Vanha 
observed  that  the  tissue  becomes  glassy  before  turning  brown.  The  little 
plants  begin  to  wilt  and  usually  break  at  the  diseased  point.  Death  results 
at  once.  If  the  disease  is  limited  to  a  small  area  on  the  hypocotyledon  stem 
and  the  plant  does  not  succumb,  the  depressed  place  will  heal  and  a  normal, 
later  growth  follows.  Because  the  diseased  place  blackens  and  often 
shrinks  to  the  size  of  a  thread  below  the  seed  leaves  the  practical  grower 
also  calls  the  appearance  "black  leg"  or  the  "threads."  The  same  term  is 
used  as  well  in  the  blackening  and  softening  of  the  hypocotyledons  of  cab- 
bage plants,  which  arise,  however,  from  other  conditions. 


It  is  noteworthy  that  often  great  numbers  of  beet  seedUngs  are  diseased, 
and  yet  frequently  perfectly  healthy  plants  may  be  formed  close  to  the  dis- 
eased ones.  It  should  be  emphasized  further  that,  when  the  disease  develops  at 
all  it  is  found  simultaneously  in  all  parts  of  the  field,  and  that,  as  a  rule,  iso- 
lated spots  are  not  attacked  in  the  middle  of  diseased  fields.  As  the  plants  be- 
come older,  the  rootblight  ceases.  The  healed  plants  usually,  however,  remain 
below  the  healthy  ones  in  size  and  sugar  content  and  show  a  tendency  to- 
ward root  splitting  and  other  deformities.  Stoklasa^  emphasizes  the  fact 
that  all  varieties  are  not  equally  susceptible  to  rootblight. 

The  disease  has  been  known  since  the  increase  in  beet  culture  in  the 
30's  of  the  last  century  and,  according  to  Stift^,  the  discussion  as  to  the 
cause  of  the  phenomenon  began  in  1858  at  the  meeting  of  the  beet  sugar 
manufacturers  of  the  Zollverein.  At  that  time  the  opinion  was  expressed 
by  practical  growers  that  the  trouble  was  due  to  the  physical  condition  of 
the  soil,  i.  e.,  a  too  great  solidity  of  the  soil.  It  was  emphasized  that  root- 
blight was  found  only  where  the  upper  surface  of  the  soil  was  bard  and  had 
not  been  loosened  on  which  account  a  thorough  cultivation  and  stirring  were 
advisable. 

At  the  time  scientists  took  up  the  question,  the  parasitic  theory  was 
already  at  the  crest  of  its  development.  At  first  Julius  Kiihn  in  1859  gave 
expression  to  the  opinion  that  the  moss  button  beetle  (Atomaria  linearis 
Stephn.)  attacked  the  plants,  and,  where  it  had  eaten,  the  rootblight  made  its 
appearance.  I  have  observed  something  similar^.  The  centipede  and  such 
animals  were  also  cited  as  causes.  This  theory  which  prevailed  for  many 
years  was  first  upset  when  Hellriegel  found  that  the  disease  could  be  pro- 
duced without  animal  injury  and  in  many  cases  came  from  the  beet- 
seed.  As  a  result  he  advised  a  soaking  of  the  beet-seed  for  20  hours  in  a 
one  per  cent,  carbolic  acid  solution*.  Karlson,  at  about  the  same  time, 
ascribed  the  phenomenon  to  a  special  fungus  and  in  this  emphasized  the  fact 
that  only  weak  specimens  succumbed  to  rootblight.  Seedlings  from  very 
good  seed  or  those  which  were  strengthened  by  an  energetic  growth,  would 
not  be  overcome  by  the  fungus  carried  in  these  seed  balls  (Scleranthus)^. 
The  experiments  in  sterilizing  with  carbolic  acid  and  with  copper  sulfate 
showed  a  decrease  of  the'rootblight.  In  spite  of  the  advantage  due  to  ster- 
ilization, Karlson  lays  especial  stress  on  the  selection  of  especially  strong 
seedlings  and  lays  the  responsibility  for  the  spread  of  rootblight  on  our 
present  cultural  methods*',  which  aim  only  at  obtaining  large  amounts  of 
seed  and  neglect  the  quality. 


1  Stoklasa,  Jul.,  Wurzelbrand  der  Zuckerriibe.  Centralbl.  f.  Bakteriologie.  Sec- 
tion II,  1898,  p.  687. 

~  Stift,  Anton,  Die  Krankheiten  der  Zucl\:ei-riibe.  Wien  1900.  Verlag  des  Cen- 
tralver.  f.  Riibenzuckerindustrie. 

3  Zeitschr.  f.  Pflanzenkr.,  1892,  p.  278. 

4  Hellriegel,  Ueber  die  Schadigung  junger  Riiben  durch  Wurzelbrand  etc. 
Deutsche  Zuckerindustrie,  Jalirg.  XV,  p.  745.    Biedermann's  Centralbl.  1S90.  p.  647. 

f*  HoUrung  also  found  a  lesser  degree  of  disease  in  sowing  large  beet  seed  balls 
(Scleranthus).     Dritt.  Jahresb.  d.  Versuchsstat.  f.  Nematodenvertilgung.    1892. 
6  Blatter  fiir  Zuckerriibenbau,  1900,  No.  17. 


The  theory  of  seed  steriHzation  was  further  developed  by  Wimmer,  one 
of  Hellriegel's  collaborators.  Of  the  different  substances  used  in  sterilizing, 
carbolic  acid  was  proved  to  be  the  most  advantageous  and,  in  fact,  when 
used  in  the  one  per  cent,  solution  of  "Acidum  carbolicum  crudum  lOO  per 
cent.  Pharm.  Germ.  II."  To  one  part  by  weight  of  seed  should  be  reckoned 
about  6  to  8  parts  by  weight  of  liquid.  A  warm  water  solution  was  proved 
favorable  as  well  as  a  cold  water  solution\ 

While  Wimmer  left  the  question  undecided  as  to  the  influence  of  the 
weather  and  the  soil  constitution  Holdefleiss  held  to  the  theory  that  this 
and  not  parasitism  caused  rootblight.  In  soils  favorable  to  the  disease,  he 
usually  found  an  abundant  amount  of  ferrous  oxid,  but  comparatively  little 
calcium.  In  this  the  tendency  to  choking  with  mud  and  incrustation  of  the 
soil  are  unmistakable  and  the  discovery  that  rootblight  was  cured  by  abun- 
dant hoeing  was  in  accordance  with  this.  On  this  account  Holdefleiss 
recommends,  in  addition  to  a  continued,  open  condition  of  beet  soils,  a  rich 
addition  of  burned  (quick)  lime  (12  to  15  centner  German  per  acre)-  which 
is  given  with  the  best  results  to  the  first  grown  crops  and  not  directly  to  the 
beet.  Loges^  had  good  results  from  the  addition  of  7  cent,  of  quick-lime  per 
acre.  As  a  further  contributory  factor,  Ilollrung  emphasizes  a  lower  temper- 
ature and  the  fact  that  rootblight  never  extends  above  the  surface  of  the  soil 
to  the  aerial  parts  of  the  axis  which  are  exposed  to  air  currents.  He  asserts 
definitely  that  rootblight  is  brought  about  by  physical  and  chemical  causes 
making  themselves  felt  in  cold  soil,  impermeable  to  air  currents.  The  theory 
that  the  soils,  in  which  black  leg  of  the  beet  occurs,  are  easily  choked  with 
mud  and  become  hard  is  substantiated  by  Marek  and  Krawczynski.  Ac- 
cording to  Stiffs  statement  (loc.  cit.  10  to  20)  in  such  a  soil  77.25  per  cent, 
fine  sand  was  found. 

Opposed  to  these  theories,  shared  by  many  other  investigators,  the  par- 
asitic theory  was  still  maintained  and  found  its  most  active  defender  in 
Frank.  Frank,  with  Kriiger,  from  1892  on,  made  various  experiments  and 
determined  that,  besides  the  Pythium  de  Baryanum  found  by  Lohde,  and  oc- 
curring in  many  diseases  of  seedling  plants  from  very  different  genera,  be- 
sides the  Rhicoctonia  violacea  mentioned  by  Eidam,  there  was  a  specific 
beet  fungus,  Phoma  Betae  Frank,  "which  not  onlj^  causes  heart  and  dry  rot 
of  the  mature  beet,  but  also  the  rootblight  of  the  young  beet  roots."''  Re- 
peated discoveries  in  field  experiments,  however,  soon  showed  even  this 
investigator  that  weather  and  soil  conditions  exert  a  decisive  influence.  "It 
is  still  undecided  whether  the  seedUng  thereby  becomes  more  susceptible  to 
the  fungus  attack  or  whether  this  is  not  sufficiently  explained  by  the  fact 
that  cold  weather  delays  the  growth  and  the  plant  remains  unusually  long 


1  Hollrung,  in  Zeitschr.  f.  Rubenzuckerindustrie  i.  D.  R.    Vol.  46.    Part  482. 

2  J.   Centner  in  German   weights   equals   50   kg-,   or   approximately   112   English 
pounds. 

3  Bericht.  d.  Landw.  Versuchsstation  Posen.    1891. 

4  Frank,  A.  B.  Kampfbuch  gegen  die  Schadlinge  unserer  Feldfruchte.     Berlin, 
Paul  Parey,  1897,  p.  117. 


223 

in  an  immature  condition  which  is  especially  susceptible  to  the  disease,  while 
seedlings  forced  by  heat  pass  rapidly  through  the  susceptible  stage  and  thus 
escape  the  danger." 

In  this  explanation,  after  many  modifications  of  Frank's  original  state- 
ment, is  expressed  the  theory  that  besides  this  specific  excitor  of  disease, 
Phoma,  a  definite  degree  of  susceptibiUty  of  the  beet  seedling  must  exist  for 
the  production  of  rootblight.  Sorauer  held  this  point  of  view  earlier  since 
he  proved  that  rootblight  can  exist  without  the  presence  of  Phoma  and  that, 
instead  of  this,  bacterial  growth  accompanies  the  disease.  We  owe  the  most 
thorough  investigations  of  the  bacteria  of  rootblight  to  Hiltner,  whose  recent 
studies  we  will  consider  with  great  thoroughness  after  sketching  Stoklasa's 
theory.  According  to  Stiffs  statements  (loc.  cit.  p.  17)  Stoklasa  admits  that 
bacteria  can  produce  rootblight  in  beets,  and  he  considers  the  following 
species  capable  of  doing  so: — Bacillus  subtilis,  B.  liqiiefaciens,  B.  fluore- 
scens  liquefaciens,  B.  mesentericiis  z'ulgatus  and  B.  mycoides;  Linhardt  de- 
clares the  latter  to  be  the  essential  cause  of  injury.  Recently  Pseudomonas 
campestris  has  been  added  to  these.  Stoklasa  considers  that  the  above  men- 
tioned atmospheric  and  soil  conditions  produce  a  predisposition  in  the  beet 
seedlings.  He  turned  his  attention  especially  to  oxalic  acid,  normally  formed 
by  the  life  process  of  the  plant  as  potassium  oxalate.  Soluble  oxalates, 
which  act  as  poisons,  are  transformed  into  an  insoluble  calcium  oxalate,  if 
calcium  oxide  can  be  taken  from  the  soil  by  the  root  hairs.  By  thus  neut- 
ralizing the  oxalic  acid  its  retarding  action  on  the  process  of  assimilation 
ceases  and  the  plant  recovers.  If  much  nitric  acid  is  present  in  the  soil  or  is 
added  in  excess  (strong  fertilisation  with  nitrate  of  soda),  an  hastened  de- 
velopment takes  place  at  any  rate,  but  at  the  same  time  the  oxalic  acid  con- 
tent increases.  In  such  a  case,  if  the  young  beet  plant  cannot  take  up  suf- 
ficient calcium,  it  becomes  predisposed  to  rootblight. 

As  already  said,  we  owe  the  most  thorough  study  of  the  relation  of  bac- 
teria to  this  disease  to  Hiltner  and  Peters^  These  investigators  made  a 
number  of  experiments  and  found  that  there  are  soils  which  almost  never 
show  any  rootblight  and,  conversely,  there  are  others  in  which  the  disease  al- 
most always  appears.  They  concluded  from  this,  that  many  soils  are  in  a  con- 
dition to  lend  a  certain  protective  power  and  they  perceive  that  this  pro- 
tective peculiarity  is  the  ability  of  the  immunizing  soil  to  provide  the  outer- 
most cell  layers  of  the  roots  of  the  beet  seedling  with  such  micro-organisms 
as  can  prevent  the  penetration  of  fungi  and  bacteria  producing  rootblight. 
Hiltner  and  Peters  call  this  protective  sheath,  which  they  had  observed 
similarly  in  peas,  "Bacteriorhiza."  If  its  formation  be  prevented  by  steri- 
hzing  the  soil  and  killing  the  protective  soil  organisms,  in  case  the  seed  had 
not  been  previously  sterilized,  the  fungi  and  bacteria  causing  rootblight 
could  enter  the  young  seedlings  and  destroy  them. 


1  Hiltner,  L.,  and  Peters,  L.,  Untersuchung-en  iiber  die  Keimlingskranklieiten 
der  Zucker-  und  Runkelruben.  Arb.  d.  Biolog.  Abt.  f.  Land-und  Forstwirtsch.  am 
Kais.  Gesundheitsamt,  Vol.  IV,  Part  3,  1P04,  p.  207. 


.    224 

The  words  of  Hiltner  and  Peters  themselves  best  show  how  Httle  the 
organisms  per  sc  are  to  be  feared  and  how  the  chief  cause  of  the  disease  is  to 
be  sought  in  the  conditions  making  the  plants  susceptible.  In  speaking  of 
the  results  of  their  experiments,  they  say  (loc.  cit.  p.  249)  "this  result,  how- 
ever, shows  that  the  production  of  diseased  seedlings  in  the  seed  bed  presents 
a  rather  complicated  phenomenon.  This  cannot  be  laid  exclusively  to  the  face 
(heretofore  almost  universally  accepted)  that  parasitic  fungi  or  bacteria  ac- 
cumulate on  the  seed  balls,  then  passing  over  to  the  roots,  for  these  organ- 
isms in  themselves  cannot  cause  the  diseased  conditions  of  the  beet.  Only 
after  the  resistance  of  the  roots  has  been  weakened  by  the  influence  of  cer- 
tain substances,  viz.,  oxalates,  can  otherwise  harmless  parasites  attack  them." 

According  to  Hiltner's  theory,  the  substances  or  circumstances  predis- 
posing a  plant  to  disease  are  produced  by  the  decomposition  of  the  tissue  in 
the  seed  balls,  either  on  the  field  as  a  result  of  unfavorable  weather,  or  later 
in  storage  because  of  too  great  warmth. 

A  work  by  Sigmund'  reports  upon  the  advance  given  to  the  occurrence 
of  rootblight  by  the  fact  that  the  micro-organisms  especially  concerned  in 
it  (Phoma  and  Bacillus  mycoides)  find  certain  organic  compounds  in  the 
nutrient  solution  of  the  host.  After  he  had  emphasized  the  fact  that  the 
parasites  are  not  able  alone  to  increase  the  disease,  he  mentions  that  the 
number  of  diseased  beet  seedlings  can  be  increased  if  glycocol,  uric  acid, 
asparagin,  hippuric  acid,  leucin,  etc.,  are  found  in  the  nutrient  solutions  of  the 
micro-organisms  named  and  the  beet  balls  are  soaked  in  this  nutrient  so- 
lution. 


In  this  important  disease  we  have  simply  listed,  first  of  all,  the  various 
theories  and  results  of  investigations  as  they  have  appeared  from  time  to 
time,  in  order  to  show  that  with  all  observers,  in  spite  of  their  very  different 
points  of  view,  one  statement  is  found  running  through  all  their  discussions 
like  a  red  line,  viz.,  the  influence  of  the  soil'-.  This  influence  shows  itself 
most  distinctly  in  heavy,  binding  soils.  It  can  make  itself  felt  also  on  other 
soils,  if  they  are  encrusted  for  any  reason  whatever.  The  prime  factor  under 
such  conditions  is  the  scarcity  of  oxygen.  At  present  we  cannot  say  defi- 
nitely what  processes  are  started  in  the  soil,  seeds  and  the  young  plants.  In 
the  same  way,  no  definite  decision  can  be  made  as  to  whether  rootblight  is  a 
constitutional  disease,  i.  e.  a  deflection  of  the  normal  life  functions  leading 
to  tissue  decomposition,  or  a  parasitic  process,  i.  e.  a  process  producing  the 
same  result  but  caused  by  the  co-operation  of  micro-organisms.  If,  as  \ye 
believe,  in  the  majority  of  cases  the  latter  should  be  granted,  we  must  bear 
in  mind  emphatically  the  fact  that  these  organisms,  no  matter  whether  fungi 


1  Sigmund,  Wilh.  Beitriige  zur  Kenntnis  dcs  Wurzelbrandes  der  Rube.  Natur- 
wissensch,  Zoitschr.  f.  Land-  und  Forstwirtschaft,  190f>,  ]).  212. 

-  Further  material  from  practical  sources  may  be  found  in  the  annual  reports 
of  the  Special  Committee  for  I'lant  Protection.  (Jahresberichte  des  Sonderaus- 
schusses  fur  I'flanzenschutz.  Deutsch.   Landw.-  Gesellscli.   1892-1905). 


225 

or  bacteria,  can  only  destroy  the  seedlings  where  they  have  some  predis- 
position to  take  up  such  organisms.  This  predisposition  is  the  product  of 
the  soil  in  which  they  are  grown  under  definite  atmospheric  conditions. 

Therefore,  the  soil  condition  is  always  the  first  cause  afifecting  the  as- 
similatory  process  and  inducing  rootblight.  The  question  wdiether  this  affec- 
tion always  takes  place  with  an  excess  of  free  oxalic  acid  and  whether  the 
abundance  of  the  acid  acting  poisonously  is  due  to  the  formation  of  more 
acid  by  the  plant  body  or  that  less  acid  is  oxidized  because  of  a  scarcity  of 
oxygen,  may  be  left  for  later  investigation.  It  is  enough  for  our  purpose  to 
know  that  the  disease  is  a  result  of  a  binding  consistency  of  the  soil  under 
unfavorable  atmospheric  conditions,  i.  e.  cold,  wet  weather. 

We  will  now  return  to  the  statements  of  practical  workers,  who,  from 
the  beginning,  have  insisted  that  the  cause  of  rootblight  lies  in  the  condition 
of  the  soil. 

When  citing  these  expressions,  we  come  to  the  self-evident  regulations 
for  fighting  it.  Briem  reports  a  case  from  the  years  1904-1905^.  On  a  newly 
broken  field  near  Prague  in  1904,  with  cold,  wet  weather,  and  a  consequent 
slow  growth,  beets  were  extensively  root  hlighted  although  until  that  time 
the  phenomenon  had  been  rare.  Also,  the  beets  did  not  revive  completely 
until  later.  The  same  field  in  the  following  year,  after  a  rich  fertilizing  with 
potassium,  nitrates  and  phosphates,  was  again  planted  with  commercial  beets. 
As  a  result  of  the  very  wet,  cold  weather,  the  seed  sprouted  only  at  the  end 
of  two  weeks  (on  the  24th.  of  April).  It  was  feaned  that,  with  the  weakened 
growth  resulting  from  the  cold  nights,  rootblight  would  again  set  in.  Fort- 
unately this  did  not  happen  and  the  warm  days,  coming  at  the  beginning  of 
May,  soon  caused  the  rapid,  vigorous  unfolding  of  the  first  pair  of  leaves. 
However,  when,  on  the  20th  of  May,  a  violent  rain  had  beaten  the  field 
down  unusually  hard  so  that  water  could  only  soak  in  very  slowly,  manv 
seedlings  showed  the  beginning  of  rootblight  after  five  days.  This  example 
of  the  result  of  a  sudden  exclusion  of  the  air  from  soil,  beaten  hard  by  rain, 
shows  therefore  that  it  is  primarily  advisable  to;  keep  the  upper  surface  of 
the  soil  constantly  open  by  cultivation.  Secondarily,  even  if  the  soil  contains 
lime,  a  further  supply  of  quick  lime  must  be  given.  The  effect  of  the  lirne 
must  not  always  be  considered  as  a  nutritive  means,  but  as  a  mechanical  one 
for  improving  the  soil  since  it  increases  its  friability.  Superphosphate  has 
given  good  results-.  In  fields  liable  to  these  conditions,  increased  attention 
should  be  given  to  the  use  of  as  vigorous  seed  as  possible. 

If  one  wishes  to  sterilize  the  seed  which,  according  to  our  theory,  is  of 
very  little  advantage'',  a  carbolic  acid  solution  should  be  used.  For  the 
sterilization  of  one  hundred  and  twelve  pounds  of  beet  seeds  1.5  k.  carbolic 


1  Briem,  H.,  Wurzelbrandentdeckung  und  kein  Ende.  Blatter  f.  Zuckerrlibenbau 
V.    .June   15,   1905. 

^  Zeitschr.  f.  Pflanzenkrankh.,  1896.  p.  54  and  p.  340.  Landwirt,  1896,  Nos.  15,  17, 
21.    Jahresber.  d.   Sonderausschusses  f.  Pflanzenschutz,  1902. 

3  Hiltner  in  Mitteil.  d.  pflanzenphysiolog.  Versuchsstat.  Tharand.  Sachs,  landw. 
Zeit.  1904,  Nos.  16-18.   • 


226 

acid  (Acidum  carholkum  liquidiim  crudum  lOO  %)  or  the  more  expensive, 
pure  crystallized  acid  in  3  hi.  water.  To  test  the  acid's  desired  solubility,  0.5 
grams  should  be  shaken  thoroughly  in  one  litre  of  water;  this  should  dis- 
solve in  from  5  to  10  minutes.  When  the  sterilizing  solution  is  ready, 
the  seeds  are  poured  into  it  and  stirred  about  repeatedly  and  vigor- 
ously in  the  course  of  the  next  few  hours.  Then  the  seed  is  pressed  down 
with  weighted  boards  so  that  it  remains  entirely  covered  by  the  solution. 
After  about  20  hours  it  is  taken  out  and  spread  in  a  thin  layer  in  an  airy 
place  and  stirred  often  with  a  rake.  As  soon  as  it  is  sufficiently  dry  it  can 
be  planted  with  a  drill,  but  it  may  lie  for  some  time,  when  completely  dr}% 
without  being  injured. 

If  it  is  desirable  to  use  the  sterilizing  solution  several  times,  it  is  neces- 
sary only  to  replace  the  liquid  lost  by  pouring  in  the  needed  quantity  of  a 
stock  solution.  However,  considering  the  cheapness  of  the  material,  it  is 
well  not  to  use  the  solution  too  often^. 

Instead  of  sterilization,  the  coating  of  the  seed  with  calcium  carbonate 
seems  to  us  to  be  advantageous. 

But  the  main  thing  is  to  work  the  soil,  for  even  the  most  carefully 
handled  seed,  found  to  be  faultless  in  the  germinating  tests,  can  become  dis- 
eased. Hiltner,  in  his  above-mentioned  work,  gives  some  suggestions  in  this 
connection  which  are  well  worth  consideration.  Up  to  the  present  in  trade, 
the  quality  of  the  seed  has  been  tested  according  to  its  behavior  in  the  seed 
bed,  by  means  of  a  suitable  method.  It  is  now  seen,  that  the  number  of 
diseased  seedlings  increases,  the  longer  the  seed  is  left  in  the  seed  bed.  Ex- 
periments show  that  if,  for  example,  the  seedlings  are  taken  from  the  sand 
seed  bed  on  the  9th  day,  often  more  than  ten  times  as  many  are  found  to  be 
diseased  as  when  taken  out  on  the  6th  day.  To  this  it  should  be  added  that 
if  the  seeds  lie  close  to  each  other  the  mutual  infection  is  considerable.  Be- 
sides this,  the  number  of  diseased  seedlings  differs  greatly,  depending  upon 
whether  the  seed  was  soaked  or  not  and  whether  distilled  water,  water 
free  from  calcium,  or  Avater  containing  calcium,  was  used  for  the  soaking. 
If  finally  it  is  taken  into  consideration  that  the  constitution  of  the  soil  de- 
cides the  subsequent  behavior  of  the  seedlings,  it  will  be  concluded  that  the 
methods  at  present  used  for  judging  of  the  quality  of  the  seed  give  no  pro- 
tection and  no  standard  for  beet  seed.  In  order  to  obtain  an  insight  into  the 
germinating  power,  the  best  seeds  will  have  to  be  tested  in  as  many  germi- 
nating seed  beds  as  possible  and  with  different  methods-.  The  best  germinat- 
ing results,  however,  in  no  way  give  a  guarantee  as  to  rootblight.  This  depends 
upon  whether  the  micro-organisms  present  in  the  dried  blossoms,  containing 
the  seeds,  find  an  opporttinity  of  so  developing  in  the  soil  that  they  can  attack 
the  young  seedlings. 

1  Wilfarth,  H.,  and  Wimmer,  G.,  Die  Bekampfung  des  Wurzelbrandes  der  Riiben 
durch  Samenbeizung.  Zeitschr.  d.  Vereins  d.  Deutschen  Zuckerindustrie,  Vol.  50, 
Part  529. 

2  For  the  difference  in  germination  of  the  seed  treated  in  the  same  way  but 
sown  in  sand  and  in  soil,  compare  the  reports  by  Marek  in  the  year  Book  of  the 
German  Agricultural  Society,     (.lahrb.  d.  Deutsch.  Landwirtsch.  Ges.  1892.) 


'2.2'J 

Tropical  Plants. 

In  consideration  of  my  standpoint,  that  in  much  of  our  cultivation  too 
Httle  account  is  taken  of  the  soil  conditions,  especially  of  its  physical  consti- 
tution, I  think  it  necessary  to  refer  also  to  the  demands  of  tropical  plants  on 
the  physical  peculiarities  of  the  cultivated  land.  In  regard  to  tropical  plants, 
I  base  my  theory  on  the  statements  of  Fesca^  who  has  often  given  his  own 
experiences,  and  further,  on  the  recent  publications  of  the  Biological  Agri- 
cultural Institute  at  Amani-. 

As  we  shall  see,  in  these  injuries,  as  in  those  in  temperate  climates, 
phenomena  are  often  involved  which  are  due  to  scarcity  of  oxygen  mani- 
fested in  heavy  soil  or  in  soils  which  have  become  compacted  through  culti- 
vation. Many  plants  in  the  tropics  can  develop  accessory  organs  with  a  scar- 
city of  oxygen,  like  the  adventitious  roots  from  the  trunks  of  trees  buried  or 
covered  with  slime.  The  palms  (Phoenix,  Kentia,  Chamaerops  etc.)  car 
develop  root  branches  growing  perpendicularly  out  of  the  soil  which  have  a 
peculiar  respiratory  arrangement  (Pneumathodes)  ;  this  appears  as  a  mealy 
coating  extending  backward  for  a  certain  distance  from  the  tip  of  the  root. 
This  mealy  condition  is  produced  by  the  increase,  enlargement  and  breaking 
up  of  the  outer  layers  of  the  rootbark  with  a  rupturing  of  the  epidermis  and 
an  almost  complete  suppression  of  the  schlerenchymatic  ring,  Jost^  deter- 
mined experimentally  with  Phoenix  that  these  pneumathodes  remain  in  the 
soil  when  it  is  well  aerated,  but,  on  the  other  hand,  are  raised  above  the  sur- 
face of  the  pot  if  it  is  submerged  in  w^ater.  Similar  arrangements  were 
found  also  in  Pandanus,  Saccharum  and  Cyperus. 

Root-Rot  of  the  Sugar  Cane. 

Among  the  numerous  diseases  of  sugar  cane,  root-rot  plays  a  prominent 
part.  In  Java  it  is  considered  the  worst  enemy  of  sugar  cane  culture.  Nat- 
urally growers  have  not  failed  to  cite  the  micro-organisms  (Verticillium. 
(Hypocrea)  Sacchari,  Cladosporium  javanicum  Wakker.  Allentospora  rad- 
icicola,  Wakker,  Pythium  etc.)  colonizing  on  the  diseased  roots  as  its  cause. 
Nevertheless  Kamerling's*  recent  experiments  have  now  confirmed  beyond 
all  doubt  the  supposition  that  a  constitutional  disease  is  concerned  here, 


1  Fesca,  Der  Pflanzenbau  in  den  Tropen  und  Subtropen.  Berlin  Siisserott.  Vol, 
I,  1904. 

2  As  said  above,  the  statements  on  the  phenomena  of  disease  in  cultivated 
tropcal  plants  serve  chiefly  as  proof  of  the  necessary  consideration  of  soil  and  at- 
mospheric conditions  as  a  cause  of  disease.  In  the  descriptions  we  can  sum  up  the 
material  more  briefly  since  abundant  literature  easily  makes  possible  special 
studies.  Besides  the  magazines  already  mentioned,  pp.  65  to  67,  the  recent  publica- 
tions of  the  Usamtaara-Post  furnish  valuable  material.  "Der  Pflanzer,"  Adviser  for 
Tropial  Agriculture"  issued  with  the  co-operation  of  the  Biological  Agricultural  In- 
stitute, Amani,  by  the  Usambara-Post,  1905.  ("Der  Pflanzer,"  Ratgeber  fiir  tropische 
Landwirtschaft  unter  Mitwirkung  des  Biologisch-Landwirtschaftlichen  Institutes 
Amani,  herausgageben  durch  die  Usambara-Post,  1905.) 

3  Jost,  Ein  Beitrag,  zur  Kenntnis  der  Atmungsorgane  der  Pflanzen.  Bot.  Zeit 
1887,  No.  37. 

4  Kamerling,  Z,  Verslag  van  het  Wortelrot-Oenderzoek,  Soerabaia,  1903,  209 
pages,  with  19  Plates. 


228 

resulting  from  compacting  the  soil.  Raciborski  with  Suringar'  has  expressed 
the  theory,  earlier  proved,  that  by  transplanting  sugar  cane,  which  had  suf- 
fered from  this  root  disease,  known  as  Domikellanciektc,  to  oilier  soil,  the 
I>lants  would  become  healthy.  The  disease  occurs  especially  on  heavy  clay 
soils  and  manifests  itself  in  Java,  when  at  the  beginning  of  the  spring  mon- 
soon the  plants  die  with  alarming  rapidity  after  they  have  already  shown  for 
some  time  an  abnormal  branching  of  roots  and  also  deformed  root  hairs.  He 
investigated  the  soils  in  which  the  disease  occurred  and  found  that  they  did 
i/ot  have  sufficient  friability  and  easily  became  compacted.  The  permeabil- 
ity of  the  soil  can  be  increased  by  supplying  humus,  since  this,  as  also  ferric 
hydroxide,  or  silicate  rich  in  iron,  favors  the  formation  of  friable  soils.  Since 
the  humus  is  gradually  lost  by  oxidation,  care  must  also  be  taken  to  retain  the 
porosity  of  the  soil  by  a  renewed  supply  of  stable  manure,  rice  straw  or 
green  fertilizer  (compost). 

According  to  Wakker's-  studies,  many  leaf  spot  diseases  seem  either 
directly  produced  by  moisture  in  the  soil  (if  of  a  parasitic  nature)  or  favored 
by  this  moisture.  Wakker  found  in  the  vicinity  of  Malang  "a  yellow  streak- 
ed, banded  disease,"  "rust,"  "ring  spot  disease,"  as  well  as  the  red  and  yellow 
spot  disease.  While  he  considers  the  first  named  as  a  parasitic  phenomenon 
favored  by  moisture,  he  explains  the  yellow  spot  disease,  in  which  the  leaves 
acquire  somewhat  elongated,  greenish  yellow  spots  running  into  one  another, 
as  a  hereditary  constitutional  disease. 

Diseases  of  Cotton. 

The  majority  of  the  cotton  diseases  may  be  considered  at  present  to  be 
of  parasitic  origin,  but  I  doubt  if  this  will  always  remain  the  case.  With  the 
conviction  that  many  of  the  micro-organisms  already  found  are  to  be  con- 
sidered parasites  of  weakness,  naturally  the  first  existing  factor  must  be 
considered  as  decisive,  viz.,  the  disturbance  in  nutrition  causing  the  weak- 
ness which  first  offers  the  possibility  of  infection  by  the  fungus.  This  will 
have  to  be  sought  primarily  in  weather  and  soil  conditions. 

Examples  of  disease,  in  which  only  the  soil  is  considered  as  the  cause 
in  the  rainy  season,  are  reported  by  Vosseler'"  from  our  East  African  col- 
onies. In  1904,  in  the  district  of  Kelwa,  there  occurred  a  "browning  of  the 
stems,"  which  produced  greater  damage  in  that  region  than  all  the  other 
diseases  which  had  appeared  up  to  that  time.  Brownish  black  spots  were 
produced  in  the  bark  below  the  tip  of  the  main  shoot,  as  a  result  of  which 
followed  the  dying  of  this  part  as  well  as  of  the  upper  lateral  shoots.  The 
disease  appeared,  however,  only  on  so-called  sour  soil. 


1  Kamerling-,  Z.,  en  Suringar,  H.,  Oenderzneking-en  over  onvoidoenden  sroei  en 
ontijdig  Afsterven  van  het  riet  als  gevolg  van  wortelziekten.  Mededeelingen  van 
het  Proefstation  vor  Suikerriet  en  West-.Java,  No.  48;  oit.  Zeitsohr.  f.  Pflanzenkr., 
1901,  p.  274,  and  1904,  p.  88. 

2  Wakker,  J.  H.,  De  Bladzeikten  te  Malang.  Archiev  voor  de  .Tava-Suikerindus- 
trie,   1894.     Aflevering  1. 

3  Vossler,  Zwei  Baumwollkrankheiten.  Immune  Baum^jvollsorten.  Mitteil. 
Biolog.-Landwirtsch.  Institut  Amani,  1904,  No.  32. 


229 

The  red  spot  disease  of  the  leaves,  occurring  to  a  devastating  extent 
along  the  v^-hole  coast,  was  a  second  phenomenon.  A  pale  border  appeared 
along  the  edge  of  the  leaves ;  the  zone  was  distinctly  cut  off  from  the  inner 
portions  by  a  zigzag  line.  Dark  red  spots,  or  a  uniform  red  coloration  with 
which  a  deforming  of  the  leaf  surface  was  often  connected,  then  appeared. 
The  disappearance  of  this  trouble  with  the  appearance  of  drought  indicates 
that  the  soil  during  the  prevailing  wet  weather  had  .unfavorably  affected  the 
growth  of  the  cotton.  Vosseler  seems  to  suspect  that  the  dreaded  "wilt  dis- 
ease" should  be  included  among  the  climatic  diseases  and  refers  in  this  to 
the  possibility -of  producing  immune  races  by  growing  plants  from  seed  of 
healthy  stock  in  diseased  fields.  According  to  Schellmann^,  cotton  cannot 
grow  on  stiff  clay  soils  and  sour  humus  soils. 

Castor  Bean  Cultures. 

Although  Ricinus  thrives  in  subtropical  and  even  in  temperate  zones, 
according  to  Zimmermann'-',  it  is  extensively  cultivated  only  in  the  tropics 
where  it  grows  from  sea  level  up  to  possibly  1600  m.  The  oily  seeds  are  the 
desired  crop.  At  any  rate  an  abundant  supply  of  nutriment  is  needed  for 
Ricinus,  since  it  makes  very  great  demands  on  the  soil.  The  plant  also  re- 
quires large  amounts  of  water  while  growing.  Later,  however,  the  physical 
constitution  of  the  soil  has  a  determining  value  in  the  matter,  since  the  plants 
do  not  thrive  in  all  soils  which,  not  well  drained,  remain  constantly 
wet.  These  observations  in  the  tropics  correspond  with  our  experience  in 
growing  Ricinus  as  a  decorative  plant.  Only  the  plants  develop  well  which 
have  plenty  of  room  and  a  porous  soil,  rich  in  nutriment.  When  grown  in 
pots,  to  which  much  nutriment  is  added  by  fertilizing  salts,  the  earth  becomes 
encrusted  and  the  plants  remain  small  and  weak. 

Tobacco. 

Very  instructive  examples  of  the  determinative  influence  of  the  soil  are 
furnished  by  Hunger's'*  observations  on  the  development  of  the  Delhi- 
tobacco  and  its  different  behavior  toward  the  "Mosaic  Disease,"  which  will 
be  reported  more  fully  in  the  section  on  enzymatic  diseases. 

Hunger  says  that  a  soil  of  white  clay  in  which  much  sand  has  been 
mixed,  is  the  best  for  thin-leaved  tobacco  if  the  amount  of  precipitation  is 
favorable,  but  at  the  same  time  this  also  favors  most  the  abundant  appear- 
ance of  the  mosaic  disease  in  the  form  of  the  so-called  "yay-head."  Here., 
after  topping,  the  plant  gives  the  impression  of  having  made  too  rapid 
growth;  long  internodes,  a  yellowish-green  foliage,  a  great  many  lateral 
shoots,  all  of  which  are  sickly. 


1  Der  Pflanzer,  Usambara-Post,  1905,  No.  1.     Here  also  older  literature. 

2  Zimmerman,  A.,  Die  Ricinus-Kultur.  Der  Pflanzer,  Ratgeber  fiir  tropische 
Landwirtschaft  unter  Mitwirkung-  des  Biologisch-Landwirtsch.  Institutes  Amani, 
herausg.  durch  d.  Usambara-Post 

?'  Zeitschr.  f.  Pflanzenliranlvh.  1905,  Part  5.  Hunger,  as  Botanist  at  the  experi- 
mental station  for  Delhi-Tobacco  (VIII  Abt.  d.  Bot.  Gart.  zu  Buitenzorg)  has  had  at 
his  disposal  most  extensive  material  for  observation. 


230 

If  the  clay  soil  lacks  sand,  however,  and  becomes  loamy,  it  is  useless 
for  tobacco  culture.  The  roots  of  the  plant  develop  scantily  and  are  often 
deformed.  The  leaves  are  not  of  the  right  length  and  are  of  poor  quality. 
The  mosaic  disease  appears  a  week  or  two  after  transplanting.  The  red, 
atmospherically  disintegrated  soils  of  Ober-Langkat  are  pretty  compact  and 
here  the  plants  are  squatty ;  the  leaves  standing  close  above  one  another  are 
not  especially  thin  while  the  mosaic  disease  occurs  rarely.  It  only  appears 
exceptionally  on  the  shoots  which,  after  topping,  develop  sparsely. 

On  dark  soils  rich  in  humus,  tobacco  has  an  enormous,  well-proportioned 
development;  the  very  large  leaves  are  dark  green  and  thin.  The  mosaic 
disease  abounds. 

This  disease  scarcely,  if  ever,  occurs  on  the  peaty,  porous,  Paja  soil, 
which  has  a  high  water-holding  capacity.  The  enormous  leaves  almost 
never  wilt  in  the  soil  containing  much  water,  but  are  very  thick  and  rich  in 
oil;  with  fermentation  they  become  dark  colored  and  are  therefore  not  \try 
valuable.  On  fresh  Paja  soil  the  mosaic  disease  cannot  be  produced  even 
by  topping. 

Coffee. 

The  tree,  which  of  all  our  tropical  plants  deserves  the  most  consider- 
ation, coffee,  is  extremely  susceptible  to  soil  conditions ;  although  droughts 
are  not  favorable  and  it  likes  best  to  grow  in  soil  which  even  at  a  time  of 
drought  keeps  fresh,  yet  it  withstands  drought  much  better  than  too  much 
moisture.  If,  during  the  rainy  season,  it  is  covered  with  water  for  only  a 
few  days,  it  becomes  irretrievably  diseased.  A  sufficient  capacity  for  water 
in  the  soil,  combined  with  abundant  aeration,  is  therefore  its  chief  need. 
Freshly  cleared  forest  soil  is  found  to  be  especially  favorable  for  its  culti- 
vation. Black  rust  (swarte  roest)  and  canker  diseases  (Natalkrebs  and  Java- 
krebs)  (Djamoer  oepas)  with  their  diseased  cambium  are  probably  physiolo- 
gical disturbances  introduced  by  unfavorable  soil  and  atmospheric  conditions 
and  result  later  in  fungus  attack.  The  Liberian  coffee  is  said  to  be  less  sus- 
ceptible to  impervious  soil  than  the  Arabian,  and  flourishes  where  the  latter 
fails^ 

The  leaf  disease  described  by  Zimmermann  as  "Blorokziekte"^  seems 
to  me  also  to  belong  here.  The  leaves  develop  convex,  yellow  spots.  Later, 
the  epidermis  ruptures  on  these  spots  and  the  cell  contents  turn  brown.  The 
trees  in  Java,  to  be  sure,  are  not  killed  by  this  disease,  but  their  fertility  is 
greatly  reduced.  As  the  result  of  an  excessive  water  supply,  Zimmermann 
observed''  the  so-called  "little  stars,"  occurring  rarely  in  Coffea  liherica  and 
more  frequently  in  C.  arohica;  i.  e.  blossoms  which  open  prematurely  when 
incompletely  developed  and  therefore  remain  sterile.     The  disease  should 


1  Delacroix,  G.,  Les  maladies  et  les  ennemis  des  cafeiers.    II  edit.   Paris,  Chala- 
mel,  1900,  p.  8. 

2  Teysmannia  1901,  p.  419. 

3  Eenige  Pathologische  en  Physiologische  Waarneminger  over  KofRe.  Mededee- 
lingen  uit  S'Lands  Plantentuin,  LXVII. 


23  i 

not  be  confused  with  the  black  discoloration  of  the  blossom  buds  passing 
under  the  same  name.  These  buds  finally  fall  off  unopened.  Different  kinds 
of  root  moulds  have  been  described  and  considered  as  the  cause  of  root-rot^. 
I  think  it  will  be  necessary  to  study  here  the  question  whether  parasitic 
fungous  forms  can  attack  the  plant  injuriously  only  when  the  roots  have 
already  been  weakened  by  unfavorable  nutritive  conditions. 

Cocoa  and  Tea. 

Fesca  says  in  regard  to  the  cocoa  tree  "extremes  of  soil  structure,  poor 
sand,  as  well  as  tough  clay,  are  not  favorable  to  the  cocoa  tree.  Rather  it 
demands  greater  soil  depth  and  freshness,  without  the  necessity  of  enduring 
standing  water,  as  well  as  greater  humus  and  nutrition  content,  than  does 
coffee."  The  same  author,  who  himself  has  analyzed  good  tea  soils  in  Japan, 
say  of  tea,  that  he  found  in  a  more  compact  soil,  30  to  40  per  cent,  of  water 
as  capillary  water.  Tea  demands  a  sufficiently  deep  soil  which  is  free  from 
standing  water,  to  which  it  is  very  sensitive.  Here  too  a  still  little  understood 
fungus  is  described  as  the  cause  of  a  root  disease.  It  is  said  to  result  in  the 
early  death  of  the  bushes,  especially  when  growing  on  damp  soil.  Neverthe- 
less Fesca-  assures  us  that  he  has  never  yet  seen  the  disease  on  well  aerated 
soils.  We  might  also  trace  the  diseases  of  young  tea  plants  described  by 
Zimmermann^  to  an  unfavorable  place  of  growth,  although  a  fungus  bearing 
iobed  haustoria  has  been  observed  at  the  disease  centres.  The  leaves  become 
flabby  and  discolored ;  the  stems  turn  brown  at  the  base  or  higher  up  where 
the  root  seems  healthy.  Often  only  the  leaves  show  brown  spots,  especiahy 
on  the  midrib.  The  fungi  developed  from  the  diseased  parts  of  the  stem 
(Nectrieae)  could  not  produce  the  disease  even  in  infection  experiments. 
In  dry  weather  the  disease  decreases  considerably.  A-lso  transplanting  the 
seedlings  from  the  closely  planted  seed  bed  arrested  the  disease.  If  we  have 
considered  here  with  the  greatest  brevity  the  soil  demands  of  our  most  impor- 
tant cultivated  tropical  plants,  it  must  still  be  added  that  naturally  the  climate 
remains  the  decisive  factor.  Among  these  climatic  factors  especial  attention 
must  be  given  to  humidity  since  the  quality  of  the  harvest  often  depends 
considerably  upon  this.  In  cocoa  plantations  in  Kamerun,  for  instance,  it 
may  be  observed  that  the  quantitative  production  of  the  trees  is  unusually 
abundant,  but  the  quality  of  the  fruit  is  only  mediocre  as  the  result  of  great 
dampness.    The  trees  also  are  short-lived  here. 

Other  Tropical  Plants. 

Of  grains.  Maize  requires,  first  of  all,  a  deep,  mellow  soil  free  from 
standing  water  and  cannot  thrive  on  tough  clay.  Sorghum  behaves  similarly, 
but  is  still  more  sensitive  to  cold  and  dampness  and,  because  of  its  deep  root 


1  BoUetim  del  Institto  Fisico-Geographico  de  Costa  Rica,  1901. 

2  Loc.  cit.,  p.  273. 

3  Zimmermann,  Untersuchungen  iiber  tropische  Pflanzenkrankheiten.     Sonder- 
berichte  iiber  Lan-  und  Forstwirtschaft  in  Deutsch-Ostafrika,  VoL  II,  Part  1,  1904. 


232 

system,  is  very  resistant  to  drought.  This  accounts  for  its  growth  on  troi)i- 
(al  and  subtropical  steppes.  The  Xegro  or  brush  millet  fPennisetum  spica- 
nim)  is  entirely  unsuitable  for  firm  soil,  but  is  excellent  for  porous  soils  in 
dry  localities.    The  other  millet  varieties  behave  similarly. 

The  Lcijuminoseae,  which  are  suitable  for  growth  as  a  second  crop  be- 
cause of  their  usually  short  vegetative  period,  may,  in  the  tropics  and  sub- 
tropics,  acquire  great  importance  not  only  as  collectors  of  nitrogen  and  as  an 
excellent  nutritive  substance,  but  are  also  valuable  on  account  of  their  close 
shading  of  the  soil,  preventing  it  from  hardening  and  as  soil  loosening,  green 
manuring  plants.  The  plants  make  good  growth  in  dry  soils ; — accordingly 
heavy  soils,  in  regions  with  abundant  precipitation,  are  not  suitable  for  them. 
Busse^  has  given  more  detailed  studies  of  sorghum  diseases  and  their  rela- 
tions to  atmospheric  conditions. 

Of  tuberous  plants,  the  szveet  potato  requires  about  the  same  cultural 
conditions  as  our  potato.  The  cassiwas  (Manniok)  require  deep,  loose,  dry 
soils,  but  rich  in  humus.  The  moisture-loving  Maranta  species,  furnishing 
arrowroot,  also  requires  looseness  of  the  soil,  on  which  account  virgin  soil  is 
found  to  be  less  suitable  because  of  its  compactness.  Even  Taro,  the  tubers 
of  the  different  Colocasia  species,  which  requires  a  great  deal  of  moisture, 
flourishes  only  when  the  soil  is  pervious.  The  same  is  true  of  the  Yam, 
which  is  derived  from  different  species  of  the  genus  Dioscora.  In  regard  to 
poppy  culture  and  the  harvesting  of  opium,  reference  should  be  made  to 
Braun's-  work,  and  in  regard  to  rubber  plants  and  especially  the  Liana, 
root  and  herbaceous  rubber  plants,  to  studies  by  Zimmermann". 

Mf.ans  for  Overcoming  the  Disadvantages  of  Heavy  Soils. 

Drainaye.  In  this  we  have  to  take  into  consideration  not  only  soils 
rich  in  clay,  but  also  those  sandy  ones  whose  graular  structure  is  so  fine 
that  they  can  become  as  closely  compacted  as  clay  soils. 

Of  the  practical  means  used  to  increase  soil  aeration,  drainage  deserves 
to  be  named  primarily.  It  facilitates  the  exchange  of  air  in  the  soil  inter- 
stices as  well  as  removing  stagnant  water  accumulations  after  every  rain. 
The  drainage  pipe  acts  as  an  apparatus  for  sucking  up  air.  When  the  rain 
fills  the  soil,  it  forces  out  the  air  which  has  a  less  oxygen  content  than  the 
atmosphere,  but  is  richer  in  carbon  dioxid.  But  since  the  rain  is  quickly 
soaked  through  the  drains,  air  rich  in  oxygen  streams  just  as  quickly  from 
the  surface  down  into  the  pores  increasing,  thereby,  the  processes  of  oxida- 
tion in  the  soil  and  the  activity  of  the  roots  and  micro-organisms  needing 
oxygen. 

The  fear  that  drainage  will  impoverish  the  fields  has  rarely  any  founda- 
tion, since  the  numerous  analyses  of  drain  water  show  only  slight  traces  of 


1  Busse,  Walter,  Untersuchungen  iiber  die  Krankheiten  der  Sorghum-Hirse.  Arb. 
d.  Biolog.  Abt.  f.  Land-  u.  Forstwirtschaft  a.  Kais.  Gesundheitsamte,  Vol.  IV,  Part  4. 
1904. 

2  Der  Pflanzer,  1905,  No.  11-12. 

3  Ibid,  Nos.  8-10. 


233 

potassium  and  ammonia  as  well  as  phosphoric  acid,  which  had  been  ab- 
sorbed by  the  friable  soil.  Nitrates,  because  of  their  easy  solubility,  at  any 
rate,  are  lost  in  larger  amounts,  but  they  are  also  partially  washed  away 
from  undrained  soil  into  the  subsoil. 

Further,  the  soil  capacity  for  heat,  increasing  with  drainage,  should  not 
be  underestimated  as  well  as  the  improvement  of  the  crop  produced,  of 
which  it  may  be  said  in  general  that  damp,  and  therefore  cold,  soil  produces 
crops  poorer  in  nutriment.  The  reason  why  damp  soil  is  cold  is  evideni 
from  considering  the  fact  that  if  water  has  a  specific  heat  equal  to  one,  the 
highest  specific  warmth  ever  shown  by  soil  is  only  equal  to  0.5 ;  i.  e.  at  most 
lialf  that  of  water.  If  this  water  which  is  the  hardest  to  warm  is  removed 
by  drainage,  the  soil  must  become  warmer.  Previous  to  drainage,  the  soil 
remained  cold  until  late  in  the  spring,  thus  causing  a  later  awakening  of 
vegetation  and  a  later  germination  of  the  seed.  A  cold  place  of  growth  is 
especially  disturbing  to  young  plants,  since  it  holds  development  back  in  a 
developing  phase,  which  is  determinative  for  the  whole  later  plant.  The 
root  system  becomes  poor,  the  appearance  sick,  and  later  favorable  temper- 
ature conditions  are  not  able  to  overcome  the  bad  condition.  One  of  Stock- 
hardt's^  experiments  with  winter  rye  may  serve  as  an  example.  The  ex- 
perimental plots  differed  in  drainage  and  soil  porosity.  One  plot  was 
traversed  at  a  slight  depth  by  a  drain  possibly  2.5  cm.  wide  and  in  such  a 
way  that  the  pipe,  bent  at  right  angles  at  one  end  of  the  drain,  opened  like 
a  chimney  toward  the  upper  surface  of  the  soil.  The  soil  of  this  plot,  as 
well  as  that  of  the  undrained  one,  was  broken  up  50  cm.  deep,  while  a  third 
plot  was  dug  only  25  cm.  deep  and  not  drained.  In  corroboration  of  earlier 
results  obtained  with  lupin,  oats  and  the  like,  the  harvest  showed  an  ap- 
preciable excess  on  the  drained  lot,  although  the  young  plants  showed  no 
difference  before  spring. 

Reckoned  per  acre  this  crop  amounted  as  follows : 

Grain  Straw             Totals 
and  Chaff 

kg.  kg.                  kg. 

Part       I,  drained  and  dug  50  cm.  deep             539  1470                2009 

Part     II,  undrained  and  (lug  50  cm.  deep             411  928.5             1339-5 

Part  III,  undrained  and  dug  25  cm.  deep             338  859-5             1 197-5 

Grain  content  Nitrogen  content 

per  bu.  of  the  grain 

Lot      I.                         40.80  kg.  2.18  per  cent. 

Lot     II.                           39-85  kg.  1.83     "       " 

Lot  III.                          37-70  kg.  1.83     "       " 

Patz-,  referring  to  the  use  of  drainage  for  removing  iron  from  neivly 
broken  soil,  says,  "usually  iron  is  found  directly  under  the  surface  of  the 
soil  and  at  the  height  of  the  usual  ground  water  level.     The  ground  water 

1   Chemische  Ackersmann,  1859,  p.  232;   IcSGl,  p.  100;   1864,  p.  22.       ,,     ^     ^      ., 
^   Hannoversche   landw.   Zeit.    1880,   No.   45;    cit.    Biederm.    Centralbl.    f.   Agnk.- 
Chemie,  1880,  p.  911. 


234 

carries  the  iron  upward  and  in  many  cases  cements  the  sand  grains  in  the 
soil  at  the  usual  height  of  the  ground  water  level  in  such  a  way  that  often  in 
laying  a  drain,  a  hard,  stone-like,  red  soil  is  found.  By  laying  drains  cor- 
rectly and  systematically,  with  the  horizontal  drains  intersected  at  right 
angles  by  the  absorbing  drains,  the  latter  having  at  least  a  depth  of  1.2  m. 
and  the  distance  between  every  two  drains  being  kept  10  times  the  depth, 
the  level  of  the  ground  water  will  be  lowered  to  the  depth  of  the  drain  and 
no  more  iron  will  be  carried  to  the  soil  above  the  pipes.  The  iron  already 
present  in  the  soil  will  be  dissolved  by  t^e  atmospheric  precipitation  and  led 
to  the  dainage  pipes  or  it  will  remain  in  the  soil  as  the  non-injurious  oxid." 

Working  of  the  soil.  Where  there  is  no  need  of  carrying  away 
excessive  water,  furrowing  and  deep  plowing,  instead  of  drainage,  will  often 
serve  the  same  end.  In  this  care  must  be  exercised  if,  with  fertile,  friable 
soil,  there  is  a  prospect  of  bringing  a  dead  subsoil  to  the  upper  surface  by 
the  furrowing  or  plowing.  In  addition  to  fertilizing  each  time,  the  gradual 
deepening  of  the  friable  soil  should  take  place  at  least  over  a  period  of 
several  years.  Since,  with  the  deepening  of  the  friable  soil,  the  root  surface 
becomes  extended  and,  accordingly,  an  increased  harvest  takes  place  with  a 
greater  utilization  of  the  soil,  an  increased  supply  of  manure  is  demanded 
with  the  increasing-  loosening  of  the  soil. 

In  soils  inclined  to  crust,  but  otherwise  not  unfavorably  constituted 
physically,  hoeing  and  hilling  suffice  for  increasing  the  soil  aeration.  Thib 
cultivation,  which  can  scarcely  be  sufficiently  recommended  to  the  agricul- 
turist and  the  gardener,  and  which  can  be  used  in  any  soil,  regulates  the  soil 
moisture. 

Some  good,  practical  experiences  as  to  the  advantages  of  loosening  the 
soil,  may  be  found  in  the  reports  of  the  German  Agricultural  Society's 
special  committee  for  the  protection  of  plants  (Landwirtschaft-Gesell- 
schaft).  We  will  cite  a  single  example  which  is  supported  by  comparative 
experimental  cultures.  In  SkoUmen^  (East  Prussia)  Mentzel  divided  into 
two  parts  a  field  planted  with  mixed  Swedish  wheat,  Epp  wheat  and  Kas- 
tromer  wheat,  and  kept  one  half  of  it  loose  by  harrowing  after  every  rain, — 
1.  e.  by  working  with  the  narrow  bladed  cultivator, — but  did  not  work  the 
other  half.  Although  its  soil  was  better,  the  latter  half  yielded  only  2160 
kg.  per  acre,  the  former,  however,  2650  kg. 

A  green  manure  fertilizer  turned  over  deep  in  light  soils  and  super- 
ficially in  heavy  soils,  acts  in  the  same  way  as  this  loosening  of  the  soil  sur- 
face. By  means  of  this  green  manure  the  capillary  raising  of  the  water 
from  the  underlyng  soil  layers  especially  is  interrupted".  On  the  one  hand, 
the  moisture  is  thus  retained  in  the  deeper  layers  of  the  lighter  soil ;  on  the 
other  hand,  in  heavy,  wet  soils,  a  well  aerated,  friable  surface  is  formed  so 


1  Jahresb.  d.  Sond.-Aussch.  f.  Pflanzenschutz.  Arb.  d.  Deutsch.  Landwirtsch. 
Ges.,  Part  107,  1905,  p.  64. 

-  King-,  F.  H.,  Tenth  Annual  Report  of  the  Agric.  Exper.  Stat,  of  -Wisconsin,  1884 
p.  194. 


235 

that  the  seeds  can  germinate  normally.  The  stronger,  more  sturdy  plants, 
which  have  passed  through  the  most  critical  germinative  stages,  are  then 
better  able  to  combat  the  soil  moisture,  which  rises  capillarily  higher  and 
more  rapidly  after  the  green  manure  has  decomposed. 

Freezing.  The  loosening  of  heavy  soils  in  winter  through  a  suitable 
freezing  is  of  the  greatest  importance  in  their  cultivation.  If  we  take  into 
consideration  that  water,  when  converted  into  ice,  expands  about  one- 
eleventh  of  its  volume,  it  is  evident  that  the  more  closely  lying  soil  particles 
are  forced  apart  by  the  ice  crystals.  Also,  since  rocks  are  covered  with  a 
network  of  fine  cracks,  into  which  the  water  gradually  soaks,  the  frost  is 
constantly  decomposing  them  and  in  fact  the  effects  are  greater  as  the 
freezing  and  thawing  alternate  during  the  winter.  Naturally  the  rapidity  of 
the  action  will  depend  upon  the  composition  of  the  soil,  i.  e.  on  its  water 
content.  The  smaller  this  is,  the  more  c|uickly  and  deeply  the  frost  can 
penetrate.  Therefore,  heavy  and  humus  soils  will  freeze  and  thaw  most 
slowly.  WoUny's^  experiments  show  the  advantage  accruing  to  the  soil 
from  the  loosening  action  of  the  frost.  He  had  two  plots  of  land  loosened 
up  in  the  fall  and  left  lying  in  open  furrows,  while  a  third  was  not  worked. 
This  plot  and  one  of  the  two  others  were  turned  over  in  the  spring  while  the 
third  was  worked  only  superficially.  It  was  then  proved  that  for  the  various 
plants  cultivated,  the  yield  was  smaller  from  the  plot  which  had  not  been 
left  fallow  in  the  fall,  while  the  largest  harvest  was  given  by  the  one  in 
v/hich  the  open  furrows  froze  during  the  winter  and  were  broken  up  once 
more  in  the  spring. 

Mulching.  We  now  come  to  the  advantage  derived  in  heavy  soils  from 
the  covering  of  the  friable  surface  with  litter,  after  having  considered  earlier 
the  protection  given  Hght  soils  by  such  a  covering.  The  greatest  advantage 
is  that  the  covering  substance  prevents  the  compacting  of  the  soil  particles 
since  it  takes  up  the  force  of  the  rain  drops  and,  conducting  the  water  slowly, 
spreads  it  over  the  surface  of  the  soil,  thereby  keeping  the  friable  surface 
more  porous.  In  nurseries  the  seed  also  germinates  more  uniformly  in 
covered  beds.  The  weeds  do  not  grow  so  vigorously  and  can  be  more  easily 
and  completely  removed,  since  they  root  more  superficially  in  the  looser 
soils. 

The  great  air  variations  between  day  and  night  produce  a  heavy  for- 
mation of  dew  in  the  porous  covering  material.  This  runs  off  to  the  benefit 
of  the  underlying  soil  and  increases  its  fertility.  If  bark  is  used  to  a  depth 
of  I  to  I  ^  inches,  it  furnishes  a  covering  for  the  seed  beds  in  winter  and, 
in  the  spring,  a  protection  against  the  penetration  of  frost  and  the  cracking  of 
the  soil. 

Seed  and  seedling  beds  should  have  water  given  them  in  June  or  July.  In 
August  the  ground  is  harrowed  and,  in  case  the  bark  should  then  be  covered 
too  deeply,  the  exposed  soil  is  covered  with  new  bark.   Snares  for  the  control 

1  Wollny,  E.,   Ueber  den  Einfluss  des  Winterfrostes  auf  die  Fruchtbarkeit  der 
Ackererden.     Biedermann's  Centralbl.    1902,  p.  301. 


23^ 

of  the  unevitable  June  hug  are  made  of  heaps  of  scattered,  moist  bark  which 
heats  itself.  The  June  bugs  lay  their  eggs  in  these  heaps  which  later,  with 
a  part  of  the  underlying  earth,  are  put  in  a  wagon  and  worked  up  with  peat, 
or  lignite,  ashes,  lime,  plaster  and  organic  refuse  to  a  compost  pile,  which, 
after  a  year  or  two,  kills  the  grubs. 

Harrowing. 

Harrowing  is  a  process  which  should  find  mention  here.  Anderegg' 
has  [>ublished  very  noteworthy  results  of  harrowing  meadows.  A  meadow 
of  uniform  soil  composition  and  mould  was  divided  into  four  equally  large 
lots.     These  yielded, — 

(i).  Unharrowed  and  unfertilized }^yy  kg.  hay 

(2).  Unharrowed  but  fertilized '"^33  kg.  hay 

(3).  Harrowed  but  unfertilized 770  kg.  hay 

(4).  Harrowed  and  fertilized 1563  kg.  hay 

Harrowing  winter  sown  grains  not  only  re-opens  the  encrusted  soil,  but 
also  increase  considerably  the  formation  of  young  shoots.  Director  Con- 
radi-,  however,  justly  points  out  the  fact  that  the  harrow  is  usuable  only  if 
the  crust  is  not  too  thick  and  the  soil  not  too  binding.  Also,  if  an  encrusta- 
tion in  spring  may  be  foreseen,  the  seed  must  be  more  thickly  sown  since 
harrowing  destroys  plants  and  the  sand  is  thinned.  For  that  reason  har- 
rowing is  very  useful  occasionally  in  thinning  the  plants.  The  increased 
standing  room  for  the  plants  left  in  place  gives  a  greater  supply  of  light  to 
the  basal  nodes  and  starts  the  lateral  shoots  into  a  rapid  growth  and  pre- 
vents their  too  rapid  lignification  when  these  buds  obtain  moisture  from  the 
earth  heaped  up  by  the  harrowing,  li  the  '"arth  is  not  pulverized  sufficiently 
by  the  harrow,  the  roller,  and  preferably  a  wheel  roller,  must  be  used  in  ad- 
dition. In  the  majority  of  cases  the  roller  will  have  to  follow  the  harrow, 
because  binding  soils  are  not  made  absolutely  fine  by  the  harrow,  and  also 
because  it  is  desirable  that  the  earth  torn  away  from  the  base  of  the  plants 
may  be  pressed  back  again.  The  best  time  for  harrowing  depends  on  the 
development  of  the  plant  and  the  water  content  of  the  soil.  If  the  plants 
have  grown  too  far  or  continuous  dry  weather  prevails,  the  harrowing 
should  be  omitted  or,  in  the  latter  case,  should  never  be  carried  out  without 
a  subsquent  rolling. 

A  few  words  also  might  be  pertinent  here  as  to  the  significance  of  stones 
in  the  soil.  In  this  connection.  W'ollny's''  experiments  have  shown  that 
with  a  high,  constant  air  temperature  (during  the  warmer  seasons)  soil 
covered  with  stones  and  mixed  with  them  is  slightly  warmer  than  is  that 
free  from  stones.  \Vith  a  falling  temperature  comes  the  reverse.  During 
the  daily  minimum  soil  temperature,  soil  containing  stones  is  for  the  most 

1  Illustr.  landw.  Verein-sblatt,  1880;  No.  8;  cit.  in  Hicdcrm.  Centralbl.  f.  Agrik.- 
Chcmie.  1880.  p.  693. 

-  From  "Der  Praktische  Landwirt"  in  Fiihling's  landw.  Zeit.,  1880,  p.  151. 
3  Wollny,  Fuhling's  landw.  Zeit.  1880,  p.  314. 


J 


'S7 

part  colder  than  that  free  from  stones,  while  during  its  maximum  it  is 
warmer.  In  regard  to  conditions  of  moisture,  field  soil  covered  with  stones 
is  found  to  be  wetter  during  the  warmer  seasons  than  uncovered  soil  of 
otherwise  similar  composition.  Soil  covered  with  stones  lets  more  water 
slip  through  than  does  one  not  so  covered. 

The  Use  of  Lime,  Marl  and  Plaster. 

The  importance  of  lime  arises  from  its  chemical  action  as  a  direct 
nutritive  substance  as  well  as  from  its  properties,  which  change  the  mechan- 
ical constitution  of  the  soil.  Aside  from  favoring  friability,  it  should  be 
emphasized  that  the  lime  attacks  the  silicate  in  clay  soils  and  sets  free  sol- 
uble potassium  compounds.  By  its  more  rapid  destruction  of  the  organic 
substances,  it  causes  a  better  decomposition  of  humus. 

In  regard  to  the  technique  in  using  lime,  it  is  advisable  to  keep  burnt 
(quick)  lime  in  baskets  under  water  until  no  more  air  bubbles  arise  (possibly 
3  to  minutes)  and  then  to  heap  up  the  pieces  in  layers.  They  decompose 
(slake)  of  themselves  and  the  lime  stone,  which  lost  its  carbon  dioxid  in  the 
previous  burning,  now  becomes  the  ^white  powdery  calcium  hydroxid 
(Ca(OH)^)  and  as  such  represents  slaked  lime,  which  is  soluble  in  730 
parts  of  cold  water,  and  only  in  1300  parts  of  boiling  water  (lime  water). 
100  parts  of  quick  lime  correspond  to  132  parts  of  slaked  lime.  The  lime 
should  be  uniformly  spread  over  the  field  in  quiet  weather  by  hand,  or  with 
a  suitable  shovel.  It  is  well  to  spread  it  in  the  fall  on  the  stubble  and  then 
to  work  it  under  the  surface.  If  it  is  necessary  to  wait  until  spring,  it  must 
be  spread  as  early  as  possible  before  seeding,  as  soon  as  the  soil  has  dried. 
Smaller  doses  (750  kg:  to  1500  kg.  per  hectare)  repeated  about  every  five 
years,  are  more  advisable  than  a  single  heavy  liming,  because,  in  the  latter,  the 
decomposition  of  the  humus  is  so  violent  that  the  subsequent  increase  in  the 
harvest  is  at  the  cost  of  a  later  production.  It  is  said  in  practice  that  fer- 
tility is  difficult  to  maintain  on  a  lime-stone  soil,  because  organic  matter  dis- 
appears rapidly. 

Naturally  the  amount  of  lime  depends  upon  the  soil.  Tough  clay  soil 
will  bear  most,  while  great  care  must  be  used  with  poor  sandy  soil.  Soils 
which  are  lacking  in  organic  matter  or  have  water  standing  on  them,  may 
not  be  limed  at  all.  The  results  which  become  evident  most  quickly  are 
given  by  a  humus  soil  poor  in  lime ; — Sorrel  (Rumex  acetosella)  indicates 
a  scarcity  of  lime.    Lime  will  act  here  splendidly  as  a  fertilizer. 

If  local  lime  deposits  be  used,  such  as  possibly  meadow-lime  or  marl,  or 
the  so-called  waste  lime  (gas  lime,  lime  ooze,  lime  ash),  it  is  distinctly  ad- 
visable, before  using  it,  to  let  the  air  pass  through  in  order  to  decom- 
pose it,  or  still  better,  to  let  it  freeze.  When  using  waste  lime  one  should 
convince  oneself  first  of  all,  by  a  simple  experiment,  that  no  injurious  sec- 
ondary action  can  take  place.     According  to  Hoffman's  experiments^   it 

1   Mitteilungen  der  Deutsch.  Landwirstchafts-Ges.  1905,  p.  367. 


238 

should  also  be  taken  into  consideration  that  the  more  lime  used,  the  less  should 
fertilizing  with  potassium  be  neglected.  In  using  stable  manure,  it  is  well 
to  put  the  lime  in  the  soil  sometime  before  the  manure  is  added.  Bone  meal 
should  be  avoided  on  soils  containing  lime.  In  the  same  way,  it  is  not  ad- 
visable to  use  ammonia  and  ammonia  superphosphates  together  with  lime. 
Pulverized  quick  lime  should  be  used  on  binding,  clayey  soils  ;  lump  or  slaked 
lime  on  better  loam  soils. 

In  regard  to  the  need  of  lime  by  the  different  plants,  Hoffmann  states 
that  the  Leguminoseae  in  general  are  distinguished  as  the  most  responsive 
to  apphcations  of  Ume,  but  that  the  Lupines  and  Serradella  may  be  con- 
sidered as  hostile  to  lime  and  sweet  peas  also  do  not  like  the  direct  use  of 
lime  or  marl. 

In  the  use  of  marl  also,  the  lime  is  the  most  active  princii>lc  and  hence 
it  follows  that  a  clayey  soil,  rich  in  humus,  bears  marling  better  than  a  poor 
sandy  soil  which  in  turn  can  be  more  benefited  by  a  clay  marl  than  by  a 
lime  or  sand  marl.  The  sometimes  dreaded  "impoverishment"  from  the  use 
of  marl  will  take  place  only  if  fertilizing  with  stable  manure  is  delayed.  The 
last  is  indispensable  for  all  soils  and  especially  for  heavy  ones  in  keeping  the 
fields  productive.    No  mineral  fertilizer  can  replace  stable  manure. 

The  influence  exerted  by  the  lime  contained  in  marl  upon  decomposition 
of  the  humus  substances  is  illustrated  very  clearly  by  Petersen's^  experi- 
ments. He  determined  the  amount  of  carbon  dioxid  produced  in  different 
soils  by  the  process  of  decomposition  with  and  without  the  addition  of  cal- 
cium carbonate.  In  using  a  heavy  clay  soil,  known  to  be  perfectly  sterile, 
with  1.98  per  cent,  humus  and  36  per  cent,  of  its  water  holding  capacity  in 
water  content,  he  obtained  in  16  days  0.07  per  cent,  of  the  weight  of  the  dry 
soil  in  carbon  dioxid.  On  the  other  hand,  the  same  soil  under  the  same  con- 
ditions with  the  addition  of  Yj  per  cent,  of  calcium  carbonate,  mixed  in  the 
clay  as  marl,  yielded  0.20  per  cent,  carbon  dioxid,  or  per  liter  of  dry  soil, 
without  addition  of  lime,  0.9153  g. ;  per  liter  of  dry  soil,  with  addition  of  ^^ 
per  cent,  lime,  2.6167  g. 

A  leaf  mould  with  strongly  acid  reaction  consisting  of  58  per  cent, 
humus  and  30  per  cent,  of  the  absorptive  capacity  in  temporary  water  con- 
tent, yielded  after  16  days,  without  and  with  the  addition  of  t  per  cent,  cal- 
cium carbonate  (when  the  earth  still  gave  an  acid  reaction)  :  per  liter  of  dry 
soil,  without  the  lime  addition,  0.891 1  g.  CO2 ;  per  liter  of  dry  soil,  with  the 
addition  of  i  per  cent,  calcium  carbonate,  3.386  g.  CO.. 

With  the  addition  of  3  per  cent,  calcium  carbonate,  the  soil  yielded 
5.3476  g.  carbon  dioxid,  while  the  series  of  check  experiments,  free  from 
lime,  produced  only  0.9664  g.  CO..  The  addition  of  the  lime,  therefore,  had 
caused  3  to  4  times  as  great  a  production  of  carbon  dioxid,  i.  e.,  humus  de- 
composition, as  in  the  soil  in  an  unmarled  condition. 

Heiden,  in  Pommritz,  summarizes  thus  the  effect  from  the  use  of  marl : 
The  chemical  action  arises  primarily  from  its  content  of  calcium  carbonate 

1  Jahresbericht  f.  Agrik.    1870-72.    Landwirtsch.  Ver.suchsstationen,  Vol.  13,  p.  155. 


239 

and  consists  in  the  hastened  decomposition  of  the  organic  elements  of  the 
soil,  in  the  combining  of  the  free  acids  so  injurious  to  plant  growth,  in  the 
conversion  of  ferrous  oxid  into  ferric  oxid,  and  in  bringing  about  the  ab- 
sorption of  the  basic  nutritive  substances  by  the  soil.  The  bases  are  held  in 
the  soil  as  hydrated  silicates  and  as  the  salts  of  humic  acid.  In  the  absorp- 
tion of  the  bases  by  the  humus  body,  these  must  be  present  combined  with 
carbon  dioxid.  The  lime  promotes  the  formation  of  carbonates.  Further, 
the  mineral  elements  of  the  soil  are  decomposed,  whereby  the  basic  nutritive 
substances  are  freed  and  made  accessible  to  the  plant.  Every  marl  does  not 
suit  every  soil, — clay  soils,  where  possible,  must  have  a  lime  or  sand  marl. 

Aside  from  these  indirect  advantages,  the  direct  effect  of  the  use  of 
marl  is  shown  in  the  addition  of  potassium,  soluble  silicic  acid,  magnesia 
and  phosphoric  acid,  which,  together  with  hme,  are  present  in  every  marl. 

A  few  words  should  be  added  here  as  to  the  use  of  piaster  or  gypsum. 
Franklin's  words, — "This  has  been  plastered,"  are  well-known.  He  wrote 
this  in  plaster  on  a  clover  field  in  order  to  recommend  to  his  countrymen 
the  process  which  had  been  known  with  great  advantage  by  the  Romans 
(Knop,  Kreislauf  des  Stoffes)  and  the  Greeks.  According  to  Knop's  experi- 
ments and  those  of  Deherain  and  Liebig,  a  solution  of  plaster  in  soils  con- 
taining absorbed  potassium,  frees  it  in  the  form  of  sulfate,  while  the  lime  it- 
self is  precipitated.  The  method  of  spreading  the  plaster  on  clover  plants 
freshly  covered  with  dew  or  rain,  recommended  by  experience,  is  found  to  be 
advantageous,  since  a  solution  of  plaster  is  formed  on  the  moist  plants ; 
dripping  from  them,  it  acts  at  once  in  the  immediate  vicinity  of  the  roots. 
It  thus  rapidly  becomes  of  advantage  to  the  bacterial  flora,  for  Pichard's^ 
researches  and  those  of  others  show  that  plaster  and  other  sulfates  (potas- 
sium and  sodium)  exercise  a  most  favorable  influence  on  the  process  of 
nitrification.  Plaster  should  be  used  in  an  unburned  state  and  indeed  for 
clover  and  lupines  from  2  to  5  centner  per  acre  in  the  spring. 

Although  the  influence  of  calcium  hydrate  or  carbonate,  favoring  de- 
composition, was  discussed  above,  it  must  still  be  emphasized,  that,  as  shown 
by  Wollny's^  work,  this  is  only  of  value  when  the  substance  is  already  de- 
composed and  contains  humic  acid,  while  the  addition  of  calcium  on  unde- 
composed  organic  substances  rather  hinders  decomposition.  This  is  especially 
true  for  calcium  sulfate  (gypsum)  which  comes  imder  consideration  as  a 
conservation  material  for  animal  manure.  In  a  mixture  of  quartz  sand 
(300  g.),  powdered  peat  (5  g.),  and  60  ccm.  water,  Wollny^  found 

Volumes  CO,  in  1000  Volumes  Soil  air — ■ 

without  the  addition  of  gypsum  with  the  addition  of  gypsum 

0.05  g.  0.1  g. 

CO,  3.194  3.029  2.713 


1  Annales  agronomiques  X,  p.  302. 

-  Wollny,    E.,    Die    Zersetzung    der    organischen    Stoffe    etc.      Heidelberg,    Carl 
Winter,  1897,  pp.  133  ff. 

3  Journal  f.  Landwirtschaft,  1886,  p.  263. 


240 

The  addition  of  the  plaster  had  accordingly  reduced  the  loss  in  organic 
substances  and  also  in  nitrogen ;  i.  e.,  had  exercised  an  arresting  influence  on 
decomposition.  The  use  of  calcium  compounds  as  a  remedy  against  dis- 
eases, in  which  an  excess  of  nitrogen  comes  under  consideration,  will  be 
discussed  under  the  individual  cases  of  disease. 

3.     THE  DISADVANTAGES  OF  MOOR  SOILS. 

The  Acids  in  the  Soil. 

Ramann^  explains  as  moors,— the  formation  of  more  moist  regions  in 
temperate  zones,  in  which  soils  poor  in  nutritive  substances,  with  an  acid 
reaction,  are  covered  with  dwarfed  bushes,  grasses,  mosses  and  peat-moss 
(sphagnum),  and  also  lichens. 

The  humic  acids*  act  freely  here,  and  cause  the  acid  reaction  of  the 
soil.  Acids  are  formed  by  the  decomposition  of  the  organic  substances  in 
the  soil  to  which  fungi  as  well  as  bacteria  surely  contribute  a  share  (Cepha- 
losporium,  Trichoderma,  etc.,  according  to  Koning-).  Formic  acid,  acetic 
acid,  butyric  acid,  etc.,  are  produced  which  decompose  rapidly  in  well 
aerated  soils.  Besides  these,  however,  the  humic  substances  also  form  the 
still  little  known  crenic  acid  with  its  salts  (crenates)  which,  widely  dis- 
tributed in  soils  and  water,  form  a  yellow,  strongly  acid  solution, 
drying  to  an  amorphous  mass.  While  its  salts  with  alkalis  and  alkaline 
earths  are  soluble,  its  ferric  oxid  remains  insoluble.  With  the  entrance  of 
air  aprocrenic  acid  is  produced  from  it,  the  salts  of  which  are  either  in- 
soluble or  dissolve  with  difficulty.  A  great  influence  on  the  weathering  and 
the  transportation  of  the  accessible  mineral  salts  may  be  ascribed  to  these 
acids  and  their  compounds\  Raw  humus,  peat  and  other  soil  substances 
with  a  strong  acid  reaction  lose  only  a  part  of  their  acids  even  after  lying 
sometime  exposed  to  the  air.  Since  even  well  aerated  forest  soil  often 
shows  an  acid  reaction,  it  may  be  concluded  that  scant  oxidation  either  does 
not  cause  the  production  of  the  soil  acids,  or  only  at  times  produces  them. 
We  must  consider  here  also  the  work  of  definite  bacteria  in  this  acid  for- 
mation. Free  acids  are  often  absent  in  good  soils,  but  poorer  moor  soils  are 
frequently  rich  in  them  and  become  even  poorer  because  extensive  leaching 
and  weathering  processes  constantly  take  place,  due  to  the  free  acids. 


1  Ramann,  Bodenkunde,  2nd.  Edition.  Jul.  Springer.  1905. 

2  Koning-,  Arch,  n^erland.  sc.  ex.  et  nat.  1902  II,  9,  p.  34. 

3  Ramann,  loc.  cit.  p.  144. 


*  In  the  light  of  recent  investigations  on  the  nature  of  the  organic  matter 
of  the  soil  it  seems  that  we  m<ust  revise  some  of  the  older  terminology.  The  term 
'•humic  acids"  is  rather  to  be  regarded  as  a  loose  generic  term  applicable  to  a  group 
of  organic  compounds  found  in  the  soil. — Vide:  — 

Mulder,  The  Chemistry  of  Vegetable  and  Animal  Physiology,  trans,  by  From- 
berg,  1849. 

Schreiner,  O.  and  Shorey,  E.  C,  Bulletins  53,  74,  and  88,  Bureau  of  Soils,  U.  S. 
Department  of  Agriculture. 

Jodidi,  S.  L.  Jour.  Amer.  Chem.  Soc.  34:  94.  1912:  Jour.  Franklin  Inst.  175:  245. 
1913. 

(Translator's  note) 


241 

In  regard  to  the  sensitiveness  of  our  cultivated  plants  to  free  acids, 
Ramann  cites  Maxwell's^  experiments  with  i-io  and  1-50  per  cent,  solutions 
of  citric  acid.  He  found  that  all  the  Cruciferae  were  quickly  destroyed,  the 
Papilionaceae  more  slowly.  Grain  suffered  greatly,  only  the  pearl  millet 
and  Inaize  could  withstand  it.  Tolf  made  discoveries  in  regard  to  humic 
acids,  according  to  which  seedlings  suffer  in  acid  moor  soils.  In  the  acid 
moor,  the  diffusion  of  the  salt  solutions  is  sharply  arrested.  According 
to  Reinitzer  and  Nikitinsk,  pure  humic  acids  are  unsuitable  for  the 
nutrition  of  bacteria  and  fungi.  On  the  other  hand,  most  of  the  higher 
plants  can  endure  a  moderate  amount  of  these  acids.  We  discover  from  our 
cultures  of  Ericas,  Azaleas,  Rhododendrons  and  other  Ericaceae  in  moor  soil 
that  a  number  of  plants  indeed  seem  directly  adapted  to  acid  soils. 

The  dark  colored  humus  parts  consist  preponderately  of  Humin  and 
humic  acid  (Ulmin,  according  to  Mulder).  The  humus  substance  must  be 
considered  as  a  mixture  of  closely  related  bodies  with  and  without  nitrogen, 
which  can  be  separated  into  two  groups  according  to  their  behavior  with  al- 
kalis. The  brown  humin  substances,  insoluble  in  the  most  diverse  solvents, 
swell  up  in  alkaline  liquids  and  pass  gradually  over  Into  humic  acids.  The 
humic  acids  (their  chemical  composition  is  insufficiently  known),  containing 
possibly  59  to  63  per  cent.  C,  4.4  to  4.6  per  cent.  H.  and  35  to  36  per  cent.  O, 
are  easily  dissolved  in  alkalis  and  are  re-precipitated  from  their  solutions 
by  stronger  mineral  acids.  If  they  are  withdrawn  from  acid  soils  (moor 
soils)  with  alkalis  or  ammonia  and  precipitated  with  hydrochloric  acid,  a 
voluminous,  jelly-like  substance  is  obtain  which,  in  drying,  forms  a  brown 
or  black  amorphous  mass.  The  humic  acids  are  separated  from  their  solution, 
by  freezing,  in  the  form  of  a  dark  colored  powder,  which  gradually  passes 
over  again  into  solution.  Ramann  emphasizes  the  fact  that  humic  acids  are 
somewhat  soluble  in  pure  water,  but  not  in  water  containing  salts.  The  salts 
of  the  alkalis  and  of  ammonia  with  humic  acids  are  soluble  in  water,  but 
not  those  of  the  alkaline  earths  (calcium  and  magnesium).  Yet  the  latter 
also  seems  to  become  soluble  with  an  excess  of  acids.  Calcium  humate  will 
decompose  quickly  into  calcium  carbonate  which  will  combine  into  new 
masses  of  humic  acids. 

On  an  average,  the  nitrogen  content  of  humus  substances  is  greater  in 
dry  regions  than  in  moist  ones.  By  the  advancing  decomposition,  the  nitro- 
gen, which  in  organic  combinations  is  accessible  to  plants  with  difficulty,  is 
carried  over  into  compounds  easily  absorbed. 

Raw  Humus. 
Humus  is  beneficial  and  indispensible  only  where,  in  pure  deposits  or 
mixed  with  the  mineral  skeleton  of  the  soil,  it  is  exposed  to  constant  aeration 
and  to  sufficient  moisture.  Its  chief  action  on  plant  growth  does  not  lie  in 
its  nutrient  content  or  in  the  carbon  dioxid  formed  by  its  decomposition  of 
minerals,  but  in  its  physical  properties. 

1  Journ.  Amer.  Chem.  Soc.  1898,  20,  p.  103. 


242 

If  humus  is  mixed  with  dense  soils,  they  are  loosened  and  made  warmer 
and  more  easily  worked.  In  sandy  soils  the  humus  acts  as  a  hinder  and  in- 
creases the  water  capacity,  whereby  the  fluctuations  in  temperature  become 
less  marked.  These  favorable  peculiarities,  which  arise  from  the  mixing 
with  mineral  elements  in  the  soil,  disappear  as  soon  as  the  humus  4s  de- 
posited on  the  soil  in  impervious  layers,  i.  e.,  is  not  broken  up  by  abundant 
decomposition  and  the  micro-organisms.  In  compact  humus  layers,  the  con- 
lent  in  free  acids  is  almost  always  greater.  The  forest  soils,  which  are  most 
rapidly  decomposed  and  worked  up,  are  the  best.  In  warm  climates  the 
work  progresses  very  quickly  of  itself. 

With  a  favorable  humus  decomposition,  we  find  that  in  forest  soils  the 
porous  forest  debris,  which  forms  the  layers  of  litter,  is  not  so  thick  and 
merges  gradually  into  a  friable,  strongly  decomposed,  structureless  humus 
layer.  If  in  any  region  the  factors  contributing  to  decomposition  are  ab- 
sent, these  layers  of  litter  are  retained,  settle  only  gradually  and  become  a 
firm,  fibrous  humus  mass,  which  is  deposited  on  the  subsoil  and  remains 
more  or  less  sharply  separated  from  it.  Such  cases  may  be  observed  in  poor 
sandy  soils,  especially  those  containing  meadow  ore. 

This  process,  in  which  therefore  the  organic  substance  acquires  no 
earthy  composition,  will  occur  everywhere  where  conditions  unfavorable  to 
decomposition  exist, — as,  for  example,  when  the  air  is  excluded  by  water,  or 
conversely,  with  too  great  drought  in  the  hot  seasons  or  in  places  exposed  to 
constant  strong  winds. 

Our  forest  tracts,  where  heather  (Calluna  vulgaris),  cranberries  and 
huckleberries  (Vaccinium)  the  pteris  and  aspidium  brakes  and  the  cushion- 
forming  mosses  grow,  are  most  inclined  to  the  formation  of  such  fibrous  and 
but  slightly  earthy  humus  layers,  the  undecomposed  elements  of  which  are 
deposited  in  dense  masses  on  the  soil  and  in  this  way  form  the  so-called 
"raw-humus."  The  upper  layer  of  such  raw-humus  deposits  still  shows  the 
interwoven  structure  of  the  plant  debris,  the  lower  layer,  in  which  the  plant 
parts  are  but  slightly  distinguishable  from  one  another,  has  a  fibrous  dark 
humus  substance  interwoven  with  roots.  In  moist  beech,  pine  and  spruce 
tracts,  such  raw  humus  may  become  peat-like. 

Ramann  (loc.  cit.  p.  162)  states  as  his  opinion  of  the  change  in  the  soil 
beneath  a  covering  of  raw  humus, — that,  besides  the  exclusion  of  air,  the 
humic  acids  especially  form  the  injurious  factors.  These  act  on  the  un- 
weathered  silicate,  decomposing  it  energetically,  bringing  into  solution  al- 
kalis and  alkaline  earths  and,  since  at  the  same  time  the  amount  of  acid 
solutions  absorbed  in  the  soil  is  slight,  leaches  the  soil,  i.e.,  the  soluble  sub- 
stances are  carried  down  to  greater  depths.  If  raw  humus  lies  on  sandy 
soils,  the  grains  of  the  uppermost  layer  appear  to  be  strongly  bleached  and 
milk-white,  the  intermixed  silicate  rock  is  greatly  weathered  and  usually 
transformed  into  white  kaolin.  The  humus  admixture  still  richly  present  on 
the  upper  surface  decreases  more  and  more  from  the  top  downwards  so  that 


243 

the  soil  becomes  light  gray  in  color  and,  because  of  this  color,  is  called  gray 
or  lead  sand. 

Below  this  Hght  colored  layer  is  found,  sharply  separated  from  it,  a 
yellow  to  brownish  looking  soil,  the  deeper  layers  of  which  gradually  be- 
come lighter.  Here,  the  sand  grains  show  mixtures  of  ferric-oxid  or  ferric 
hydrate.  Then  comes  the  white  raw  sand,  still  but  little  affected  by  weather- 
ing. The  uppermost  humus  soil  layer  is  found  to  be  most  weathered  and  the 
layer  most  impoverished  by  leaching.  If  the  leaching  of  such  an  upper  soil 
layer,  under  the  influence  of  the  raw  humus  deposited  on  it,  be  carried  to  a 
given  stage,  the  action  of  the  salts  in  the  soil  on  the  soluble  humic  acid  must 
cease,  the  salts  then  remain  in  solution  and  can  penetrate  to  the  lower  layers 
of  the  soil.  If  they  come  in  contact  here  with  soluble  salts,  they  are  precipi- 
tated and  coat  the  separate  soil  grains  with  a  structureless  layer  of  organic 
substances.  Under  the  microscope,  I  found  the  sand  grains  covered  with 
brown,  chart-like  etchings.  If  this  process  keeps  up,  the  precipitated  or- 
ganic substances  finally  cement  the  separate  sand  grains  into  compacted 
layers  below  the  lead  sand, — meadow-ore  has  been  produced. 

Meadov/-Ore. 

According  to  Ramann's  explanation  of  the  production  of  meadow-ore, 
given  in  the  previous  section,  this  is  a  humus  sand  stone.  It  occurs  in  var- 
ious forms  and  first  of  all  as  "Branderde"  or  "Orterde,"  which  has  a  white 
easily  pulverized  form  and  shows  a  large  content  of  organic  substances. 
This  is  formed  in  rich  soils  which  are  but  little  changed  unfavorably.  The 
real  swamp  ore  is  a  firm,  stone-like,  hard  mass,  deposited  on  easily  pulver- 
ized or  loose  soil  layers,  with  a  medium  content  of  organic  substances 
and  a  brown  to  black  color.  This  is  the  form  most  widely  distributed  in 
North  Germany  (Liineburger  moor).  Besides  this,  there  is  a  lighter  brown 
swamp-ore  which  is  ytry  firm  and  tough  and  holds  but  small  amounts  of 
organic  substances.  This  is  the  hardest  form,  offering  the  greatest  resistance 
to  a  working  of  the  soil  and  frequently  occurring  in  great  thickness. 

In  judging  the  processes  of  leaching,  an  analysis  taken  by  Graebner^ 
from  Ramann's"  work  may  be  useful.  The  swamp  ore  soil  in  the  Main 
Forestry  District  Hohenbriick  in  Pomerania  contained  in  its  different 
layers : — • 

(a)  Lead  sand,  which  was  15  to  20  cm.  thick  and  contained  1.05  per 
cent,  of  organic  substances^. 

Soluble  in  Residue  insoluble  in 

Hydrochloric  acid.         Hydrochloric  acid. 

Potassium    0.0076  per  cent,  of  the  soil         0.618 


(Sodium o.oiii 

Calcium  o.oiio 

Magnesia 0.0026 

(Manganous  oxid 0.0032 

Ferric  oxid   0.0964 

Aluminum  oxid 0.0268 

Phosphoric  acid 0.0058 


0.167) 

0.060 

0.020 

0.060) 

0.450 

0.650 

0.043 


Total  content  except  silicic  acid. 0.1645  2.068 

1  Paul  Graebner,   Handbuch   der  Heidekultur.   Leipzig,   Wilh.   Engelmann.   1904, 
p.  194. 

2  Die  Waldstreu,  Berlin,  1890,  p.  30. 

3  Ramann  in  his   "Bodenkunde"   1905,  p.   166,  gives   the  same  analysis  without 
the  elements  enclosed  in  parantheses. 


M4 

(b)  Swamp  ore,  5  to  8  cm.  thick  with  7.2S  per  cent,  of  organic  sub- 
stances : 

Soluble  in  Residue  insoluble  in 

Hydrochloric  acid.         Hydrochloric  acid. 

Potassium 0.0178  per  cent,  of  the  soil         0.754 

(Sodium 0.0033     "       "       "  "       "  0-360) 

Calcium 0.0194     "       "       "  "       "  0.170 

Magnesia 0.0137     "       "       "  "       "  0.028 

(Manganous  oxid 0.0044     "       "       "  "       "  0.047) 

Ferric  oxid 0.1936     "       "       "  "       "  0.690 

Aluminum  oxid 1.5266     "       "       "  "       "  2.320 

Phosphoric  acid 0.2956     "  0.042 

Total  mineral  substances  except 

silicic  acid   2.0744  4.41 1 

(c)  The  yellowish  brown  sand  underlying  the  swamp  ore: 

Soluble  in  Residue  insoluble  in 

Hydrochloric  acid.  Hydrochloric  acid. 

Potassium    0.0085  per  cent,  of  the  soil         1.103 

(Sodium 0.0213     "       "  "  "  "  0.528) 

Calcium   0.0254     "       "  "  "  "  0.225 

Magnesia 0.0401     "       "  "  "  "  0.064 

(Manganous  oxid 0.0068     "       "  "  "  "  0.026) 

Ferric  oxid 0.3448     "       "  "  "  "  0.760 

Aluminum  oxid 0.4000     "       "  "  "  "  3-2IO 

Phosphoric  acid   0.0281     "       "  "  "  "  0-043 

Total  mineral  substances  except 

silicic  acid    0.8750  5-959 

We  perceive  from  the  above  figures  that,  by  leaching,  the  lead  sand  has 
not  only  lost  in  soluble  substances,  but  that  the  greatest  part  of  all  the 
rock  debris  containing  nutritive  substances  has  been  decomposed  by 
weathering  and  being  washed  deeper  down.  It  is  therefore  a  fact  that  cer- 
tain soil  layers  in  forests  and  in  open  moors  (usually  formed  from  such  soil 
layers)  become  impoverished.  This  is  very  significant  agriculturally  if  the 
impoverishment  exceeds  the  supply  of  nutriment  furnished  by  weathering 
and  the  annual  rain  fall. 

Meadow  ore  must  be  distinguished  from  the  real  swamp  ore ;  the  for- 
mer is  insoluble  in  an  acid  solution,  such  as  hydrochloric  acid,  while  the 
swamp  ore  is  abundantly  dissolved. 

Especially  in  humus  moor  soils,  where  the  deposition  of  raw  humus 
leads  to  the  formation  of  swamp  ore,  do  two  chief  injurious  factors  come 
under  consideration : — the  lack  of  oxygen  due  to  the  density  of  the  soil  and 
the  content  in  humic  acids.  The  processes  taking  place,  with  an  exclusion  of 
oxygen,  have  been  considered  in  another  place  (for  example,  p.  99). 
We  have  here  to  take  only  the  humic  acids  under  consideration.  Graebner 
pays  the  desired  attention  to  this  points  Continuing  Wolf's-  investigations  on 


1  Loc.  cit.  p.  228. 

2  Tagebl.  Naturf,  Vers.,  Leipzig,  IS'i 


^45 

the  wilting  of  the  leaves  and  their  ultimate  death,  resulting  from  the  de- 
tention of  the  plant  roots  in  water  excessively  charged  with  carbon  dioxid, 
Graebner  cites  Maxwell's  experiments^  with  citric  acid  and  those  of  Tolf 
and  Blank  with  humic  acids,  all  of  which  lead  to  similar  results.  This  is  the 
place  to  record  Ramann's  statement  as  to  the  cause  of  retarded  diffusion  in 
acid  soils.  Either  the  colloidal  composition  of  the  moor-substances  can  re- 
duce the  capacity  for  diffusion  and  the  colloidal  substances  are  precipitated 
by  neutralization  with  lime,  or  some  direct  action  of  the  humic  acids  is 
present.  If  one  thinks  of  the  discoveries  showing  the  influence  exerted  by 
slight  acid  increases  on  the  protoplasm^,  whereby  its  currents  are  arrested, 
one  must  consider  the  direct  action  of  the  acid  to  be  of  the  chief  importance. 
Special  proof  already  exists  of  the  retarding  of  transpiration  by  acids  (tar- 
taric, oxalic,  nitric  and  carbonic  acids,  etc.)  and  its  hastening  by  alkalis 
(potassium,  sodium,  ammonia)^.  It  can  therefore  be  said,  with  Schimper, 
that  plants  in  a  strongly  acid  soil  will  suffer  from  physiological  drought  even 
in  the  presence  of  abundant  water.  To  this  must  be  added  that  the  great 
power  of  humus  to  retain  water  makes  the  mechanical  withdrawal  of  the 
water  from  the  soil  particles  much  more  difficult  for  the  roots  than  if  in 
sandy  soil.  Plants  are  found  to  wilt  in  peaty  soil  or  loam  with  a  percentage 
of  water  sufficient  to  keep  them  perfectly  fresh  in  sandy  soils,  as  Sachs'* 
experiment  has  already  shown. 

All  these  injuries  due  to  the  soil  find  expression  most  of  all  in  the  culti- 
vation of  pines,  which  subject  Graebner^  has  treated  with  especial  thorough- 
ness. He  found  in  young  pine  plantations,  which  had  grown  tolerably  well 
for  some  years,  that  the  shoots  formed  in  May  at  first  developed  normally, 
but,  with  the  appearance  of  the  summer  drought,  became  grayish  green  in 
color.  If  the  dry  period  continued,  the  shoots  begin  to  curl,  the  needles  of 
the  previous  year  became  blunt  and  brown  and  in  many  cases  the  little  trees 
dried  up  in  a  few  weeks.  By  digging  in  the  soil,  it  was  found  that  swamp 
ore  had  been  formed  below  the  roots  or  even  around  the  still  rather  slender 
ones. 

To  supplement  his  description,  Graebner  pictures  in  the  figures  here 
reproduced  root  development  on  swamp  ore  soils.  We  see  in  figure  29,  that 
the  strongest  and  longest  roots  are  spread  out  not  far  below  the  surface  of 
the  soil  and  parallel  to  it,  so  that  its  nutrition  must  take  place  through  the 
raw  humus  and  the  lead  sand,  which  is  poor  in  nutritive  substances.  Since 
root  development  is  greater  in  solutions  poor  in  nutritive  substances  than  in 
concentrated  solutions,  this  results  in  a  wide  reaching  out  of  the  root 
branches,  which,  in  the  present  case,  according  to  Graebner,  seem  several 
meters  long  and  but  little  branched.    The  aerial  axis,  however,  is  scarcely  a 


1  Journ.  Ann.  Chem.  Soc.  XX   (1898)  p.  103. 

2  Pfeffer,  Pflanzenphysiologie  II  Vol.  1904,  p.  798. 

3  Pfeffer,  Pfianzenphysiologie  I  Vol.  p.  231. 

4  Sachs,  Handb.  d.  Exp.-Physiol.  Leipzig,  1865,  p.  173. 

5  Graebner,  R.,  Handbuch  der  Heidekultur,  Leipzig,  1904,  W.  Engelmann,  p.  231. 


24t) 


meter  high.  Poverty  in  nutritive  substances  in  combination  with  the  lack  of 
moisture,  easily  becoming  great  in  lead  sand,  are  the  causes  of  an  ultimate 
blighting  at  the  tops. 

Figure  30  shows  the  root  growth  of  an  oak.  Tiic  oak  was  planted  after 
the  layer  of  swamp  ore  had  been  broken  through  artificially.  But  this  layer 
of  swamp  ore  had  later  re-united  and  the  portion  of  the  root  in  g,  nearly 
shut  away  from  an  air  supply,  had  practically  stopped  growing.  No  mycor- 
rhiza,  or  scarcely  any,  could  be  found  on  this  part  of  the  root. 

Graebner  attaches  the  fol- 
lowing significance  to  such 
phenomena.  If  the  swamp 
ore  is  deposited  below  the 
roots,  the  earth  lying  above  it 
is  naturally  exposed  to  great 
fluctuations  in  moisture,  and 
in  times  of  drought  becomes 
so  dry  that  the  plants  die  from 
a  lack  of  moisture.  In  cases 
of  this  kind,  however,  the 
plants  forming  their  roots  en- 
tirely in  the  lead  sand,  exhibit 
a  very  weak  growth,  grad- 
ually making  itself  evident  by 
short,  yellow  needles.  If  the 
swamp  ore,  however,  lies  di- 
rectly around  the  roots,  which 
are  about  as  large  as  knitting 
needles,  and  have  penetrated 
in  to  the  better  soil,  it  presses 
against  them,  causing  knotty 
swellings.  This  takes  place  if 
the  roots  reach  the  better  sub- 
soil through  an  opening  in  the 
swamp  ore  layer.  Such  me- 
chanical constrictions  disturb 
further  root  growth.  The  tree 
is  therefore  essentially  dependent  on  the  roots  lying  above  the  swamp  ore 
layer.  Growth  and  vital  activity  are  normal  during  the  spring  dampness,  but 
all  activity  stops  if  a  hot  summer  dries  out  the  soil.  Graebner  found  the  root 
tips  shrivelling,  turning  to  resin  or  dying  entirely.  In  larger  trees,  with  a 
renewal  of  moisture,  time  and  material  are  necessary  for  new  root  growth. 
This  loss  in  time  and  substance  becomes  evident  in  the  growth  of  the  aerial 
axis  and,  in  combination  with  the  results  of  the  period  of  drought,  causes  in 
great  part  the  weak  growth  of  the  moor  pines.  The  plantations  improve  as 
soon  as  the  fluctuations  of  moisture  are  less  extreme. 


Fig-  29.  "A  meadow  ore  pine"  from  the  Liine- 
burg-er  moor,  grown  after  the  formation  of  the 
meadow  ore. 

r  raw  humus,  b  lead  sand,  o  meadow  ore.  Below  the  meadow 
ore  the  yellow  sand  begins.     (After  Graebner.) 


247 

Usually  pines  on  high  moor  soil  develop  a  very  crooked  form^  Yet 
ihe  seeds  of  these  crippled  pines,  after  the  moor  has  been  drained  dry,  grow 
into  erect  trunks.  Schroter  and  Kirchner-  also  state  that,  on  too  wet  places 
in  the  high  moor,  Pinus  montana  makes  a  reduced  cripple  growth 
("Kusseln"),  but  recovers  after  the  water  has  been  drained  from  the  soil. 
Our  pines  form  such  ("Kusseln")  also  on  wet  meadows.  In  the  cases  I 
have  observed,  this  form  of  growth  was  produced  by  the  resinification  of  the 
terminal  bud  of  the  main  shoot,  because  of  insect  and  fungus  injury;  there 
then  develops  below  this  bud  a  number  of  shoots  which  remain  short  (and 
in  part  some  rosette 
shoots). 

Figure  31  shows  a 
pine  48  years  old  which 
came  from  the  Liinebur- 
ger  moor  and  which  Dr. 
Graebner  most  kindly 
placed  at  my  disposal. 
The  height  of  the  whole 
tree,- — including  the  tops 
and  measured  from  the 
root  neck  up,  amounted 
to  74  cm. ;  the  length  of 
the  trunk  up  to  the  first 
branch,  39  cm. ;  the  girth 
of  the  trunk  below  the 
lowermost  branch,  8 :3 
cm. ;  the  average  length 
of  the  needles,  2  cm.  The 
foliage  of  the  whole  tree 
is  very  sparse.  The 
needles  have  remained 
only  on  the  latest  shoots, 
all  the  older  ones  have 

fallen.  The  branches  are  greatly  thickened  in  places  and  cracked  open 
as  a  result  of  injury  from  frost.  The  perpendicularly  growing  tap 
root  is  8  cm.  long  to  its  place  of  horizontal  bending;  the  largest  horizontal 
root  branch,  18  cm.  The  branch  growth  is  sparse  and  the  branches  have 
sharp  angles  {k)  and  often  dead  tips  (a).  These  sharp  angles  or  bow-like 
curves  {k)  arise  because  the  branches  and  the  main  trunk  have  received  one- 
sided, canker-like  frost  wounds  to  which  correspond  an  increased  wood  for- 
jnation  and  a  stretching  on  the  opposite  side.  Greater  frost  wounds,  extend- 
ing over  more  than  half  the  circumference  of  the  axis,  are  found  at  /  and  /'. 


l-'iy.  30.  An  (juls  from  the  Liineburger  moor  planted 
after  the  meadow  ere  had  been  broken  through. 
The  layer  of  meadow  ore  had  closed  later. 

r  raw  humus,  b  layer  of  sand  20  cm.  thick,  o  meadow  ore. 
g  yellow  sand.     (After  Graebner.) 


1  V.    Sievers,    Ueber    die    Vererbung-    von    Wuchsfehlern    bei    Pinus    silvestris. 
Forstl.-naturwiss.    Zeitschr.  1898.    Part  5. 

-  Lebeng-eschichte  der  Blutenpflanzen  Mitteleuropas,  Part  III,  1905.  p.  222. 


248 

In  figure  32  /'  on  the  main  trunk  is  reproduced  in  natural  size,  in  order  to 
show  that,  like  "open  canker,"  the  wounded  surface  consists  of  many  very 
small,  over-growth  edges  of  different  years  which  recede  like  terraces. 

In  accordance  with  the  paltry  branch  growth  in  figure  31,  the  root  is 
also  small ;  it  cannot  follow  its  natural  tendency  to  send  its  tap  root  downward 


Fig.  31.  A  moor  pine  with  flatly  extended  roots  from  the  LUneburger  moor.  (Orig.) 
a  dead  tips  of  branches,  k  parts  of  the  branch  which  have  t;rown  out  at  sharp  angles,  k'  parts  of  the  branch 
curved  like  bows,  /  frost  wound  where  the  branch  leaves  the  trunk,  f  frost  wound  in  the  form  of  an  oijen 
canker  with  a  distinctly  limited  wood  body,  /;  roots  which  had  grown  ajjainst  the  layer  of  meadow  ore. 

perpendicularly  (compare  figures  5  and  6,  p.  95),  but  must  extend 
its  root  branches  in  the  upper  soil  layers  and  moss  cushions.  Part  of  the  lowest 
root  branches  are  partially  bent  upwards  at  a  sharp  angle,  probably  because 
they  have  met  with  a  layer  of  swamp  ore  or  some  similar  impenetrable  body. 


M^ 


In  his  study  of  the  high  moor  of  Augstumal  in  the  Memel  delta, 
Weber^  gives  very  interesting  illustrations  of  the  crippled  forms  of  pines, 
corresponding  to  the  Pinus  silvestris  f.  turfosa,  \A^illk.  Here  he  describes 
also  the  crippled  birches,  whose  roots,  like 
those  of  the  Scotch  fir,  always  show  splen- 
didly developed  mycorrhiza.  The  trunk, 
usually  only  a  few  centimetres  thick,  is  most- 
ly bent  and  knarled,  and  covered  below  with 
a  seamed  bark,  a  very  striking  feature  in  such 
small  trees.  To  this  it  should  be  added  that 
these  small  birches  usually  only  about  1.5 
m.  high  form  a  well  set  top.  On  an  average, 
the  main  root  penetrates  only  15  to  20  cm.  in- 
to the  soil,  then  bends  to  one  side,  to  run 
parallel  with  the  surface.  The  roots,  spreading 
sidewards,  attain  to  3  to  4  times  the  length  of 
the  trunk.  The  vegetation  on  the  high  moor 
is  best  characterized  by  a  specimen  of  Betula 
pubescens  described  by  Weber-.  The  upper 
trunk,  which  had  white  rot  at  the  top,  was 
1.8  m.  high;  the  wood  from  which  the  bark 
had  been  removed  was  possibly  34  mm.  in 
diameter  above  the  root  neck  and  had  51 
annual  rings,  the  last  eleven  of  which  alto- 
gether were  only  0.9  to  2.6  mm.  wide.  The 
little  tree  was  just  beginning  to  become 
blasted  at  the  top  and  was  overgrown  for  30 
cm.  above  the  root  neck  with  Sphagnum 
medium  and  >S.  acutifolium. 

In  cultivation,  it  is  not  only  necessary  to 
break  through  the  swamp  ore  layer,  but  also 
to  bring  it  up  to  the  surface  of  the  soil.  In 
the  air,  it  decomposes  to  a  brown  sand, 
which  gradually  becomes  lighter  in  color  be- 
cause the  organic  elements  have  weathered. 
Freezing  the  swamp  ore  hastens  this  process 
greatly.  The  decomposition  usually  takes 
place  more  quickly  when  the  content  in  or- 
ganic substances  is  higher.  Brown  colored 
swamp  ore  (rich  in  humus)  is  usually  de- 
composed in  a  year;  on  the  other  hand, 
the   light   colored    (which   is   poor   in   humus),   only   after   2 


Fig'.  32.    Canker-like,  wounded 

place  on  the  moor  pine. 
c  the  (deepest  lyiner)  wood  centre, 
/  edges  of  the  wound  rising:  like  ter- 
races in  which  the  most  recent,  /,  are 
the  most  rolled  back  and  the  old  bark. 
r.  covering  it,  which  is  breaking  loose 
in  squarrous  pieces,  7t'  dying,  outer- 
most edge  of  the  wound,  /  lichen 
growths.     (Orig.) 


to  4  years. 


1  C.  A.  Weber  Ueber  die  Vegetation  und  Entstehung-  des  Hoclimoors  von  Aug- 
stumal Im  Memeldelta,  etc.    Berlin.    Paul  Parey,  1902,  pp.  40  ff. 

2  Log.  cit.  p.  47. 


250 

Poisoning  of  the  Soil  by  Metallic  Sulfur. 

In  considering  factors  injurious  to  plant  growth  ferric  sulfid  as  pyrites 
(and  rhomboidally  crystallized  as  markasit)  must  be  noticed  primarily  since 
it  is  one  oi  the  most  widespread  precipitates  produced  in  the  formation  of 
moors.  Ferric  sulfid  is  found  less  in  moors  themselves  than  in  the  under- 
lying sand  and  on  the  Une  between  the  organic  deposits  and  the  subsoil.  If 
pyrites  weathers,  there  is  produced  by  oxidation  and  absorption  of  water  sul- 
furic ferrous  oxid,^ferrous  sulfate,  copperas,  and  free  sulfuric  acid  (FeS.+ 
70+HoO=FeSo,+H2SO,) . 

The  ferrous  sulfate  oxidizes  with  the  formation  of  basic  salts  to  ferric 
oxid.  In  the  presence  of  sufficient  amounts  of  calcium  carbonate,  calcium 
sulfate  (gypsum)  is  produced.  If  ferrous  carbonate  occurs,  it  passes  over 
into  ferric  oxid  or  ferric  hydrate  with  the  loss  of  carbon  dioxid  and  the 
taking  up  of  oxygen.  As  is  well  known,  the  ferric  hydrates  cause  the  yellow 
to  brown  color  of  the  soils  and  are  able  to  absorb  gases  (carbon  dioxid,  nit- 
rogen, etc.)  to  a  very  marked  degree.  Among  them  is  the  brown  clay  iron 
ore  (limonite  Fe2[OH]c)  which  cements  together  the  surrounding  sand^  In 
moor  regions,  however,  the  layers  containing  pyrites  are  often  not  oxidized 
at  all ;  because  of  the  presence  of  water  and  the  strongly  reducing  action  of 
the  moor  substance  they  cannot  obtain  any  oxygen. 

The  most  disasterous  effect  of  the  iron  sulfid  is  its  inhibition  of  the  com- 
bining of  the  bases  present  in  the  soil  and  the  free  sulfuric  acid  formed  by 
weathering.  As  a  rule,  calcium  carbonate  is  present  in  the  soil,  so  that  gy'p- 
sum  can  be  formed,  often  alum  or  magnesium  sulfate  are  also  produced.  An 
excess  of  the  last  can  act  injuriously.  When  experimenting  with  an  exces- 
sive supply  of  alum,  I  found  spotted  necrosis  appearing  in  barley.  However, 
if  the  bases  are  absent,  the  free  sulfuric  acid  will  act  directly  as  a  plant 
poison. 

If,  in  improving  the  soil,  the  layer  containing  the  pyrites  is  brought  to 
the  surface,  the  soil  will  at  first  remain  infertile. 

Minssen-  shows  that  at  times  the  upper  layers  of  the  moor  also  contain 
iron  sulfid.  In  a  sample  from  Silesia  he  found  7.286  per  cent,  of  the  dry 
substance  of  the  surface  soil  to  be  sulfuric  acid,  soluble  in  water,  3.940  per 
cent,  ferrous  sulfate  and  3.346  per  cent,  free  sulfuric  acid  and  approximately 
twice  as  much  in  the  deeper  layers,  aside  from  great  masses  of  still  un- 
weathered  iron  bisulfid.  The  top  of  the  sulfate  here  analyzed  was  later  re- 
moved 62  cm.  deep,  so  that  the  lower  layers  richly  impregnated  with  iron  sul- 
fid were  laid  bare.  The  oxidation  of  the  pyrites  gave  such  large  amounts  of 
compounds  injurious  to  vegetation  that  any  agricultural  use  of  the  moor 
within  a  conceivable  time  seemed  impossible.  Such  a  case  shows  the  neces- 
sity for  the  use  of  foresight  in  opening  up  lowland  moors. 


1  Ramann,  Bodenkunde,  1905,  p.  87. 

-  Mitteilungen  d.  Ver.  z.   Forderung"  der  Moorkultur  im  Deutsch.    Reich,   1904. 
No.  1. 


tUbAK    lULLIS 

251 

The  question  as  to  the  injuriousness  of  the  Hack  colored  water  flozmng 
on  to  the  meadozvs  from  the  alder  hogs  of  forests  has  been  treated  in  detail 
by  Klien^.  In  one  especial  case  which  gave  rise  to  complaints  against  the 
forestry  commission,  the  water  coming  from  the  forest  was  viscid,  brown  and 
at  times  smelled  bad.  In  100,000  parts,  it  contained  31.28  parts  organic  sub- 
stances (humic  acids,  etc.)  and  17.59  parts  mineral  substances,  among  others 
7.81  parts  calcareous  earth,  3.07  parts  ferric  oxid,  etc.  The  humic  acids 
formed  the  injurious  factor  here.  In  similar  cases  it  depends  on  the  kind  of 
soil  overflowed  by  such  bog  water.  It  will  be  especially  injurious  if  it  flows 
over  ferruginous  soils  or  those  with  a  clay  subsoil,  while  a  soil  rich  in  lime 
can  more  easily  withstand  overflowing  from  the  alder  swamp,  such  as  oc- 
curs in  spring  floods,  because  of  the  hastened  decomposition  of  the  humus, 
peculiar  to  such  a  soil.  Nevertheless  such  water  should  be  avoided  for  irri- 
gation and  back  water. 

The  formation  of  ferruginous  sand  depends  on  the  precipitation  of  fer- 
ric hydrate  and  iron  silicates.  Mixtures  of  ferric  hydrates  with  varying 
amounts  of  ferric  silicates  and  phosphates  also  give  the  so-called  meado-m- 
ore.  This  combination  occurs  in  moors,  standing  bodies  of  water  and  other 
places,  where  water  containing  iron  comes  in  contact  with  the  air,  together 
with  the  co-operation  of  bacteria  (iron  bacteria  according  to  Winogradski)-. 
One  is  inclined  of  late  to  lay  stress  on  the  co-operation  of  the  micro-organ- 
isms^ 

Susceptibility  to  Frost  of  Moor  Vegetation. 

In  moor  soils  which  have  been  brought  under  cultivation,  their  especial 
sensitiveness  to  frost  as  compared  with  other  kinds  of  soil  has  been  proved 
by  repeated  experiments.  In  this,  important  differences  are  found  if  the 
moor  soil  has  a  sandy  covering  or  if  it  is  mixed  with  sand.  Wollny*  found 
in  his  experiments  that  the  latter  is  more  fertile  than  the  former,  in  which 
the  ground  water  was  higher.  Instead  of  the  sand,  a  covering  with  clay  has 
also  been  proved  to  be  beneficial.  In  meadow  cultivation  when  too  much 
water  has  been  removed,  Fleischer''  recommends  covering  with  sand,  rich  in 
feldspar,  or  loam,  or  clay  to  avoid  too  great  drying  out.  Jungner*^  gives  fur- 
ther examples  from  the  province  of  Posen.  In  them  moor  fields  which  had 
not  been  covered  with  soil  containing  clay,  showed  also  a  second  total  freez- 


1  Klien,  Die  nachteiliqe  Einwirkung-  dps  aus  Eller-Briichen  und  Torfmooren 
kommenden  schwarzen  Wassers  auf  die  Wiesen.  Konigsberger  land-  und  forst- 
wirtschaftliche  Zeitung-  1879,  No.  28;  cit.  in  Biedermann's  Centralbl.  f.  Agrik- 
Chemie,   1880,   p.  568. 

2  Winogradski,  Ueber  Ei&enbakterien.    Bot.  Zeit.  1888,  p.  260. 

3  E.  Roth,  Die  Moore  der  Schweiz,  unter  Beriicksichtigung  der  gesamten  Moor- 
frage.    Leopoldina,  1905,  No.   3,  p.  34. 

4  Wollny,  Untersuchungen  tiber  die  Beeinflussung  der  physikalischen  Eigen- 
schaften  des  Moorbodens  durch  Mischung  und  Bedeckung  mit  Sand.  II.  Mitteil. 
Forsch.  a.  d.  Geb.  d.  Agrik.-Physik.  20.  1897-1898,  p.  187. 

5  Fleischer,  M.,  Ueber  die  zweckmafsige  Behandlung  von  Moorwiesen;  cit. 
Biederm.  Centralbl.  f.  Agrik.-Chemie,  1888,  p.   ]  37. 

6  Zweiter  Jahresber.  d.  Sond.-Aussch.  f.  Fflanzenschutz  fur  1904.  Arbeit,  d. 
Deutsch.  Landw.-Ges.    Part  107,  Berlin,  1905,  p.  61. 


ing  back  of  potatoes  and  pasturage,  while  those  which  had  been  covered 
had  sufifered  no  especial  injury. 

This  discovery  indicates  that  we  have  to  look  for  the  chief  period  of 
injury  in  spring,  so  far  as  frost  phenomena  in  moor  soils  are  concerned.  In 
cultivating  trees  this  becomes  clear,  if  we  consider  that  the  humus  soils  in 
cold  seasons  usually  contain  an  excess  of  moisture.  The  fine  pored  humus, 
saturated  with  water,  will  cool  more  slowly  in  the  fall  than  do  soils  less  rich 
in  water,  but  will  warm  up  much  more  slowly  in  the  spring.  However,  the 
longer  the  roots  are  in  a  warm  location,  the  longer  they  remain  active  and 
the  more  water  will  be  forced  up  into  the  aerial  axes.  Trees  growing  poorly 
on  moor  soil  with  its  diluted  nutrient  solutions  start  the  winter  with  a  large 
water  content  in  their  tissues.  The  more  water  the  tissues  contain  and  the 
less  cytoplasm,  the  more  susceptible  are  they  to  frost,  no  matter  whether  the 
effects  of  winter  or  spring  frosts  are  concerned.  Hence  the  frequent  and 
great  injury  from  frost  in  moor  pines,  as  is  shown  in  the  example  from  the 
Liineburger  moor. 

For  short-lived  field  plants  the  most  disasterous  are  the  spring  frosts 
w^iich  are  produced  in  rays  of  cold.  This  may  be  easily  recognized  from  the 
fact  that  the  phenomena  of  discoloration  produced  on  the  leaves  and  stems 
by  the  cold  are  abruptly  cut  off,  if  such  a  part  of  the  plant  is  partially  cover- 
ed by  overlying  leaves. 

It  is  now  pertinent  to  ask  when  cold,  due  to  radiation,  will  be  greatest 
and  how  much  of  it  is  due  to  evaporation.  If  both  factors  become  effective 
to  a  high  degree,  the  air  layers  close  above  the  surface  of  the  soil  will  be 
noticeably  colder  than  the  average  temperature.  Polis^  has  proved  such  a 
lowering  of  the  temperature  of  the  air  layers  above  a  covering  of  snow.  This 
will  be  the  greater,  the  less  the  movement  of  the  air.  Hence  May  frosts  in 
still,  clear  nights.  The  moor  soils  and  those  bordering  on  moors  with  their 
wealth  of  water  wall  evaporate  strongly  in  the  early  spring  when  the  soil  and 
subsoil  have  not  been  warmed  through,  even  if,  as  cultivated  land,  they  have 
been  mixed  with  sand  and  accordingly  more  cooled  down.  Evaporation  will 
also  be  still  more  increased  by  the  dark  color  of  the  soil,  as  Wollny's-  experi- 
ments show.  Covering  with  a  layer  of  sand  from  6  to  lo  cm.  deep  acts  as  a 
preventive.  Then  but  little  water  can  reach  the  sand  from  the  humus  layer 
and,  correspondingly,  only  small  amounts  will  be  evaporated.  For  the  same 
reason  the  dead  layer  also  acts  as  a  protection  against  drought.  One  dis- 
.^dvantage  of  the  sand  covering  is  found  when  fine,  surface-rooting  grasses, 
are  sown  which  are  easily  stunted  in  sand,  poor  in  nutrition^. 

If  the  cultivation  of  fruit  trees  on  moor  soils  is  involved,  the  following 
may  be  recommended  for  protection  against  frost:  (i)  The  planting 
of  trees  on  the  west  and  southwest  side  of  the  orchard,  in  order  to  modify 
the  temperature  differences  in  spring.     The  bark  cracks  almost  without  ex- 


1   Meteorologische  Zeitschr.  1896,  Part  I. 

^  Blatter  fiir  Zuckerriibenbau,  1899,  No.  9. 

3  Mitteil.  d.  Ver.  z.  Ford.  d.  Moorkultur,  1895,  Nos.  5  and  6. 


2y:> 

ception  on  the  sides  turned  towards  these  points  of  the  compass  and  the  nor- 
mal phenomena  of  loosening  bark  scales  (for  example,  on  plane  trees)  also 
begin  earlier  and  to  a  greater  extent  on  those  sides  of  the  trees.  (2)  A 
strong  liming  and  supply  of  Thomas  slag  with  a  sufficient  provision  of  other 
nutritive  substances.  (3)  Above  all.  however,  those  varieties  of  fruit  should 
be  chosen,  wdiich  endure  moor  soil.  Huntemann^  recommends  the  common 
house  plum,  from  practical  experience.  Of  apples,  the  following  have  stood 
the  test :  Bosb.ook's  Beauty,  Golden  noble.  Double  pigeon.  White  winter 
apple,  Orleans,  Parkers  Pippin,  Purple  red  Cousinot.  The  winter  Yellow 
Pearmain,  Gravenstein,  Prince  and  xA.lant  apple  should  not  be  planted,  since 
they  are  too  susceptible  to  frost  and  also  to  canker.  According 
to  the  experiences  of  Mr.  Klitzing,  a  nurseryman,  the  following  apple  var- 
ieties are  adapted  to  cultivation  on  moor  soils, — red  Eiser  apple,  Burchardt's 
Reinette,  and  Cludius'  Autumn  apple.  Of  pears,  he  recommends  CharneuK 
Delicious,  St.  Germain  and  New  Poiteau.  If  cherries  are  tried  at  all, 
sour  varieties  should  be  chosen  rather  than  sweet  ones. 

The  Usefulness  of  the  Spruce. 

In  considering  forest  plantations  on  moist  soil,  we  only  reiterate  our 
opinion  that  it  is  a  mistake  to  plant  pines  so  extensively  as  is  now  done.  The 
example  cited  on  p.  248  from  the  Liineburger  moor  .show's  clearly  enough 
what  disadvantages  arise.  If  they  are  not  so  distinctly  noticeable  in  other 
places  and  especially  if  frost  injuries  do  not  appear  so  sharply,  yet  a  weaken- 
ed growth  is  always  induced,  which  sooner  or  later  becom.es  evident. 

For  the  plains  in  northern  Germany  we  should  return  to  the  spruce. 
We  use  the  term  "return,"  for  Conwentz-  has  actually  proved  that  often,  in 
moor  regions,  spruce  was  the  original  covering.  Even  now  in  Pomerania 
and  Hanover,  even  on  the  Liineburger  moor,  original  spruce  woods  are 
often  still  in  existence,  and  the  various  cases  especially  studied  by  Conwentz 
give  excellent  indication  that  the  spruce  is  still  found  in  a  developmental 
stage,  resembling  the  primeval  forests,  on  soils  where  wide  stretches  are 
covered  with  peat  moss  and  the  moisture  in  usual  years  makes  access  to  the 
soil  impossible. 

This  opportunity  should  be  taken  to  consider  the  layering  formations  of 
spruces,  which  at  any  rate  may  be  found  only  in  forests  not  touched  by  for- 
estration  and  it  is  advisable  on  this  account  to  preserve  accounts  of  especially 
good  examples  of  increase  by  means  of  layering.  Hence  an  illustration  and 
description  of  a  spruce  family  should  be  given  here,  which  has  been  observed 
in  the  vicinity  of  the  city  Kragero  on  the  south  eastern  coast  of  Norway 
(see  Fig.  33).  Schiibeler^  describes  it  as  follows.  The  parent  trunk,  which 
stands  at  the  foot  of  a  hill,  had  a  height  of  approximately  9.4  m.  and,  about 

1  Huntemann,  Das  Erkranken  der  Obstbaume  auf  Moorboden.  Mitt.  d.  Ver.  z. 
Ford.   d.   Moorkultur.   1898,  No.   7. 

-  Conwentz,  H.,  Die  Fichte  im  norddeutschen  Flachland.  Berichte  d.  Deutsch. 
Bot.  Gesellschaft  1905,  Part  5,  p.  220. 

3     Schiibeler,  F.  C,  Die  Pflanzenwelt  Norwegens.    Christiania  1873-75,  p.  164. 


254 

6.6  cm.  from  the  ground,  a  circumference  of  94  cm.  At  a  height  of  31  to  ^6 
cm.  three  branches  left  the  main  trunk,  and  took  root  in  several  places.  At 
a  distance  of  1.6  to  2.5  m.  from  the  present  trunk,  six  regular  spruces  have 
gradually  developed  with  a  height  of  2.5  to  4.7  m. 


Fig.  33.     A  spruce  family  produced  by  natural  layering-.     Three  of  the  branches  at 

the  base  of  the  trunk  have  rooted  again  in  several  places  and  their  buds 

have  there  developed  into  secondary  trunks.     (After  Schiibeler.) 

The  spruce  stands  by  itself  in  its  easy  formation  of  adventitious  buds, 
giving  rise  to  gnarls,  and  in  the  ability  of  parts  of  its  aerial  axis  to  form 
roots  quickly.  To  be  sure  Schiibeler  (loc.  cit.  p.  163)  has  also  observed 
rooting  in  low  branches  of  Juniperus  and  also  in  Taxiis  haccata,  v^^hich  have 
been  bent  to  the  earth,  and  certainly  such  conditions  will  occur  also  in  other 
conifers  w^hich  grow  well  from  cuttings.  But  cases  of  this  kind  will  always 
remain  isolated. 


255 

The  capacity  for  increase,  explained  here  by  means  of  the  one  example, 
has  a  greater  significance  in  moor  regions,  where  the  spruce  will  have  to  be 
grown  as  the  only  possible  means  of  forestration. 

Only  very  few  varieties  of  conifers  possess  this  facility  for  forming 
layers  and  developing  new  regular  top  growth  from  lateral  sprouts.  Gar- 
deners make  abundant  use  of  this  peculiarity  in  propagating  young  individ- 
uals from  cuttings.  In  other  conifers,  cuttings  from  the  lateral  branches 
retain  the  structure  of  laterals  and  do  not  form  handsome  trunks.     The 


^^rQ. 


'*®ft^'-i,-r/j»' 


Fig.  34.     Oak  from  Rogau  (Upper  Silesia)  with  a  formation  of  sinlvers.     (Orig.) 

genus  Araucaria  also  has  a  great  tendency  to  form  head  shoots  and  this  is 
often  shown  in  individual  lateral  branches,  which  remain  on  the  parent 
plant,  when  the  top  shoot  has  been  lost. 

In  connection  with  this  layering  formation  of  the  spruce,  occurring  on 
damp  soils,  we  give  in  figure  34  the  sketch  of  a  case  of  root  formation  from 
a  branch  of  an  oak,  which  has  been  observed  only  once.  In  the  8o's  of  the 
last  century,  I  had  an  opportunity  in  the  castle  park  at  Rogau  (Upper 
Silesia)  of  seeing  the  very  hollow  trunk  of  an  old  oak  which  stood  on  a  low 
lying  meadow,  liable  to  be  overflowed  by  the  Oder  at  flood  time.    The  tree 


256 

had  already  lost  most  of  its  leaves  on  the  lower  branches.  The  upper  parts 
of  the  two  lowest  branches,  probably  at  some  time  bent  down  intentionally, 
lay  deep  in  the  earth,  but  their  tips  had  been  turned  upward.  At  the  point 
where  the  branch  was  bent  (at  the  right  in  the  figure)  a  strong  root  was 
traceable  which  might  have  been  produced  when  the  still  young  branch  tip 
was  covered  with  silt  by  the  first  floods.  The  increased  nutrition,  produced 
by  this  root,  showed  itself  in  the  development  of  a  considerable  number  of 
younger  shoots,  resembling  an  independent  bushy  growth.  I  noticed  noth- 
ing especial  in  the  vigorous  spruce  plantations  standing  at  some  distance. 

Changes  in  Moor  Soil  Through  Cultivation. 

One  must  determine  finally  how  far  the  injurious  factors  of  humus 
soil  show  in  cultivation  and  what  changes  it  undergoes  with  cultivation. 
"Sanding"  has  been  discussed  already.  Fertilising  comes  next  under  con- 
sideration, since  the  nutriment  content  especially  in  highland  moors  is  so 
scanty  that  only  plants  needing  little  nutriment  and  highly  resistant  to  humic 
acids  thrive  there  (Sphagnum,  Eriphorum,  many  Carex  varieties,  Calluna. 
etc.).  All  fertilizers  must  act,  first  of  all,  by  increasing  those  micro- 
organisms which  can  decompose  the  soil,  since  in  soils  containing  humic 
acid,  the  bacterial  flora  is  very  scanty.  Fabricius  and  v.  Feilitzen^  gained 
much  information  on  the  methods  to  be  used  in  increasing  the  bacterial  flora 
of  moor  soils.  Stalstrom-  had  already  determined  that  draining  the  water 
from  moor  soil,  very  poor  in  bacteria,  naturally  will  increase  the  number  of 
organisms.  This  is  especially  significant  for  highland  moors,  since  they  have 
not  nearly  as  many  bacteria  as  the  lowland  moors ; —  a  fact  related  to  the 
scanty  nitrogen  content  of  the  highlands.  Moor  soil  mixed,  wdth  clay  or  im- 
proved by  fertilizing,  has  a  higher  bacterial  content.  The  bacterial  flora  re- 
mains almost  exclusively  in  the  upper  soil  layer,  15  to  25  cm.  thick.  Fab- 
ricius and  V.  Feilitzen  also  tested  the  moisture  content  in  the  upper  soil  layer 
and  found  that,  in  uncultivated  highland  moors,  this  fell  only  from  90  to  87 
per  cent,  by  draining,  while,  on  the  other  hand,  it  could  fall  to  about  64  per 
cent,  with  other  cultural  measures.  These  consisted  in  mixing  the  friable 
soil  with  sand,  with  the  result  that  vegetation  of  a  different  character  de- 
veloped. The  soil  temperature  was  lowest  on  the  virgin  moor.  Simple 
draining  exerted  but  little  influence  (-|-o.3°C.),  but  cultivation  gave  a  per- 
manent increase  of  almost  2°C.  In  regard  to  the  chemical  composition,  it 
was  found,  as  was  to  be  expected,  that  the  calcium  content  was  very  small 
in  natural  highland  moors  and  the  nitrogen  content  equally  scanty,  while  in 
the  lowland  moors  the  latter  was  found  to  be  satisfactory.  The  disappear- 
ance of  the  humic  acids  through   cultivation  is  very  interesting.     In  the 


1  Fabricus,  O.,  and  Hjalmar  von  Feilitzen.  Uebor  den  Gehalt  an  Bakterien  in 
jungfraulichem  und  kultiviertem  Hochmoorboden  auf  dem  Versuchsfelde  des 
Schwedischen  Moorkulturvereins  bei  Flahult.  CentralbL  f.  Bakteriolog-ie  etc.  II 
Section,  Vol.  XIV,  p.  161.    1905. 

^   Om  lerslag-ningens  betydelse.  Finska  Mosskulturftlreningens  a,rsbok.  1898.  p.  44. 


^S7 

natural  highland  moor  the  content  amounted  to  more  than  2  per  cent,  and 
through  sanding,  liming,  and  fertilizing  became  reduced  to  possibly  0.3  per 
cent. 

These  same  investigators  found  the  bacterial  flora  only  sparsely  de- 
veloped, as  a  result  of  the  acid  soil  in  the  highland  moor,  and  also  but  little 
increased  by  draining.  On  the  other  hand,  a  great  increase  was  found  after 
sanding,  liming  and  fertilizing  together  with  the  necessary  attendant  work- 
ing of  the  soil.  Sand  introduced  new  bacteria,  stable  manure  furnished  rich 
nutriment  of  such  a  kind  that  the  bacterial  content  become  as  great  as  in  a 
lowland  moor  under  the  same  cultural  conditions.  In  both  the  bacterial  con- 
tent increases  and  falls  directly  with  the  soil  temperature. 

The  experiences  of  practical  workers  disagree  greatly  as  to  the  use  of 
stable  manure.  In  many  places  there  has  been  failure.  But,  on  the  other 
hand,  reports  are  found,  which  determine  a  very  beneficial  effect  from  stable 
manure  even  on  moors  with  a  large  nitrogen  content,  as  Count  Schwerin 
reports^ 

This  contradiction  can  be  explained  as  follows.  Even  in  moors,  which 
contain  nitrogen  in  excess,  fertilizing  with  stable  manure  can  act  very  bene- 
ficially if  the  moor  is  but  little  decomposed,  the  nitrogen  in  it  therefore  being 
probably  still  in  a  form  not  easily  taken  up  (for  example  in  organic  com- 
pounds). On  cultivated  moors,  however,  the  yields  after  fertihzation  with 
manure  are  actually  poor  and  the  weeds  grow  in  excessive  quantities  because 
an  excess  of  nitrogen  probably  makes  itself  felt,  due  to  the  addition  of  ma- 
nure without  the  sufficient  counterbalance  of  a  phosphate  and  calcium  supply. 

Potassium  is  a  factor  primarily  involved  in  the  cultivation  of  moors. 
This  holds  good  also  for  moor-meadows,  on  which,  however,  a  good  hay 
harvest,  according  to  M.  Fleicher^,  requires  the  addition  of  phosphoric  acid 
(Thomas  slag)  besides  potassium.  (In  this  connection,  he  warns  against 
over-fertilizing  if  the  ground  water  level  does  not  lie  deeper  than  20  to  40 
cm.).  The  form  in  which  the  potassium  is  given  may  also  be  determinative 
in  the  majority  of  cases,  for  Tacke^  obtained  the  best  results  for  potatoes 
with  potassium  chlorid.  While  the  tubers  contained  17.67  per  cent,  starch 
without  fertilizing  and  17.02  per  cent,  when  fertilized  with  kainit,  and  only 
16.48  per  cent,  with  karnallite,  they  contained  18.02  per  cent,  with  the  ad- 
dition of  potassium  chlorid.  The  fertilizers  were  added  in  the  fall ;  spring 
fertilizing  reduced  the  quantity  and  quality  of  the  tubers.  Hensele** 
found  in  his  potato  cultural  experiments  that  kainit  on  meadow 
moor  soils  considerably  repressed  the  starch  content  of  the  potatoes. 
In  comparative  cultures  on  mineral  and  moor  soils,  the  yields  from  the  for- 
mer were  larger  and  the  starch  content  of  the  moor  potatoes  never  equaled 
that  of  the  tubers  from  a  mineral  soil  or  that  of  the  seed. 


1  Mitt.  d.  Ver.  z.  Ford.  d.  Moorkultur,  1895,  Part  6. 

2  Milchzeitung  1887,  No.  8. 

3  Mitt.  d.  Ver.   z.  Ford  d.  Moorkulture  1895,   No.   6. 

4  Hensele,  J.  A.,  Bericht  der  Moorkulturstation,  "Erding-er  Moos,"  1900-01.  Cen- 
tralbl.  f.  Agrik.-Chemie,  1903,  Part  3. 


258 

In  regard  to  the  injuriousness  of  spring  fertilizing,  reference  should  be 
made  to  the  reports  of  the  General  Assembly  of  the  Society  for  the  Advance- 
ment of  the  Cultivation  of  Moors\  Here  it  is  especially  emphasized,  that 
kainit  and  Thomas  slag  must  be  scattered  in  the  fall  because  spring  fertiUz- 
ing  reduces  the  sugar  and  starch  content  in  vegetables  which  require  hoeing. 
For  Thomas  slag,  the  fall  fertilizing  is  said  also  to  be  more  beneficial  because 
the  acid  of  the  moor  can  then  act  as  a  solvent  for  a  longer  time.  Chili  saltpetre 
in  cultural  experiments  had  decreased  the  sugar  content  in  edible  roots  about 
1.5  per  cent.  The  preceding  crop  also  seems  to  have  an  influence  on  moor 
cultures,  as  is  shown  by  a  case  from  the  province  of  Posen-.  There  sugar 
and  late  grown  fodder  beets  became  diseased  when  grown  after  mustard.  In 
regard  to  beet  cultivation,  Hollrung^  arrives  at  the  conclusion  that  pure  moor 
land  should  be  avoided  entirely  and  even  that  which  has  been  sanded  should 
be  used  only  with  care. 

Rotten  Bark. 

Up  to  this  point  we  have  learned  to  recognize  the  characteristic  starved 
types  of  growth  on  acid  moor  soil ;  these  are  due  not  only  to  the  scarcity  of 
nutriment  but  to  moisture  conditions  as  well,  either  a  lack  of  water 
arising  from  the  fluctuations  in  the  subsoil,  or  an  excess.  These  manifest 
themselves  in  older  trees  by  a  greater  formation  of  bark,  when  high  cushions 
of  heather  and  moss  surround  the  base  of  the  trunk.  These  dense  cushions 
store  up  water,  in  part  retaining  that  of  the  moor  soil,  in  part  collecting  that 
of  the  atmosphere,  and  in  this  way  forming  a  moist  felt  constantly  growing 
up  higher  around  the  base  of  the  trunk.  Such  damp  cushions  decrease  the 
temperature  variations  necessary  for  the  pushing  off  of  the  old  bark  scales. 
However,  they  hinder  the  supply  of  air  especially  and  cause  the  decom- 
position of  those  cell  layers  in  the  bark  scales,  which  are  especially  loosely 
constructed,  into  a  deep  brown  mass,  powdery  in  a  dry  condition  and  slimy 
when  very  damp,  which  is  called  "rotted  bark."  In  these  are  found  the 
brooding  places  of  many  animal  and  vegetable  organisms  which  carry  on 
and  hasten  decomposition. 

An  investigation  of  the  younger  layers  under  the  old  bark  scales  throws 
light  on  the  production  of  these  rotted  masses.  One  of  the  pieces  of  bark 
furnished  by  Dr.  Graebner  from  the  Liineburger  moor  was  3.5  cm.  thick  and 
differed  from  equally  old,  healthy  bark  in  that  it  could  be  peeled  with  un- 
usual ease  into  separate  layers  varying  in  thickness.  The  upper  surface  of 
the  different  bark  layers,  as  they  fell  apart,  was  rough  like  a  relief  map  and 
covered  in  places  with  hard,  woody  processes  in  the  form  of  broad  cones  up 
to  2.5  mm.  high  and  often  with  crater-like  depressions.    Such  processes,  just 


1  Berichte  der  Generalversammlung  des  Vereins  zur  Forderung-  der  Moorkultur 
Jahrg.  1895,  p.  123. 

2  Elfter   Jahresber.    d.    Sonderausschusses   f.    Pflanzenschutz.   Arb.   d.    Deutsch. 
Landw.  Ges.  Part  71,  p.  130. 

3  Hollrung-,  Die  verschiedenen  Bodenarten  und  ihre  Eignung  fiir  den  Riibenbau. 
Blatter  f.  Zuckerrubenbau,  1905,  No.  14,  p.  217. 


259 

like  the  tissue  cushions  on  the  various  deciduous  bark  layers,  which  are  like 
warts  and  occur  in  lines,  were  found  always  on  the  inner  side  of  the  layer 
which  was  being  raised  up  and  had  exactly  the  appearance  pictured  later 
under  the  section  "Bark  Refuse"  in  the  elm.  This  section  should  be  con- 
sulted. 

The  greatest  possibility  of  separation  of  the  lamellae  from  one  another 
was  found  where  a  rotted  tissue  layer,  i.  e.,  in  a  condition  of  humifaction,  be- 
gan to  disintegrate  and  formed  a  surface  of  separation.  The  rotted  bark  con- 
sisted of  cork  cells,  as  shown  on  the  upper  side  B  in  the  accompanying  cross- 
section  (Fig.  35),  while  H  shows  the  bark  which  lay  nearer  the  wood,  and 


rp'. 


Fig.  35.     Mouldy  bark  scale  of  a  pine  from  the  Liineburger  moor.     (Orig-.) 

therefore  was  younger;  rp  is  corked^  firm  bark  parenchyma  while  k  is  the 
full  cork,  loose  bark  parenchyma  and  t  the  plate  cork.  The  bark  scales  were 
therefore  composed  of  bark  parenchyma  elements,  which  advance  further 
and  further  toward  the  fresh  bark  and  the  cambium.  They  are  separated  by 
layers  of  sheet  cork  and  become  suberized.  Besides  this,  we  also  find  clus- 
ters of  loose  cells,  which  are  more  abundant  the  deeper  the  base  of  the  trunk 
has  stood  in  the  moss.  The  spongy  constitution  of  the  underside  of  the  dif- 
ferent bark  lamellae  arises  from  the  morbid  luxuriousness  of  the  parenchyma 
and  full-cork  masses.  As  a  result  of  the  moisture  and  the  scanty  supply  of 
oxygen,  these  excrescence  tissues  become  slimy  and  form  the  rotted  bark, 
which  facilitates  the  separation  of  the  lamellae. 


26o 

The  great  part  which  the  bark  parenchyma,  with  its  abnormal  phenom- 
ena of  stretching,  plays  in  the  formation  of  the  bark  shows  that  this  de- 
velopment of  rotten  bark  in  the  moor  pine  is  related  to  the  "hark  refuse"  of 
the  elm  and  distinguishes  both  cases  from  the  actual  tan  disease  (see  page 
215)  in  which  the  formation  of  full  cork  has  the  upper  hand,  as  in  the  many- 
layered  lenticels. 

Horticultural  Moor  Plants. 

The  growers,  probably  because  of  their  study  of  the  natural  habitat  of 
our  heather  plants,  have  used  for  imported  Ericaceae  the  soil  in  which  our 
Calluna  grows  splendidly: — i.  e.,  heath  moor.  The  properties  of  Sphagnum 
peat,  thus  ascertained,  have  made  this  a  desired  article  in  trade.  Its  ad- 
vantages consist  in  its  loosening  properties.  The  results  of  experiments  in 
cultivating  Ericaceae  led  to  the  mixing  of  the  so-called  moor  soil  with 
heavier  nutritious  soils  as  a  loosening  substance.  In  this  way,  the  moor  soil 
has  been  introduced  as  a  necessary  element  in  soil  mixtures  for  most  of  the 
tiner  horticultural  plants.  Since  no  standard  was  known,  however,  for  a 
good  moor  soil,  many  kinds  came  into  trade,  with  the  growing  demand.  Some 
were  either  over  rich  in  raw  humus,  or  resembled  the  character  of  the 
meadow  moor.  The  dark  color  of  the  meadow  moor  led  to  the  incorrect 
opinion  that  a  very  nutritive  earth  was  present.  The  results  of  this  mis- 
conception were  very  evident.  The  complaints  of  gardeners  about  acid  heath 
soils  are  almost  universal  and  the  degeneration  of  many  favorite  plants,  such 
as  the  so-called  new  Holland,  or  "Cape  plants,"  could  not  be  arrested. 

Where  meadow  moor  was  used  as  an  admixture  in  soils  for  potted 
plants,  its  properties  quickly  manifested  themselves.  In  a  dry  condition, 
this  moor  soil  seems  to  be  easily  pulverized,  decomposing  into  a  powder,  or 
remaining  crusty.  When  wet,  however,  it  becomes  smeary  and  cements  the 
other  particles  of  soil  into  dense  masses  with  a  poor  air  content.  Since 
meadow  moor  heats  greatly,  the  upper  layers  in  the  flower  pot  dry  out  easily, 
become  lighter  colored  and  suggest  to  the  gardener  that  the  whole  ball 
of  soil  is  dry  and  should  be  watered.  Here  is  the  danger,  for  meadow  moor 
deceives  as  does  no  other  soil.  If  such  moors  be  investigated  in  nature,  the 
smeary  condition  is  found  directly  under  the  dusty  surface,  a  few  centi- 
metres deep,  since  the  very  binding  substance  retains  the  water  unusually 
long.  Potted  plants  are  often  killed  by  a  lack  of  oxygen  at  the  roots,  even 
if  the  humic  acids  are  not  taken  into  consideration.  These,  however,  play  a 
disasterous  role  and  often  cause  the  injury  arising  in  many  cases  from  the 
use  of  loose,  fibrous  marsh  soil.  Sphagnum  peat  is  the  most  beneficial  be- 
cause the  leaf  is  so  constructed  that  it  makes  a  very  porous  soil,  giving  rapid 
moistening  and  as  rapid  an  aeration  of  the  soil  in  the  pot.  The  excellent  re- 
sults obtained  in  growing  orchids  with  sphagnum  are  well  known.  Good  re- 
sults will  only  be  had  with  fibrous  moor  soils,  full  of  fragments  of  Vaccin- 
ium  and  other  moor  plants  and  taken  from  forest  soils,  if  the  raw  humus  is 


26 1 

removed  and  the  decomposed  layers  used;  even  an  admixture  of  lime,  or  still 
better,  of  calcium  phosphate  is  advisable. 

I  have  mentioned  the  poor  growth  of  plants  in  moor  earth  in  a  special 
section,  because  I  am  of  the  opinion  that  a  very  considerable  number  of  phe- 
nomena of  disease  may  be  traced  to  the  acids  in  the  soil, — the  gardener  says 
that  the  soil  smells  sour.  Even  those  specific  plants,  such  as  Rhododendron, 
Azalea,  etc.,  only  thrive  when,  as  in  their  natural  habitat,  they  stand  in 
fibrous  earth  which  is  easily  aerated.  In  the  moment  when  a  mixture  of 
moor  soil  with  more  nutritive  solid  soils  is  used  for  potted  plants,  we  find 
root-decay,  which  is  indicated  by  the  brown  edges  of  the  leaves.  I  consider 
the  theory  of  the  necessity  of  an  admixture  of  moor  soil  in  cultivating  the 
majority  of  our  finer  potted  plants  to  be  erroneous.  As  far  as  my  experience 
goes,  sand  can  give  incomparably  better  results  as  a  loosening  material.  The 
gardener  should  work  with  well  decomposed  leaf  mould  or  compost  earths 
and  add  large  amounts  of  sand.  If  care  also  is  taken  to  have  good  pot 
drainage,  there  will  not  be  so  many  complaints  about  root  diseases  in  the 
future. 

Specking  of  Orchids. 

A  special  illustration  of  the  advantages  of  the  use  of  sphagnum,  de- 
scribed in  the  previous  division,  is  found  in  the  peculiar  black  spotted  con- 
dition of  the  leaves  of  epiphytic  orchids.  In  our  green  houses  there  are 
many  leaf  diseases  which  frequently  arise  from  fungus  infection  (Gloeo- 
sporium  and  Colletotrichum,  Phoma,  Phyllosticta,  etc.).  We  find  many  cases 
however,  in  which  fungi  take  no  part  or  occur  only  secondarily  and  among 
these  an  infection  should  be  emphasized  especially  which  may  be  found  in 
Cattleya,  Laelia,  Dendrobium  and  the  members  of  the  group  of  the  Vandeae. 

The  course  of  the  disease  is  explained  best  by  the  description  of  a  special 
case,  which,  occurring  in  Phalaenopsis  amahilis  var.  Rimenstadiana^ ,  has  re- 
cently been  studied  more  closely.  All  except  the  youngest  leaves  of  plants 
grown  in  leaf  mould  in  pierced  pots  and  watered  with  tap  water  were 
spotted  yellow  to  black.  The  disease  advanced  apparently  from  the  older  to 
the  younger  leaves  and  manifested  itself,  in  its  early  stages,  by  the  appearance 
of  irregularly  round  or  oval,  pale,  translucent  spots.  These  were  scattered 
over  the  whole  leaf,  but  usually  appeared  first  and  most  abundantly  at  the 
tip.  When  such  leaves  were  cut  off  and  lost  water  by  evaporation,  the  spots 
which  became  pale  at  the  beginning  of  the  attack,  could  be  felt  like  w^arts 
over  the  healthy  leaf.  These  conditions  changed,  however,  as  the  disease  ad- 
vanced, since  the  yellow  spots  at  once  took  on  a  whitish  appearance  and 
were  depressed  like  saucers.  In  this  it  was  seen  that  different  adjacent  cen- 
tres of  disease  coalesced,  forming  connected,  thin  surfaces,  which  finally 
turned  a  deep  blackish  brown  and  were  enclosed  like  a  wall  by  the  healthy 
tissue.     After  turning  brown,  however,  the  spots  did  not  increase  in  size. 


1   Sorauer,  Erkrankung  von  Phalaenopsis  amabilis.    Zeitschr.  f.  Pflanzenkrankh., 
1904,  Part  V. 


262 

There  were  also  centres  of  disease,  which  remained  restricted  to  definite 
groups  of  tissues. 

When  one  of  the  browned  spots,  covered  with  longitudinal  bands  due  to 
the  darker  veining,  was  cut  through,  it  was  found  that  its  paper-like  consis- 
tency was  not  produced  by  a  possible  atrophy  of  the  tissues,  resulting  from 
an  injury  due  to  insects,  or  from  bacteriosis,  but  only  by  the  drying 
together  of  the  mesophyll  cells,  which  have  been  almost  entirely  depleted  of 
their  contents.  The  boundary  between  the  dead  and  the  wall-like  convex 
bordering  healthy  tissue  was  sharp,  with  no  transitions.  The  collapsed  brown 
or  (mostly)  light  walled  tissue  when  treated  with  iodine,  showed  only  iso- 
lated flakes  of  cytoplasmic  contents  together  with  little  drops  of  a  colorless 
or  golden-yellow  substance.  With  the  entrance  of  water,  the  cell  walls,  like 
the  folds  of  an  accordion,  were  raised  somewhat  from  one  another,  without 
the  cells  having  been  brought  to  their  previous  size.  In  the  absolutely  dead 
tissue  isolated,  colorless,  slender  mycelial  threads  were  found  at  times. 

If  glycerine  was  allowed  to  act  on  the  fresh  sections,  which,  moreover, 
also  gives  a  strong  acid  reaction  at  the  diseased  spots  and  shows  no  oxydases 
and  peroxydases  with  guaiak  and  hydrogen  peroxid,  large,  irregular  or 
usually  spherical  masses  were  drawn  together  in  the  cell  contents.  This  phe- 
nomenon was  often  found  in  especially  sappy  tissue,  rich  in  sugar.  At  the 
periphery  of  these  masses  lay  the  chloroplasts.  In  the  badly  diseased  parts 
these  groups  of  substances  could  not  be  found  at  all,  but  only  numerous  very 
small  or  somewhat  larger  drops.  Just  as  Httle  can  this  contraction  of  the 
cell  contents  into  strongly  refractive  drops  be  proved  in  the  healthy  part  of 
the  leaf.  We  might  place  it  in  the  list  of  glucoses  because,  with  the  Trom- 
mer  test,  they  show  in  places  precipitates  of  cuprous  oxid. 

Further  anatomical  investigations  led  to  the  discovery  that,  in  the  var- 
ious yellowish  tissue  centres,  the  cell  content  was  used  up  too  strongly,  and 
the  mesophyll  cells  had  grown  out  wider.  The  diseased  place  thus  became 
somewhat  swollen  up  over  the  healthy  surface,  but  at  once  the  diseased  tissue, 
which  had  lived  out  its  life  very  rapidly,  showed  this  by  the  appearance  of 
carotin  drops ;  it  collapsed,  turned  brown,  and  dried  up.  This  process  of 
drying,  however,  is  limited,  in  all  cases  observed  as  yet,  to  the  leaf  region 
characterised  in  the  beginning  by  the  turning  yellow.  In  this  the  phenome- 
non is  distinguished  from  fungous  infections.  Since  now  enormously  in- 
creased formation  of  sugar  can  be  proved  and  the  absence  of  parasites  de- 
termined in  the  majority  of  spots,  we  have  under  consideration  a  constitu- 
tional disease  which  set  in,  where  the  orchids  named  were  cultivated  in  leaf 
mould. 

This  cultural  method  has  been  especially  recommended  in  the  last  few 
years  by  Belgian  and  English  gardeners  and  introduced  into  Germany  in 
part  with  the  use  of  Flemish  leaf  mould.  After  the  rapid  spread  of  the  dis- 
ease, the  old  process  of  growing  the  plants  in  a  mixture  of  sphagnum  with 
bits  of  moor  soil  was  again  followed  and  the  earlier  results  were  again  ob- 


263 

tained.  From  this  it  is  evident  that  leaf  mould,  an  extremely  favorable  sub- 
stratum for  most  other  plants  and  in  which  the  orchids  named  at  first  grow 
very  well,  gradually  becomes  slimy  when  copiously  watered  (especially  with 
water  containing  algae)  and  does  not  let  the  necessary  supply  of  oxygen 
reach  the  roots  of  the  orchids. 

Much  better  results  have  been  obtained  with  the  so-called  Jadoo  fibre, 
a  very  porous  moss  peat  saturated  with  nutritive  salts.  Yet  the  result  does 
not  justify  the  increased  expense  and  the  old  sphagnum  culture  always 
proves  to  be  the  most  advantageous.  The  modern  endeavor  of  growers  to 
force  the  orchids  to  an  earlier  and  more  luxuriant  development  by  abundant- 
ly supplying  nutritive  substances,  high  temperatures  and  great  moisture, 
gives  actual  good  results  only  for  a  Hmited  time.  Usually  a  reaction  sets  in 
in  the  over-stimulated  plants,  which  can  be  prevented  only  by  a  dormant 
period  in  a  relatively  cooler,  drier  place. 

Cooler,  drier  sand  is  also  in  many  cases  the  best  protection  against  decay 
from  fungus.  Klitzing  observed  a  very  instructive  example  in  a  spot  dis- 
ease of  Vanda  coerulea,  called  forth  by  Gloeosporium  which  is  now  pretty 
universal  on  the  continent  and  in  England,  as  well  as  even  in  our  country.  The 
statements  of  the  collectors  show  that  this  Vanda  is  found  in  the  Himalayas 
on  Gordonia,  which  grows  in  moderately  warm,  windy  habitats.  Here,  in 
our  conservatories,  the  plants  are  cultivated,  on  an  average,  more  than  10°  C. 
warmer  and  kept  year  in  and  year  out  in  closed,  moist  greenhouse  air.  Nat- 
urally the  plants  become  more  tender  on  this  account  and  succumb  within  a 
few  days  when  artificially  infected  with  Gloeosporium,  while,  in  their  native 
habitat,  the  fungus  is  restricted  and  the  plants  develop  further  and  increase, 
despite  its  presence. 


CHAPTER  III. 


UNFAVORABLE  CHEAllCAL  SOIL  CONSTITUTION. 


I.     Relation  of  the  Food  Stuffs  to  the  Soil  Structure. 


A.     Soil  Absorption  Resulting  from  Chemico-physical  Processes. 

Injuries  to  vegetation  can  take  place  either  because  the  capital  of  nu- 
tritive substances  in  the  soil  takes  a  form  quantitatively  or  qualitatively  un- 
favorable for  the  nutrition  of  the  plants,  or  because,  with  an  abundant  sup- 
ply and  normal  composition  of  the  nutritive  substances,  the  plant's  capacity 
for  taking  them  up  will  be  arrested  by  other  factors  of  growth.  Thus,  either 
a  lack  or  an  excess  of  the  nutritive  substances  can  make  itself  felt,  or,  be- 
cause of  modified  conditions  of  absorption,  one  single  nutritive  substance 
can  be  present  in  amounts  too  scanty  or  too  great  for  effectiveness,  and  thus 
disturb  the  equilibrium  in  the  organism.  This  second  form  of  nutritive 
disturbance  will  be  treated  in  the  following  division  under  the  headings, 
"Lack  of  moisture  and  nutritive  substances"  and  "Excess  of  moisture  and 
nutritive  substances." 

The  consideration  of  the  supply  of  water  in  this  connection,  together 
with  nutritive  substances,  is  justified  by  the  fact  that  the  water  not  only 
furnishes  these  by  its  decomposition  in  the  plant  body,  but  also,  as 
a  transporting  medium,  causes  weak  or  strong  concentrations  of  the 
nutrient  solutions  according  to  the  amount  of  water  present,  thus  influencing 
beneficially  or  disadvantageously  the  process  of  nutrition.  In  view  of  the 
constantly  changing  concentrations,  the  influence  of  the  water  will  therefore 
have  to  be  taken  into  consideration,  when  studying  the  relation  of  the  nutri- 
tive substances  to  the  soil  structure. 

The  soluble  salts  produced  by  the  decomposition  of  the  minerals  or  in- 
troduced by  fertilization,  serve  as  a  basis  for  soil  absorption.  The  retention 
and  giving  up  of  the  salts,  as  also  their  transformations  continually  taking 
place  in  the  soil,  were  thought  at  first  to  be  predominantly  physical  processes, 
while  they  now,  in  substance,  are  considered  chemical  processes^     In  any 

1  See  Ramann,  Bodenkunde,  2nd.  Edition,  p.  21,  Berlin,  1905,  Jul.  Springer.  In  the 
remainder  of  this  section,  if  other  authors  are  not  cited,  we  relj'  chiefly  on  the  work 
here  named. 


265 

case,  it  is  difficult  to  draw  a  line  between  physical  combination  (absorption) 
and  chemical  combination. 

Absorption  becomes  of  importance,  only  where  large  absorptive  sur- 
faces are  offered,  as  in  organic  substances  and  certain  inorganic  ones,  to 
which  belong  the  colloidal  silicic  acid  and  the  colloidal  ferric  oxid  of  the 
tropical  red  soils.  Those  humus  substances,  capable  of  being  swollen,  seem 
of  the  greatest  significance  which  are  precipitated  in  soils  rich  in  nutritive 
substances,  such  as  salt-like  compounds,  but  remain  to  a  great  part  in  solution 
in  impoverished  soils.  In  the  absorption  of  humus  substances  the  first  role  is 
played  by  their  capacity  to  take  up  free  bases  and  their  carbonates.  The 
acid  humus  substances  are  especially  effective  for  the  ammonia  found  in  the 
soil  and  for  ammonium  carbonate  and  we  take  advantage  of  this  fact 
especially  when  using  a  peat  mulch. 

Besides  colloidal  substances,  the  finely  distributed  mineral  elements 
should  be  kept  in  view  as  a  means  of  absorption.  Of  the  minerals,  how- 
ever, quartz  always  and  kaolin,  when  not  combined  with  alkali  silicates  to 
form  the  absorptive  double  silicate,  have  no  capacity  for  absorption.  The 
chief  bearers  are  the  hydrated  silicates,  especially  the  double  silicates  of 
aluminum,  which,  crystallized  as  zolites,  are  found  in  rocks,  and  also  those 
of  ferric  oxid.  They  make  possible  the  exchange  of  bases  observable  in  the 
soil. 

This  becomes  effective  with  the  exhaustion  of  the  soluble  nutritive  sub- 
stances in  the  soil  as  is  made  clear  by  the  following  experim.ent  carried  out 
by  Lomberg\  A  hydrated  silicate  was  kept  for  three  weeks  in  contact  with 
water  containing  carbon  dioxid,  and,  after  some  time,  the  following  compo- 
sition was  found : — 

I.  11. 

Original  silicate.  After  treatment  with  water 

containing  carbon  dioxid. 

Silicic  acid   46.64  per  cent.  54-03  per  cent. 

Aluminum   oxid    29.38     "       "  39-65     "       " 

Potassium   22.75     "       "  5-34     "       " 

Sodium   1.83     "       "  0.00     "       " 

If  this  leached  silicate  II.  was  agaixi  treated  with  a  solution  of  caustic 
potash,  the  following  composition  was  found, — silicic  acid,  46.60  per  cent. ; 
aluminum  oxid,  35.67  per  cent. ;  potassium,  17.73  per  cent.  Therefore,  in  the 
silicate  skelton,  the  greatest  part  of  the  potassium  had  been  taken  up  again, 
so  that  a  new  condition  of  chemical  equilibrium  had  been  set  up. 

If  ammonium  chloride  was  added  to  the  original  silicate  I,  the  reaction 
resuhed  in, — siUcic  acid,  56.17  per  cent.;  aluminum  oxid,  34.59  per  cent. ; 
potassium,  0.89  per  cent.;  ammonia  (NH3)  8.37  per  cent.  If  a  very  large 
excess  of  calcium  salts  had  been  present,  instead  of  the  ammonia,  the  cal- 
cium could  have  replaced  the  potassium  entirely  in  the  silicate,  as  has  act- 

1  Zeitschr.  d.  Geol.  Ges.  1876,  p.  318.. 


266 

ually  been  shown  by  Riimpler's  experiments  and  later  those  of  Schloszing 
Such  processes  are  constantly  present  and  show  how  quickly  a  soil  can  be 
leached  by  continued  abundant  precipitation,  or  can  be  impoverished  in  the 
supply  of  its  other  valuable  food  stuffs  by  a  one-sided  supply  of  fertiUzer. 

The  addition  of  fertilizer  and  the  consequent  increase  of  nutriment  does 
not  always  give  the  expected  increase  in  the  yield.  This  occurs  especially  in 
rich  soils  and  is  explained  by  the  fact  that  such  a  soil  is  no  longer  in  a  con- 
dition to  absorb,  as  a  direct  result  of  its  wealth  of  nutriment.  Soils  poor  in 
clay  are  especially  able  to  cause  such  phenomena  because  of  their  small  ab- 
sorptive power. 

A  further  painful  surprise,  connected  with  absorption,  is  the  poisoning 
of  the  soil  from  metallic  salts.  All  heavy  metals  combine  actively  and,  on 
this  account,  for  example,  the  failure  of  crops,  observable  near  smelting 
works,  may  not  always  be  ascribed  to  the  sulfuric  acid  of  the  fuel  alone,  but 
often  also  to  the  larger  accumulations  of  metalUc  compounds.  The  fact,  as 
shown  by  experience,  that  plants  will  live  In  soil  containing  small  quantities 
of  copper,  lead,  zinc,  etc.,  has,  up  to  the  present,  prevented  paying  the  neces- 
sary attention  to  this  kind  of  soil  poisoning. 

With  potassium  and  ammonium,  both  of  which  combine  actively,  ab- 
sorption often  takes  place  by  exchange  in  equivalent  amounts  (3  parts  KgO 
for  I  part  NH3),  whereby  sodium,  calcium  and  magnesia  pass  over  into 
solution.  The  easily  dissolved,  salt- forming  sodium  is  only  weakly  absorbed 
and,  to  a  still  lesser  degree,  the  calcium,  present  in  the  form  of  its  humate, 
carbonate  or  phosphate,  which  can  easily  be  replaced  in  the  silicates  by  other 
bases.  Magnesium  acts  similarly.  Acids  are  combined  only  when  they  form 
insoluble  salts.  This  is  especially  the  case  with  phosphoric  acid,  which 
forms  insoluble  compounds  with  calcium,  magnesium,  ferruginous  earth  and 
aluminum  oxid.  Sulfuric  acid  is  very  weakly  absorbed,  nitric  acid  and 
chlorin  not  at  all.  The  latter  case  deserves  consideration  in  the  chlorin 
poisoning  near  hydrochloric  acid  factories. 

By  the  different  absorptive  capacity  and  the  constant  exchange  of  nu- 
tritive substances  is  explained  the  effect  of  many  fertilisers  which  have  a 
two-fold  action, — disintegrating  and  thereby  increasing  nutriment  and  ex- 
hausting the  supplies.  Thus  an  abundant  supply  of  potassium  salts  and 
Chih  saltpetre  exhausts  the  calcium  and  magnesium  in  the  soils.  The  ex- 
pression, "soil  impoverished  from  marling"  indicates  that  marl,  as  well  as 
g}^psum,  can  prematurely  exhaust  the  nutritive  stores  in  the  soil  by  a  disin- 
tegrating action.  In  this  disintegration  lies  also  the  value  of  sodium  chlorid 
(common  salt).  A  greater  source  of  poor  production  is  found  in  the  acid 
content,  especially  in  the  abundance  of  humic  acids  which  greatly  weaken 
the  absorption  and  are  in  a  condition  to  dissolve  all  the  elements  in  the  soil. 
This  subject  has  been  treated  more  thoroughly  under  the  disadvantages  of 
moor  soils  and  under  the  formation  of  swamp  ore. 


26; 

The  less  the  various  nutritive  substances  are  retained  and  the  more 
soluble  their  compounds,  the  more  easily  they  are  leached  out.  At  best,  they 
reach  the  deeper  soil  layers,  and  in  regions  of  strong  sudden  precipitation, 
they  can  be  carried  away.  The  chlorids  present  in  small  amounts  in  most 
soils  are  most  easily  removed,  then  the  nitrates,  later  the  sulfates.  This 
takes  place  slowly  with  carbonates  of  calcium  and  magnesia  and  the  phos- 
phates are  the  most  persistent  of  all.  Chlorids  are  dangerous  for  agriculture 
in  regions  of  very  slight  precipitation,  where  they  accumulate  in  low  lying 
places,  and  produce  highly  concentrated  soil  solutions.  Under  the  same  con- 
ditions, the  so-called  "alkali  soils"  are  produced  by  carbonates  and  sulfates. 

The  question  of  nitrogen  is  the  most  important.  The  nitrates  are  so 
very  soluble  that  the  upper  soil  layers,  containing  the  superficial  roots,  can  be 
leached  of  all  their  nitrates  even  if  the  subsoil  contains  abundant  nitrogen. 
This  can  only  be  made  available  by  means  of  deeply  rooted  plants.  In  the 
face  of  general  practice,  not  enough  emphasis  can  be  laid  on  the  great  losses 
occurring  with  unsuitable  fertilization  of  the  fields.  Of  the  calcium  salts, 
gypsum  must  be  considered  since  it  contains  sulfuric  acid.  With  calcium 
carbonates  in  damp  cHmates,  even  on  soils  made  from  disintegrated  lime 
stone,  the  calcium  content  may  be  poor  because  the  carbonate  is  slowly 
leached  out^  On  the  other  hand,  all  the  potassium  phosphates  as  well  as 
the  phosphoric  compounds  (with  the  exception  of  the  alkalis)  belong  among 
the  most  persistent  minerals.  An  exception  takes  place  only  in  soils  with 
free  humic  acids.  Here  the  phosphates  and  also  the  iron  compounds  be- 
come soluble  and  even  the  resistant  silicates  are  decomposed  and  carried  over 
in  a  soluble  form.  In  this  way  moor  soils  are  exhausted  of  all  their  mineral 
elements,  excepting  quartz. 

The  natural  process  of  enrichment  of  the  soil  by  weathering  and  by  the 
action  of  wind  in  moving  soil  masses,  by  the  decay  of  organic  substances, 
etc.,  which  effectively  counteract  leaching,  is  of  value  only  in  long-lived 
plantations.  Here  the  fact,  that  the  deep  growing  roots  get  the  nutritive  sub- 
stances from  the  subsoil,  again  made  available  for  the  upper  soil  layers  by  the 
falling  of  the  leaves,  is  surely  of  great  importance.  In  our  plantations  of 
one  and  two-year  old  plants,  we  find  this  help  only  in  the  use  of  green 
manuring. 

Finally,  soil  impoverishment  from  draining  must  not  be  passed  over. 
However  useful  this  practice  is,  as  already  acknowledged  under  soil  aeration, 
in  places  it  can  act  most  injuriously.  This  refers  especially  to  the  leaching 
of  nitrates  from  the  soil  in  localities,  where  the  fertilizer  cannot  be  exten- 
sively supplied.  Naturally  the  loss  reaches  a  significant  amount  where  an 
abundant  supply  of  nitrogen  is  present,  as  is  shown,  for  example,  in  Levy's 
analyses  of  the  drain  water  from  the  Parisian  sewage  fields-.     In  a  liter  of 


1  (If  water  containing-  carbon  dioxid  comes  in  contact  with  calcium  carbonate 
it  forms  calcium  bicarbonate,  wliicli  is  mucli  more  soluble  and  passes  off  in  the 
drainage  waters.     This  always  occurs  in  soils  containing  organic  matter. — H.  S.  R.) 

2  Wollny,  E.,  Die  Zersetzung  der  organischen  Stoffe,  etc.    Heidelberg  1897,  p.  4. 


268 

the  drainage  liquid,  as  it  flowed  away,  were  contained  0.8  to  0.9  mg.  of  nitro- 
gen in  the  form  of  ammonia  and  between  19. i  to  27.1  mg.  of  nitrogen  in  the 
form  of  saltpetre.  The  liquid  sewage  used  for  the  irrigation  contained  24.9 
mg.  ammonia  nitrogen  and  0.9  mg.  saltpetre.  A  comparison  of  these  figures 
shows  that  the  fertilizing  nitrogen  introduced  in  the  form  of  ammonia  is 
oxidized  almost  entirely  to  nitric  acid  by  bacterial  action  during  its  filtering 
through  the  soil.  Way's  investigations^  show  that,  on  an  average,  no  very 
large  amounts  of  mineral  elements  may  be  detected  in  drain  water.  He 
found  in  1000  parts  only  0.003  parts  of  potassium,  0.186  of  calcium,  0.138 
of  sulfuric  acid,  0.002  of  phosphoric  acid,  etc.  Nevertheless  we  should  not 
forget  that  continued  reductions  are  involved  which  are  added  to  one  an- 
other, in  case  there  is  abundant  drainage. 

A  comprehensive  summary  of  lysimeter  experiments  in  Rothamsted, 
which  covered  35  years,  and  more  recent  investigations  in  Holland-  show 
how  rapidly,  as  a  rule,  the  nitrification  of  the  fertilizers,  such  as  the  ammonia 
salts,  takes  place  of  itself.  Even  in  the  fall  and  winter  the  nitrification  is  so 
active,  that  great  nitrogen  losses  may  be  expected.  On  this  account  it  is  ad- 
visable to  use  ammonia  salts  as  a  top  fertilising  in  the  spring. 

When  using  sulfates  and  chlorids  of  ammonia,  the  calcium  combined 
with  the  sulfuric  and  hydrochloric  acids  is  washed  away  in  large  quantities 
in  the  drain  water.  This  process  is  necessarily  preliminary  to  the  combi- 
nation of  the  ammonia  in  the  soil  and  the  subsequent  nitrification.  H  the 
calcium  carbonate  does  not  suffice  for  this  conversion,  the  ammonia  salts 
easily  become  dangerous  for  the  plants.  Since  the  sulfates  and  chlorids  of 
potassium,  like  those  of  ammonium,  form  gypsum  and  calcium  chlorid,  which 
are  not  absorbed  by  the  soil,  the  necessity  of  a  periodic  I'nning  is  evident. 

B.     The  Work  of  the  Soil  Organisms. 

The  activity  of  animal  life  in  relation  to  the  changes  in  the  soil  is  men- 
tioned in  the  third  volume  of  this  work.  In  this  is  concerned  primarily  the 
work  of  the  soil  bacteria,  the  agricultural  significance  of  which  has  been 
shown  in  a  Very  comprehensive  short  summary  by  Behrens^  and  Hiltner*. 

According  to  the  chief  work  performed  by  the  bacteria,  we  could  speak 
of  those  which  set  free  the  nitrogen  and  others  which  attack  the  carbon 
compounds  (as,  for  example,  the  pectin  and  cellulose  ferments)  and  finally 
those  forming  humus  and  those  decomposing  it.  But  not  only  the  action  of 
these  organisms  on  their  substratum  is  of  importance  here,  but,  especially, 
their  influence  on  each  other.  Some  genera  or  species  disintegrate  one  an- 
other, others  nourish  each  other. 


1  Further  analyses  by  A.  Mayer,  Agrikulturchemie.   5th.   Edition,   1902,  Vol.   2, 
Section  I,  p.  118. 

2  Beleuchtung-  der  Bodennitriflkation  durch  Drainwas-seruntersuchungen.    Mit- 
teil.  d.  D.  I.andn-.  Ges.  lOOfi,  Stiick  13. 

3  Behrens,  Die  durch  Bakterien  hervorgerufenen  Vorgange  im  Boden  und  Diin- 
ger.     Arb.  d.  Deutsch.  Landwirtsch.-Ges.  1901,  Part  64. 

4  Hiltner,  L.,   Ueber  neuere  Erfahrungen   und   Probleme  auf  dem  Gebiete   der 
Bodenbakteriologie  etc.  Arb.  d.  Deutsch.  Landwirtsch.-Ges.   1904,  Part  98. 


269 

The  influence  of  carbon  disulfid  serves  as  an  important  example,  for, 
besides  a  poisonous  action,  a  stimulus  directly  beneficial  to  growth  has  been 
assumed  for  it.  The  latter  is  thought  to  be  recognized  in  the  fact  that  a 
clearly  recognizable  increase  of  fertility  sets  in  after  the  disappearance  of 
the  carbon  disulfid  and  its  influences  which  arrest  growth.  Hiltner  suc- 
ceeded in  proving  that  the  carbon  disulfid  chiefly  conditions  the  changing 
phenomenon  by  disturbing  the  equilibrhtm  of  the  bacterial  flora  of  the  soils. 
By  means  of  its  ability  for  dissolving  fats,  it  suddenly  forces  back  the  bac- 
teria which  had  prevailed  up  to  that  time,  just  as  it  also  stops  entirely  the 
increase  of  all  species,  so  long  as  it  is  present  unchanged  in  the  soil.  If  the 
poison  become  diluted,  or  disappears  through  conversion,  the  long  repressed 
numerical  growth  of  the  soil  organisms  increases  in  such  a  way,  that,  for 
example,  an  increase  of  9  millions  of  the  species  growing  on  meat-pepton- 
gelatine  to  50  millions  in  one  gram  of  soil  could  be  proved  in  one  case.  Thus 
an  increase  in  the  nitrogen  production  and  with  it  of  the  potato  harvest 
could  be  determined  chemically  by  Moritz  and  Scherpe. 

With  reference  to  the  behavior  of  the  nitrogen  bacteria  described  in  the 
second  volume^  under  soil  bacteria,  we  will  here  only  supplement 
the  facts  stated  there.  After  \\^inogradski  especially  had  proved  the  con- 
version of  the  ammoniacal  nitrogen  to  nitric  nitrogen  to  be  the  successive 
achievements  of  two  different  groups  of  bacteria  (builders  of  nitrites  and 
nitrates),  it  was  determined  by  Omeliansky  that  the  nitrogen  of  the  organic 
substances  must  have  been  previously  converted  by  other  bacteria  to  am- 
monia. Disturbances  can  easily  occur  in  this  work,  since  these  bacteria  are 
most  sensitive  to  dissolved  substances.  Thus,  for  example,  the  activity  of 
the  organism  forming  nitric  acid  stops  absolutely  if  any  traces  of  ammonia 
are  present. 

In  contrast  to  the  above,  numerous  other  species  of  bacteria  (more  than 
twenty  have  already  been  identified)  possess  the  ability  of  denitrification,  i.  e.; 
the  reduction  of  the  saltpetre  to  free  nitrogen  which  passes  off  into  the  air. 
People  have  wanted  to  trace  to  this  process  the  fact  that  fresh  stable  manure, 
under  certain  circumstances,  injures  the  saltpetre  contained  in  the  soil  and 
that  straw  fertilizing  acts  disadvantageously.  This  phenomenon  is  now 
chiefly  explained  by  the  fact  that  protein  forming  organisms  have  laid  hold 
of  the  available  nitrogen  in  the  soil.  (Pfeift'er  and  Lemmermann  as  well  as 
Gerlach  and  Vogel).  These  bacteria  transform  the  saltpetre  first  into  the 
nitrite  and  then  into  protein-like  compounds.  That  definite  secondary  con- 
ditions belong  here  is  shown  by  Hiltner's  experiment  in  which  straw  fertiliz- 
ing was  proved  to  be  very  injurious  for  potted  plants,  while  the  same 
amounts  on  open  land  had  a  beneficial  effect.  This  contradiction  may  prob- 
ably be  traced  to  the  fact  that  the  protein  thus  produced  can  be  transformed 
more  quickly  in  open  ground  to  products  which  can  be  utilized  again. 


(Page  89  in  th^  German  edition.) 


2/0 

In  studying  the  conversion  of  nutritive  substances  and  their  transfor- 
mation by  soil  bacteria,  the  process  of  the  storage  of  nitrogen,  i.  e.,  the  assim- 
ilation of  free  nitrogen  by  bacteria,  is  to  be  considered.  Besides  the  anaerobic 
Clostridium  Pastorianum  (Pasteurianum),  determined  some  time  ago  by 
VVinogradski,  which  with  sufficient  amounts  of  carbo-hydrates  can  make 
use  of  the  atmospheric  nitrogen  for  its  nutrition, — aerobic  species  have  been 
found  by  Beijerinck  such  as  Asotohacter  chroococcum.  This  species,  present 
in  every  field  soil,  consumes  extremely  large  amounts  of  carbo-hydrates  by  its 
nitrogen  assimilation  (according  to  Gerlach  and  Vogel  8.9  mg.  nitrogen  in 
I  gram  grape  sugar). 

The  changes  in  forest  litter  should  be  included  liere.  The  nitrogen  en- 
richment due  to  them  has  been  caluculated  by  Henry \  He  emphasizes  that 
nitrogen  is  stored  up  with  the  decomposition  of  dead  oak  and  beech 
leaves  and  spruce  needles.  This  decomposition  is  very  active  on  damp  soil  in 
summer,  but  scarcely  noticeable  in  winter,  or  when  mixed  with  soil.  Ac- 
cording to  his  calculations,  fallen  oak  leaves  accumulate  20  kg.  of  nitrogen 
per  hectare  within  a  year.  On  dry  soil  the  dead  foliage  either  does  not  be- 
come enriched  at  all  (in  the  red  beech),  or  only  very  insignificantly  (white 
beech,  spruce).     In  no  case,  however,  was  any  loss  of  nitrogen  noticed. 

The  active  enrichment  of  the  soil  by  the  symbiotic  tubercle-forming 
bacteria  should  also  be  mentioned  here.  Cultures  of  these  bacteria  liave  been 
introduced  into  commerce  under  the  name  "Nitragin"-  and  cultures  of  non- 
symbiotic  nitrogen  gatherers  are  sold  under  the  name  "Alinit.'*  More  recent 
investigations  indicate  that  not  only  bacteria  of  the  same  species  adapted  to 
individual  host  plants  may  be  assumed,  but  that  even  different  species  may 
be  distinguished.  Hiltner  contrasts  two  species  chiefly  on  account  of  their 
morphological  and  physiological  differences ;  viz.,  Rhizohium  radicicola  and 
Rh.  Beijerinckii.  The  activity  of  these  tubercle  bacteria  in  their  relation  to  the 
Leguminoseae  begins  only  when  the  Leguminoseae  have  suffered  for  some- 
time from  nitrogen  hunger  and  they  are  inactive  when  nitrates  are  present  in 
the  soil.  This  should  be  mentioned  only  in  passing  to  illustrate  further  the 
dependence  of  bacterial  life  on  various  factors.  The  root  secretion  of  each 
plant  must  also  count  as  such  a  factor.  Even  the  very  healthy  seeds  which 
get  into  the  soil  and  the  green  parts  of  healthy  seedlings  have  a  specific  bac- 
terial flora,  which  can  increase  greatly  and  swarm  out  into  the  soil.  Other 
micro-organisms  can  be  pressed  back  by  these^.  From  such  inequalities  of 
the  growth  conditions  in  the  soil  must  arise  necessarily  significant  fluctua- 
tions in  the  individual  number  of  each  species  of  bacteria  and  thereby  in  the 
whole  achievement  so  far  as  the  production  of  nutriment  favorable  for  culti- 


1  Henry,  E.,  Ueber  die  Zersetzung-  der  abgefallenen  Blatter  im  Walde  etc.  (Annal. 
Sc.  Agron.  franc.  VIII).  cit.  Centralbl.  Agrik.  Chem.  1904,  p.  703. 

2  In  regard  to  soil  inoculation,  it  should  be  taken  into  consideration  that  bac- 
teria, lilve  all  plants,  will  thrive  only  when  the  soil  is  so  constituted  that  it  favors 
their  increase.  As  Homy  has  very  characteristically  expressed  it,  "they  must  find 
their  proper  soil   climate." 

3  Diigg-eli,  M.,  Die  Bakterienflora  gesunder  Samen  etc.  Centralbl.  f.  Bakt.  II. 
1904,  Vol.  XIII,  p.  198. 


271 

vated  plants  is  concerned.  If  now,  for  various  reasons,  as,  for  example, 
specific  root  secretions,  certain  species  of  bacteria,  which  are  attracted  to 
any  definite  plant  variety  and  incited  to  great  increase,  carry  over  various 
nutritive  substances,  primarily,  nitrogen,  in  a  form  unfavorable  for  the  culti- 
vated plants,  it  can  happen  that  chemically  the  supply  of  nutritive  substances 
may  be  sufficient,  perhaps  even  abundant,  and  yet  the  product  may  fall  off. 
We  then  face  the  phenomena  of  soil  exhaustion  or  "fatigue."  Hiltner  men- 
tions experiments  in  reference  to  this.  He  perceived  definite  indications  of 
soil  exhaustion  in  the  third  generation  of  peas,  which  during  a  period  of 
three  years  were  grown  seven  times  in  pots  in  the  same  soil,  but  differently 
fertilized.  "The  plants  became  sick,  were  easily  susceptible  to  attack,  turned 
yellow  prematurely  and  gave  poor  seeds."  In  the  later  generations,  the  dis- 
eased conditions  were  overcome  in  this  experiment.  "The  roots  of  the  pea 
plants  were  now  noticeably  browned,  but  were  perfectly  white  and  healthy 
inside,  and  it  could  be  proved  that  a  regular  bacteriorhiza  was  present,  which, 
formed  by  well-adjusted,  beneficial  bacteria,  prevented  the  further  penetra- 
tion of  the  injurious  organisms."^ 

In  regard  to  the  exhaustion  of  the  grape,  Behrens  (loc.  cit.,  p.  no)  cites 
the  observations  of  A.  Koch,  according  to  which  it  couldbe  produced  by  an 
accumulation  of  injurious  micro-organisms.  After  sterilizing  the  diseased 
soil  (not  the  healthy  soil),  the  growth  of  the  vines  improved. 

If  such  a  change  in  the  composition  of  the  bacterial  flora  takes  place  in 
a  direction  injurious  to  cultivation,  it  explains  the  increase  of  soil  exhaustion 
due  to  the  repeated  growth  of  the  same  plant  on  any  given  piece  of  land, 
with  short  intermissions.  And  this  accumulation  of  destructive  elements  is 
of  importance  not  only  for  the  bacteria,  but  also  for  other  vegetable  and 
animal  enemies  which  can  cause  soil  exhaustion. 

Among  the  bacteria  which  accumulate  in  the  soil  with  repeated  culti- 
vation of  the  Leguminoseae,  Hiltner  found  that  the  pectin  fermenting  organ- 
isms became  active.  He  found  that  in  soil  greatly  exhausted  by  peas,  per- 
fectly healthy  pea  seed  rotted  especially  because  of  these  bacteria  known  as 
acid  formers. 

Another  variation  in  the  normal  work  of  soil  bacteria  is  the  turning  the 
fertiliser  to  peat.  In  heavy  soils,  often  after  some  years,  the  fertilizer  has 
been  found  pretty  much  undecomposed.  In  the  same  way  green  manure 
turned  under  too  deep,  turns  to  peat.  As  a  result  of  the  limited  supply  of 
air,  the  formation  of  raw  humus  is  completed.  The  end  and  aim  of  working 
the  soil,  however,  is  the  production  of  a  suitable  humus  covering,  for  by 
the  humus  we  obtain  an  equalization  of  the  extremes  of  heat  and  cold,  mois- 
ture and  drought  and  the  suitable  nutritive  soil  which  alone  makes  the  exis- 
tence of  most  bacteria  possible.  If  this  is  present,  field  soil  can  develop  its 
actual  life,  which,  to  a  certain  degree,  is  measurable  by  the  production  of  car- 
bon dioxid.  How  the  bacteria  co-operate  in  this,  is  shown  by  some  statements 


1  Bodenpflege  und  Pflanzenbau.  Arb.  d.  D.  Landwirtsch.-Ges.  Part  98,  p.  74. 


2.^2 

of  Stoklasa  and  Ernst^  who  reckoned  the  respiratory  intensity  from  lOO  g.  of 
dry  substance  of  the  Bacterium  Hartlebi,  a  denitrifying  bacterium,  to  be  2.5 
g.  of  carbon  dioxid  per  hour;  in  the  same  amount  of  dry  substance  of  Clost- 
ridium gelatinosum,  an  ammonia  former,  the  culture  gave  2.t)  g.  carbon 
dioxid.  The  fact  that  the  carbon  dioxid  production  of  a  field  is  actually  de- 
pendent primarily,  on  bacterial  life,  is  demonstrated  by  the  circumstance  that 
no  carbon  dioxid  was  produced  in  observable  quantities  after  experimental 
earth  had  been  sterilized. 

We  find  the  following  statements  in  the  work  of  the  above  named 
authors  on  the  influence  of  aeration.  Forest  soil  taken  from  a  deep  position 
gave  59  mg.  per  kilo,  of  carbon  dioxid  within  24  hours  in  aerobiosis  o  mg. 
in  anaerobiosis,  while  peat  soil  yielded  41  mg.  in  aerobiosis  and  7  mg.  in 
anaerobiosis.  Naturally,  heat  and  moisture  also  act  determinatively.  The 
greater  the  production  of  carbon  dioxid'  in  a  field,  the  more  completely  does 
the  chemical  process  of  the  combination  of  the  free  ammonia  take  place,  as 
Schneidewind-  has  observed.  This  question  comes  under  consideration  here 
in  as  much  as  the  losses  in  nitrogen  with  an  addition  of  animal  manure  rep- 
resent an  impoverishment  of  the  stores  in  the  soil.  If  stable  manure  with 
ordinary  treatment  is  left  in  a  manure  pit,  it  shows  a  nitrogen  loss  of  30.31 
per  cent,  after  lying  three  months.  If  it  lies,  however,  on  an  underlayer  of 
old  manure,  producing  a  great  deal  of  carbon  dioxid,  the  loss  amounts  only 
to  16.94  per  cent.  Here  the  abundant  carbon  dioxid  must  have  combined  the 
free  ammonia  or  have  prevented  the  disassociation  of  the  ammonium  carbo- 
nate already  formed. 

Among  the  most  serious  injuries,  because  the  most  frequent,  be- 
longs the  so-called  "unripe  soil."  This  is  distinguished  by  its  lack 
of  elasticity  from  the  ripe  soil  which,  under  the  influence  of  the  soluble 
salts  in  the  soil  and  the  micro-organisms,  takes  on  the  friable  structure  al- 
ready described.  In  consideration  of  the  great  work  which  the  bacteria  per- 
form in  soil  decomposition,  we  can  assert  that  the  ripeness  of  the  soil  is  due 
to  their  work.  If  we  do  not  know  by  far  all  the  processes  taking  place  in 
ripening  soil,  we  do  know  that  we  may  consider  the  ripening  up  to  a  certain 
stage  as  actual  fermentation.  Attention  need  be  called  here  only  to  the  special 
pectin  fermenting  organisms  (Plectridia)  which  seem  of  importance  in  germ- 
inating seeds  of  the  Leguminoseae  and  further  to  the  cellulose  fermenting 
organisms  with  the  great  formation  of  hydrogen  and  methane  (marsh  gas 
CH4).  Further,  the  Streptothrix  species  come  under  consideration  as  humus 
fermenting  organisms,  but  especially  the  granulose  organisms  forming  acids '', 
which  produce  chiefly  butyric  acid  and  carbon  dioxid.  In  this,  the  Plectri- 
dia take  over  the  chief  share  in  the  mineralization  of  the  organic  substances. 

1  Stoklasa,  J.,  and  Ernst,  A.,  Ueber  den  Ursprung,  die  Menge  und  die  Bedeutung 
des  Kohlendioxyds  im  Boden.  Centralbl.,  fiir  Bakteriologie  etc.  Section  II,  1905,  Vol. 
XIV.  Nos.  22  and  23,  p.  725. 

2  Schneidewind,  Zur  Frage  der  Stalldiingerkonservierung.  Deutsche  landw. 
Presse  1904,  No.  73. 

3  Lohnis,  P.,  Ueber  die  Zersetzung  des  Kalkstickstoffs.  Centralbl.  f.  Bakt.  II,  1905, 
No.  3-4,  p.  87, 


^7Z 

The  nitrogen  collectors  {Bacillus  radicicola  and  B.  mtgaterium,  Clostridium 
Pasteurianum,  Azotobacter)  as  also  the  ones  forming  ammonia  (Bacillus 
ureae,  B.  alhuminis,  B.  proteus  vulgaris'^,  B.  butyricus,  B.  mycoides,  B.  sub- 
tilis,  B.  mesentericus  vulgatus,  B.  foetidus,  Bacterium  coprophilum,  etc.)  the 
nitrifying  Bacterium  nitrobacter,  etc.,  and  the  denitrifying  genera 
{Bacillus  mycoides,  B.  substilis,  B.  liquidus,  B.  nubilus,  B.  vulgaris,  B. 
coli,  B.  prodigiosus,  B.  liquefaciens,  Bacterium  fuscum,  Closteridium  gel- 
atinosa,  etc.),  have  been  considered  and  attention  should  now  be  called  to  the 
specific  organisms  of  decomposition.  All  these  biological  processes  are 
enacted  in  ripe  soils,  supplementing  or  combatting  one  another,  according  to 
the  climatic  conditions  of  the  soil  at  the  time. 

Besides  bacteria,  green  algae,  the  appearance  of  which  counts  as  a  sign 
of  good  ripening,  have  been  considered  to  be  nitrogen  collectors.  According 
to  Koch^,  however,  this  is  not  the  case,  but  their  value  lies  in  the  fact  that 
by  their  chlorophyll  activity  they  furnish  carbon  for  the  soil  bacteria,  which 
combine  nitrogen.  Beijerinck,  Schlosing  and  Laurent  insist  that  the  blue- 
green  algae  can  assimilate  free  nitrogen  and,  according  to  Saida^,  a  number 
of  mold  fungi  should  also  have  this  ability. 

As  Treboux*  has  recently  emphasized,  the  activity  of  the  nitrite  and 
nitrate  bacteria  may  frequently  be  lost,  but  the  ammonia  retained  in  the  soil 
is  always  at  the  disposal  of  the  plants  and  used  up  by  them;  this  may  still  be 
taken  for  granted  for  many  cases.  Other  investigators  have  also  proved  the 
usefulness  of  ammonia.  Ultimately,  however,  the  formation  of  the  ammonia 
in  the  soil  is  based  on  the  decomposition  in  which  bacteria  participate. 

The  growth  of  the  majority  of  micro-organisms  afifecting  the  fertility 
of  the  soil  is  connected  with  an  abundant  fluctuation  in  moisture,  and  the 
passage  of  heated  air  over  the  soil  with  its  drying  eflfect.  These  conditions 
are  lacking  in  heavy  soils  in  wet  periods, — i.  e.,  the  soil  remains  unripe. 
Here  the  cultivation  of  useful  soil  bacteria  succeeds  only  with  a  constant 
working  of  the  soil.  Acknowledged  practical  workers  recommend  the 
quickest  possible  turning  over  of  the  grain  stubble  on  loamy  soils  in  order 
to  obtain  a  greater  nitrogen  gain  by  an  earlier  soil  ripening.  In  the  Lauch- 
stadt  experiment  station  about  the  same  results  were  obtained  by  early 
ploughing  as  by  a  green  manuring.  In  spring  planting  on  all  heavy  soils,  a 
fall  ploughing  is  the  best  precaution  against  unripe  soils. 

Recently,  letting  the  ground  lie  fallow'^  has  again  come  into  use  for 
heavy  soils.  In  Hght  soils  it  should  be  considered  a  wasteful  process.  The 
benefit  of  letting  ground  lie  fallow  is  its  disintegrating  action;  no  final  de- 


1  Stoklasa,  J.,  Ueber  die  Schicksale  des  Chilisalpeters  im  Boden  etc.  Blatter  f. 
Zuckerriibenbau  1904,  No.  21. 

2  Koch,  A.,  Bodenbakterien-  und  Stickstofffrage.  Verb.  d.  Gesellsch.  deutcher 
Natur.  zu  Kerlsbad.  1903.  Part  I,  p.  182. 

3  Vog-el,  J.,  Die  Assimilation  des  freien  elementaren  Stickstoffs  durch  Mikro- 
crganismen.     Centralbl.  f.  Bakteriol.  II,  1905.    Vol.  XV,  p.  174. 

*  Treboux,  O.,  Zur  Stickstoffernahrung-  der  griinen  Pflanzen.  Ber.  d.  botan. 
Gesellsch.  1905.  p.  570. 

5  Hillmann,  Bedeutung-  der  Agrikulturphysik  etc.  Nachrichten  aus  dem  Klub 
der  Landwirte,  1902,  No.  453  and  Mitteil  d.  D.  Landw.-Ges. 


cision  has  been  reached  as  yet  as  to  how  this  effect  is  produced.  It  is  thought 
that  in  this,  physical,  chemical  and  soil  bacteriological  processes  interact 
supplementarily.  The  frequent  thawing  and  freezing  in  the  winter  serves 
to  break  and  loosen  the  soil.  Thus  the  action  of  the  atmospheric  processes 
is  favored  and  the  soil  opened  for  the  beneficial  species  of  bacteria.  It  has 
not  been  determined  with  certainty  to  which  genera  these  belong.  Hiltner 
has  proved  first  of  all,  that  they  are  not  the  Alinit  bacteria.  In  the  end  the 
usefulness  will  be  decided  by  the  greatest  accomplishment  of  the  nitrifying 
bacteria;  for,  according  to  Reitmair^  the  nitrification  in  good  mild  soils  with 
sufficient  heat  begins  immediately  after  the  fall  harvest  in  such  a  way  that 
the  nitrate  requirement  of  the  subsequently  planted  grain  will  be  met  until 
the  next  spring.  In  this,  however,  a  suitable  friability  and  a  definite  calcium 
content  is  taken  for  granted".  (See  also  the  statements  under  Drain  Water.) 
Naturally  it  must  be  emphasized  with  Stutzer^  that  the  land  may  be  al- 
lowed to  lie  fallow  only  under  certain  fixed  circumstances.  It  is  thought 
that  this  may  be  done  if  it  seems  financially  most  advantageous  for  the  agri- 
culturalist to  do  without  the  field  for  the  long  time  while  it  is  lying  fallow, 
rather  than  to  use  the  more  quickly  acting  green  manure  and  stable  manure. 
When  working  with  soils  tending  to  unripeness,  emphasis  should  be  laid  on 
this  lying  fallow  only  because  it  loosens  the  soil  mechanically  and  does  not 
affect  the  fertilizing  salts.  The  nitrogen  of  the  organic  fertilizing  masses 
seems,  as  Pfeiffer*  especially  emphasizes,  to  be  held  fast  in  the  soil,  capita- 
lized as  it  were,  and  then  shows  a  long  subsequent  action.  This  author  is, 
however,  an  opponent  of  the  theory  of  letting  ground  lie  fallow,  which  he 
characterizes  as  a  robber  cultivation,  so  far  as  the  stock  of  nitrogen  is  con- 
cerned. He  sees  in  this  an  incomplete  restitution  of  the  amounts  of  nutri- 
ment removed  from  the  soil  by  the  crops.  In  Pfeiffer's  opinion,  the  soluble 
nitrogen  compounds  obtained  by  letting  the  land  lie  fallow  are  lost  again  in 
great  part  from  uncultivated  soils  by  the  water  which  soaks  through.  Such 
considerations,  in  my  opinion,  are  entirely  justifiable  for  light  soils,  Init  do 
not  hold  good  for  heavy  soils  provided  with  an  abundant  absorptive  power 
by  the  clay  and  weakened  by  the  harvests. 

2.     Relation  of  the  Nutritive  Substances  to  the  Plants. 

The  phenomena  treated  in  this  and  the  following  division,  are  rarely  the 
result  of  only  a  lack  or  an  excess  of  the  nutriment  in  the  soil.  They  are 
usually  the  result  of  the  co-operation  of  numerous  factors,  among  which 
atmospheric  humidity  plays  an  especially  decisive  role.  We  will  not  forget 
that  almost  all  diseases  are  produced  by  an  unsuitable  combination  of  the 


1  Reitmar,  O.,  Die  Stellung  der  Brache  und  der  Griindiingung-  in  unsern  moder- 
nen  Fruchtfolgen.  D.  Landw.  Presse.  Sond.  1903. 

2  Wohltmann,  F.,  Fischer,  H.,  and  Schneider,  Ph.,  Bodenbakteriologische  and 
bodenchemische  Studien  aus  dem  Poppelsdorfer  Versuchsfelde.  Journ.  f.  Landwirt- 
schaft  1904,   p.   97. 

3  Stutzer,  A.,  Die  Nutzbarmacliung  des  Stickstoffs  der  T-.uft  fiir  die  Pflanzen. 
D.  Landw.  Presse  1904,  Nos.  10-19. 

4  PfeifCer-Breslau  Stickstoffsammelnde  Bakterien.  Brache  und  Raubbau.  Berlin, 
P.  Parey,  1904.  cit.  Centralbl.  f.  Agrik.  Chem.  1905,  p.  599. 


^75 

normal  vegetative  factors  and  are  disturbances  in  the  equilibrium  of  the 
interacting  nutritive  processes  whereby  certain  ones  are  repressed  while 
others  predominate. 

If  we  now  speak  of  diseases  due  to  a  lack,  or  an  excess  of  moisture  and 
nutritive  substances  we  also  involve  in  this  the  phenomena  in  which  atrophies 
and  hypertrophies  occur  in  various  parts  of  the  plant  body.  These  need  not 
arise  from  an  actual  lack  or  excess  of  moisture  and  nutritive  substances,  but 
are  simply  produced  by  the  unfitness  of  the  plant,  from  the  combination  of 
the  factors  of  growth,  to  nourish  all  its  organs  advantageously  for  the  de- 
velopment of  the  whole.  The  absolute  phenomena  due  to  lack  and  excess 
are  approximated  on  this  account  by  the  relative  ones  in  the  form  of  dis- 
turbances of  the  local  equilibrium. 

A.     Lack  of  Moisture  and  Nutritive  Substances. 

a.     Lack  of  Moisture. 

Influence  of  the  Various  Plant  Coverings. 

After  having  considered  the  physical  processes  leading  to  a  lack  of 
moisture  in  the  soil,  and  after  having  discussed  a  number  of  phenomena  of 
diseases  arising  therefrom,  we  must  consider  supplementarily  the  influence 
which  the  covering  of  vegetation  itself  exercises  on  the  water  content  of  the 
soil.  On  the  same  soil,  with  the  same  atmospheric  conditions,  a  cultivated 
plant  will  find  a  supply  of  moisture  sutficient  for  its  development  on  one 
part  of  a  field,  and  not  on  another  part,  if  on  the  former  some  species  has 
been  grown  which  makes  a  small  demand  on  the  water  content.  Therefore 
the  preceding  crop  is  of  significance  for  each  planting. 

As  Wollny^  has  determined,  the  water  content  is  less  in  the  root  region 
of  a  planted  field  than  in  the  corresponding  layers  of  the  naked  soil.  The 
more  luxuriant  the  plant  growth  and  the  thicker  and  longer  lived,  the  more 
v/ater  is  lost  from  the  soil.  Experiments  have  not  determined  any  fixed 
scale  for  the  use  of  water,  yet  they  indicate  that,  on  an  average,  the  ever- 
green conifers  require  the  greatest  quantities  while  deciduous  trees  and 
perennial  fodder  plants  follow  in  a  descending  scale  and  the  superficially 
rooting  field  plants  make  less  demand  on  the  whole  supply  of  the  water  in 
the  field.  Of  the  latter  group,  the  large,  richly  leaved,  erect  Papilionaceae, 
such  as  the  field  and  bush  beans,  seem  to  require  the  most  water  at  the  time 
of  their  chief  development,  while  the  roots  and  tuberous  plants  cultivated  in 
wide  rows  should  be  named  last.  In  summer  the  perennial  fodder  plants 
use  somewhat  greater  quantities  than  field  plants  and  conifers.  This  is  re- 
versed in  the  spring  and  fall.  In  winter  the  requirements  of  the  different 
plants  equalize,  except  the  conifers,  which  in  mild  winter  weather 
constantly  withdraw  definite  amounts  of  water  from  the  soil. 


1  WoUny,   E.,   Ueber   den   Einfluss   der   Pflanzendecken   auf   die   Wasserfiihrung 
der  Fliisse.  Vierteljahrsschr.  d.  Bayer,  Landwirtschaftsrates  1900,  p.   389. 


2^6 

V.  Seelhorst'  treats  the  same  subject  and  comes  to  the  conclusion  that 
so  far  as  moisture  is  concerned,  rye  exhausts  the  field  much  less  than  wheat. 
This  circumstance  is  very  important  when  planting  possible  subsequent  crops 
for  green  manuring,  for,  after  wheat,  which  is  cleared  later  from  the  field, 
tills  crop  not  only  reaches  the  soil  later,  but  also  finds  the  soil  much  drier. 
Clover  exhausts  the  water  in  the  soil  very  greatly  so  that,  aside  from  the  fact 
that  the  soil  easily  becomes  loosened  by  the  clover  stubble,  in  dry  years,  the 
winter  crops  following  the  clover  can  only  develop  slowly  and  unevenly  be- 
cause of  the  lack  of  moisture. 

On  the  other  hand,  the  potato,  at  least  the  variety  ripening  moderately 
early,  seems  to  form  a  very  good  early  crop,  since  it  leaves  the  soil  fairly 
moist.  Peas  also  form  a  good  early  crop  for  winter  grain.  Oats  are  con- 
sidered by  V.  Seelhorst  to  be  especially  unfavorable,  not  so  much 
because  they  exhaust  the  nutritive  substances  as  because  they  remove  water 
to  so  marked  an  extent. 

In  connection  with  field  plants,  we  should  consider  also  the  injurious 
influence  of  grass.  It  is  easy  to  understand  that  a  close  turf  keeps  water 
from  the  roots  of  plants,  especially  fruit  trees  and  impoverishes  the  friable 
soil,  but  recently  a  direct  poisonous  effect  of  grass-  has  been  mentioned 
which  may  possibly  be  due  to  the  fact  that  beneficial  bacteria  species  are 
suppressed  by  it  and  injurious  ones  favored.  In  the  case  given, 
the  roots  of  the  apple  trees  were  long,  abnormally  thin  and  browned,  the 
leaves  were  very  light  in  color  and  dropped  4  days  earlier.  The  foliage  was 
sparse,  the  wood  growth  scanty.  As  soon  as  the  roots  or  even  only  a  greater 
part  of  them  reached  soil  not  covered  by  grass  the  phenomena  of  disease  dis- 
appeared. These  phenomena  agree  essentially  with  those  produced  on  heavy, 
impervious  soils,  with  a  scarcity  of  oxygen,  so  that  it  seems  in  no  way  neces- 
sary to  assume  any  poisonous  action.  We  find,  in  many  cases,  especially  on 
light  soils,  that  the  turf  does  no  injury,  if  care  is  taken, to  have  nutritive  sub- 
stances within  reach  of  the  roots.  On  close  clay  soils,  the  grass  is  kept  green 
for  a  long  time  by  the  water  rising  by  capillary  action  from  the  subsoil, 
thereby  removing  a  great  deal  of  moisture  from  the  subsoil  without  return- 
ing it  in  quantities  worth  mentioning  during  the  period  of  vegetation,  since 
the  grass  uses  the  atmospheric  precipitation  itself. 

Wilting. 

In  discussing  "physiological  wilting,"  mention  was  made  of  the  fact 
that  the  phenomena  of  wilting  can  appear  even  with  an  abundance  of  mois- 
ture in  the  soil,  since  the  roots  function  incompletely.  In  soils  with  a  high 
content  of  soluble  salts,  the  water,  under  certain  circumstances,  can  be  held 
so  fast  that  the  roots  meet  their  need  only  with  great  difficulty.    Phenomena 


1  V.  Seelhorst,  Untersuchungen  liber  die  Feuchteigkeitsverhaltnisse  eines  Lehm- 
bodens  unter  verschiedenen  Friichten.  Journ.  f.  Landwirtsch.  1902.  Vol.  50.  cit.  Cen- 
tralbl.  f.  Agr.  Chemie  1903.    Part  6. 

~  Bedford,  Duke  of,  and  Pickering,  Spencer  U.,  The  effect  of  grass  on  trees. 
Third  report  of  the  Woburn  exper.  fruit  farm.     London,  1903. 


^77 

then  become  evident,  which  can  also  be  produced  experimentally  by  the  use 
of  highly  concentrated  nutrient  solutions : — short  internodes,  smaller  leaves, 
short  roots  having  a  great  tendency  to  decay,  reduced  production  and  trans- 
piration. A  further  cause  of  wilting  is  a  lowered  soil  temperature.  If  a  de- 
gree of  heat  is  not  reached  which  is  required  by  a  certain  plant  so  that  the 
roots  can  begin  absorbing  the  water,  while  the  temperature  of  the  air  permits 
evaporation  by  the  leaf  apparatus,  this  disturbed  equilibrium  between  water 
demand  and  supply  makes  itself  felt  by  wilting. 

A  special,  not  rare  case,  is  the  zvilting  of  hot  bed  plants  when  the  pots 
are  cooled  during  the  re-working  of  the  hot  beds  or  during  transplanting. 
Inexperienced  gardeners  then  water  the  plants  abundantly  and  the  turgidity 
is  restored  if  the  water,  previously  warmed,  awakens  root  activity.  By  a 
repetition  of  the  cooling,  the  same  experiment  can  be  carried  out  until  finally 
the  pot  is  overloaded  with  water  and  the  roots  break  down  from  a  lack  of 
oxygen. 

Another  case  of  the  wilting  of  potted  plants  was  observed  by  Hellriegel. 
He  found  that  plants  wilted  in  large  pots,  which  held  three  or  four  times  as 
much  water  as  small  pots  of  plants  of  the  same  species,  which  did  not  wilt. 
This  circumstance  is  explained  by  the  relative  water  content  of  the  soil, 
which  in  the  smaU  pots  amounted  to  14  to  20  per  cent.,  while  the  absolute 
larger  quantities  of  water  in  the  larger  amount  of  soil  in  the  large  pots  was 
so  disturbed  that  it  represented  only  11  to  15  per  cent,  of  soil  moisture.  In 
this  case,  absorption  was  made  more  difficult  for  the  roots  in  the  larger  pots, 
by  the  less  easily  transported  water  held  more  firmly  in  the  capillaries  of  the 
soil,  so  that  evaporation  was  in  excess. 

In  contrast  to  this  physiological  wilting  we  might  term  mechanical  wilt- 
ing those  phenomena  due  to  an  actual  lack  of  soil  moisture  be- 
cause the  mechanical  transportation  of  water  slackens  in  the  ducts.  Nat- 
urally with  the  great  demand  for  moisture  in  the  leaves  and  the  scanty  re- 
inforcement in  the  ducts,  the  air  content  increases  and  in  this  increase  of  the 
air  content  above  a  certain  degree  may  be  seen  the  arrest  of  the  water  cur- 
rent in  the  axial  organs,  as  Strasburger^  emphasizes.  In  this,  the  air  in  the 
tracheal  elements  will  be  more  dilute,  as  the  transpiration  and  assimilation 
on  warm  days-  are  stronger,  and  the  result  is  that  a  moistening  of  the  soil 
becomes  so  much  the  more  quickly  effective.  In  general,  watering  exerts  a 
lesser  influence,  the  greater  the  turgidity  of  the  plant'^  The  great  tracheal  air 
dilution  shows  itself  also  in  the  well-known  fact,  that  field  plants,  wilting 
rapidly  in  hot  weather,  will  stiffen  from  the  dew  on  the  soil  at  night, — 
especially  since  leaf  evaporation  is  repressed  at  this  time. 

1  Strasburger,  Ed.,  Ueber  den  Bau  und  die  Verrichtungen  der  Leitungsbahnen  in 
den  Pflanzen.    Jena  1891.  cit.  Bot.  Zeit.  1892,  p.  261. 

2  Noll,  Ueber  die  Luftverdiinnung  in  den  Wasserleitungsbahnen  der  hoheren 
Pflanzen.  Sitzungsber.  d.  Niederrheinischen  Ges.  f.  Natur-  und  Heilkunde.  Bonn 
1897,  11.  p.  148. 

3  Chamberlain,  Houston  Stewart,  Recherches  sur  la  seve  ascendante.  cit.  Bot. 
Jahresb.  1897,  p.  73, 


278 

Change  ix  Production  Due  to  Lack  of  i^Joisture. 

The  difference  in  the  harvest  yield,  resulting  from  a  lack  of  moisture,  has 
also  been  considered  in  previous  divisions,  so  that  here  we  need  cite  supple- 
mentarily  only  a  few  other  cases.  Hellriegel's^  experiments  are  most  de- 
cisive. Two  tests  of  clover  were  taken  from  a  field,  in  which,  in  places,  the 
plants  had  begun  to  wilt.    There  was  found : — 

In  wilted  plants Leaves  71.0  per  cent,  water,  petioles  78.4  per  cent. 

Leaves  7 1. 1    "       "      water,  petioles  80.8    " 
In  turgid  leaves  among 

the  wilted  ones Leaves  82.5    "       "      water,  petioles  90.0    "       " 

The  wilted  leaves  contained  in  the  leaf-blades  ca.  29  per  cent,  of  dry 
substances;  in  the  petioles,  19  to  21  per  cent.;  while  the  turgid  leaves  con- 
tained in  their  leaf-blades  17.5  per  cent,  and  in  the  petioles  10  per  cent., — i.  e., 
only  about  half  that  of  the  wilted  plants. 

An  example  of  the  influence  of  drought  on  grain  is  given  by  Prianisch- 
nikow's"  investigations,  according  to  which  the  nitrogen  content  increases  in 
corn,  if  the  moisture  decreases.  Stahl-Schroeder's^  studies  give  a  more 
detailed  representation  of  the  influence  exerted  by  the  taking  up  of  nutritive 
substances  and  their  assimilation  in  dry  years.  After  mentioning  the  well 
known  fact,  that  phosphoric  acid  hastens  ripening,  while  nitrogen  and  potas- 
sium delay  it,  he  notes  the  importance  of  the  months  before  blossoming  for 
the  taking  up  of  the  nutritive  substances.  If  the  soil  moisture  is  deficient  at 
this  time,  the  organic  substances  will  be  in  smaller  quantity.  But  the  nitric 
acid,  which  penetrates  easily  through  the  cell  walls,  will  find  its  way  into  the 
plants  and  in  its  turn  again  incite  the  taking  up  of  phosphoric  acid,  in  order 
to  effect  the  formation  of  the  proteins.  In  this  way,  in  dry  years,  scanty 
harvests  are  produced  with  a  high  nitrogen  and  phosphoric  content.  The 
nitrogen  increase  becomes  the  more  evident,  since,  with  drought,  the  grain 
stores  up  the  starch  with  much  greater  difficulty.  The  reverse  may  be  de- 
termined in  the  Norwegian  com  tests,  the  high  absolute  weight  of  which  is 
caused  by  an  abundant  starch  deposit.  This  is  explained  by  the  growth  of 
the  grain  with  abundant  moisture  under  the  influence  of  the  long  days. 

In  Hellriegel's  experiments  with  barley,  in  pots  filled  with  sand,  we 
find,  expressed  in  exact  figures,  the  lowering  of  production,  as  the  amount  of 
moisture  at  the  disposal  of  the  plant  is  reduced. 

Soil  moisture  in  percentages  Dry  Substance 

of  saturation  capacity.  in  wStraw  and  Chaff  in  Grain 

80 — 60  7394  mg.  4896  mg.  1  averages 

60—40  5988     "  4133     "      \      for 

40 — 20  4842     "  7942     "     J  3  Plants 


1  Loc.  cit.  p.  544. 

2  Prienischnikow,  Ueber  den  Einfluss  der  Bodenfeuchtigkeit  auf  die  Entwicklung 
dei'  Pflanzen.     Journ.  f.  experim.  Landw.  1900.    Vol.  I,  p.  19. 

3  Stahl-Schroeder,  Kann  die  Pflanzenanalyse  uns  Aufschlufs  iiber  den  Gehalt 
an  assimilierenden  Nahrstoffen  geben?  Journ.  f.  Landw.  1904.  cit.  Biedermann's 
Centralbl.  f.  Agr.  Chem.  1905.    Part  2. 


The  pots  with  a  soil  moisture  under  20  per  cent,  of  the  saturation  ca- 
pacity of  the  sand  suffered  so  much  from  the  summer  heat,  that  the  heads 
in  the  upper  leaf  sheaths  stood  still,  without  advancing  to  the  formation  of 
kernels. 

In  apparent  contradiction  to  such  results  stand  the  observations  of 
practical  agriculturalists  that  in  perfectly  dry,  so-called  dust-dry  soils,  the 
plants  can  keep  on  growing,  although  nutritive  substances  are  entirely  lack- 
ing in  the  subsoil  (it  is  sterile).  Such  cases  are  explicable  as  soon  as  the 
sterile  subsoil  contains  water  and  the  roots  remain  in  the  moisture.  Haber- 
landt^  studied  this  case  experimentally.  He  let  the  lower  part  of  the  roots 
of  his  experimental  plants  dip  into  distilled  water,  while  the  upper  roots  re- 
mained in  soil  layers,  which,  as  shown  by  control  experiments,  were  so  dry 
that  plants  wilted  in  them.  The  plants  of  which  the  outermost  roots  dipped 
into  distilled  water  showed  a  marked  increase  in  dry  substances ;  from  this  it 
is  evident  that  the  roots  found  in  the  dry  soil  must  have  taken  up  the  mineral 
substances.  This  division  of  labor  by  the  roots  explains  the  growth  of  our 
cultivated  plants  in  spite  of  dry  surface  soil  when  their  roots  reach  deep  into 
a  sterile,  but  moist,  subsoil. 

According  to  Hellriegel,  these  changes  in  production,  so  well  shown  in 
grain,  take  place  in  the  same  sense  in  other  cultivated  plants. 

Discoloration  of  Woody  Plants. 

The  typical  result  of  a  lack  of  moisture  and  abundant  illumination  is 
the  vigorous  development  of  the  mechanical  tissues.  We  need  refer  only 
to  the  conditions  found  in  dry  climates.  For  example,  Jonsson^  reports  that, 
among  other  characteristics  of  arid  plants,  the  walls  of  the  epidermal  cells 
often  become  slimy.  In  Haloxylon,  Eurotia,  Calhgonum,  Halimodendron, 
layers  of  slime  cork  alternate  with  those  of  common  cork.  The  slime  cork 
is  very  capable  of  swelling  and  is  laid  bare  after  the  protective  cork  splits, 
so  that  it  can  take  up  water  and  hold  it.  Cells  containing  slime  are  found 
also  in  the  assimilatory  tissues.  In  Halimodendron,  the  secondary  bark 
often  becomes  thick  and  spongy,  thereby  modifying  the  temperature  extremes 
and  easily  storing  up  water.  In  the  peripheral  parts,  abundant  secretions  of 
salts  form  a  protection.  These  characteristics  vary  in  regions  where  the 
water  supply  is  abundant  in  the  soil  and  in  the  air.  Thus,  for  example,  no 
slime  cork  is  found  in  Halimodendron  when  grown  in  Copenhagen. 

Swanlund^  reports  from  new  Amsterdam  on  the  extremely  thick  outer 
walls  of  the  epidermis,  the  frequent  depression  of  the  stomata,  the  rolling  in 
of  the  leaves  with  the  resulting  restricted  transpiration.  We  have  touched 
upon  this  subject  earlier  in  the  divisions  on  differences  in  latitude  and  on 
the  defects  of  sandy  soils  and  at  the  same  time  have  considered  the  nature  of 


1  Cit.  Biedermann's  Centralbl.  f.  Agr.  Chem.  1878,  p.  314. 

2  Jonsson,  B.,  Zur  Kenntnis  des  anatomischen  Baues  der  Wiistenpflanzen.  Lunds 
Univ.-Arsskrift  XXXVIII.  Bot.  Jahresb.  1902,  II,  p.   292. 

3  Swanlund,    J.,    Die    Veg-etation    Neu-Amsterdam's    und    St.    Pauli's    in    ihren 
Beziehungen  zum  Klima.  Dissert.  Basel  1901. 


28o 

the  red  coloration.  By  artificial  interference,  a  localized  lack  of  moisture 
and  thereby  a  formation  of  anthocyanin  is  stimulated  if  the  leaves  of  plants, 
of  which  a  red  autumnal  coloration  is  characteristic,  be  nicked  or  the 
branches  girdled.  Then  in  the  middle  of  summer  a  red  color  appears  on  the 
upper  parts  above  the  injury. 

In  regard  to  the  phenomena  of  discoloration  produced  by  heat  and 
drought,  I  will  give  some  observations  from  1892,  in  which  year,  in  August, 
unusually  high  temperatures  occurred  together  with  hot  winds.  I  found  on 
the  19th  of  August  a  temperature  of  52.7°C.  on  especially  heavy  loam  soil. 
All  the  plants  wilted  and  the  majority  gradually  lost  their  foliage.  Naturally 
great  individual  differences  were  also  noticeable. 

The  leaves  became  discolored  and  fell,  the  lowest  leaves  of  the  branches 
being  the  first  affected. 

In  the  Alder,  the  leaves  fell  without  losing  their  green  color. 

Acer  Pseudoplatanus  var.  Schwedleri,  the  under  side  of  the  leaf  is  red. 
From  the  tips  backward  the  intercostal  fields  of  the  leaves  turned  a  reddish 
brown  to  leather  color.  Besides  this,  deep  brown,  perfectly  dry  rust  spots 
were  scattered  irregularly  over  the  surface  of  the  leaf.  The  injured  leaves 
remained  in  place. 

Acer  Negundo.  The  upper  leaves  were  somewhat  flabby.  The  edges 
of  the  leaflets  were  curled  upward.  The  leaves  next  below  were  a  pale  yel- 
lowish green,  the  lowest  light  yellow,  uniformly  rolled  up  on  the  dry  edges. 

Acer  plantanoides.  The  leaves  show  on  their  under  side  Dale  yellow, 
irregular,  small  rust  spots  running  into  one  another  and  extending  betv^een 
the  ribs.    The  dried  tips  bend  upward  like  hooks. 

Fagus  silvatica.  On  the  various  leaves,  not  always  the  lowest,  but  the 
most  exposed,  were  irregular,  dry  places  with  yellow,  faded  edges  in  the  in- 
tercostal fields.  At  times,  the  whole  upper  surface  is  equally  lightly 
browned.    There  is  never  any  outlining  of  the  edges. 

Vitis  vinifera.  At  the  beginning  of  the  drought,  among  the  normal 
green  leaves  are  found  yellowish  ones.  The  lemon  yellow  discoloration,  red 
in  other  varieties,  begins  at  one  place  on  the  edge  and  advances  into  the 
intercostal  fields  until  only  the  veins  seem  green.  In  spite  of  the  drought,  I 
found  on  various  lower  leaves  the  dry,  angular  spots  of  Plasmopara  viticola. 

Prunus  Persica.  All  the  leaves  are  somewhat  languishing,  some  (but 
not  always  the  lowest)  turning  yellow  from  the  tips  backward.  On  some 
trees,  the  discoloration  advances  more  quickly  along  the  veins  so  that  at  first 
the  veining  and  then  the  rest  of  the" surface  of  the  leaf  colors  yellow-red  to 
wine-red.    Then  the  leaves  drop.     (Peculiarity  of  the  variety). 

Prunus  doniestica.  All  the  leaves  are  flabby.  The  majority,  however, 
are  still  uniformly  green  with  the  exception  of  the  lowest,  which  on  many 
branches  have  become  a  whitish  yellow  and  have  slender,  brown,  reflexed,  dry 
peripheral  spots.    Easily  shaken  off  by  the  wind. 

Prunus  avium.  The  lower  leaves,  especially  on  the  short  shoots 
(brachyblasts),  turn  a  uniform  lemon  yellow  and  fall. 


28l 

Pruniis  Cerasus.  Only  a  few  leaves  turn  yellow,  otherwise  the  entire 
foliage  is  still  fresh.     A  proof  that  the  cherry  loves  drought. 

Pirns  communis.  According  to  the  exposure  rust  spots  are  found  in 
greater  or  less  numbers  showing,  however,  no  yellowing.  At  times  dry  areas 
appear  on  the  edges  of  the  leaves,  but  more  frequently  the  whole  surface  is  a 
dark  umber  brown  (the  under  side  lighter  in  color  with  a  still  fresh  green  or 
lightly  brownish  mid-rib).  The  edges  strongly  rolled  upward.  Because  the 
petioles  remain  green,  the  injured  leaves  do  not  fall  at  all  or  only  much 
later. 

From  these  and  numerous  other  observations  it  is  evident  that,  on  an 
average,  the  parts  of  the  leaves  furthest  from  the  veins  discolor  and  dry  first 
and  most.  When  periods  of  heat  follow  one  another  rapidly  with  a  strong 
sun  action,  the  rust  spots  become  very  conspicuous ;  with  a  lesser  intensity  of 
the  sunshine,  a  general  discoloration  in  the  form  of  spots  prevails. 

Here  belongs  also  the  especially  strong  development  of  anthocyanin  in 
dry,  poor  locahties,  which  becomes  noticeable  even  in  the  arctic  regions, 
where  the  red  coloration  with  the  strong  illumination  is  a  prevailing 
phenomenon.  Wullt^  cites  a  very  characteristic  example.  He  found  in 
places,  fertilized  by  the  excreta  of  birds,  that  the  formation  of  anthocyanin 
disappeared  in  plants  of  which  the  vegetative  organs  seemed  strongly  redden- 
ed in  arid  regions. 

Finally,  there  must  be  considered  the  decrease  in  the  power  of  move- 
ment of  clover  leaflets  and  related  organs,  with  a  continued  lack  of  moisture. 
In  Mimosa  pudica  the  periodic  irritabihty  is  lost  and  the  leaflets  remain 
open, — "drought  cramp." 

The  Red  Coloration  in  Grain. 

The  red  coloration  in  grain  in  continued  dry,  hot  summers  has  often 
called  forth  the  theory  that  parasitic  influences  participated  in  it.  Klebahn- 
tested  more  closely  a  special  case,  which  was  universally  striking  because  of 
its  wide  distribution  and  intensity.  He  found  that  the  red  coloring  matter 
appeared  gradually  in  place  of  the  cholorophyll.  While  the  alcoholic  ex- 
tract of  normal  leaves  appears  green,  it  is  colored  only  slightly  yellow  in  red 


1  Wulff,  Thorild,  Botanische  Beobachtungen  aus  Spitzbergen,  Lund.  1902.  In 
regard  to  the  theory  at  present  generally  held  that  anthocyanin  is  said  to  form  a 
protection  for  the  chlorophyll  against  an  excess  of  light,  Wulff  (p.  67)  calls  attention 
to  Engelmann's  investigations  from  which  it  is  evident  that  the  light  absorption  of 
the  red  anthocyanin  is  complementary  to  that  of  the  chlorophyll  and  accordingly 
does  not  retard  the  decomposition  of  the  carbon  dioxid.  "This  fact  has  moreover 
proved  most  fully  the  untenability  of  the  Pringsheim-Kny-Kerner  theory  of  pro- 
tection from  light."  Wulff  sees  the  advantage  of  the  anthocyanin  in  its  greater 
storage  of  heat.  As  I  have  mentioned  already,  I  am  unable  to  accept  the  above 
utility  arrangements  or  the  expressions  of  a  "finality"  in  the  organism  and  I  per- 
ceive everywhere  the  necessary  phenomena  resulting  from  definite  combinations  of 
the  factors  of  growth.  The  formation  of  anthocyanin  seems  to  me  to  be  the  result 
of  an  excess  of  light  on  the  cell  content,  rich  in  free  acids,  at  the  disposal  of  which 
there  is  no  assimilate  containing  sufficient  nitrogen.  This  condition  can  be  pro- 
duced, as  in  plants  of  cold  regions,  by  a  lack  of  heat;  in  other  cases  by  a  scarcity 
of  water,  a  decreased  supply  of  nutriment,  etc. 

2  Klebahn,  H.,  Einige  Wirkungen  der  Diirre  des  Friihjahrs  1893.  Zeitschr.  f. 
Pflanzenkrankh.   1894,   p.    262. 


282 

leaves  in  which  the  cholorophyll  has  been  destroyed.  The  red  coloring  mat- 
ter is  soluble  in  water  and  glycerin,  insoluble  in  alcohol  and  turpentine, 
turning  blue  with  potassium  and  ammonia  and  again  red  with  acids.  It  is  in 
combination  with  the  cell  sap,  partly  in  the  epidermis,  partly  in  the  assimila- 
tary  tissue.  In  oats,  the  development  of  the  reddened  plants  and  their  grain 
production  was  proved  to  be  less  than  that  of  green  ones.  We  have  just  made 
a  study  of  the  reddening  of  grains^  and,  in  agreement  with  Klebahn,  have 
come  to  the  conclusion  that  in  this  redness  only  phenomena  of  a  premature 
ripening  are  to  be  seen,  together  with  a  lack  of  moisture  and  great  intensity 
of  light.  In  our  treatise  will  be  found  also  anatomical  details  as  to  the 
blasting  and  the  appearance  of  the  so-called  "drought  spots."  A  yellow 
coloration  of  the  walls  of  the  bast  fibres  is  worth  noticing,  which  increases 
to  a  yellow  brown,  as  is  also  the  hardening  of  the  cell  contents  in  various 
groups  of  the  assimilatory  tissues. 

The  death  of  leaves,  due  to  sudden  heat  periods,  should  be  distinguished 
from  a  normal  death.  The  leaf  does  not  shrivel  up  as  completely  as  the  nor- 
mally ripened  one, — i.  e.,  a  leaf,  the  contents  of  which  are  nearly  exhausted — 
or  it  can  do  so  only  in  places.  In  the  normally  ripened  leaf,  only  the  entirely 
impoverished  cells  of  the  leaf  tissue,  which  therefore  collapse  to  a  waved 
folded  layer,  are  found  between  the  epidermis  of  the  upper  and  of  the  lower 
sides,  while  in  the  former  leaf  just  the  remaining,  more  abundant  contents 
stiffen  the  walls  by  drying,  thereby  more  or  less  preventing  the  collapse. 

I  also  found  the  same  discoloration  phenomena  in  wild  grasses  (Arrhen- 
atherum)  and  expressed  a  warning  against  deceptions  from  anatomical  in- 
vestigation. Especially  angular  or  spherical  masses  appeared  in  the  contents 
which  reacted  with  iodine  like  starch  and  thereby  could  give  the  appearance 
of  a  still  existing,  greater  assimilatory  activity.  The  other  reactions  prove, 
however,  that  "residue  bodies"  of  the  chlorophyll  decomposition  are  here  in- 
volved which  belong  to  the  carotin  group.  They  could  be  compared  with 
adipocere. 

"Reds"  of  Hops. 

The  disease,  called  by  practical  growers  "summer  rust/'  "Fox"  or  "red 
tan,"  consists  in  a  spotting  of  the  leaves,  which  advances  from  their  bases. 
The  spots  attack  the  peripheral  parts  as  well  as  the  tissue  groups  lying 
between  the  different  veins.  By  a  partial  destruction  of  the  chlorophyll,  the 
diseased  places  at  first  appear  yellowish,  then  reddish  and  finally  dry  and 
browned.  In  the  meantime  the  leaf  continues  longer  in  a  wilted  condition, 
finally,  it  shrivels  and  drops  off,  while  the  upper,  younger  parts  of  the  vine 
are  still  fresh,  green  and  developing.  The  new  structures  produced  during 
this  time  are  smaller  in  comparison  with  those  of  other  plants  which  are  un- 
affected and  have  not  lost  the  lower  leaves.  If  the  disease  remains  restricted 
to  the  lower  parts  of  the  vine,  the  injury  is  not  important;  but,  if  it  attacks 


1   Sorauer,  P.,   Beitrag  zur  anatomischen  Analyse  rauchbeschadigter   Pflanzen. 
Landw.  Jahrb.  1904,  p.  596,  Plates  XV  to  XVIII. 


283 

the  upper  portions  with  the  blossoming  catkins,  the  han^est  will  be  ver)^  light 
and  an  immediate  gathering  is  advisable. 

The  disease  may  be  confounded  easily  with  the  "copper  rust,"  caused  by 
the  weaver  moth,  but  is  distinguished  by  its  location  since  the  copper  rust 
colors  the  leaves  on  the  upper  part  of  the  vines  a  reddish  yellow  and  is 
recognizable  from  its  finely  spun  threads  on  the  underside  of  the  leaf,  while 
the  summer  rust  causes  a  yellowing  and  drying  of  the  leaves,  beginning  at 
(he  base  of  the  vine.  It  is  a  sapping  of  the  older  organs  by  the  younger 
ones,  which  require  the  organic  material  there  present  for  their  further 
development. 

The  so-called  "Pole  Red"  seems  to  correspond  to  the  "blast"  of  grain 
and  to  be  the  result  of  a  sudden  dry  period  when  the  catkins  mature. 

In  this  and  the  related  diseases  of  reddening  the  lack  of  atmospheric 
moisture  plays  an  especially  decisive  role,  because  watering  only  the  soil 
rarely  proves  a  remedy.  It  is  better,  if  possible,  to  water  regularly  in  the 
evening.  But  for  larger  areas  in  practical  cultivation  the  necessary  number 
of  laborers  and  the  great  quantities  of  water  may  rarely  be  had.  Hence  re- 
sort must  be  had  to  preventative  measures,  in  which  either  the  excessive 
evaporation  is  reduced  by  extensive  shading,,  or  the  saturation  capacity  of  the 
soil  is  increased  by  the  supply  of  fertilizing  salts  (not  animal  manure).  Fr. 
Wagner^  cites  an  example  for  the  later  case.  He  found  in  his  cultivation 
that  hop  vines,  without  having  been  given  nitrates,  did  not  resist  drought 
and  vegetable  or  animal  parasites  so  well  as  those  fertilized  with  chili  salt- 
petre and  also  their  lower  leaves  turned  yellow  earlier.  In  the  same  way  it 
has  often  been  observed  in  practical  agriculture  that  fodder  and  sugar  beets 
withstand  drought  better  when  the  soil  has  been  fertilized  with  potassium 
salts  or  nitrates,  or  even  with  abundant  stable  manure-. 

Similar  discoloration  resulting  from  a  lack  of  moisture  has  been  ob- 
served in  flax.  This  is  described  partly  as  the  "Reds"  {le  rouge)  and  partly, — 
when  the  points  of  the  stems  turn  yellow  prematurely, — as  the  "yeUozvs" 
(le  jaiine). 

"Leaf  Scorch"— "Parching  of  Vines" — "Red  Scorch." 

The  above  are  collective  names  for  a  group  of  phenomena  distinguished 
with  difficulty  from  one  another,  in  which  the  leaves  are  colored  red.  As  a 
rule,  the  discoloration  is  followed  by  a  partial  or  complete  drying  up  of  the 
foliage,  which  begins  to  fall  prematurely.  Recently  Muller-Thurgau^  has 
determined  a  parasitic  cause  for  a  definite  form  of  reddening*  and  takes 
pains  to  emphasize  the  characteristics,  apparent  to  the  naked  eye,  distinguish 


1  Wag-ner,  Fr.,  Salpeterdiingungsversuche  des  Deutschen  Hopfenbau-  Vereins 
Wochenbl.  d.  Landw.  Ver.  in  Bayern  1904,  p.  182. 

-  See,  for  example.  Jahresb.  d.  Snnderpu«schu«ees  f.  Pflanzenschutz  fiir  das 
Jahr.  1904.     Arb.  d.  Deutsch.     Landw.-Ges.  1905,  p.  91. 

3  Mtiller-Thurgau,  H.,  Der  rote  Brenner  des  Weinstocks.  Centralbl.  f.  Bakt.  II, 
1903.    Parts  1-4. 

4  Another  form  of  Red  Scorch  connected  with  Botrytis  vegetation  is  described 
by  Behrens  (Untersuchungen  tiber  den  Rotbrenner  der  Reben)  in  Ber.  d.  Grofsh. 
Bad.  Versuchsanstalt  zu  Augustenborg  1902,  p.  43. 


284 

ing  this  disease  from  others.  With  reference  to  the  form  of  "Red  Scorch," 
described  in  the  second  volume  of  this  manual  and  caused  by  Fseudopeziza 
fracheiphila  (see  Vol.  II.,  p.  278*)  in  which  the  discoloration  often  begins  in 
the  form  of  spots  in  the  angles  of  the  veins,  it  should  be  emphasized  here 
that  the  leaf  scorch,  which  is  due  to  a  lack  of  moisture  together  with  strong 
sunshine,  begins  as  a  rule  with  a  discoloration  of  the  intercostal  fields  start- 
ing from  the  edge.  The  phenomena  vary  greatly,  according  to  the  variety 
and  habitat,  and  at  times  only  a  shining  yellow  color  is  found  instead  of  the 
reddening.  The  edges  of  the  leaves  often  dry  up.  The  kind  of  discoloration 
runs  parallel  with  the  progress  of  the  summer  blight  in  other  woody  plants, 
whereby  it  may  usually  be  observed  how  the  deficient  moisture  supply  be- 
comes evident  at  first  on  the  parts  lying  furthest  away  from  the  petioles  and 
the  mid-rib  and  then  advances  until  finally  only  the  immediate  surroundings 
of  the  veins  remain  green.     (See  Changes  due  to  place  of  growth.) 

In  regard  to  the  physiological  activity,  Miiller-Thurgau  had  proved 
earlier  that  the  formation  of  starch  and  its  solution  took  place  the  more 
slowly,  the  less  the  water  content  of  the  leaves^ ;  irrigated  vines  formed  more 
sugar. 

A  phenomenon  manifesting  itself  like  the  parasitic  scorch  has  been  de- 
scribed by  Sauvageau  and  Perraud-  as  the  pectin  disease  (maladie  pectique), 
the  result  of  continued  drought.  In  this,  the  leaf  blades  are  loosened  from 
the  petiole. 

Yellowing  Due  to  the  Grafting  Stock. 

In  our  species  of  fruit  there  is  often  a  lack  of  water,  because  a  rapidly 
growing  variety  grafted  on  a  dwarf  stock,  in  times  of  great  evaporation,  is 
not  able  to  convey  the  necessary  water  to  the  graft. 

On  good  soils  pears,  grafted  on  quince  stock,  often  turn  yellow,  while 
trees  on  wild  stock  thrive  well.  In  Avy  summers  I  found  with  such  dwarf 
trunks  that  well  grown  scions,  inserted  later  in  the  bark,  formed  strong  but 
j^ellowish  shoots,  while  the  older  top  was  green.  In  this  too  I  see  phenomena 
of  the  lack  of  moisture  due  to  the  quince  stock  which  (especially  if  planted 
shallow)  cannot  obtain  the  necessary  water.  Pears  on  shallow  planted 
quinces  ripen  their  foliage  more  quickly  and  lose  it  earlier. 

Premature  Drying  of  the  Foliage. 

When  the  foliage  dies  as  a  result  of  the  summer  drought,  in  which  it 
usually  hangs  on  the  branch,  because  the  petiole  has  remained  fresh,  the 
injury  suffered  by  the  tree  is  far  greater  than  is  generally  understood. 

It  is  thought  that  the  injury  consists  primarily  in  the  premature  stopping 
of  leaf  activity  and  the  lessened  formation  of  wood.    Kraus'^  investigations 


*  Paging  in  the  German  originaL 

1  III.  .lahresber.   d.  A^ersuchsstat.  Waden.sweil.     Zi'rich   1894.  p.  56. 

2  Sauvageau.   C.  et  Perraud,  J.,   La  maladie   pectique  de  la  vigne.     Revue   de 
viticulture  1894,  p.  9. 

3  Bot.  Zeit.  1873,  Nos.  26  and  27. 


285 

have  proved,  however,  that,  besides  this  lack  of  additional  growth,  a  positive 
loss  in  substance  takes  place,  which  is  much  greater  than  in  normal  fall  de- 
foliation. The  leaves  killed  by  blight  do  not  behave  as  do  those  which  drop 
ofif  in  the  fall.  These  have  gradually  given  up  to  the  trunk  most  of  the  sub- 
stances still  utiUzable  for  the  plant  body  and  in  the  end  have  been  loosened 
l)y  a  round-celled  layer  of  separation.  The  dried  leaves,  in  which  no  such 
layer  has  been  formed,  retain  the  elements  which  contain  nitrogen  together 
with  phosphoric  acid  and  only  the  starch  with  the  potassium  reaches  the 
trunk  before  the  death  of  the  leaf.  By  the  premature  drying  of  the  foliage 
approximately  twice  as  much  nitrogen  and  phosphoric  acid  are,  lost  to  the 
plant  as  by  the  autumn  leaf-fall.  This  is  proved  by  analysis  of  the  leaves 
of  a  syringa  carried  through  by  Maerker. 

In  percentages  of  dry  substances,  there  was  contained  in 

Summer  blighted  leaves       Autumn  fallen  leaves 

Nitrogen  1-947  i-370 

Phosphoric  acid 0.522  0-373 

Potassium    2.998  3-831 

Calcitun    i  .878  2.416 

All  mineral  substances 

(free  from  carbon  dioxid) 8.028  9.636 

The  above  amounts,  if  expressed  in  percentages  of  the  whole  ash,  would 
be  as  follows  : — 

Summer  blighted  leaves  Autumn  fallen  leaves 

Nitrogen   24.0  14.0 

Phosphoric  acid 6.5  3.8 

Potassium 37.3  39.7 

The  Burning  Out  of  Grass. 

With  the  drying  of  the  turf,  as  the  result  of  hot  periods  in  summer,  the 
loss  of  nutritive  substances  must  be  considered  especially  in  meadows. 
Where  there  are  no  irrigating  arrangements,  there  is  no  possibility  of  avoid- 
ing the  injury.  In  ornamental  planting,  however,  it  may  be  avoided  if  the 
action  of  the  light  and  thereby  evaporation  is  repressed  at  the  right  time  by 
mulching  with  hay  or  other  light  shading  material.  Sprinkling  the  grass 
surfaces  is  effective  only  when  it  can  be  carried  out  repeatedly  during  the 
day.     In  other  cases,  shading  must  be  resorted  to. 

Silver  Leaf. 

The  "Silver  Leaf"  belongs  among  the  phenomena  which  have  not  yet 
been  tested  experimentally  in  regard  to  their  causes  and  therefore  can  be 
classified  only  provisionally. 

The  disease  so  manifests  itself  in  fruit  trees  that  the  leaves,  otherwise 
normally  developed,  lose  their  dark  green  appearance  and  give  a  silvery, 
whitish  reflection.     As  a  rule  only  individual  branches  sufifer  and  possibly 


286 

after  June  or  July.  In  the  following  year,  or  in  the  second,  at  the  latest  in 
the  third  year,  after  the  appearance  of  the  silver  leaf,  the  branch  dies.  In 
the  specimens  which  I  could  examine  after  the  lapse  of  a  year,  the 
phenomenon  appeared  often  on  the  other  branches  after  the  dead  branch 
had  been  removed,  so  that,  for  the  present,  I  have  formed  the  hypothesis 
that  the  silver  leaf  is  an  absolutely  certain  precursor  of  the  death  of  a  branch. 
It  is  found  most  wide-spread  among  apricots.  I  found  the  phenomenon 
also  in  plums  and  apples. 

The  change  begins  in  the  older  leaves  of  the  spring  growth,  the  youngest 
more  often  escape ;  likewise  the  late  shoots  developing  suddenly  in  old  wood 
from  preventative  eyes.  First  of  all  only  a  certain  dullness  of  color  is 
found,  a  loss  of  the  gloss  in  places  and,  as  it  seems  to  me,  an  increased 
amount  of  air  in  the  intercellular  spaces  between  the  various  palisade  cells 
or  between  them  and  the  epidermal  cells.  Gradually  the  dull  places  become 
whitish,  in  fact  because  of  a  glandular  breaking  up  of  the  epidermal  cells 
between  the  finest  ramifications  of  the  veins  which  remain  green.  This 
loosening  up  consists  of  a  dissolving,  in  places,  of  the  connection  between 
epidermis  and  palisade  parenchyma. 

AderholdS  who  also  observed  the  disease  in  cherries  and  found  that  the 
cells  of  the  epidermis  mutually  separate  from  one  another,  could  prove  that 
the  variations  from  the  healthy  leaf,  in  places  displaying  the  silver  leaf,  were 
found  in  the  solvability  of  the  intercellular  substances  (middle  lamellae). 
He  surmised  that  the  intercellular  substance  in  the  diseased  organs  consisted 
of  more  soluble  pectin  compounds  than  in  the  the  healthy  leaf  and,  since  the 
calcium  compounds  of  pectic  acid  represent  insoluble  conditions,  the  theor}^ 
is  pertinent,  that  the  disease  may  be  due  to  a  lack  of  calcium. 

According  to  this  theory,  the  disease  would  also  belong  in  the  group  of 
phenomena,  due  to  deficient  moisture  and  nutritive  substances ;  only  it  must 
be  emphasized  in  this,  that  the  content  of  moisture  and  nutritive  substances 
in  the  soil  cannot  come  under  consideration  here,  but  that  only  in  the  plant 
itself  can  it  be  manifested  locally.  And  this  circumstance  points  to  dis- 
turbances in  the  vascular  system.  This  is  favored  also  by  the  fact  that  the 
branches  with  silver  leaf  die  prematurely. 

The  apricots  and  plums  which  I  observed  showed  gummosis  and  the 
apple  trees  suffered  from  the  gnawing  of  bark  beetles.  It  might  be  possible 
to  strengthen  the  whole  organism  by  rejuvenescence  of  the  diseased  trees 
and  by  supplying  calcium. 

The  Water  Core  of  Apples. 

In  the  same  way  the  phenomenon  may  be  traced  to  the  local  vascular 
disturbances  in  which  individual  fruits  of  a  tree  in  part,  or  as  a  whole,  re- 
main hard  and  become  glassy  and  transparent, — develop  less  color  and  are 
tasteless. 


1  Aderhold,  R.  Notizen  liber  einijre  im  vorigen   Sommer  beobachtete  Pflanzen- 
krankheiten.  Zeitschr.  f.  Pflanzenkrankh.  1S95,  p.  86. 


287 

In  investigating  an  apple,  which  was  only  partially  glassy,  I  found  in 
longitudinal  section,  that  the  particles  of  the  skin  were  most  intensively 
glassy  and  that,  inside  the  fruit,  the  white,  normal  flesh  extended  from  the 
base  pretty  nearly  to  the  bud  end.  The  glassy  zone  had  a  whitish  marbling 
due  to  wedged-in  groups  of  normal  flesh.  The  seeds  were  mostly  deformed, 
not  ripe  and  still  white.  The  healthy  part  contained  abundant  starch  and 
intercellular  spaces  strongly  filled  with  air.  These  spaces  were  poorer  in  air 
in  the  glassy  part  and  there  was  no  starch  except  in  isolated,  wedged-in  cell 
groups.  The  glassy  part  turned  brown  more  quickly  in  the  air;  some  dex- 
trin could  be  found  together  with  abundant  grape  sugar.  In  dr}'  substances 
there  was  found  in 

The  healthy  half  The  glassy  half 

With  the  skin 21.48  per  cent.  T9.43  per  cent. 

Without  the  skin 20.24     "       "  17.97     " 

Aderhold^  found  in 

Healthy  fruit  flesh  Glassy  fruit  flesh 

Specific  gravity O.718  0.925 

Dry  substances  in  percentages  of  the 

fresh  weight    T4.44  per  cent.  12.60  per  cent. 

Ash  in  percentages  of  the  dry 

weight 2.093  per  cent.  1.76  per  cent. 

Malic  acid  in  100  ccm.  juice 0.92  g.  0.53  g. 

The  most  recent  determinations  come  from  Behrens^.    He  found  in 

100  ccm.  of                                                   Water  Invert  sugar  Acid 

Pressed  juice  of  the  normal  apple 87.38  g.                 5-05  g.  0.56  g. 

Pressed  juice  of  the  partially  glassy 

apple   88.06  g.                 4.40  g.  0.47  g. 

In  agreement  with  my  statements,  the  above  figures  show  that  the  flesh 
of  the  glassy  apple  is  considerably  poorer  in  acid,  dry  substances  and  ash. 
The  glassy  appearance  and  the  smaller  size  is  explained  by  the  fact  that  the 
intercellular  spaces  of  the  glassy  part  are  filled  with  water  and  the  cells  are 
smaller. 

Practical  growers  believe  they  have  observed  that  the  following  varie- 
ties tend  especially  to  the  production  of  glassy  fruits : — Zurich  Transparent 
apple,  Gloria  mundi,  white  Astrachan  and  Virginia  summer  Rose  apple.  On 
an  average,  in  the  first  year  of  bearing,  the  little  trees  were  more  disposed  to 
the  production  of  such  fruits  than  in  later  years. 

b.     Changes  in  Production  Due  to  Lack  of  Nitrogen. 
Starvation  Conditions  in  Cryptogams. 

In  reference  to  the  parallelism  of  phenomena  in  lower  and  in  more  high- 
ly organized  plants,  an  example  may  be  cited  first  of  all  from  the  fungi. 

1  Aderhold,   loc.   cit.,   y.   8. 

2  Behrens,  J.,  Bericht  d.  Grofsh.  Bad.  Landes-Versuchsanstalt  Augustenburg  i. 
J.  1904,  p.  53.     Karlsruhe  1905. 


288 

Fliorow'  tested  the  effect  of  starvatioi*  c.i  respiration  in  Mucor  and  PsaUiota 
campestris.  In  Mucor,  respiration  immediately  falls  to  a  great  extent  be- 
cause in  this  fungus  there  exists  no  storage  of  reserve  stuffs  in  the  mycel- 
lium.  In  the  fruiting  body  of  the  basidiomycete,  however,  there  is  a  great 
deal  of  reserve  material  and,  for  this  reason,  it  is  very  independent  of  the 
nutritive  substratum  so  that  its  respiration  only  falls  very  slowly  with  star- 
vation. In  regard  to  the  exchange  of  the  proteins,  Fliorow  concludes  from 
experiments  with  Amanita  muscaria  that  the  percentage  of  nitrogen  as  a 
whole  increases  during  starvation  chiefly  because  the  substances  free  from 
nutritive  substratum  so  that  its  respiration  only  falls  very  slowly  with  star- 
takes  place,  which  is  simultaneous  with  the  periods  of  spore  formation  and 
ripening.    A  rapid  decomposition  of  the  protein  follows  at  once. 

To  be  sure,  the  production  of  carbon  dioxid  and  the  taking  up  of  oxy- 
gen gradually  decrease  in  the  starvation  of  fungi,  but  in  unequal  propor- 
tions, as  was  observed  by  Purjewicz-,  with  Aspergillus  niger. 

PrantP  has  given  very  good  experimental  observations  on  the  prothallia 
of  ferns.  His  experience  shows  especially  that,  in  the  seeding  of  fern 
spores,  the  most  diverse  variations  occur  in  the  prothallia.  Some  of  them 
have  a  tissue  capable  of  developing  further  (meristem),  while  others  lack 
it  and  therefore  are  "ameristic."  Earlier  investigations*  had  shown  Prantl 
that  the  ameristic  condition  can  occur  with  too  small  supply  of  air  as  with 
a  scanty  supply  of  water  and  indeed  also  of  mineral  substances"'.  The  ob- 
servation, that  under  the  most  favorable  conditions  of  illumination,  ameristic 
individuals  appear  when  the  prothallia  grow  too  close,  led  to  the  experiment 
of  testing  directly  the  influence  of  the  nitrogen  supply.  Spores  of  the  rapidly 
germinating  Osmunda  regalis  and  of  Ceratopteris  thalictroides  were  sown  on 
different  nutrient  solutions.  It  was  thus  shown  that  the  spores,  germinated 
in  distilled  water,  produced  ameristic  prothaUia.  They  formed  surfaces  of 
15  to  25  cells  of  pretty  uniform  size  and  similar  content.  The  chlorophyll 
grains  were  poor  in  starch.  On  the  other  hand,  the  prothallia  grown  in  a 
nutrient  solution,  free  from  nitrogen,  but  otherwise  normal,  were  dis- 
tinguished by  an  extremely  large  starch  content,  but  otherwise  resembled  the 
individuals  grown  in  distilled  water.  Only  the  specimens  grown  in  a  nutri- 
ent solution  with  a  nitrogen  admixture  (0.64  per  cent,  ammonium  nitrate) 
were  meristic.  If  specimens  of  meristic  prothallia  were  transferred  into  a 
nutrient  solution  free  from  nitrogen,  the  meristem  disappeared  after  14  days, 
while  the  cells  as  a  whole  increased,  had  divided  here  and  there  and  had  been 
filled  with  starch.    If,  on  the  other  hand,  ameristic  prothallia  were  placed  in 


1  Fliorow,  A.,  Der  Einflufs  der  Ernahrung  auf  die  Atmung  der  Pilze.    Bot.  Cen- 
tralbl.    1901.    Vol.  87,  p.  274. 

2  Purjewicz,  K.,  Pliysiolog-.  Unteisucli.  iiber  die  Atmung-  der  Pflanzen.  cit.  Bie- 
derm.    Centralbl.  1902,  p.  180. 

3  Prantl,  Beobaclitungen  iiber  die  Ernahrung  der  Farnprothallien  und  die  Ver- 
teilung  der  Sexualorganc.    Bot.  Zeit.  1881,  p.  753. 

4  Flora  1878,  p.  499. 

5  Reed  has  shown  (Annals  of  Bot.  21;  501,  1907)  that  prothallia  of  G.  sulphures 
were  unable  to  form  archegonia  where  calcium  was  absent.     Translator. 


289 

a  complete  nutrient  solution,  they  at  once  formed  a  meristem  on  their  outer 
edges  by  a  repeated  cell-division,  while  the  starch  supply  decreased. 

The  distribution  of  the  sexual  organs  varies  according  to  the  nutritive 
conditions.  Ameristic  prothallia  bear  only  antheridia,  never  archegonia, 
which  are  associated  with  the  presence  of  a  meristem.  Of  especial  impor- 
tance at  this  point  is  Prantl's  observation  that  ameristic  prothallia  of  Os- 
munda,  which  had  borne  isolated  antheridia,  developed  abundant  archegonia 
after  nitrogen  had  been  supplied;  besides  the  archegonia,  antheridia  also 
appeared. 


PART  IV. 


MANUAL 


OF 


Plant  Diseases 


BY 


PROF.  DR.  PAUL  SORAUER 


Third  Edition-Prof.  Dr.  Sorauer 

In  Collaboration  with 

Prof.  Dr.  G.  Lindau       And       Dr.  L.  Reh 

Private  Docent  at  the  University  Assistant  in  the  Museum  of  Natural  Hiatory 

of  Berlin  io  Hamburg 


TRANSLATED  BY  FRANCES  DORRANCE 


Volume  I 
NON-PARASITIG  DISEASES 

BY 

PROF.  DR.  PAUL  SORAUER 

BERLIN 


WITH  208  ILLUSTRATIONS  IN  THE  TEXT 


PART  IV. 


MANUAL 


OF 


PLANT  Diseases 

BY 

PROF.  DR.  PAUL  SORAUER 


Third  Edition—Prof.  Dr.  Sorauer 

In  Collaboration  with 

Prof.  Dr.  G.  Lindau        And       Dr.  L.  Reh 

Private  Decent  at  the  University  Assistant  in  the  Museum  of  Natural  History 

of  Berlin  in  Hamburg 


TRANSLATED  BY  FRANCES  DORRANGE 


Volume  I 
NON-PARASITIC  DISEASES 

BY 

PROF.  DR.  PAUL  SORAUER 

BERLIN 


WITH  208  ILLUSTRATIONS  IN  THE  TEXT 


Copyrighted,    1915 

By 

FRANCES  DORRANCE 


THE  RECORD   PRESS 
Wilkes -Barre,   Pa. 


289 

a  complete  nutrient  solution,  they  at  once  formed  a  meristem  on  their  outer 
edges  by  repeated  cell-division,  while  the  starch  supply  decreased. 

The  distribution  of  the  sexual  organs  varies  according  to  the  nutritive 
conditions.  Ameristic  prothallia  bear  only  antheridia,  never  archegonia, 
which  are  associated  with  the  presence  of  a  meristem.  Of  special  impor- 
tance at  this  point  is  Prantl's  observation  that  ameristic  prothallia  of  Os- 
munda,  which  had  borne  isolated  antheridia,  developed  abundant  archegonia 
after  nitrogen  had  been  supplied ;  besides  the  archegonia,  antheridia  also 
appeared. 

From  these  changes  produced  by  the  nutritive  substances  is  explained 
without  forcing  the  tendency  to  "dioecia"  ascribed  to  some  ferns  by 
various  authors ;  by  Millardet^  for  Osmunda,  by  Bauke-  for  the  Cyatheaceae 
and  for  Platycerium,  and  by  Jonkmann^  for  the  Marattiaceae. 

H.  Hoffman*  cites  further  notes  pertinent  here ;  first  of  all,  Von  Hof- 
rneister,  who  assumes  that  in  Equisetum  the  prothallia  produce  decidedly 
more  antheridia  in  the  light  and  in  a  dry  locality,  i.  e.,  bear  more  male  plants 
since  the  prothallia  are  almost  entirely  dioecious. 

•Borodin  found  that  germinating  spores  of  Allosurus  Sagittatus  de- 
veloped antheridia  when  placed  in  the  dark. 

The  Production  of  Sterile  Blossoms.      (Sterility.) 

Sterile  blossoms  in  phanerogams  are  due  primarily  to  a  lack  of  nitro- 
gen. This  may  manifest  itself  in  very  different  ways ;  as  already  mentioned 
in  the  blasting  of  grain,  a  sufficient  supply  of  nitrogen  may  be  present  in 
the  soil  but  as  result  of  a  prolonged,  intense  drought  there  is  lacking  the 
carrier,  the  water,  to  bring  to  a  further  normal  development  the  already 
differentiated  stamens  and  pistils.  On  the  other  hand  there  may  be  in  heavy 
seeding  a  struggle  for  nitrogen  in  which  the  plants  that  earliest  attain  most 
vigorous  vegetative  development  take  the  nutriment  from  the  less  vigorous 
ones.  In  a  consideration  of  sterility  there  must  further  be  taken  into  ac- 
count the  cases  where  the  existing  nutritive  material  is  used  up  in  some 
other  way,  so  that  a  one-sided  increase  or  decrease  of  a  growth  factor  favors 
the  vegetative  utilization  of  the  elaborated  organic  material  to  such  an  ex- 
tent that  nitrogen  sufficient  to  mature  the  sexual  organs  is  lacking.  Finally 
it  not  infrequently  happens  that  the  material  is  abundantly  used  in  the  de- 
velopment of  the  lesser  nitrogen  requiring  male  organs  and  no  longer 
suffices  for  the  development  of  the  ovary.  The  cases  among  phanerogams 
where  starvation  conditions  induce  blossom  development  are  not  in  opposi- 
tion to  this  view.  Examples  of  this  are  found  in  our  fruit  trees,  where  dis- 
eased specimens  with  a  pronounced  decrease  of  shoot  development  "bloom 
themselves  to  death."  In  horticultural  practice  plants  are  purposely  starved 
in   order  to  attain   flower  production    (Kantua   dependens,    Correa.   etc.) 


1  Pring-shelm's  Jahrbiicher,  X,  p.  97. 

2  Bot.   Zeit.    1878,    p.   757. 

3  Extrait  des  Actes  du  Congr&s  international.     Amsterdam,  1877. 

4  Hoffmann,  H.,  Zur  Geschlechtsbestimmung.  Bot.  Zeit.  1871.     Nos.  6  and  7. 


290 

Lovers  of  cacti  sometimes  pull  their  plants  from  the  pots  in  winter  and  let 
them  shrivel,  so  that  they  may  bloom  more  freely.  In  this  case  nitrogen  is 
not  lacking  but  the  scarcity  of  water  causes  the  plants  to  make  use  of  the 
elaborated   food  in  flower  production. 

In  treating  of  the  bearing  of  sterile  blossoms,  due  to  insufficient  water, 
Oberdieck^  reports  that,  as  a  result  of  drought,  the  blossoms  of  large- 
flowered  pansies  drop  prematurely  while,  with  sufficient  moisture,  they 
develop  the  seed  capsules.  Double  zinnias  behave  in  the  same  way,  like- 
wise the  red  flax  and  often,  indeed.  Phlox  Drummondii.  Garden  beans  do 
not  set  so  well  in  dry  years.  Raspberries  and  strawberries  give  small,  poorly 
seeded  fruits.  In  the  case  of  the  ever-flowering  wood  strawberry  there  is 
a  degeneration  with  continued  drought,  making  the  plants  resemble  the 
"Vierlandcr  strawberries,"  since  they  no  longer  develop  fertile  blossoms. 
Zacharias-  states  that  the  latter  variety  of  strawberries  is  one  which  is 
usually  either  staminate  or  pistillate,  hut  rarely  monoecious.  He  is  of  the 
opinion  that  pollination  is  incomplete  where  only  a  few  staminate,  so  called 
"wild"  plants,  distinguished  by  their  weaker  growth,  weaker  runners  and 
lower  growing  inflorescences  with  larger  blossoms,  are  present  on  the  fields. 
He  emphasizes  the  fact  that  invariably  few  pistils  develop,  so  that  only  a 
portion  of  the  swollen  receptacal  is  covered.  We  would  lay  the  chief  weight 
on  the  latter  point  and  advise  remedially  a  change  of  soil  and  variety. 
Zacharias  recommends  putting  more  staminate  plants  among  the  pistillate 
ones. 

Phenomena  similar  to  those  in  the  Vierlander  strawberry  have  been 
observed  in  the  black  currant^.  The  sterility  is  said  to  be  caused  neither  by 
dryness  nor  by  a  shady  position,  but  is  ascribed  by  practical  workers  to  a 
varietal  peculiarity.  Likewise  complaints  are  made  as  to  the  scanty  setting 
of  fruit  in  the  Schattenmorelle  (shad,ow  Amorelle  cherry).  The  "Praktische 
Ratgeber"  (Practical  Adviser)  advises  in  grafting  the  taking  of  scions  only 
from  the  trees  of  that  variety  which  experience  has  proved  to  bear  well. 
We  often  meet  with  such  indications  of  the  inheritance  of  undesirable 
peculiarities. 

Numerous  statements  may  be  found  in  regard  to  the  increasing  pre- 
dominance of  staminate  over  pistillate  blossoms.  One  of  the  earliest  is 
the  statement  by  Knight,  that  melons  and  cucumbers  at  higher  temperatures 
without  sufficient  light  almost  always  produce  only  stamens.  Manz*,  in  his 
experiments,  comes  to  the  conclusion  that  in  monoecious  as  well  as  in 
dioecious  plants  drought  favors  the  development  of  male  plants,  while 
moisture  and  good  fertilization  favor  female  plants.  It  is  said  that  male 
plants  can  be  made  to  bear  perfect  blossoms  by  removing  whole  branches. 
This  might  then  indicate  that  the  nitrogen  taken  up  by  the  roots  is  now  dis- 
tributed among  a  lesser  number  of  blossoms  and  thus  better  nourishes  these. 

1  Oberdieck,  Deutschlands  beste  Obstsorten,  p.  9  footnote.     Leipzif,   1881. 

2  Zacharias,  E.,  t)ber  den  man^elhaften  Ertras  der  Vierlander  Erdbeeren.  Verb, 
d.  Naturw.  Vereins,  Hamburg-,  1903.     3.  Folg-e,  XI,  p.  26. 

3  Prakt.  Ratgeber  im  Obst-  und  Gartenbau.     Frankfurt  a.   O.,  1904,  No.  10. 

4  Vierte  Beilage  zur  Flora,  1822,  Vol.  V  (after  Hoffmann  loc.  cit.),  p.  88. 


291 

Conditions  are  similar  with  our  fruit  trees,  most  of  which  rest  a  year, 
that  is  to  say,  bear  one  year  a  smaller  crop  and  then  the  next  a  larger  one. 
After  a  heavy  crop  the  trees  are  usually  so  exhausted  that  they  need  one 
year  in  order  to  store  up  sufficient  nutritive  substances  for  the  next  crop. 
Hoffman^  mentions  further  that  many  trees  (the  horse  chestnut  and  the 
Scotch  Pine)  exhibit  a  normal  alternation  of  sexes,  since  they  bear  staminate 
flowers  one  year  and  perfect  ones  the  following.  The  increase  of  carpels 
in  the  giant  poppy  (Papaver  somniferum  forma  polycarpica  monstrosa) 
occurs  only  in  the  most  vigorous  plants.  During  his  travels  Karsten^  found 
that  the  palms  growing  in  swamps  and  damp  woods,  as  a  rule,  bear  perfect 
blossoms,  but  become  polygamous  again  from  a  lack  of  nutrition.  The 
genera  growing  on  dry  cliffs  or  arid  plains  have  ordinarily  but  not  naturally 
separated  sexes,  and  these  bear  staminate  and  pistillate  flowers  on  separate 
branches.  At  the  beginning  of  the  dry  season  the  fruit  ripens,  requiring  a 
great  deal  of  nutritive  material,  and  then  only  staminate  flowers  develop; 
while  after  the  dormant  period,  at  the  beginning  of  the  rainy  season,  pis- 
tillate blossoms  are  formed  in  great  abundance. 

Cugini^  found  in  starved  plants  of  maize,  which  he  obtained  by  heavy 
seeding,  that  various  individuals  bore  only  staminate  flowers.  De  Vries* 
was  also  able  to  demonstrate  the  inheritance  of  sterility  in  the  case  of  maize. 
He  took  seeds  from  plants  in  which  the  pistillate  inflorescences  were  entirely 
wanting  or  extremely  weak  and  obtained  in  the  first  year  12  per  cent,  of  such 
imperfect  plants.  The  sowing  of  the  following  year  yielded  19  per  cent,  of 
sterile  plants. 

A  case  described  by  Miiller-Thurgau^  shows  that  aside  from  nitrogen 
hunger  sterility  can  often  be  due  to  a  lack  of  moisture  alone.  He  found 
the  stigmas  on  fruit  trees  so  dry  that  the  pollen  grains  could  not  germinate. 
In  comparative  test  experiments  with  pears,  trees  which  had  been  abundantly 
watered  during  the  time  of  blossoming  exhibited  an  evident  increase  in  yield. 
Not  only  did  numerous  blossoms  on  the  unwatered  trees  fall,  shortly  after 
the  time  of  blossoming  was  past,  but  even  the  young  fruits,  when  about  the 
size  of  cherries,  fell  in  strikingly  large  numbers.  On  trees  standing  in  dry 
places,  usually  one  fruit  remained  to  each  umbel,  while  in  the  case  of  water- 
ed trees,  on  an  average,  three  developed. 

But  sterility  occurs  even  with  good  pollen  and  with  stigmatic  conditions 
favorable  for  germination.  Waite''  in  his  experiments  on  pear  blight  kept 
insect  visitors  away  from  the  flowers  and  found  that  the  fruit  set  to  a  very 
small  extent.  Further  investigations  convinced  him  that  certain  varieties 
of  pears  and  apples  cannot  he  fertilized  at  all  by  their  own  pollen  (nor  by 
that  from  other  individuals  of  the  same  variety),  but  that  the  pollen  from  an- 


1  Bot.  Zeit.  1882,  p.  508. 

2  Linnaea,  1857,  p.  259. 

3  Cugini,  Intorno  ad  un  anomalia  della  Zea  Mays.  cit.  Bot.  Centralbl.  1880,  p.  1130. 

4  de  Vries,  H.,   Steriele  Mais  als  erfelijk  Ras.     Bot.   Jarbook  II,   p.   109. 

5  III.  Jahresber.  d.  Versuchsstat.  Wadensweil.  Zurich,    1894,  p.  56. 

6  Cit.  Galloway,  B.  T.,  Bemerkenswerftes  Auftreten  einiger  Plflanzenkrankheiten 
in  Amerika.     Zeitschr.  f.  Pflanzenkrankh.  1894,  p.  172. 


292 

other  variety  was  necessary  for  this.  This  would  explain  the  observed 
sterility  in  large  fruit  orchards  composed  of  a  single  variety. 

Ewert^  acknowledges  that  self-sterility  has  been  determined  for  many 
species,  but  is  of  the  opinion,  nevertheless,  that  large  plantations  of  only  one 
variety  do  not  fall  behind  those  made  up  of  mixed  varieties,  because  cross- 
pollination  will  be  secured  promptly  by  honey  and  bumble  bees.  The  setting 
of  the  fruit  fails  only  if,  because  of  unfavorable  weather,  the  insects  are 
unable  to  fly. 

According  to  our  theory  there  should  also  be  noted  in  this  connection 
the  alternation  between  chasmogamic  flowers  (sterile  with  large  petals), 
and  cleistogamous  flowers  (fertile  with  aborted  petals).  With  E.  Loew", 
we  perceive  in  these  conditions  no  mutations  in  de  Wies'  sense,  but  simple 
variations  which  depend  on  the  form  of  nutrition.  Goebel  found  that 
cleistogamous  flowers  formed  earlier  and  he  was  able,  by  keeping  them 
dry  and  exposed  to  abundant  sunshine,  to  force  violets  which  had  previously 
borne  cleistogamous  flowers,  to  form  chasmogamic  blossoms  in  July,  which 
is  a  very  unusual  occurrence  at  that  time  of  year.  The  alternation  was 
called  forth  by  the  postponement  of  the  use  of  the  plastic  food  material  at 
hand.  The  cleistogamous  bud  cannot  develop  with  a  lack  of  moisture  and 
abundance  of  light  and  the  plastic  building  materials  then  remain  at  the 
disposal  of  later  produced  blossoms.  Since  in  these  the  pistils  are  rarely 
formed  and  do  not  mature,  the  material  is  free  for  the  especially  vigorous 
development  of  the  petals  which  need  the  light. 

Seedless  Fruits. 

Sterility  is  often  connected  with  the  appearance  of  seedless  fruits,  and 
can  in  the  same  way  become  a  peculiarity  of  the  variety. 

In  a  new  American  variety  of  apples  (the  "Wonder  of  Horticulture") 
this  charactistic  has  recently  been  considered  an  especial  recommendation 
of  the  variety',  since  the  blossoms  yield  fruit  without  having  been  fertilized. 
In  this  way,  the  harmful  agents  threatening  other  varieties  at  the  time  of 
blossoming,  such  as  frost,  mist,  rain,  drought,  poor  insect  pollination,  etc., 
are  avoided.  The  new  variety  has  no  corolla  and  to  this  fact  is  attached  the 
hope  that  blossom  pests  and  other  insects,  which  would  be  attracted  by  the 
petals,  may  spare  such  flowers. 

Seedless  varieties  of  fruits,  i.  e.,  those  in  which  poorly  matured  seeds 
are  found,  have  been  known  from  the  earliest  times  as,  for  example,  the  pear 
"Rihas  Seedless,"  ("Rihas  Kernlose")  and  the  Seedless  Father  Apple 
("Vaterapfel  ohne  Kern")  It  is  said  that  it  frequently  happens  that  vari- 
eties free  from  seeds  appear  from  grape  seedlings,  unfortunately  dis- 
tinguished, however,  by  their  small  size  and  the  great  hardness  of  the 
grapes. 

1  Ewert,  Welche  Erfahrungen  sind  gemacht  in  bezug  auf  g-eringere  Frucht- 
baxkeit,  etc.     Proskauer  Obstbau-Zeitung,  1902. 

2  Loew,  E.,  Bemerkungen  zu  W.  Burck's  Abhandlung  uber  die  Mutation  als 
Ursache  der  Kleistogamie.  Biol.  Centralbl.  XXVI,  1906,  Nos.  5-7. 

3  Janson,  A-,  Der  kernlose  Apfel.  Gartenflora,  1905,  p.  490. 


293 

The  production  of  seedless  fruits  is  mentioned  often  in  the  more  recent 
works.  Kirchner^  who  also  cites  Waite's"  observations,  declares  that 
typically  and  normally  developed  fruits  are  obtained  only  by  crossing  with 
the  pollen  of  a  different  variety.  The  largest  fruits  are  always  produced  by 
cross-pollination.  Pears  produced  by  self-pollination  developed  at  times 
almost  no  seeds.  The  flowers  exposed  to  the  visits  of  bees,  or  artificially 
cross-pollinated,  on  the  contrary,  yielded  fruit  with  abundant  healthy  seeds. 
Thus  it  would  be  advisable  to  grow  a  mixture  of  varieties. 

In  opposition  to  this  theory,  Ewert',  even  in  his  latest  papers,  holds  to 
his  point  of  view,  advocating  for  practical  reasons  the  cultivation  of  a 
single  variety  in  blocks. 

In  regard  to  seedless  grapes,  we  will  refer  to  the  investigations  of 
Miiller-Thurgau*.  Ewert  emphasizes,  in  reference  to  seed-bearing  fruits 
that,  for  the  setting  of  the  fruit,  the  amount  of  organic  material  at 
the  disposal  of  the  individual  blossoms  is  of  especial  importance.  In  various 
cases  a  better  nutritive  condition  for  the  individual  blossoms  can  be  obtained 
artificially  by  ringing,  since  they  vary  in  their  development.  The  pistils 
are  either  greatly  developed  and  project  as  much  as  one  centimeter  above 
the  anthers  (protogyny),  or  both  sexual  organs  are  equally  long  (homog- 
any),  or  the  pistils  are  shorter  than  the  stamens  (protandry).  Ewert's 
experiments  do  not  confirm  absolutely  the  conclusion  that  the  stronger  pro- 
togny  is  developed,  the  more  the  blossom,  which  is  consequently  self-sterile, 
demands  the  pollen  of  some  other  variety,  and,  conversely,  the  more  homog- 
any  and  protandry  manifest  themselves,  the  greater  the  possibiUty  of  self- 
pollination.  It  is  evident  that  the  organic  nutriment  is  carried  first  of  all  to 
those  fruit  buds,  in  which  cross-pollination  has  made  seed  formation  possible. 
In  comparing  fruits  containing  seeds  and  those  without  seeds  on  the  same 
tree,  the  seedless  ones  are  smaller  and  are  often  malformed.  If  seedless  fruits 
alone  are  produced  on  a  tree,  by  keeping  away  all  foreign  pollen,  they  attain 
the  same  size  as  do  those  bearing  seeds.  Probably  fruits  can  also  be  pro- 
duced without  the  action  of  pollen. 

In  some  cases  fruits  can  be  observed  in  which  the  core  does  not  exist, 
or  is  scarcely  indicated.  In  reference  to  the  former,  Burbidge^  reports  that 
pears  without  seeds  and  core  represent  very  sohd  parenchymatous  fruits, 
said  to  be  larger,  better  flavored  and  possessing  a  better  keeping  quality 
than  pears  containing  seeds. 

I,  myself,  some  years  ago,  received  a  branch  of  pears,  one  specimen  of 
which  is  given  half-size  in  Fig.  36.     The  fruits  were  perfectly  hard  and 


1  Kirchner,  O.,  Das  Bliihen  und  die  Befruchtung  der  Obstbaume.    Vortrag.  Ref. 
Zeitschr.  f.  Pflanzenkrankh.  11)00,  p.  297. 

2  Waite,    Merton    B.,    The   pollination    of   the    pear   flowers.     Washington,    1894, 
U.   S.  Dept.  Agric.  Bull.   5. 

3  Ewert,    Bliitenbiologie    und    Tragbarkeit    unserer    Obstbaume.      Lrandwirtsch. 
Jahrbucher,  1906,  p.  259. 

4  Muller-Thurgau,    Folgen    der   Bestiiubung    bei    Obst-    und    Rebenbliiten   VIII. 
Ber.   d.  Zuricher  Bot.   Ges.   1900-1903. 

5  Royal  Horticultural  Society  of  London.     Cit.  Bot,  Centralbl.  1881.     Vol.  VIII, 
p.  319. 


294 


healthy  until  injured  by  the  autumn  frosts.  At  A  we  see  a  normal  woody 
branch ;  at  5  a  branch,  the  terminal  bud  of  which  is  swollen  up  to  a  seedless 
fruit ;  at  C  is  shown  a  fruit  grown  from  a  lateral  bud  with  primordia  of 
core ;  n  is  the  scar  of  a  fallen  leaf ;  s  an  undeveloped  lateral  bud  ;  k  a  per- 
fectly matured  leaf  bud  on  the  fruit  stem ;  sch  scale-like  leaf  on  this  stem ; 
at  (J  are  the  normally  extended  vascular  bundle  fibres,  arranged  about  the 
compartments  of  the  core  (/)  enclosing  the  rudimentar}'  ovules.  At  c  are 
visible  the  dried  remains  of  the  calyx  and  at  st  the  branches  of  the  style. 

This  case  differs  from  the  one  described  by  Burbidge  and  from  most 
others  described  as  yet,  in  that  the  fruit  is  the  product  of  the  buds  of  the 
current,  not  of  the  previous    year.     It    is    not    rare    for   the    pear   to   bear 

occasional  fall  flowers.  They  can,  in 
fact,  arise  from  buds  set  the  previous 
}ear,  as  is  often  stated,  but,  as  yet,  I 
have  had  opportunity  to  observe  only 
such  blossoms  as  were  produced  on 
the  branches  of  the  current  year,  ma- 
tured in  the  summer,  a  fact  which 
could  be  determined  easily  from  the 
wood  ring  of  the  branch  bearing  the 
fruit.  The  proleptic  blossoms  had, 
with  the  relatively  scanty  nutritive 
supply  and  the  short  time  granted 
them  for  development  in  the  fall, 
naturally  little  opportunity  to  develop 
the  parts  of  the  cortex  into  well  fla- 
vored fruit  flesh.  This  explains,  on 
the  one  hand,  the  lack  of  size  and,  on 
the  other,  the  lack  of  flavor  of  the 
pears  here  described.  If  the  fruit  buds 
had  not  been  stimulated  by  the  un- 
usually increased  supply  of  water  at 
the  then  autumnal  season,  they  would  probably  have  yielded  perfectly 
normal  fruits  the  following  year. 

While  the  fruit  remained  seedless  in  this  case,  because  in  the  proleptic 
development  the  accumulated  building  materials  are  insufficient,  other  cases 
also  occur  in  which  enough  material  is  present,  but  is  utilized  in  some  other 
way  because  of  the  destruction  of  the  normal  embryo.  Thus  Miiller- 
Thurgau^  states  that  pears  whose  carpel  layers  had  been  destroyed  by  a  late 
frost,  produced  fruit  then  exhibiting  in  place  of  a  core  a  hollow  chamber  in 
which  tissue  excrescences  had  grown  out  from  the  side  wall. 

The  appearance  of  seedless  fruits  is,  therefore,  to  be  treated  primarily 
as   a  question  of   food  supply.     The  organic  building  substances  are  not 


PMg.   36.     Seedless  Pear. 


1   Miiller-Thurgau,  H.,  Eigentiimliche  Frostschaden  an  Obstbaumen  und  Reben. 
X-XII.  Jahresb.  der  Deutsch-schweizer.  Versuchsstat.  Wadensweil,  1902,  p.   66. 


295 

sufficient  to  nourish  the  embryo,  no  matter  whether  this  arises  from  a  fail- 
ure of  the  stimulus  of  fertilization,  from  the  poor  position  of  the  various 
blossoms,  from  the  exhaustion  of  the  tree  as  a  result  of  a  previous  heavy 
crop,  or  from  a  proleptic  developm.ent  of  a  fruit  bud.  In  consideration  of 
the  fact  that  seed-containing  fruits  develop  better  than  seedless  fruits  from 
the  same  tree,  it  is  more  advisable  agriculturally  and  horticulturally,  as  long 
as  seedless  varieties  cannot  be  cultivated  with  absolute  certainty,  to  en- 
courage the  possibility  of  seed  formation. 

Even  if  Ewert  has  proved  that  although  in  orchards  of  one  variety 
the  number  of  seedless  and  poorly  seeded  fruit  is  large,  the  fruits  producing 
seeds  still  predominate,  on  which  account  he  has  asserted  that  " pure  planting" 
is  advisable,  yet  for  the  present  we  would  give  preference  to  mixed  planting. 
The  practical  disadvantages  in  regard  to  the  protection  and  harvesting  of 
varieties  growing  and  ripening  dififerently  may  be  decreased  by  cultivating 
each  variety  in  rows.  In  avenues  of  trees  at  all  times  that  variety  which  is 
most  nearly  ripe  should  be  especially  watched. 

The  Behavior  of  Weak  Seeds. 

The  causes,  which  have  affected  the  failure,  or  the  poor  maturing  of 
the  seeds  in  seedless  fruits,  have  been  felt  more  or  less  in  other  cultivated 
plants,  so  that  we  must  also  consider  the  behavior  of  poorly  developed  seeds. 
The  scanty  amount  of  nutriment  must  manifest  itself  in  the  specific  gravity 
and,  in  this  connection,  Clark's^  experiments  show  that  seeds  of  low  specific 
gravity  do  not  germinate  at  all  while  those  somewhat  heavier  germinate 
sparsely  and  often  produce  weak  plants.  The  highest  percentage  of  germi- 
nation is  found  in  seeds  with  the  highest  specific  gravity. 

According  to  Hosaeus'-  experiments,  normal  plants  can  be  produced 
even  from  immature,  i.  e.  specifically  light,  seeds  by  carefully  providing  ver}^ 
favorable  conditions.  But  the  death  rate  is  considerably  larger  in  compari- 
son with  that  of  normal  seeds.  This  refers  especially  to  the  use  of  grain, 
for  example,  which  had  necessarily  been  harvested  in  the  milk  stage.  Some- 
times the  immature  seeds  undergo  a  sufficient  subsequent  ripening,  outside 
of  their  fruit  covering,  and  can  then,  under  certain  circumstances,  germi- 
nate more  quickly  than  the  incompletely  matured  ones.  According  to 
KinzeP  this  may  occur  in  parasites  of  silk  varieties  (Cuscata)  and  is  very 
well  worth  consideration  in  combatting  them. 

At  times,  with  a  poor  quality  of  seed,  a  careful  soaking  is  beneficial  in 
order  to  shorten  as  much  as  possible  the  time  the  seed  lies  in  the  soil  before 
its  germination.  Immature  seeds  especially  decay  much  more  quickly,  par- 
ticularly in  heavy  soils.  But  this  soaking  of  the  seed  is  disadvantageous 
because  the  seed  must  he  longer  in  the  soil  ungerminated  if  a  period  of 


1  Clark,  A.,  Seed  selection  according  to  specific  gravity.  New  York  Exper. 
Stat.   Bull.   256.    1904. 

"  Deutsche  Landwirtsch.  Presse,  1875,  No.  4. 

3  Kinzel,  W.,  tjber  die  Keiming'  halbreifer  und  reifer  Samen  der  Gattung  Cus- 
cuta.   Landwirtsch.   Versuchsstat.    1900.    Vol.    54,   p.    125. 


296 

drought  occurs,  than  if  it  had  been  sown  naturally.  Zawodny^  has  proved 
this  experimentally  for  cucumbers.  In  this  connection  reference  must  be 
made  to  the  already  discussed  interruption  of  germination  by  drought. 

Droppixc  of  the  Fruit. 

Besides  the  dropping  of  pears  already  mentioned,  which  Miiller-Thur- 
gau  observed  as  the  result  of  drought  at  the  time  of  blossoming,  fruit-bearing 
trees  have  an  annual  house  cleaning  during  which  poorly  nourished  blossoms 
or  young  fruits  are  dropped.  The  flowers  developing  last  at  the  tips  of  the 
inflorescences,  especially  those  at  the  ends  of  branches,  are  the  ones  cast  off. 
There  is  not  enough  plastic  nutriment  at  hand  for  development.  The  fruits 
nearest  to  the  source  of  supply,  the  trunk  axis,  take  up  the  nutritive  sub- 
stances at  the  expense  of  the  organs  further  out.  For  fruits  cultivated  on 
trellises,  these  nutritive  relations  can  be  regulated  artificially,  since  a  large 
part  of  the  unfavorably  placed  specimens  can  be  removed  with  shears  soon 
after  the  fruit  is  set. 

In  growing  fruit  for  market  very  exact  consideration  must  be  given  the 
moisture  requirement,  especially  that  of  peaches  and  apricots.  When  the 
stone  begins  to  harden,  the  most  water  is  needed,  and  the  dropping  is  often 
caused  by  a  single  dry  period.  Before  and  after  this  stage  of  development, 
however,  more  care  must  be  used  in  watering,  since  otherwise  sprouts  are 
produced  tOo  early,  which  divert  the  material  necessary  for  the  maturing  of 
the  fruit.  Then,  at  a  later  stage,  the  fruit  will  drop  from  a  lack  of  nutri- 
ment, or,  at  least,  be  injured  by  it. 

We  have  already  mentioned  in  previous  chapters  that  mature  fruits 
may  drop  because  of  a  late  dry  period,  and  it  is  now  necessary  to  recall  that 
fruit,  injured  by  a  late  spring  frost,  is  sometimes  found  in  great  quantity 
on  the  ground.  All  causes  which  lead  to  the  sudden  lost  of  function  of  an 
organ  ultimately  efifcct  its  dropping. 

The  Drying  of  the  Inflorescences  on  Decorative  Plants. 

This  phenomenon  is  often  met  with  especially  by  amateur  growers  of 
potted  plants.  Aside  from  the  effect  of  dry  air  which  will  be  treated  later, 
and  the  dryness  of  the  soil  already  mentioned,  there  are  two  circumstances 
that  come  under  consideration  here.  Both  represent  a  starving  of  the  blos- 
som buds.  In  one  case  it  is  actually  a  lack  of  nitrogen  which  manifests  it- 
self when  the  plants  stay  in  the  pots  too  long,  in  the  other  case  it  is  a  lack 
of  food  for  the  blossoming  organs,  since  other  organs  have  taken  it. 

Our  azaleas  and  camellias  serve  as  the  most  usual  example  of  the  latter 
case.  Plant  lovers  complain  very  frequently  that  the  plants  which  have  a 
great  many  buds  do  not  open  their  buds  in  the  house.  In  azaleas  the  buds 
become  dry,  in  camellias  they  fall.  In  both  cases  fresh,  rapidly  and  vigor- 
ously growing  shoots  develop  prematurely  directly  under  the  blossom  buds. 


1  Zawodny,  J.,  Keimung-  der  Znaimer  Gurke.    Cit.  Bot.  Jahresber.  1901.    Part  II, 
p.  236. 


297 

In  this  premature  breaking  forth  of  the  young  branches  Hes  the  cause  of  the 
"fall  of  the  blossoms."  The  error  in  treatment  is  that  the  plants  are  kept 
too  warm  and  moist  and  insufficiently  lighted  for  the  given  stage  of  their 
development.  While  the  flower,  to  be  sure,  needs  warmth  and  atmospheric 
humidity  for  its  development,  too  great  moisture  in  the  soil  injures  it.  This 
incites  the  leaf  buds  near  the  blossoms  to  a  premature  exfoliation  and  these 
attract  the  current  of  nutritive  substances  to  themselves,  squeezing  out  the 
functionally  weak  blossom  buds. 

In  forcing  bulbs,  especially  tulips,  we  also  find  such  conditions  of  star- 
vation of  a  flower  bud  resulting  from  too  vigorous  a  development  of  the 
vegetative  organs.  In  the  newer  cultivated  varieties  we  often  find  that  the 
flower  stalk  is  not  leafless,  but  has  one  or  two  leaves  borne  on  clearly 
marked  nodes.  In  such  examples,  the  bud  is  so  weak  that,  when  forced  in 
winter,  it  cannot  develop  at  all,  but  dries  up,  because  of  preponderating  leaf 
growth,  resulting  from  the  excess  of  moisture  and  warmth. 

An  experiment  made  with  V eltheimia  glauca  may  be  cited  as  an  ex- 
ample of  the  drying  up  of  the  flower  buds,  due  to  a  lack  of  nitrogen.  A 
vigorous  double  bulb  had  been  divided  several  years  previously  and  each 
daughter  bulb  had  bloomed  regularly  every  winter  after  this  division.  When 
later  one  of  the  bulbs  was  not  transplanted,  while  the  other  was  set  in  new, 
rich  earth,  the  inflorescence  developed  earlier  in  the  former,  to  be  sure,  and 
was  more  slender,  but  the  flowers  dried  up  before  being  completely  formed. 
This  plant  was  now  given  homshavings  as  a  source  of  nitrogen,  without 
changing  the  soil  in  the  pot.  In  the  following  year  the  inflorescence  appear- 
ed to  be  more  vigorous  and  the  flowers  more  numerous;  part  of  them  de- 
veloped and  became  colored,  but  not  so  deeply  as  those  from  the  bulb  which 
had  been  transplanted  each  year. 

It  is  well  known  that  a  supply  of  nitrogen  will  increase  the  product  of 
agricultural  plants. 

The  Formation  of  Thorns. 

The  formation  of  thorns,  i.  e.,  the  replacing  of  a  bud  on  the  end  of  a 
shoot  by  a  woody,  pricking  tip,  may  be  perceived  as  an  indication  of  the  lack 
of  nitrogen.  A  comparison  of  figures  37  and  38  (cross-sections  of  Rhamnus 
cathartica)  shows  what  changes  have  taken  place.  The  tissues,  indicated  in 
both  figures  by  the  same  letters,  should  be  compared.  We  see  that  in  the 
formation  of  thorns,  the  thick-walled  elements  gain  the  upper  hand,  and  that 
even  the  parenchyma  cells  of  the  bark  and  of  the  pith  have  unusually  thick 
walls.  A  young  branch  ending  in  a  thorn,  can  at  times  form  lateral  buds  at 
its  base,  if  enough  nitrogen  is  still  present  for  the  formation  of  the  meriste- 
matic  centers.  But  these  lateral  axes  begin  to  assume  thorn-like  character- 
istics early  in  their  development.  Ducts  may  be  found  as  far  along  on  the 
thorns  as  leaf  buds  can  be  recognized  and  even  for  a  distance  beyond  them. 
These  usually  disappear  in  the  apical  region. 

The  elimination  of  thorns  is  especially  desirable  horticulturally  because, 
for  example,   the  thorns   of  such  plants   as   Crataegus,   Pirus  communis, 


Priinns  spinosa,  etc.,  are  \txy 
apt  to  injure  people  working 
among  them.  The  transfor- 
mation of  the  thorns  into  nor- 
mal leafy  shoots,  ending  with 
a  terminal  bud,  results  from 
|)runing  and  transplanting  the 
wild  plants  to  rich,  loose,  well 
drained  soils. 

c.     Changes  in  Production 
due   to   a   lack    of 

Potassium. 
By  way  of  introduction, 
reference  must  be  made  once 
more  to  the  fact  that  a  lack 
of  potassium  in  the  soil  condi- 
tions a  lack  of  moisture.  Holl- 
rung's^  recent  experiments 
have  proved  that  a  soil  mixed 
with  potassium  salts  contains 
much  more  moisture  than  the 
same  soil  under  otherwise 
similar  conditions. 

The  potassium  enters  the 
plant  in  the  form  of  potassium 
nitrate,  sulfate  and  phosphate, 
chlorid  or  even  silicate.  In 
the  plant  it  may  be  found  in 
combination  with  organic  and 
inorganic  salts  and  especially 
in  the  tissues  in  which  carbo- 
hydrates may  be  found.  Hell- 
ricgel  andW'ilfarth  proved  ex- 
perimentally that  the  amount 
of  carbo-hydrates  deposited 
as  reserve  substances  (starch 
and  sugar)  in  potatoes,  grain 
and  sugar  beets,  depends 
directly  on  the  amount  of 
potassium  supplied.  Thus 
it  is  evident  that  a  lack 
of   potassium   must   manifest 


Fig.  37.     Cross-section  through  a  one-year  old 
branch  of   Rhamnus   cathartica. 


1  Hollrung-,  Vortrag-  im  An- 
haltinischen  Zweigverein  fiir 
Zuckerriibenkultur.  Blatter  f. 
Zuckerriibenbau   1905   p.   76. 

a  Cuticiila,  h  Epidermis,  c  Cork  layer,  li 
I'lielloKen  (cork  cambium),  e  CoUen- 
chyma./and/'  Bark  parenchyma,  5" and.tr' 
Bast  bundles.  /;  Secondary  bark.  /  Wood, 
and  on  its  i)erii)lierv.  the  cambial  zone, 
k  Pitli,  III  pith  disc,   (.\fter  I)obner-NobV)e) 


299 


itself  in  a  scarcity  of  the  reserve  substances.  Besides  this,  the  lack  of 
potassium  explains  also  the  fact,  already  observed,  that  shoot  formation  is 
retarded,  since  the  cellulose,  necessary  for  the  formation  of  the  parenchyma, 
is  likewise  a  carbo-hydrate. 

Without  potassium,  the  plant  becomes  green,  to  be  sure,  but  does  not 
grow  much  beyond  the  amount  of  material  furnished  from  the  seed.  All 
other  nutritive  material,  therefore,  can  not  have  been  used  (law  of  the 
minimum).  According  to  Nobbe's 
studies,  if  the  very  valuable  com- 
pound, potassium  chlorid,  was 
given  to  potassium  hungry  plants, 
even  after  they  had  lain  dormant 
for  months,  an  increase  in  growth 
was  produced  in  two  or  th.ree 
days.  The  formation  of  starch 
began  immediately \  An  addition 
of  potassium  becomes  fully  effec- 
tive, however,  only  when  it  is  not 
rendered  inactive  by  calcium.  Ad. 
Meyer-  emphasizes  the  especially 
favorable  action  of  potassium 
chlorid,  but  he  found  this  con- 
siderably weakened  when  calcium 
bi-phosphate  was  also  present. 
With  sugar  beets  potassium 
chlorid,  as  well  as  calcium  chlorid, 
when  used  alone,  worked  very 
well,  but  not  if  added  simul- 
taneously. 

Hellriegel  found  in  grain  that 
with  a  scanty  potassium  supply, 
the  green  parts  matured  at  the 
expense  of  the  kernels.  This  is 
not  the  case  with  a  lack  of  nitro- 
gen ;  the  plants  then  develop  com- 
pletely but  remain  small.  In  trees 
a  continued  lack  of  potassium 
always  leads  to  a  weaker  develop- 
ment of  the  end  shoots  and- finally  to  "tip  blight"  and  Janson'*  states  that  he 
has  cured  this  disease  by  a  direct  addition  of  40  per  cent,  potassium  salt. 
Naturally  tip  blight  can  be  produced  by  ver^^  different  causes,  and  on  loamy 
soils  especially  other  causes  must  often  be  sought  primarily. 

1  Nobbe,   Schroder  and  Erdmann,  Die  organische  Leistung  des  Kaliums  in  der 
Pflanze.     Landwirtsch.  Versuchsstat.  XIII  p.  321. 

2  Jahresber.  f.  Agrik.   Chemie  1880  p.   269. 

3  Janson,  A..   Kalidiingung  geg-en  die  Spitzendiirre.     Prakt.  Ratg-.  f.  Obst-   und 
Gartenbau  1905  No.  38. 


Fig 


Cross -section  through  the  thorn  of 
Rhamnus  cathartica. 


Explanation  of  letters  as  in  Fig.  37,  only  here  the  phello- 
Ren  (d)  and  secondary  bark  Ui)  are  lacking.  They  appear 
transformed  into  permanent  cells.  (After  Dobiier-Nobbe) 


300 

Agriculturally  worth  consideration  is  the  fact,  confirmed  experi- 
mentally*, that  with  a  lack  of  potassium,  as  contrasted  with  complete  nu- 
trition, a  larger  part  of  the  nutritive  substances  taken  up  (excepting  the 
[ihosphoric  acid)  will  wander  back  into  the  soil  at  the  time  of  ripening. 
This  was  observed,  at  least,  in  summer  wheat,  barley,  peas,  and  mustard. 
Potatoes  formed  an  exception. 

The  manifestation  of  a  lack  of  potassium  in  fungi  is  very  interesting. 
Molliard  and  Coupin-  found  in  Sterigmatocystis  nigra  a  malformation  of  the 
conidia  which  were  produced  only  very  exceptionally  and  matured  incom- 
pletely. As  under  other  conditions  due  to  starvation,  the  conidia  germi- 
nated at  once,  but  their  contents  grew  into  a  chlamydospore  form. 

The  most  important  question  for  agriculture  is,  whether  positive  ex- 
ternal cliaracteristics  may  be  found  which  indicate  with  certainty  the  lack  of 
potassium? 

We  owe  the  most  important  experiments  along  this  line  to  Wilfartli 
and  Wimmer'',  who  set  up  comparative  cultures  of  sugar  beets,  potatoes 
buckwheat  etc.  They  tested  also  for  scarcity  of  nitrogen  and  phosphoric 
acid  and  found  that  Avith  a  lack  of  nitrogen  leaves  took  on  a  light  green 
to  yellowish  coloration  and  finally  dried  up  with  a  light  brownish  yellow  color. 
With  a  lack  of  phosphoric  acid  they  were  colored  a  deep,  dark  green,  cor- 
responding to  the  occasional  excess  of  nitrogen,  and  in  extreme  cases  black- 
ish brown  spots  were  formed  at  the  edges  and  later  distributed  over  the 
entire  surface  of  the  leaf,  which  sometimes  had  a  reddish  color  at  first. 
Finally  followed  a  drying  up  accompanied  by  a  dark  green  to  a  blackish 
brown  coloration.  If,  however,  sufficient  potassium  lay  at  the  disposal  of 
such  starved  plants,  abundant  quantities  of  starch  and  sugar  were  formed 
in  spite  of  this ;  even  with  a  lack  of  nitrogen,  this  process  seems  to  be  in- 
creased rather  than  decreased.  If,  however,  in  an  otherwise  normal  nutri- 
tive supply,  the  potassium  is  lacking,  the  above-mentioned  increased  forma- 
tion of  straw  in  grain  as  against  the  formation  of  kernels  becomes  manifest. 
Under  these  conditions  the  amount  of  green  growth  in  edible  roots,  or 
tuberous  plants,  was  increased  in  proportion  to  the  containers  of  the  reserve 
substances,  which  possessed  appreciably  less  carbo-hydrates  tlian  with  a 
lack  of  nitrogen  and  phosphoric  acid. 

Since  the  plants  use  first  of  all  the  potassium  supply  in  building  their 
vegetative  skeleton,  they  retain  longer,  by  their  habit  of  growth,  the  appear- 
ance of  normally  nourished  plants  with  a  lack  of  potassium  than  with  a 
lack  of  nitrogen  and  phosphoric  acid,  but  then  the  internodes  are  shortened 
and  the  leaves  curl  upward  convexly.  At  first  near  the  leaf  edges  and  then 
later  scattered  over  the  whole  surface  of  the  leaf,  appear  yellowish  spots 
which  rapidly  turn  brown  or  often  change  to  white,  while  the  petioles  and 


1  Wilfarth,  Romer  and  "Wimmer,  tJber  die  Nahrstoffaufnahme  der  Pflanzen   in 
verschiedonen  Zeiten  ihres  Wachstums.  cit.  Centralbl.  f.  Agrik.-Chemie  1906  p.   263. 

2  Molliard  et  Coupin,    Sur  les  formes  teratologiques  du   Sterigmatocystis   nigra 
prive  de  Potassium.     Compt.   rend.  1903.  CXXXVI  p.  1659. 

•''  Wilfarth,   H.   W.   and  "Wimmer,   G.    (Ref.)    Die   Kennzeichen   des   Kalimangels 
an  den  Bliittern  der  Pflanzen.    Zeitschr.  f.  Pflanzenkrankh.  1903  p.  82. 


30I 

veins  together  with  the  immediately  adjacent  tissue  remain  green.  Finally  the 
leaves  dry  up,  beginning  usually  at  the  edges,  with  a  dark  brown  color  (see 
the  adjoining  Fig.  39).  Flower  and  fruit  formation  are  scanty.  With  a  lack 
of  potassium,  not  infrequently,  individual  plants  go  to  pieces  prematurely'^ , 
while,  with  a  lack  of  nitrogen  and  phosphoric  acid,  even  the  smallest  plants 
can  be  maintained  until  the  end  of  the  time  of  growth. 

Of  especial  importance  is  the  observ^ation  of  the  above-named  authors, 
that  the  roots  as  well  as  the  tubers  of  plants  grown  with  a  lack  of  potassium 
tend  very  easily  to  decay  .and  that  plants  lacking  any  nutritive  substance 
are  always  more  predisposed  to  attack  from  animal  and  vegetable  parasites. 

Von  Feilitzen-  made  the  same  observ^ation  on  timothy  grown  on  moors. 
It  was  attacked  by  fungi  only  after  it  had  been  weakened  by  a  lack  of  potas- 
sium. He  noticed  in  clover  that  the  lots  sown  without  potassium,  or  with 
a  slowly  soluble  compound  of  it,  were  "scorched"  as  if  grown  on  poor 
sandy  soil,  after  long  periods  of  drought. 

When  experimenting  with  different  fertilizers,  MoUer  found  that  with 
a  lack  of  potassium  the  seedling  plants  of  the  Scotch  pine  had  less  growing 
power,  their  needles  had  a  faded  appearance. 

Valuable  as  are  these  attempts  to  find  positive  characteristics  due  to  a 
lack  of  potassium,  I  still  think  that  for  a  long  time  we  will  have  to  make  use 
of  these  characteristics  only  with  great  care  in  diagnosis.  In  the  first  place, 
we  do  not  know  whether  the  same  characteristics  always, — i.  e.  with  all  vari- 
ations of  the  factors  of  growth, — become  visible  in  the  same  species.  In  the 
second  place,  we  still  know  too  little  of  the  phenomena  of  starvation  which 
make  themselves  felt  with  other  nutritive  substances.  In  the  third  place,  the 
influence  of  injurious  gases  at  times  gives  such  deceivingly  similar  effects, 
aside  from  parasitic  attacks,  that  it  might  be  difficult  to  draw  definite  con- 
clusions from  the  changes  in  habit  alone.  It  should  be  taken  into  consider- 
ation that  almost  all  injuries  to  the  leaf  manifest  themselves  first  in  the 
regions  lying  farthest  away  from  the  veins  conducting  water,  hence  the  fre- 
quent beginning  of  the  diseased  condition  at  the  edge  of  the  leaf  or  in  the 
middle  of  the  intercostal  areas,  upcurved  between  the  larger  veins. 

d.     Changes  Due  to  a  Lack  of  Calcium. 

It  is  well  known  that  the  plant  uses  calcium  as  stiffening  for  the  cell 
walls  and  as  a  means  for  combining  the  poisonous  oxalic  acid  produced. 
In  the  phenomena  of  disease,  the  fact  that  an  excess  of  oxalic  acid  can  re- 
dissolve  small  amounts  of  calcium  oxalate  is  important^.  The  calcium  oxa- 
late produced  is  re-dissolved  only  in  a  few  cases*.     Usually  the  organism 


1  Compare  also,  v.  Seelhorst,  Die  durch  Kalimange]  bei  Vietsbohnen  (Phaseolus 
vulgaris   nanus)   he7vor.e:erufenen  Erscheiniinsren.     Zeitschr.  f.  Pflanzerkr.  1906,  p.  2. 

-  V.  Feilitzen -Jonkoping',  Wie  zeigt  sich  der  Kalimangel  bei  Klee  und  Timothee- 
gras?     Mitt.  d.  Ver.  z.  Ford  d.  Moorkultur    1904.  No.  4.  n.   41. 

3  "Wiiitz,  Dictionaire  de  chimie  II,  p.  647,  cit.  by  de  Vries  in  Landwirtsch.  Jahrb. 
1881  p.  81. 

4  Sorauer,  P.,  Bertrage  zur  Keimungsg-eschlchte  der  KartofEelknolle.  Berlin. 
Weigandt  &  Hempel.  1868,  p.  27,  and  de  Vries,  H.,  tjber  die  Bedeutung  der  Kalkab- 
la.gerungen  in  den  Pflanzen.  Landwirtsch.  Jahrb.  v.  Thiel,   1881,  p.  80. 


302 


Fig.  39.     Lack  of  potassium. 


/,  Defornieil  tobacco  leaf,  resulting  from  a  lack  of  potassium,  with  partially  split,  brown  edges:  only  the 
veins  are  still  green  while  the  intercostal  fields  appear  discolored  yellow  to  white;  2,  Leaf  of  a  normally 
nourished  potato  plant;  3,  that  of  one  starving  for  potassium.  In  this  the  leaflets  stand  closer  to  one  anotlier 
and  are  curled  under.  The  places  drawn  in  light  are  yellowish,  the  intercostal  fields  are  flecked  with 
brown,  as  also  the  edges  of  the  leaves;  ■/  and  5,  leaves  of  the  buckwheat  plant  with  spots  which  are  yellow- 
ish, then  brown,  and  finallv  white.     (After  Wilf-^RTU  and  Wimmer). 


303 

does  not  possess  the  ability  of  re-dissolving  the  calcium  already  deposited  in 
old  tissues  in  appreciable  amounts  and  transporting  it  where  it  can  instantly 
become  effective  for  new  structures,  when  there  is  a  lack  of  calcium.  At 
least  the  experiments  of  Bohm\  Raumer  and  Kellermann-  and  Benecke'^ 
prove  that  no  calcium,  or  very  little  passes  from  the  containers  of  reserve 
substances  into  the  young  tissues  when  the  plants  are  grown  in  distilled 
water,  in  solutions  free  from  calcium,  or  in  quartz  sand.  The  fact  that  no 
calcium  is  necessary  for  the  formation  of  starch  itself  has  been  proved  by 
^Bohm.  He  found  that  primordial  leaves  free  from  starch  with  shrivelled 
petioles  became  filled  with  starch  when  grown  without  lime,  but  under 
otherwise  favorable  conditions.  In  order  to  dissolve  the  reserve  substance 
and  to  transport  it  chemical  combination  with  calcium  is  necessary,  for  an 
investigation  of  plants  grown  in  media  lacking  calcium  proved  that  the 
organs  (leaves,  cotyledons)  had  not  given  up  all  the  starch,  the  leaf  body 
or  the  adjacent  internodes  retained  considerable  quantities,  while  the  young 
plant  starved  to  death  despite  its  sugar  content.  My  own  experiments*  also 
led  to  the  conclusion  that  the  plant  needs  new  mineral  substances  originating 
from  the  solution  in  the  soil,  even  at  a  time  when  it  is  working  up  the  re- 
serve material  into  cellulose,  etc. 

Thus  in  the  germination  of  seeds  an  addition  of  calcium  acts  bene- 
ficially; in  fact,  it  often  seems  necessary.  The  statement  that  calcium  is 
disadvantageous  for  germinating  seed^  may  have  arisen  from  a  use  of  too 
highly  concentrated  solutiors.  Loew  and  May  declare  that  definite  excess 
of  calcium  in  the  soil  over  the  magnesium  content  can  produce  starvation 
symptoms  in  the  plant  (see  Lack  of  Magnesium).  An  earlier  assertion  of 
Deherain  and  Breal*'  that,  with  a  lack  of  calcium  the  plants  can  better 
utilize  the  lime  stored  in  their  bodies,  if  the  temperature  is  raised,  has 
not  held".  Molisch,  as  well  as  Portheim,  has  also  proved  the  error  of  these 
statements^. 

Among  the  older  observers®,  Nobbe  describes  the  phenomena  due  to  a 
lack  of  calcium  in  water  cultures.  Buckwheat,  peas,  Robinia,  etc.,  grew  but 
little  beyond  the  germinating  stage.  The  pale  leaves  exhibited  spots,  simi- 
lar to  these  produced  by  the  action  of  acid,  which  dried  up  gradually,  and 
then  the  petioles  often  broke.  On  conifers,  the  tips  of  the  first  year  needles 
became  yellow  to  brown. 


1  Bohm,  tJber  den  veg-etabilischen  Nahrwert  der  Kalksalze.  Sitzungsber,  d.  k. 
Akad.  d.  Wissensch.,  Vol.   71,  1875,  p._  287  ff. 

2  V.  Raumer  and  Kellermann.  tJber  die  Funktion  des  Kalks  im  Leben  der 
Pflanze,  Landwirtsch.  Versuchsstationen  XXV,  1880,  Parts  1   and  2. 

3  Benecke,  W.,  Uber  Oxalsaurebildung-  in  grijnen  Pflanzen.  Bot.  Zelt.  1903,  Part  5. 

4  Sorauer,  Studien  fiber  Verdunstung.  Forsch.  auf  d.  Geibiete  d.  Agrikultur- 
f  hysik.  1880,  p.  429. 

5  Windisch,  R.,  tJber  die  Einwirkung  des  Kalkhydrates  auf  die  Keimung-. 
Landwirtsch.   Versuchsstationen.    1900,   p.    283. 

6  Annales  agronomiques.  Vol.  IX,  1883,  No.   52. 

7  Kriiger,  W.,  und  Schneidewind,  W.,  Zersetzungen  und  Umsetzungen  von  Stick- 
stoffverbildungen  im  Boden  durch  niedere  Organismen,  etc.  Landwirtsch  Jahr- 
bucher,   1901,   p.   633ff. 

8  V.  Portheim,  L.,  tJber  die  Notwendigkeit  des  Kalkes  fur  Keimlinge.  etc 
Cit.  Bot.  Jahresber.  1901,   Section  II,  p.  141. 

9  Dobner-Nobbe,  Botanik  fur  Forstmanner.  1882,  p.  314. 


304 

Recent  cultural  experiments  with  grain,  buckwheat  and  Elodea  cana- 
densis'^ in  nutrient  solutions,  free  from  calcium,  showed  that  after  a  five  day 
retention  in  a  solution  free  from  calcium,  the  root  growth  became  less  and 
later  ceased  entirely.  The  roots  turned  brown  and  the  root  cap  died.  Pe- 
culiar, brownish  spots  were  found  on  the  leaves,  which  soon  went  to  pieces. 
The  content  in  acid  potassium  oxalate  and  in  starch  was  greater  than  ixi 
normal  plants.  The  death  of  plants,  in  a  nutrient  solution  without  calcium, 
has  been  traced  by  Loew  to  a  poisonous  action  of  the  magnesium  salt. 
Rruch's  cultural  experiments  with  magnesium  sulfate,  nitrate,  carbonate, 
and  phosphate  in  aqueous  solutions  showed  that  the  roots,  to  be  sure,  soon 
stopped  growing,  but  the  aerial  parts  developed  further  perfectly  normally 
and  even  blossomed.  W'heat  plants  in  solutions  free  from  calcium  and 
magnesium  died  far  more  quickly  than  those  in  solutions  lacking  only  the 
calcium. 

Amar'-'  observed  the  absence  of  calcium  oxalate  crystals  in  those  leaves 
which  were  formed  after  the  i)lants  had  been  put  in  a  solution  free  from 
calcium. 

A  further  insight  into  the  conditions  due  to  a  lack  of  calcium  is  given 
by  Kriiger  and  Schneidewind  through  Schimper's  statement  that,  when  the 
calcium  is  removed,  all  the  symptoms  of  poisoning  from  an  enormously  large 
content  of  acid  potassium  oxalate  are  indicated.  In  Phaseolus  these  authors, 
to  be  sure,  could  prove  no  especial  increase  of  a  strong  organic  acid.  They 
succeeded,  however,  in  keeping  the  plants  until  all  the  reserve  substances 
had  been  used  up  by  painting  dying  seedlings  with  a  calcium  solution  either 
on  the  hypocotyles  or  at  the  place  where  death  usually  begins.  This  sub- 
stantiates Bohm's  observations  that  seedlings  of  the  scarlet-runner  bean 
take  up  calcium  as  well  as  water  through  the  outer  skin  f)f  the  petioles  and 
leaves. 

The  experiments  of  Moisescu''  confirm  the  above  observations.  He 
found  in  different  cultures  in  nutrient  solutions  that  those  seedlings  had  be- 
came aiTected  earliest  and  most  extensively  which  had  grown  in  solutions  free 
from  calcium.  In  Platanus  orientalis,  the  leaves  of  which  partially  became 
brown  and  dry  along  the  veins,  it  was  found  that  the  diseased  ones  contained 
twice  as  much  acid  as  the  healthy  ones.  Gloeosporium  nervisequum  in- 
fested the  diseased  leaves.  On  this  account  it  must  be  assumed  that  the 
parasite  named  attacks  only  weakened  leaves.  This  weakness  would  con- 
sist here  of  "Cakipenuria,"  that  is  to  say,  a  lack  of  calcium.  In  the  author's 
opinion,  not  enough  calcium  was  present  to  convert  the  excessive  potassium 
oxalate  into  calcium  oxalate. 

Besides  cultural  experiments  of  this  nature,  a  large  number  of  practi- 
cal results  point  to  the  injuriousness  of  calcium  poverty.  At  least  we  find 
in  many  cases  a  cessation  of  the  phenomena  of  disease  after  an  addition  of 

1  Bruch,  p.,  Zur  physiologischen  Bedeutung-  des  Calciums  in  der  Pflanze. 
I.nndwirtsch.  .lahrb.   1901.   Suppl.  III.   p.   127. 

2  Amar,  Maxime,  Sur  le  role  de  I'oxalate  de  calcium  dan.s  la  nutrition  des 
vegetaux.  Annal.  sc.   nat.   bot.   1904.  XIX,  p.   195. 

3  Moisescu,  N.,  p:in   Fall  von  Calcipenuria.     Zeitschr.  f.  Pflanzenkr.  1905,  p.  21. 


305 

calcium.  In  this,  the  calcium  may  often  act  beneficially  on  the  constitution 
of  the  soil  and  often  directly  on  the  composition  of  the  cell  sap.  According 
to  our  explanation  of  the  matter,  a  considerable  number  of  cases  of  disease 
exist  which  are  called  forth  directly  by  nitrogen  excess,  and  for  which  the  ad- 
dition of  calcium  and  phosphoric  acid  remains  the  only  effective  remedy. 
In  the  division  "Enzymatic  Diseases,"  we  will  also  have  to  consider  the 
beneficial  action  of  calcium  fertilization.  There  we  will  also  touch  upon 
the  subject  of  the  over-abundant  formation  of  acid  in  the  plant  which  cer- 
tainly sometimes  influences  unfavorably  the  mode  of  production.  Thus, 
for  example,  with  a  lack  of  calcium  in  the  soil,  the  sap  of  sugar  cane  con- 
tains a  great  deal  of  acid  and  but  little  sugar\  We  will  mention  later  special 
cases  of  oxalic  acid  poisoning. 

e.     Changes  Due  to  a  Lack  of  Magnesium. 

Plants  grown  in  a  nutrient  solution  lacking  magnesium  often  live  longer 
than  when  the  nutrient  solution  does  not  contain  calcium.  It  might  be  con- 
cluded from  this  that  the  plant  is  able  more  easily  to  remobilize  the  mag- 
nesium compounds  already  deposited  in  its  tissues  and  to  make  them  partially 
accessible  again  for  the  young  organs.  If  the  grain  becomes  diseased  slowly 
from  magnesium  hunger,  the  leaves  are  a  light  green  and  appear  limp,  but 
not  directly  wilted.  From  the  beginning  it  is  possible  to  imagine  a  very 
considerable  effect  on  the  formation  of  seeds,  if  one  considers  that,  for  ex- 
ample, the  globoids  enclosed  in  the  protein  grains  may  be  assumed  to  be 
calcium  and  magnesium  compounds  of  a  double  phosphoric  acid.  In 
reality,  with  a  lack  of  magnesium,  there  is  a  decrease  in  the  formation  of 
fruit,  as  stated  by  Nobbe-.  He  gives  the  following  symptoms.  The  leaves 
become  pale  in  color,  with  yellow  to  orange  red  spots  here  and  there. 
The  chlorophyll  grains  are  pale  yellow  green  and  contain,  as  a  rule,  small 
amounts  of  starch.  Diminished  cell  division  is  noticeable  in  the  epidermis. 
Nobbe  found  that  plants  grown  with  a  lack  of  magnesium  correspond  to 
those  from  nutrient  solutions  free  from  nitrogen,  in  that  red  spots  are 
present  on  the  petioles  and  the  leaves  fall  prematurely.  The  latter  character- 
istic may  well  be  present  in  all  starved  plants,  since  the  young  organs  ex- 
haust the  older  ones  when  the  supply  of  nutriment  is  insufficient. 

Moller^  also  observed  an  orange  red  coloring  in  his  cultivations  of 
Scotch  pine  seedlings  with  a  lack  of  magnesium.  He  says  that  the  needles 
in  October  had  bright  orange  yellow  tips  but  farther  back  passed  through 
a  bright  red  zone  into  a  normal  green  one.  The  discoloration  appeared 
when  the  seedlings  had  been  given  magnesium  in  the  second  year. 
Ramann  analyzed  the  orange  tipped  needles  of  two-year  old  Scotch  pines 
and  found  that  these  contained  0.2791  per  cent,  magnesium  (calculated  on 
the  dry  weight),  while  the  adjacent  normally  green  specimens  showed  a 
content  of  0.6069  P^r  cent. 

1   Semler,   Tropische  Agrikultur.    II  Edition.    Vol.   Ill,   p.   236. 
^   Dcibner's  Botanik  fiir  Forstmanner,  edited  by  Nobbe.     4th  Edition,  p.  315. 
■■!  Moller,  A.,  Karenzerscheinungen  bei  der  Kiefer.  Sond.  Z.  f.  Forst-  und  Jagd- 
wesen,   1904,  p.  745. 


3o6 

In  regard  to  the  action  of  magnesia,  Loew  and  May^  have  expressed 
the  opinion  that  a  definite  quantitative  proportion  between  soluble  calcium 
and  magnesium  compounds  is  necessary  for  favorable  growth  (corres- 
ponding approximately  to  their  molecular  weights,  i.  e.  5  to  4).  Magnesium 
in  the  soil  in  great  excess  over  calcium  is  injurious.  Plants  which  in  so  far 
lack  magnesium,  as  that  calcium  is  present  in  excess,  exhibit  symptoms 
of  starvation.  A  small  excess  of  calcium  arrests  the  poisonous  action  of  the 
magnesium.  In  the  use  of  fertilizers  containing  magnesium,  calcium  should 
also  be  given  at  the  same  time.  This  advice  should  be  taken  to  heart.  Even 
if  plants  can  well  endure  magnesium,  and  even  actually  need  it,  any  excess  is 
certainly  injurious,  as  has  also  often  been  proved  in  fertilization  with  raw 
potassium  salts. 

f.     Changes  Duk  to  a  Lack  of  Chlorine. 

It  should  perhaps  be  assumed  that  chlorine  and  calcium  arc  antagonistic 
in  plants.  Mayer's  conclusion,  mentioned  under  potassium,  that  the  action 
of  potassium  chlorid  is  weakened  by  calcium  and,  conversely,  would  indicate 
this.  In  the  same  way  Knop-  found  that  less  calcium  is  taken  up  when  the 
nutrient  solution  contains  chlorine,  and  the  calcium  did  not  appear  to  be 
represented  in  any  corresponding  way  by  potassium  or  any  otlier  base.  Thus 
the  chlorine  compounds  (by  the  retention  of  the  calcium)  cause  an  essential 
increase  in  the  acid  content  of  the  plant  sap.  Since,  among  the  acids  ab- 
sorbed, the  phosphoric  acid  predominates,  Knop  thinks  it  permissible  to 
ascribe  to  this  acid  the  greater  fertility  with  a  use  of  nutrient  solutions  con- 
taining chlorine,  which  was  observed  by  Nobbe.  Accordingly  one  would 
like  to  explain  the  process  thus, — the  chlorine  which  accumulates^  in  greatly 
dififerent  quantities  in  the  plant  body,  according  to  the  amounts  offered  the 
roots,  can  increase  the  transportability  of  the  phosphoric  acid,  since  it 
decreases  the  absorption  of  calcium  and  thus  prevents  the  appearance  of  the 
phosphoric  acid  in  the  slowly  soluble  form  of  calcium  phosphate.  If  t'^c 
phosphoric  acid,  co-operating  in  the  formation  of  the  proteins,  reaches 
very  easily  the  meristematic  areas  of  the  growing  tips,  an  abundant  forma- 
tion of  cytoplasm  occurs  together  with  cell  increase  and,  in  connection  with 
this,  a  plenteous  streaming  of  the  carbo-hydrates  for  the  protein  regenera- 
tion. Accordingly,  vigorously  growing  shoots  with  but  little  stored  up  reserve 
substances  will  necessarily  be  found  in  plants,  fertilized  with  chlorine. 
Actually,  the  many  fertilization  experiments  show  a  decrease  in  starch  ard 
reserve  sugar  in  the  luxuriantly  growing  cultivated  plants. 


1  Loew,  O.,  and  May,  W.,  The  relation  of  lime  and  magnesia  to  plant  growth. 
U.  S.  Departm'-nt  of  Asric.  Bull.  I.  cit.  Bot.  Jahresber.  19'^].  H    n.   141. 

2  Chemisch-physiolog-iscne  Ilntersuchung-en  ijber  die  Ernahruner  der  Pflanze 
von  Knop  and  Dworzak.  Aus  Berichte  d.  Kgl.  sachs.  Gesellsch.  d.  Wissensch.  vom 
23.  April,  IST,"^.     Cit.  Jahresber.  f.  Agrikulturchcmie.   1875.   p.   267. 

3  Pag-noul,  Sur  le  role  exerc#  par  les  sels  alcalin  sur  la  vegetation  de  la  b-^tter- 
a,ve  et  de  la  pomme  de  terre.  Compt.  Rend.  1875.  Vol.  LXXX,  p.  1010.  Fertilizing 
experiments  carried  on  for  five  years  with  chlorids  showed  for  beets  a  fliurtuation  in 
contents  from  1  to  50.  In  potatoes,  the  smallest  yield  in  tubers  coincided  with  the 
least  amount  of  potassium  carbonate  in  the  ash  but  with  the  greatest  amount  of 
chlorides. 


30/ 


Besides  the  probable  increase  in 
the  transportability  of  the  phos- 
phoric acid,  it  can  be  proved  that 
chlorine  has  a  favorable  influence 
on  the  transference  of  the  starch 
prepared  in  the  leaves.  According 
to  Nobbe's  experiments,  the  plant 
starving  for  chlorine  continues  to 
grow,  exhibits  a  very  dark  green 
color  and  gives  a  considerable  pro- 
duction of  substances  rich  in  carbo- 
hydrates, but  sooner  or  later, — at 
any  rate  before  the  time  of  blos- 
soming,— there  occurs  a  peculiar 
change  in  form  and  structure. 
Nobbe  found  the  dark,  abnormally 
fleshy  leaves  crammed  full  of 
starch  (in  oak  and  buckwheat) 
rolling  up,  becoming  brittle  and 
dropping.  The  stems  and  petioles 
seem  puffed  up,  the  internodes  of 
the  stems  always  are  shorter  and 
many  finally  dry  from  the  tips 
backward.  If  the  plant  reaches 
the  blossoming  stage,  only  scat- 
tered, unusually  poor  small  fruits 
develop,  despite  the  abundant 
starch  material  in  the  leaves.  The 
effect  of  a  lack  of  chlorine  is  best 
recognized  by  a  comparison  of  a 
normal  buckwheat  plant  with  one 
grown   with   a 


40.     Blossoming-  buckwheat  plant  gi-own  in 
nutrient    solution.     (After   Nobbe.) 


lack  of 

chlorine 

^^  (figures 

40  and 

^      41). 

g.  Lack  of  Iron 

AND 

dice" 

"Jaun- 

(ICTER- 

us). 

The 

expres- 

s  i  o  n  s, 

"jaun- 

dice," 

"yellozu- 

sickness 

"white- 

I  e  a  V  e  d  n  ess," 
normal 

V  a  r  I  egation, 

3o8 


"chlorosis,"  "alhication,"  "etiolation,"  are  the  most  common  names  for  the 
condition  in  which  a  leaf  loses  its  green  coloring  matter  in  spots,  or  over 
the  whole  extent  of  its  surface.  The  causes  for  this  change  in  color  are 
very  different,  but  always  represent  a  condition  of  weakness. 

In  order  to  survey  the  manifold  causes  of  the  disease,  we  will  endeavor 
to  group  them  into 

I.     Induced  and  non-transmissible  conditions. 

(a).  The  discoloration  attacks  the  whole  surface  of  the  leaf, 
which  has  matured  in  the  light.  After  having  been  green 
in   its  young  stages,   the  whole  leaf   assumes   a  yellowish, 

yellow   to  yellow- 
white    color   tone. 
Icterus    or    jauyi- 
dicc.    Cause :  usu- 
ally a  lack  of  nu- 
tritive substances, 
(b).  The    pale    discol- 
oration is  present 
in  the  young  organ 
and  the  leaves  re- 
main    in     a     con- 
dition   resembling 
youth    until    their 
p  r  e  m  a  t  ure  end. 
Cause :   lack  of 
light  and  at  times 
of  heat  (see  these 
topics). 
.    Innate  and  transmis- 
sible conditions. 
Portions      of     the 
plant  show  yellow 
to  pure  white  spots  or  stripes.     Those  plants  suffer  especially  in 
which  pure  white  leaves  appear  near  the  ones  spotted  with  green 
or    all    green.     The    spots    have    usually    a    sharp    demarcation. 
White-leovedness,  alhication,  variegation,  sometimes  transmissible 
through  seeds  or  by  grafting.     Cause:  probably  enzymatic  dis- 
turbances (see  these). 
Of  course  there  are  intermediate  stages  between  the  types  named,  since 
the  individual  causes  often  work  together. 

In  the  present  division  we  will  examine  only  the  icteric  conditions  and 
treat  them  under  lack  of  iron  because,  since  the  investigations  of  the  Gris', 
father  and  son,  it  is  customary  to  consider  jaundice  as  caused  especially  by 


Fig.   41.     Buckwheat    plant 
free   from   clilorine. 


grown    in    a   solution 
(After  Nobbe.) 


Gris,  A.,  Ann.  scienc.  nat.,   1875,  VI  ser.     Vol.  VII.  p.  201. 


309 

a  lack  of  iron.  The  authors  named  found  jaundiced  leaves  turning  green 
where  painted  with  a  soluble  iron  salt.  A  change  to  green  may  also  be  ob- 
served if  the  roots  of  such  plants  have  a  dilute  iron  solution  at  their  disposal. 
The  experiments  on  the  effectiveness  of  the  iron  solution  were  often  re- 
peated; as,  for  example,  by  Knop^  and  Sachs-,  who  observed  in  cultures  of 
maize  in  nutrient  solutions  free  from  iron,  that  the  plants  remained  green 
only  as  long  as  the  reserve  material  from  the  seeds  lasted.  After  this  time, 
leaves  developed  which  were  green  only  at  the  tip  and  were  already  yellow 
at  the  base,  until  the  next  leaves  appeared  uniformly  icteric.  Similar  dis- 
colorations,  at  first  appearing  in  stripes,  were  found,  on  mature  plants  which 
had  developed  normally  at  first,  and  then  were  placed  in  a  nutrient  solution 
free  from  iron.  The  blossoms  then  became  sterile  and  the  production  in  dry 
weight  was  considerably  less.  Frank=*  observed  that  there  occurred  with  a 
lack  of  iron  an  universally  noticeable  phenomenon  of  starvation,  viz.,  the 
newly  produced  leaves  exhausted  the  older  ones,  which  lost  their  color  and 
died.  In  icteric  organs,  the  chlorophyll  grains  have  a  normal  form,  but  their 
number  and  size  is  possibly  smaller  and  their  color  pale.  Although  the 
chlorophyll  pigment  contains  no  iron*,  the  whole  nutritive  condition  of  the 
chlorophyll  grain  will  become  weakened  by  the  lack  of  iron.  But  at  first 
ihe  chloroplast  exists  in  a  normal  form  which  is  not  destroyed  until  later.  In 
this  lies  the  difference  between  the  phenomena  of  starvation  and  enzymatic 
albication. 

In  order  not  to  be  obUged  to  separate  the  phenomena  whose  similar 
symptoms  lead  to  confusion,  we  will  mention  here  icterus  due  to  cold.  We 
find  in  cold,  wet  seasons  a  gradual  yellowing  in  most  cultivated  plants,  which 
disappears  of  itself  with  a  rise  in  temperature.  Often  in  spring,  the  leaf 
points  of  our  flowering  bulbs  are  yellow  when  they  push  out  of  the  earth 
and  the  young  leaves  push  out  gradually  with  a  normal  green  color  only  as 
the  weather  becomes  warmer. 

From  this  transitory  jaundice  must  be  distinguished  the  chronic  form, 
in  which  the  yellow  leaves  always  remain  yellow.  This  may  be  observed  if 
sudden  great  cold  affects  the  young  cells  and  destroys  the  chloroplasts. 
Then,  in  place  of  these,  are  found  only  fine  grained  yellowish  groups  and 
at  times  also  yellow  drops.  These  cells  do  not  recover  later.  At  the  place 
of  transition  to  the  parts  of  the  leaves  which,  protected  by  the  earth,  have 
become  green,  colorless,  swollen  and  also  light  green  chlorophyll  grains 
which  later  partly  turn  green  may  be  found  at  the  place  of  transition  to  the 
portions  of  the  leaf,  which,  protected  by  the  earth,  have  become  green. 

1  Knop  (Jahresberichte  f.  Agriculturchemie,  1868-69,  p.  288)  observed  in  such 
experiments  that  the  iron  which  got  into  the  plant  could  not  be  proved  in  the  cell 
sap,  and,  therefore,  must  be  present  in  a  combined  form.  In  1860  (Bot.  Z.  p.  357), 
Weiss  and  Wiesner  determined  that  iron  occurs  only  in  insoluble  compounds  and 
in  the  contents  of  the  older  cells  as  well  as  in  their  walls. 

2  Experimentalphysiolog-ie,  p.   144. 

3  Krankheiten  der  Pflanzen.  1895,  I,  p.   290. 

i  Molisch,  Die  Pflanzen  in  ihren  Beziehungen  zum  Eisen.    1892,  p.  81. 


3T0 

With  the  action  of  sudden  cold,  lasting  for  several  hours,  Haberlandt' 
found  that  a  noticeable  change  occurred  at  a  temperature  of  minus  4  to  6 
degrees  C.  and  only  at  minus  12  to  15  degrees  C.  does  the  destruction  of  the 
chlorophyll  grains  become  complete  (with  the  exception  of  those  in  ever- 
green plants).  With  the  formation  of  vacuoles  there  was  produced  a  dis- 
tortion of  the  form  of  the  chloroplasts  which  were  either  passing  over  into 
the  position  along  the  side  walls  (apostrophe)  or  were  rolled  up  in  lumps. 
Of  these  the  ones  inclosing  ttarch  grains  were  destroyed  more  quickly  than 
those  without  starch.  In  the  leaves  of  Vicia  odorata  no  difference  could  be 
perceived  in  the  destruction  of  the  chlorophyll,  dependant  upon  the  age  of 
the  leaf. 

We  will  touch  upon  this  subject  again  under  autumn  coloring.  A 
yellow  leaved  condition  in  spring  is  found  often  in  pears  growing  in  nurse- 
ries, as  the  after  effect  of  frost  disturbances. 

The  grape  is  very  susceptible  to  icteris.  Different  factors  have  been 
recognized  here  as  the  cause.  In  the  cases  observed  by  Mach  and  Kiirmann- 
in  the  Tyrolean  vineyards,  the  analyses  of  green  and  icteric  vines,  growing 
close  together,  showed: 

Water  Content  of  the  yellow  leaves 77-97  per  cent. 

Water  Content  of  the  green  leaves 73-17  P<-'r  cent. 

Based  on  dry  weight,  the  green  leaves  possessed  a  higher  percentage  of 
organic  substances  and  of  nitrogen,  but  considerably  less  ash.  The  ash  of 
the  yellow  leaves  contained  six  times  as  much  of  the  elements  insoluble  in 
hydrochloric  acid  as  did  that  of  the  green  leaves.  On  the  other  hand,  there 
was  less  potassium  in  the  former.  Watering  with  liquid  stable  manure 
acted  beneficially.  A  similar  case  is  described  by  E.  Schultz^.  The  leaves 
and  woody  portion  of  the  diseased  vines  contained  only  half  as  much  potas- 
sium as  those  of  the  healthy  plants,  which  were  found,  however,  to  be 
poorer  in  calcium  and  magnesium.  Besides  this  icterus  due  to  a  lack  of 
potassium,  a  jaundice  of  the  grape,  resulting  from  an  excess  of  calcium,  has 
been  determined  by  numerous  observations.  It  seems  to  me  that  the  amount 
of  calcium  in  itself  is  not  the  injurious  factor,  but  chiefly  the  lack  of  potas- 
sium, since  calcium  soils,  as  a  rule,  are  poor  in  potassium.  We  will  return 
to  this  case  in  the  section  on  the  excess  of  calcium. 

Nitrogen  starvation  is  also  a  frequent  cause.  This,  differing  from  the 
phenomena  due  to  a  lack  of  other  nutritive  substances,  does  not  manifest 
itself  in  the  death  of  the  plant  in  an  early  stage  but  only  retards  the  growth 
and  reduces  all  the  organs  to  a  minimum. 

The  oft  repeated  experiments  with  the  cultivation  of  non-leguminous 
plants  in  nutrient  mixtures  without  the  addition  of  nitrogen  have  shown 
that  under  otherwise  favorable  conditions,  with  certain  races,  a  new  min- 


1  Haberlandt.  tlber  den  Einfluss  des  Frostes  auf  die  Chlorophyllkorner.     Osterr. 
Bot.  Zeit.     Cit.  Jahresbericht,  1876,  p.  718. 

2  Biedermann's  Centralbl.  1877,  p.   58. 

3  Zeitschr.    d.    landwirtsch.     Centralver.    fiir    das    Grossherzogtum    Hessen.    cit. 
Centralbl.  f.  Agrikulturchem.  1872,  p.   99. 


iature  plant  can  be  produced  from  a  seed,  developing  even  to  the  production 
of  a  few  blossoms  and  new  seeds.  The  entire  nitrogen  content  of  the  whole 
plant,  however,  does  not  in  this  case  equal  that  of  the  original  seed.  It  is 
evident  from  this  fact,  firstly,  that  the  plant  is  not  in  a  condition  to  make 
use  through  its  leaves  of  the  nitrogen  from  the  air  in  quantities  worth 
mentioning;  secondly,  however,  we  perceive  that  nitrogenous  substance 
stored  up  in  the  seed  enables  various  individuals  to  run  through  their  whole 
developmental  cycles,  that  is  to  say,  to  perform  all  the  life-processes,  in  a 
minimum  compass.  This  demonstrates  further  that  the  nitrogen  stored  in 
the  seeds  is  easily  mobilizable  and  capable  of  transportation,  indeed,  that  the 
same  molecule  may  probably  be  utilized  more  than  once  for  the  same  pur- 
pose in  the  construction  of  the  cell  cytoplasm.  A  consideration  of  the 
growth  of  plants,  with  a  lack  of  nitrogen,  indicates  such  a  condition,  for  it 
is  found  that  the  lowermost  leaves  are  exhausted  to  the  amount  of  growth 
of  the  Vp  of  the  stem  and  begin  to  dry,  beginning  at  the  edge,  or  at  the  tip. 

In  the  rapid  convertibility  and  capacity  for  transportation  of  the  nitro- 
gen a  lack  of  this  nutritive  substance  occurs  very  rapidly  and  manifests 
itself  in  jaundice.  In  our  cultures  such  cases  can  also  occur,  if  the  supply 
of  nitrogen  in  the  soil  is  still  abundant  but  not  in  a  form  available  for  the 
special  requirements  of  the  definite  plant  under  cultivation.  The  best  ex- 
ample is  found  in  our  sugar  beets,  to  which,  besides  stable  manure,  nitrogen 
is  given  chiefly  in  the  form  of  Chile  saltpetre.  The  frequent,  very  favor- 
able results  of  fertilizing  various  other  cultivated  plants  with  ammonium 
sulfate  have  now  led  to  the  use  of  this  fertilizer  in  beet  culture.  But  in  a 
practical  way  these  results  have  not  been  satisfactory,  since  the  polarization 
of  the  beets  was  far  from  normal. 

In  a  thorough  discussion  of  this  point  Hollrung^,  Kriiger  and  Schneide- 
wind  emphasize  that  the  sugar  beet  is  a  pronounced  nitrate  plant,  but  since 
the  ammonia  is  not  converted  so  rapidly  and  directly  to  nitric  acid  by  the 
micro-organisms  of  the  soil,  a  lack  of  nitrogen  compounds  may  occur  and 
the  beets  suffer  although  enough  nitrogen  is  present  as  ammonia.  The  phe- 
nomena of  a  yellow  leaved  condition  may  be  due  to  the  constitution  of 
the  nitrogen  fertilizer  which  is  unsuited  to  beets,  although  it  may  be  suit- 
able for  grain  and  potatoes. 

An  older  note  has  already  pointed  to  the  difference  in  effect  secured 
according  to  the  form  of  nitrogen  provided.  Analyses  by  Lagrauge-  showed 
that  in  beets  fertilized  with  ammonium  sulfate,  twice  as  great  an  ammonia 
content  was  demonstrable  as  in  those  fertilized  with  sodium  nitrate. 

It  is  a  well-known  fact  that  a  yellow  color  can  be  caused  in  beet  leaves 
by  drought  alone,  so  that  we  need  to  cite  only  a  very  characteristic  example. 
In  1896  (according  to  Troude"),  the  beets  in  France,  especially  in  the 
northern  part,  suffered  extensively  from  a  yellow  leaved  condition.     The 

1  Hollrung,  Inwieweit  ist  eine  Diingung-  mit  schwefelsaurem  Ammoniak  geeig- 
net,  bei  den  Zuckerriiben  eine  Schadigung  hervorzurufen?  Vortrag.  Blatter  fiir 
Zuckerriibenbau,   1906,  p.  70. 

•^  Biedermann's  Centralbl.    1876.  I,   p.    258. 

3  Cit.  Zeitschr.  f.  Pflanzenkrankh.  1897,  p.  55. 


312 

phenomenon  appeared  in  June  after  a  longer  period  of  intense  drought  and 
became  widespread  especially  in  sunny  positions  and  on  light  soils,  while 
regions  with  a  damp,  sea  climate  showed  the  disease  only  slightly.  The  sugar 
content  of  the  slowly  growing  beet  was  from  2  to  3  per  cent,  less  than  that 
of  healthy  specimens. 

By  a  survey  of  the  individual  cases  just  cited,  we  are  led  to  the  con- 
viction that  icterus  is  one  of  the  most  widespread  symptoms  of  disturbed 
assimilation.  No  conclusion  as  to  any  definite  cause  has  been  furnished  as 
yet,  however,  in  the  occurrence  of  jaundice. 

h.     Changes  Due  to  a  Lack  of  Phosphorus  and  Sulfur. 

The  distribution  of  phosphorus  in  the  various  parts  of  the  plant,  de- 
termined earlier  by  Ritthausen's  macro-chemical  studies,  was  proved  later 
micro-chemically  by  Lilienfeld  and  Monti,  as  well  as  by  Pollacci'.  The 
last  found  that,  in  general,  the  ceil  walls  are  free  from  phosphorus  while 
the  proptoplasm,  and  especially  the  nucleus,  with  the  chromatin  bodies,  con- 
tain this  element  in  abundance.  Among  the  aleurone  bodies  the  crystalloides 
and  globoids  likewise  contain  phosphorus.  The  proteins  depend  especially 
on  the  amount  of  phosphoric  acid  at  hand  and  a  lack  of  it  will  make  itself 
felt  especially  in  the  blossom  buds  and  in  the  maturing  of  the  seed.  Accord- 
ing to  Nobbe's  cultural  experiments^,  phosphorus  does  not  seem  to  play  any 
part  in  the  formation  of  the  chlorophyll  pigment ; — the  foliage  of  oaks  which 
had  stood  for  three  years  in  nutrient  solutions,  free  from  phosphoric  acid, 
was  still  green.  In  other  plants  Nobbe  ultimately  observed  that  a  deep 
orange  red  color  appears  in  the  leaves  and  petioles.  There  is  no  production 
of  any  new  dry  substance,  or  only  a  small  amount.  Moller"'  observed  in 
*he  needles  of  his  pine  seedlings  a  blue-red  (dull  violet)  color  due  to  a  lack 
of  phosphoric  acid.  In  two-year  old  plants  the  violet  color  tended  more  to 
olive  brown. 

In  the  reports  on  discoloration  phenomena,  which  set  in  with  a  lack  of 
various  nutritive  substances,  the  results  obtained  with  one  plant  species 
cannot  be  applied  to  a  different  species,  since  discoloration  is  not  every- 
where the  same.  In  regard  to  phosphoric  acid,  I  found  that  when  plants  of 
beets,  peas,  and  seradella  were  grown  without  phosphoric  acid  they  dried  a 
gray  green  when  they  had  j-reviously  been  a  faded  green,  but  not  yellow, 
while,  with  a  lack  of  nitrogen,  the  same  species  turned  a  pure  quince  yellow. 

Nobbe  found  a  somewhat  better  development  with  a  lack  of  sulfur  in 
the  nutrient  solution,  yet  his  experimental  plants  scarcely  attained  half  the 
normal  height  and  the  yellowish  green  leaf  blades  exhibited  a  correspond- 
ingly scanty  development.  The  starch  was  scanty  and  small  grained.  Cell 
division  was  considerably  impaired.  The  forming  of  fruit  either  did  not 
take  place,  or  only  very  scantily. 


1  Pollacci,   G.,    Sulla   distribuzione   del   fosforo   nei    tessuti   veg'etali.      Malpighia. 
Vol.  VIII.     Cit.  Zeitschr.  f.  Pflanzenkrankh.   1895,   p.   299. 

2  Dobner-Nobbe,  Botanik  fiir  Forstmanner.     4th  Ed.,   p.   317. 

3  Karenzerscheinungen  etc.  Zeitschr.  f.  Forst-  u.  Jagdwesen,  1904,  p.  74.'> 


313 

i.     Changes  Due  to  a  Lack  of  Oxygen. 

General  Phenomena. 

It  is  to  be  assumed  as  well  known  that,  with  the  cessation  of  the  supply 
of  oxygen,  the  protoplasmic  currents  gradually  come  to  a  standstill  (oxygen 
rigor.)  Kiihne^  observed  that  in  an  atmosphere  of  hydrogen  the  motion  in 
the  stamen  hairs  of  Tradescantia  virginica  stopped  after  15  to  20  minutes. 
Wortmann-  found  that  the  parts  of  plants  in  air  free  from  oxygen  respired 
at  first  exactly  as  much  carbon-dioxid  as  those  with  an  unimpaired  supply. 
Later  a  difference  made  itself  felt  in  favor  of  the  latter  plants.  Like  the 
gradual  cessation  of  the  cytoplasmic  currents,  this  gradual  retrogression  in 
the  amount  of  carbon-dioxid  with  the  exclusion  of  oxygen  (intramolecular 
respiration)  indicates  that  the  oxygen  stored  in  the  plant  body  is  consumed 
at  first.  Death  from  suffocation,  therefore,  takes  place  slowly,  especially 
since  the  green  plant  with  sufficient  illumination  still  decomposes  carbon- 
dioxid  and  water  and  thus  forms  oxygen  for  some  time.  Bohm^  detected  a 
small  amount  of  oxygen  in  the  volume  of  gas  evolved  when  he  enclosed  the 
green  leaves  of  land  plants  in  an  atmosphere  of  hydrogen  with  sufficient 
illumination. 

Aside  from  the  cases  which  have  been  observed  already  in  the  divisions 
on  "Loamy  soils"  and  "Too  deep  planting  of  trees,"  we  will  consider  a  few 
occurrences  of  bad  aeration  as  a  result  of  closing  the  lumina  of  the  ducts 
forming  the  main  water  system.  Such  stoppage  is  especially  serious  for  the 
sap  wood*.  With  Bohm^  we  may  picture  to  ourselves  the  process  of  aera- 
tion as  follows :  There  is  not  only  a  difference  in  pressure  between  the 
outer  air  and  the  diluted  air  inside  the  ducts,  but  also  a  difference  in  con- 
stituents. The  enclosed  air  will  give  up  its  oxygen  in  the  respiratory  pro- 
cesses more  rapidly  and  take  up  the  carbon-dioxid  produced.  This  is  either 
soaked  up,  by  the  filling  of  the  ducts  with  water,  and  carried  off  in  the  rising 
sap  current,  or,  since  it  penetrates  the  moist  walls  rather  easily,  is  given  out 
in  a  radial  direction  by  diffusion.  The  new  and  necessary  oxygen  which  hi 
lesser  amounts  may  also  enter  through  the  roots  with  the  air  rich  in  oxygen, 
dissolved  in  the  water,  will,  nevertheless,  under  normal  conditions  get  into 
the  plant  mainly  through  transverse  conduction.  It  diffuses  more  easily 
through  moist  walls  than  does  the  nitrogen  of  the  air,  because  water  absorbs 
it  more  abundantly  than  it  does  nitrogen.  Since  now  the  oxygen  within  the 
plant  body  is  utilized  most  but  is  also  most  easily  capable  of  moving  from 
part  to  part,  there  results  a  prevailing  diffusion  stream  of  oxygen  from  with- 
out inwards  in  each  horizontal  plane  of  a  trunk. 


1   Untersuchungen  iiber  das  Protoplasma.    1864,  p.   89  and  p.  106. 
-    Wortmann,    tJber    die    Beziehungen    der    intramolekularen    zur    normalen    At- 
mung.     Inauguraldis.sertation,  Wurzburg,  1879. 

3  Bohm,  tJber  die  Respiration  von  Landpflanzen.  Sitzungsber.  d.  Kais.  Akad.  d. 
Wissensch.  in  Wien,  Vol.   67    (1873). 

4  Elfving,  tJber  die  Wasserleitung  im  Holze.  Bot.  Z.   1882,  No.  42. 

5  Bohm,    J.,   tJber   die   Zusammensetzung   der   in    den   Zellen    und   Gefafsen    des 
Holzes  enthaltenen   Luft.      Landwirtsch.  Versuchsstationen  Vol.  XXI,   p.    373. 


314 

Wiesner^  made  further  observations  on  gas  exchange.  He  shows  that 
the  periderm,  the  cork  covering,  is  completely  impermeable  to  air  even  with 
great  differences  in  pressure.  The  exchange  takes  place  only  through  the 
lenticels  which  are  permeable  even  in  winter.  In  wood  free  from  ducts  the 
equalization  takes  place  through  the  cell  walls,  especially  through  the  deli- 
cate pitted  walls  in  which,  besides  the  diffusion,  absorption  through  the  col- 
loidal walls  comes  into  effect.  In  woody  bodies,  rich  in  ducts,  transpiration 
and  the  penetration  of  gases  through  the  ducts,  functioning  as  capillary 
tubes,  should  also  be  taken  into  consideration.  The  equalization  of  the 
pressure  takes  place  more  quickly  axially  than  transversely.  The  more 
turgid  a  parenchyma  or  wood  cell  is,  the  more  slowly  does  the  equalization 
of  the  pressure  occur.  This  relation  is  reversed  in  the  periderm  cell.  If  it 
incurs  the  loss  of  its  aqueous  contents  and  is  filled  with  air,  whereby  its  wall 
becomes  dry,  the  cell  loses  its  permeability  for  gases.  In  parenchyma 
which  conducts  air,  a  part  of  the  air  flows  through  the  intercellular  passages 
during  the  equalization  of  the  pressure,  another  part  passes  through  the 
closed  membranes  and,  indeed,  most  easily  through  the  places  which  have 
remained  unthickened. 

A  statement  by  Mangin-  throws  light  on  the  processes  taking  place  in 
trees,  with  poor  soil  aeration.  He  found  that  the  ducts  in  Ailanthus  were 
filled  with  tyloses,  and,  in  explaining  the  process,  states  that,  correlative  with 
a  lack  of  air  in  the  soil,  a  deficiency  in  the  supply  of  air  in  the  ducts  takes 
place.  Consequently  the  air  in  the  ducts  becomes  diluted  beyond  the  opti- 
mum and  the  tyloses  of  the  adjacent  cells  push  into  the  tube  of  the  duct  and, 
on  their  part,  also  hinder  the  conducting  of  water. 

In  regard  to  the  influence  of  a  lack  of  oxygen  on  seeds,  Bert's^  investi- 
gations should  be  considered  first  of  all,  according  to  which  germination 
progresses  more  slowly  in  a  lesser  air  pressure.  Many  years  ago  Cofti* 
observed  that  a  dilution  of  the  air  had  an  arresting  influence  on  the  cyto- 
plasmic currents.  Since,  however,  with  a  normal  air  pressure  and  only  de- 
creased oxygen  content,  germination  takes  place  more  slowly  and,  con- 
versely, with  a  lowered  air  pressure  but  increased  supply  of  oxygen  the 
seeds  germinate  more  rapidly,  it  is  evident  that  even  the  partial  pressure  of 
the  oxygen  alone  is  a  decisive  factor. 

In  the  phenomena  due  to  lack  of  oxygen,  opportunity  is  again  offered 
of  pointing  to  the  fact  that  sudden  changes  are  more  disturbing  than  gradual 
changes.  Stich^  found  that  in  an  atmosphere  poor  in  oxygen  the  normal 
respiratory  quotient  is  recovered  by  decreasing  the  absolute  amounts  of  oxy- 


1  Wiesner,  Versuch  iiber  den  Ausgleich  des  Gasdruckes  in  den  Geweben  der 
Pflanzen.  Sitz.  d.  Kais.  Akad.  d.  Wissensch.  zu  Wien  am  17  April,  cit.  in  Oesterr. 
Bot.   Zeit.   1879,    p.    202. 

2  Mangin,  Influence  de  la  rarefaction  produite  dans  la  tige  sur  la  formation 
des  thylles  gommeuses.  Compt.  rend,  1901,  II,  p.  305. 

3  Bert,  Recherches  experimentales  sur  I'influence  que  les  changements  dans  la 
pression  barometrique  exercent  sur  les  phenomenes  de  la  vie.  Compt.  rend  LXXVI 
et  LXXVII. 

4  Meyen,  Pflanzenphysiologie,  1838,  II,  p.  224. 

5  Stich,  C,  Die  Atmung  der  Pflanzen  bei  verminderter  Sauerstoffspannung 
und  bei  Verletzungen.       Flora,  1891,  p.  1. 


315 

gen  and  carbon-dioxid.  With  a  gradual  removal  of  oxygen,  intramolecular 
respiration  is  aroused  only  with  a  considerably  lower  percentage  of  oxygen, 
than  it  is  when  the  oxygen  is  suddenly  decreased. 

The  discovery  that  phenomena  of  suffocation  occur  also  in  seeds  if  their 
tissue  is  entirely  filled  with  water  is  of  great  value  to  the  practical  worker. 
Usually  when  seeds  are  soaked  they  get  the  water  necessary  for  germination 
^vithout  having  all  the  air  pressed  out  of  the  intercellular  spaces.  If.  how- 
ever, the  seeds  are  kept  too  long  in  water,  decomposition  sets  in,  in  which 
often  a  distinct  ordor  of  butyric  acid,  a  result  of  bacterial  decay,  becomes 
very  evident.  In  the  same  way  experiments,  like  those  of  Just^,  for  example, 
show  that  when  air  has  been  removed  by  a  pump  from  the  tissues  ordinarily 
containing  air  and  the  space  filled  with  water,  the  percentage  of  germi- 
ratio-'T  is  very  greatly  reduced. 

Wlien  seeds  have  been  put  in  layers  on  top  of  each  other  while  damp, 
it  is  not  the  excess  of  water,  which  so  quickly  destroys  the  germinating 
power,  but  the  excessive  heating  and  formation  of  carbon-dioxid.  Wiesner- 
found  also  that  the  carbon-dioxid  is  developed  later  than  the  heat.  Hence 
its  development  is  not  the  only  source  of  heat ;  this  is  to  be  sought  also 
in  the  absorption  of  water.  The  seed,  coming  in  contact  with  water,  con- 
derses  it  as  it  enters  the  tissues  and  thereby  frees  heat. 

That  an  excess  of  oxygen  is  just  as  injurious  as  a  lack  of  it,  is  natural. 
Bert  found  that  the  oxidizing  processes  in  plants  are  arrested  by  too  high  a 
tension  of  the  oxygen.  A  mimosa  died  at  6  atmospheres  in  common  air,  hav- 
ing lost  its  irritability  because  of  a  lack  of  oxygen.  If  the  air  was  made 
richer  in  oxygen,  a  pressure  of  2  atmospheres  was  sufficient  to  cause  death. 

The  Brusone  Disease  of  Rice. 

The  unusually  dreaded  brusone  disease  which  manifests  itself  by  the 
appearance  of  rusty  spots  in  the  leaves  together  with  a  blackening  and 
drooping  of  the  blades,  has  often  been  the  subject  of  earnest  study,  ever 
since  Garovaglio  in  1874  began  investigating  it.  The  majority  of  investi- 
gators considered  the  phenomenon  parasitic.  Some  thought  it  necessary  to 
assume  bacteria  to  be  its  cause,  and  some  held  various  fungi  responsible, — 
among  others,  Piricularia  Oryzae  Br.  et  Cav. 

Recently,  however,  Brizi'  has  made  comparative  cultural  experiments 
from  which  it  becomes  evident  that  an  exclusion  of  air  from  the  roots  in 
high  temperatures  in  water  cultures  induces  disease  of  the  plants  with  the 
phenomena  of  the  Brusone  disease.  With  these  experimental  results  agree 
very  well  the  discoveries  which  have  been  made  in  Italy  and  Japan.  It  has 
been  especially  observed  that  the  Brusone  disease  usually  appears  if  com- 
pact, only  slightly  pervious  soils  are  healed  greatly  and  a  rapid  change  of 
temperature  sets  in.     There  then  follows  an  affection  of  the  root  which 


1  Bot.   Z.   1880,   p.   143. 

2  I.andwi'-tsch.  Versuchsstationen,  1872,  No.   2,  p.   133. 

■i  Brizi,  U.,  Ricerche  sulla  malatti  del  riso  delta  Brusone.  Ann.  Instituto  agrar. 
Ponti.    1905.   Milano.   Cit.   Zeitschr,   f.   Pflanzenkrankh.    1906. 


3i6 

brings  disease  of  blades  in  its  train  and  only  later  do  para.-itic  organisms 
infest  the  diseased  parts. 

We  consider  Brizi's  experiments  as  decisive  and  think  that  suflfocation 
of  the  roots  during  high  temperature,  which  greatly  increases  the  leaf  activ- 
ity, is  the  first  impulse  to  the  disease.    The  soil  should  be  aerated  at  once. 

THK    DlSKASKS   of    (il.ADIOLI. 

A  phenomenon  of  disease,  not  rare  in  cultivating  gladioli  in  heavy  soils, 
or  on  pieces  of  ground  with  a  lighter  soil,  but  a  higher  ground  water  level 
in  wet  years,  may  be  traced  to  a  lack  of  oxygen.  The  disease  manifests 
itself  in  the  often  sudden  oeath  of  the  plant  at  a  time  when  the  inflore- 
scence is  already  developed.  At  first  the  lower  leaves  seem  marbled  with 
yellow  (noticeable  at  first  only  when  the  light  falls  through  them).  The 
chlorophyll  bodies  decompose  and  leave  yellow  drops  which  look  like  oil. 
^Vhile  this  process  advances  apparently  in  stripes  between  the  veins  in  the 
aerial  parts  of  the  leaves,  brown,  depressed  places  are  found  on  the  leaf 
bases  still  below  the  soil  which  initiate  a  complete  decomposition  of  the  leaf 
parenchyma.  No  real  weakening  takes  place,  but  the  decomposition  repre- 
sents a  process  of  humification.  Bacteria  and  often  also  fungi,  small  worms, 
mites,  etc.,  are  always  found  in  these  tissues  which  smell  sour  like  humic 
acid.  The  aerial  parts  of  the  leaves  dry  quickly  and  become  covered  with 
black  pits  of  Cladosporium  and  Alternaria. 

Despite  the  wealth  of  parasitic  organisms  present,  the  disease  should  not 
be  characterized  as  parasitic,  since  the  first  stages,  viz.,  the  brown  coloring  of 
the  ducts  and  of  the  parenchyma,  lying  close  to  them,  are  produced 
within  the  iiealthy  tissue  without  the  co-operation  of  such  organisms.  Later 
a  number  of  the  duct  tubes  are  filled  with  a  cloudy,  brown  mass  which  be- 
comes firm  like  gum.  The  latter  phenomenon  has  been  observed  also  in 
other  plants,  the  roots  of  which  were  injured  by  continued  moisture  in  the 
soil  and  the  lack  of  oxygen  thus  produced  artificially. 

(iladioli  like  a  great  deal  of  moisture  in  the  soil  but  it  should  not  be 
long  continued.  In  dry  years  the  mistake  is  often  made  of  watering  bulbs 
and  tuberous  plants  every  day.  This  is  wrong,  the  excessive  drying  of  the 
soil  must  be  prevented  by  mulching  with  litter. 

k.     Change.s  Due  to  a  Lack  of  Carbon-Dioxid. 

Despite  the  small  content  of  possibly  0.036  to  0.040  volume  per  cent, 
of  carbon-dioxid,  which  the  air'  possesses,  while  consisting  of  nearly  79 
parts  of  nitrogen  and  21  parts  of  oxygen,  it  suffices  everywhere  for  a  high 
rate  of  growth;  if  this  important  nutrient  substance  is  entirely  lacking,  the 
other  factors  of  growth  are  without  value,  even  in  a  most  favorable  com- 
bination, as  may  be  observed  experimentally  by  placing  vessels  of  caustic 


1  According  to  Jolly's  investigations  (cit.  in  Forsch.  a.  d.  Gebifte  der  Agrikul  - 
turphysik.  1879,  p.  325)  the  oxygen  content  of  the  air  varies  not  inconsiderably 
(between  20.53  and  20.86  per  cent.).  The  largest  oxygen  content  is  found  with  a 
prevailing  polar  current  and  the  least  with  a  prevailing  equatorial  current. 


317 

potash  under  closed  bell-jars.  Corenwinderi  found  that  buds  and  young 
leaves  do  not  develop  further  in  air  free  from  carbon-dioxid.  In  Bous- 
signault's-  experiments  two  maize  kernels  developed  into  plants  of  which 
the  dry  weight  itself  and  the  carbon  and  oxygen  contents  were  less  than  in 
the  seed,  while  the  nitrogen  content  was  just  as  large.  Hydrogen  and  ash 
had  undergone  a  slight  increase.  Bohm^  found  in  leaves  of  the  scarlet 
runner  bean,  cut  off  from  the  plant  during  growth,  from  which  the  starch 
had  been  removed  by  darkness,  that  these  leaves  not  only  formed  roots 
from  the  petioles  in  full  daylight  and  in  an  atmosphere  containing  carbon- 
dioxid,  but  also  increased  in  breadth  even  if  they  were  watered  only  with 
distilled  water.  On  the  other  hand  the  seedlings  of  the  scarlet  runner  bean 
grown  in  distilled  water  and  exposed  to  the  action  of  full  daylight  under 
bell-jars  with  caustic  potash  showed  only  an  increase  in  length  up  to  lo  cm. 
while  the  stems  shrivelled  below  the  primordial  leaves  which  as  a  rule  were 
free  from  starch.  Seedlings  of  the  scarlet-runner  bean  which  had  been 
grown  in  garden  soil  rich  in  humus  but  were  robbed  of  all  but  a  small 
amount  of  their  starch  by  weak  illumination,  did  not  form  any  new  starch 
but  went  to  pieces  when  later  strongly  illuminated  in  an  atmosphere  robbed 
of  its  carbon-dioxid.  Therefore,  the  carbon-dioxid  in  the  soil  and  the  other 
favorable  conditions  for  growing  were  of  no  value.  Godlewski*  found  that 
the  starch  also  disappeared  in  plants  exposed  to  full  daylight  if  the  carboa- 
dioxid  of  the  air  was  kept  from  them. 

A  further  insight  into  the  method  of  growth  of  plants  from  which  the 
carbon-dioxid  of  the  air  had  been  removed  is  given  by  my  own  experiments''. 
Young  cabbage  plants  were  left  in  a  0.5  per  cent,  nutrient  solution,  part 
under  bell-jars  with  caustic  potash,  part  under  others  without  caustic  potash 
and  the  remainder  left  free  between  the  bell-jars.  After  ten  days  the  har- 
vest yielded : — 

Bell-jars  Bell-.iars 

Uncovered  plants  with  Potash     without  Potash 

Plant    No I.  11.  III.  IV.  V.  VI.  VII.     VIII.      IX. 

Fresh  weig-ht  of  root  and 

stem    0.457      0.367      0.414      0.470     0.17.5     0.2305      0.297     0.313     0.232 

Fresh  weig-ht  of  leaves .  .  1.598  1.494  1.564  1.682  0.765  1.011  1.736  1.712  1.850 
Upper     leaf     surface     in 

square    cm 50.6       47.5        50.1        47.3        25  4  26.6        50.4        54.1        37.1 

Total     dry     weight 0.2755   0.2510   02.685   0.2760   0.0760     0.0985   0.1705   0.1740   0.1765 

Percentage    of    the    fresh 

weight    in    dry    weight     13.4        13.5        13.5        12.8  8.4  7.9  8.1  8.6  8.4 

Total       evaporation       in 

grams     69.3       74.4        82.5        75.0        27.4  34.4       43.1        40.4       43.3 

Evaporation      per     gram 

dry    weig-ht     251.5      296.4     307.2     271.7     360.6       349.2     252.8      232.2      245.3 

The  table  shows  that  the  production  in  fresh  and  dry  weight  was  the 
smallest  under  the  bell-jars  with  potash.     The  absolute  amount  of  evapora- 


1  Recherches  chimiques  sur  la  vegetation.  Fonctions  des  feuilles.  Compt.  rend, 
t.  LXXXII,  1876,  No.   20,  p.  1159. 

-  Boussingault,  Vegetation  du  Mays,  commence  dans  une  atmosphere  excempte 
d'acide  carbonique.     Compt.  rend.  Vol.  LXXXII,   No.   15,   p.   788. 

•■!    Biihm,   in   Sitzungsber.   d.  Wierner  Akad.    1876,   cit.   Bot.   Zeit.   1876.   p.   808. 

■i  Bibliographische  Berichte  iitaer  die  Publikationen  der  Akademie  der  Wissen- 
schaften  in  Kraukau.     Part  I,  cit.  Bot.  Zeit.  1876,  p.  828. 

5  Sorauer.  Studien  iiber  Verdunstung.  Forschungen  auf  dem  Gebiete  der 
Agrikulturphysik,  Vol.  Ill,  Parts  4  and   5. 


3i8 

tion  is  greater  or  less  according  to  the  amount  of  newly  produced  dry  sub- 
stance ;  it  is  smallest  in  the  plants  under  the  bell-jars  with  potash.  Naturally 
the  effect  of  the  bell-jars.  i.  e.,  the  humidity  prevailing  under  them,  is  to 
be  taken  into  consideration.  This  factor  manifests  itself,  when  compared 
with  the  uncovered  specimens,  by  the  lower  percentage  of  dr^-  weight  in 
the  plants,  i.  e.,  by  a  loose  structure  and  longer  petioles. 

If  the  specimens  from  the  bell-jars  containing  pota.-h  are  compared 
only  with  those  of  the  other  bell-jars,  the  result  is  more  certain.  The  lack 
of  carbon-dioxid  manifests  itself  most  by  the  lessened  total  production, 
especially  in  the  leaf  apparatus;  the  upper  surface  is  only  about  half  as 
large.  The  most  striking  effect  is  the  amount  of  evaporation,  which  is  cal- 
culated per  gram  of  dry  substance  present.  This  is  greatest  in  the  plants 
deprived  of  the  carbon-dioxid  supply.  The  same  condition  is  found  in  the 
calculation  of  the  evaporation  per  square  centimeter  surface  in  the  plants 
grown  under  both  conditions.  This  fact  should  be  associated  with  the  re- 
sults of  other  experiments,  according  to  which  it  is  evident  that  the  amount 
of  evaporation  increases  also  in  plants  which  lack  other  nutritive  substances. 
Tf.  for  example,  plants  from  a  normal  favorable  nutrient  solution  are  placed 
in  one  of  too  low  concentration,  or  in  distilled  water,  evaporation  is  in- 
creased ;  it  increases  also  in  seedlings  after  the  removal  of  the  organs  con- 
taining reserve  food,  the  cotyledons.  It  may  be  assumed  that  the  plant 
must  force  itself  to  a  greater  transportation  of  water  through  its  roots,  i.  e., 
to  a  greater  one-sided  kind  of  labor,  in  order  to  meet  lesser  amounts  of  re- 
serve substances  contained  in  the  solution  due  to  their  increased  absorption 
by  the  roots  from  the  surrounding  soil. 

For  practical  work,  the  above  investigations  suggest  an  attempt  to  in- 
crease production  by  increasing  the  supply  of  carbon-dioxid.  Experiments 
actually  show  that  a  much  more  rapid  formation  of  starch  is  obtained  by 
increasing  the  carbon-dioxid.  In  many  plants  an  increase  up  to  6  to  8  per 
cent,  was  possible.  Of  course,  a  different  absolute  quantity  of  carbon-dioxid 
is  necessary  for  each  plant  and  in  the  same  plant  for  every  other  combination 
of  the  vegetative  factors  in  order  to  obtain  an  optimum  production.  The 
strengthening  of  the  vegetative  processes  by  the  addition  of  carbon-dioxid 
manifests  itself  in  the  more  compact  growth  and  thicker  leaves\ 

While  previous  experiments  have  taken  up  the  results  of  a  lack  of  car- 
bon-dioxid for  the  whole  plant,  Vochting-  tested  the  behavior  of  various 
branches,  which  were  left  on  the  normally  growing  plant,  but  transferred 
to  an  atmosphere  free -from  carbon-dioxid.  It  was  found  thereby  that  each 
branch  and  leaf  must  be  maintained  by  its  own  work  and  that  their  life 
activity  gradually  dies  away  if  this  work  is  prevented  by  a  lack  of  carbon 
dioxid.  The  plant  can,  indeed,  develop  further  the  branches  in  the  atmos- 
phere free  from  carbon-dioxid,  but  the  leaves  on  these  branches  are  a  faded 

1  Feodoresco,  E.,  Einfluss  der  Kohlensaure  auf  Form  und  Struktur  der  Pflanzcn. 
Cit.  Centralbl.  f.  Agrikulturchemie,  1900,  p.  137. 

-  Vochting,  H.,  tJber  die  Abhang-igkeit  des  Laubblattes  von  senier  Assimi- 
lationstatig-keit.     Bet.  Zeit.  1891,  Nos.  8  and  9. 


319 

green  and  form  no  starch.  They  also  do  not  recover,  if  the  branch  is 
brought  back  to  air  containing  carbon-dioxid,  but  go  to  pieces  after  a  short 
time.  It  thus  becomes  evident  that  each  leaf  has  its  independent  existence 
and  that  any  disturbance  of  it  cannot  be  adjusted  by  the  organism  as  a 
whole.  The  organ  which  has  become  functionless  is  thrown  off  from  the 
body. 

B.     EXCESS  OF  WATER  AND  NUTRITIVE  SUBSTANCES, 
a.     Excess  of  Water. 

MOISTURE. 

The  phenomena  of  yellowing  and  decomposition  connected  with  stag- 
nate water  have  been  considered  when  discussing  the  disadvantages  of  heavy 
soils.  We  are  thus  concerned  here  only  with  proving  by  example,  how  an 
excess  of  water,  like  a  lack  of  it,  retards  production.  Thus  Stahl- 
Schroeder's^  experiments  with  oats  in  sterile  sea-sand  to  which  the  nutrient 
solution  had  been  added,  gave  the  following  results.  With  the  addition  of 
water  there  were  produced : 


%  of  the 

No. 

Weight   of 

Weight  of 

Medium 

Phos- 

Nitro- 

entire water 

of 

1000  kernels 

straw  and 

lengtli  of 

Ash 

phoric 

gen 

capacity 

ker- 

chaff 

the  plants 

acid 

of  the  sand 

nels 

g- 

g- 

cm. 

% 

% 

% 

35 

84 

15.5  (calculated) 

6.2 

49 

9 

•? 

3.752 

50 

1723 

21.6 

73.9 

102 

2.933 

1.444 

2.915 

70 

2074 

18.5 

101.8 

140 

2.712 

1.090 

2.501 

90 

1827 

16.3 

115.0 

157 

3.007 

1.207 

2.407 

95 

469 

ll.K  calculated) 

90.8 

162 

5.892 

1.847 

3.444 

Thus  only  the  vessels  containing  a  medium  amount  of  water  yielded  a 
good  harvest  in  grains.  With  a  larger  water  content,  the  harvest  of  grains 
fell,  while  the  yield  in  straw  increased.  With  a  lack  of  water  in  the  sand 
(35  per  cent.)  and  with  an  excess  (95  per  cent.)  none  of  the  grains  ripened. 
The  poorer  the  growth  of  the  plants,  the  greater  their  percentage  of  ash  con- 
tent, and  wealth  of  phosphoric  acid  and  nitrogen. 

Clogging  of  Drain  Tile.    . 

Wherever  flat  lying  drains  extend  through  the  root  systems  of  perennial 
plants,  an  unusually  luxuriant  root  growth  may  stop  up  the  drains.  The 
long  whip-like,  very  slender  and  comparatively  thin  roots  lying  side  by  side, 
like  cords,  in  this  way  form  mats  ten  or  more  meters  long  and  as  thick  as 
the  width  of  the  drain  allows.  The  most  dangerous  tree  seems  to  be  the  wil- 
low for  most  of  the  drain  mats  seem  to  be  formed  by  it,  yet  all  plants  may 
form  similar  root-growths  and  Magnus-  once  found,  for  example,  the 
rhizome  of  the  horse  tail  (Equisetum  palustre,  L.)  growing  very  luxuriantly 
in  such  a  mat.     Cohn^  found  a  drain  mat  which  came  from  a  pipe  laid  125 


1  of.  Biedermann's  Centralbl.  f.  Agrikulturchem.  1905,  Part  2. 

2  Sitzungsber.  d.  Bot.  Vereins  vom  26  Mai,  1876.  Vol.  XVIII,   p.  72. 

3  Verh.  d.  schles,  Gesellsch.  f.  vaterl.  Kultur,   25   Oktober,  1883. 


320 

cm.  deep  and  was  formed  entirely  from  the  ramifications  of  the  root  of  a 
single  Equisetum  from  which  a  piece  12  meters  long  could  be  separated. 

Mijller-Thurgau  experimented  with  roots  from  one  plant,  putting  some 
in  a  nutrient  solution,  others  in  distilled  water;  each  experiment  showed  a 
stronger  growth  in  the  solution.  These  experiments  showed  that  root 
growth  increases  locally  when  the  roots  reach  places  containing  food  sub- 
stances. 

If  the  drain  mats  return  after  removal,  it  is  advisable  to  take  out  care- 
fully both  trees  and  roots  by  uprooting  and  not  by  chopping  down.  If  the 
trees  must  remain  it  is  better  (especially  with  double  lines  of  drainage)  to 
lower  the  surface  laid  pipes  (as  a  rule  between  80  to  90  cm.)  to  the  level  of 
the  pipe  system  lying  deeper  (1.5  m.). 

Sprouted  Grain. 

In  the  phenomena  to  be  cited  here  which  are  connected  with  an  excess 
of  water,  injury  is  caused  either  by  the  fact  that  water  from  outside  acts 
mechanically  on  the  tissues  at  an  unsuitable  time,  or  the  water  taken  up  by 
the  roots  cannot  find  utilization  and  be  carried  off  in  corresponding  amounts. 
To  the  first  group  belongs  grain  si)routed  on  the  field  during  the  harvest 
because  of  rain.  The  disadvantage  is  the  greater  in  this  instance,  since  the 
sprouted  kernels  can  neither  be  used  for  nutritive  purposes  nor  are  they 
suitable  for  seed.  Of  course  the  germinative  capacity  for  subsequent  use 
as  seed  decreases  according  to  the  amount  the  kernels  have  sprouted. 
Ehrhart^  found  that  the  weakness  and  thus  the  mortality  of  the  seedlings 
increased  as  their  development  had  already  advanced  because  of  the  pre- 
mature sprouting.  We  owe  to  Marcker  and  Kobus-  thorough  investigations 
of  the  changes  in  the  seed  due  to  sprouting.  The  former  investigated  barley, 
half  of  which  was  harvested  uninjured,  but  the  other  half  was  left  standing 
for  almost  14  days,  wet  through  by  rain.  The  differences  were  shown  by  a 
determination  of  the  elements  soluble  in  water,  for  they  amounted  to  the 
following  in 

Sprouted  and  in  ivell-han'estcd  barley 

Soluble  starch    1.17  per  cent.  1.76  per  cent. 

Dextrin   0.00  per  cent.  i.io  per  cent. 

Dextrose   4.92  per  cent.  0.00  per  cent. 

Maltose   7.32  per  cent.  3.12  per  cent. 

Other  soluble  substances...    5.23  per  cent.  5.64  per  cent. 

18.64  per  cent.  11.62  per  cent. 

A\'c  thus  see  that  the  vigorous  diastase  action  has  resulted  in  a  very 
abundant  sugar  formation  from  the  starch  and  dextrin.  The  starch  con- 
tent had  fallen  from  64.10  per  cent,  to  57.98  per  cent.,  because  of  the 
sprouting.     If  the  kernels  are  used  for  making  starch,  the  great  amount  of 

1  Deutsche  landwirtsch.  Presse,  1881,  No.  76. 

2  Aus  Braunschweiger  landw.  Z.,  1882,  No.  22,  cit.  in  Biedermann's  Centralbl. 
f.  Agrikulturchemie,  1883,  p.  326. 


321 

diastase  would  now  presumably  convert  more  starch  into  dextrin  and  sugar, 
when  softened,  and  result  in  appreciable  losses  in  manufacture.  The  great- 
est changes  due  to  sprouting,  however,  are  found  in  the  nitrogen-containing 
elements  of  the  grain.  While  especially  the  ammonia  content  had  remained 
unchanged  (nitric  acid  was  not  found  in  quantities  worth  mentioning  in 
either  of  the  two  kinds  of  grain)  the  soluble  proteins  had  decreased  to  a 
great  extent,  the  insoluble  to  a  lesser  one.  This  decrease  is  explained  by 
the  relatively  great  increase  of  the  amides.  Thus,  in  sprouting,  first  the 
soluble  proteins  had  been  consumed  in  the  formation  of  the  amides  and 
later  even  a  part  of  the  insoluble  ones. 

Kobus  arrived  at  the  same  results  in  his  investigations  of  sprouted 
wheat,  whose  gluten  content  had  decreased  from  20  to  25  per  cent.  This 
fact  explains  the  well-known  loss  in  baking  qualify  of  a  flour  made  from 
sprouted  grain. 

The  germinating  capacity  in  the  experiments  carried  out  by  Marcker 
had  fallen  from  98  per  cent,  to  45  per  cent. 

It  thus  becomes  evident  how  worth  while  are  the  great  efforts  which 
must  be  exerted  in  any  case  to  make  possible  harvesting  the  grain  while 
dry.  Similar  losses  may  befall  other  field  crops  as  well,  as,  for  example, 
lupines,  rape,  beet  roots.  The  cases  in  which  the  seed  germinates  inside  the 
fruit  without  being  noticeable  externally  are  interesting  but  not  of  importance 
agriculturally.  I  found  such  cases  in  pears,  apples,  melons,  and  pumpkins. 
Other  observers  found  the  same  phenomena  in  oranges,  as  well  as  pumpkins, 
and  indeed  in  other  fruits  also  which  had  remained  very  long  on  the  trees, 
and  in  that  which  had  only  colored  late.  Further  statements  on  this  subject 
may  be  found  in  the  section  on  germination  interrupted  by  drought. 

The  Rupturing  of  Fleshy  Parts  of  Plants. 

Fleshy  roots,  stems  and  fruits  frequently  crack  open  in  long  periods  of 
dampness.  Among  vegetables,  kohlrabi,  carrots  and  parsley  sufifer  especially. 
Hallier^  proved  that  the  rupturing  is  due  to  excessive  water  supply,  for  by 
banging  parsley  roots  in  water  he  found  after  three  days  that  all  the  part 
which  was  in  the  water  had  cracked  open.  Boussingault"  observed  the 
rupturing  of  cherries,  mirabelle  plums,  pears,  grapes,  and  blueberries  after 
the  fruits  had  hung  in  water.  I  obtained  the  same  results  by  imbedding 
them  in  wet  sand.  Of  herbaceous  stems,  those  of  rape  crack  open  very 
freely  shortly  before  the  time  of  blossoming.  The  figure  here  given  shows 
the  change  in  a  bean,  which  I  had  planted  too  deep  in  wet  sand.  In  July, 
1882,  in  Proskau,  I  found  ruptured  potato  stems  and  Beta  vulgaris  roots. 
At  that  time  a  very  rainy  July  had  followed  a  dry  spring  after  a  small 
amount  of  winter  moisture.  The  phenomenon  was  apparent  at  first  on  light 
places  in  the  soil  and  in  the  best  developed  plants.  I  found  similar  cases 
in  roses  and  in  plum  seedlings,  which  had  been  taken  from  the  sand  and 


1   Hallier,   E.,  Phytopathologie,  p.  87. 

^   Compare  Bot.  Jahresbericht,  1873,  p.   253, 


placed  deeper  in  a  nutrient 
solution  than  they  had  been  in 
the  sand.  The  base  of  the 
stem  split  in  those  specimens 
reviously  exposed  to  the  air. 
In  the  souring  of  crops  in 
fields  planted  with  horse 
beans,  peas,  vetches,  etc., 
the  base  of  the  stem  is  rup- 
tured at  times  above  the 
I)laces  where  the  (rotted) 
roots  arise,  and  it  is  found 
that  a  spongy,  loose  tissue 
protrudes  from  the  torn  place, 
as  in  the  bean  here  illus- 
trated. 

All  these  phenomena  have 
one  characteristic  in  common 
— that  they  are  initiated  only 
when,  after  a  considerable 
period  of  normal  develop- 
ment, or  still  more  after  a 
prexious  dry  period,  an  un- 
usual supply  of  water  is  given 
suddenly.  If  the  plants  are 
in  contact  with  water  from 
the  beginning  of  their  de- 
velopment, they  adjust  them- 
selves to  their  surroundings. 
The  same  adjustment  can  be 
observed  especially  in  those 
varieties  which  develop  in 
water  as  well  as  on  dry  land. 
Levakoffski's'  experiments  on 
Epilobium  hirsutum,  Lycopus 
europaeus  and  Lythrum  serve 
as  examples.  The  compari- 
son of  water  and  land  speci- 
mens shows  that  in  the  water 
plants,  two  rows  of  colorless 


1  Levakoffski.  De  rinfluence 
de  I'eau  sur  la  croissance  de  la 
tig-e  etc.    Cit.  Bot.  Zeit.  1875.  p.  696. 


Fig.  -4  2.     Bean  plant  split  at  the  base  as  the  result  of  excess 
of  water,     The  torn  place  has  scarred  over. 


323 

cells,  free  from  chlorophyll,  3  to  4  times  as  long  as  they  are  broad,  exist 
between  the  cambium  and  the  bark  parenchyma  which  are  not  present  in 
the  land  specimens.  This  difference  becomes  greater,  when  the  older  parts 
of  the  plant  are  compared  with  one  another.  Below  the  surface  of  the 
water  these  cell  rows  become  a  thick,  lacunar  tissue  Epidermis  and  bark 
soon  go  to  pieces  here.  The  cells  which  form  this  special  tissue  are  de- 
veloped from  the  cambium. 

The  sudden  excess  of  water,  which  causes  the  rupturing  of  part  of  the 
plant,  destroys  the  equilibrium  in  the  epidermis,  or  the  cork  layer  present 
instead  of  the  epidermis,  and  in  the  fleshy  parenchyma  body.  Especially 
after  previous  periods  of  drought,  the  elements  of  the  upper  epidermis  be- 
come thicker  walled  and  less  elastic  and  are  not  able  to  accommodate  them- 
selves rapidly  enough  to  the  swelling  inner  tissue. 

If  the  rupturing  takes  place  in  succulent  organs  without  any  previous 
dry  period,  due  to  a  long  continued  supply  of  water  in  damp  surroundings, 
the  torn  places,  as  a  rule,  differ  from  those  due  to  drought,  in  that,  in  the 
latter,  the  wounded  surface  turns  to  cork  or  is  cut  off  by  a  new  cork  layer. 
In  the  former,  on  the  other  hand,  the  parenchyma  cells,  exposed  by  the 
rupture,  remain  thin  walled,  at  times  elongated  into  pouches  and  decaying 
easily.  Boussingault  found  that  the  fruits  lost  sugar  to  Ihis  excessive  water. 
This  loss  of  sugar  together  with  the  increased  absorption  of  water  may 
explain  the  watery  taste  of  the  fruit  after  rainy  weather.  Some  blossoms, 
left  under  water,  also  lost  sugar.  On  the  other  hand,  in  sugar  beets,  rape, 
in  the  seedling  roots  of  wheat,  barley  and  maize  no  sugar  was  lost  although 
the  tissue  was  rich  in  sugar. 

There  is  a  method  of  storing  zvinter  apples  which  is  well  worth  recom- 
mending, viz.,  placing  the  fruit  in  layers  in  sand.  If  the  sand  is  kept  too 
moist,  a  large  percentage  of  the  fruit  may  lose  in  selling  value  because  the 
skin  ruptures. 

Miiller-Thurgau^  made  similar  observations  in  related  experiments. 
After  apples  had  lain  eight  months  in  boxes  of  earth  he  found  the  fruit  was 
wet,  some  of  it  ruptured,  some  mealy,  and  its  acid  and  sugar  content  much 
lower.  The  percentage  of  decaying  apples  was  much  less,  however,  than  in 
fruit  lying  free  in  the  cellar. 

The  rupturing  of  fruits  and  vegetables,  due  to  storage  methods,  can  be 
overcome  by  supplying  a  dry,  well  ventilated  place.  In  fruit  on  the  tree, 
especially  the  tgg  plum  which  is  very  delicate,  it  is  advisable  in  longer 
periods  of  rain  to  shake  the  water  from  the  tops  of  the  trees. 

Finally,  attention  must  still  be  called  to  the  fact  that  the  tendency  to 
rupture  can  also  become  hereditary.  An  observation  of  this  was  made  with 
cucumbers-.  In  forcing  these,  the  owner  always  chose  for  his  seed  the 
finest  specimens  of  a  variety  which  ruptured  easily,  and  observed  that  this 
bad  condition  manifested  itself  more  abundantly  and  earlier  from  year  to 


1  Fiinfter  Jahresb.  d.  deutsch-schweizerischen  Versuchsstation  zu.  Wadensweil. 
Zurich,   1896. 

2  Zeitschr.  f.  Pflanzenkrankh.  1899,  p.  183. 


324 

year.  He  then  planted  half  of  his  greenhouse  with  the  forcing  variety  pre- 
viously used  and  the  other  half  with  an  outdoor  variety.  The  latter  gave 
healthy  fruit  up  to  autumn,  while  the  half  planted  with  the  first  variety 
produced  ruptured  fruit  from  the  beginning  of  May  on.  Such  observations 
give  hints  well  worth  noticing  when  choosing  seed  of  vegetables  which  tend 
to  rupture. 

Thf.  Woolly  Streaks  in  Apple  Cores. 

In  describing  apple  varieties  the  expression  "The  carpels  of  the  cores 
rui)ture,"  is  found  stated  here  and  there,  as  a  characteristic  of  the  variety. 
According  to  the  illustration  here  given,  a  condition  of  membranous  carpels 
is  said  to  be  indicated  in  which  the  inner  walls  of  the  core  divisions  are  not 
uniformlv  smooth  and  solid,  but  show  a  surface  crossed  by  streaks  which 


Fig.  43.     Cut  apple,   the  coie  of  which   shows  woolly  streaks    (w). 


look  white  and  woolly,  and  extend  slantingly  from  the  centre  to  the  outside. 
The  phenomenon  occurs  fre(|uently  and  is  considered  to  be  normal, — which 
deduction  I  do  not  care  to  hold  to.  Aside  from  the  fact  that  under  certain 
circumstances  all  the  fruit  in  the  same  variety  does  not  show  such  woolly 
streaks  and  that,  in  different  years,  it  is  developed  to  a  diiiferent  degree, 
even  appearing  in  isolated  cases  in  varieties  which,  as  a  rule,  have  a  smooth 
core,  the  conditions  found  microscopically  also  prove  splendidly  the  ab- 
normal nature  of  these  streaks. 

If  a  carpel  with  such  streaks  is  cut  through,  as  shown  in  Fig.  43  at  w, 
the  appearance  is  found  as  given  in  Fig.  44.  In  this  the  side  designated  by 
K  is  the  inner  wall  of  the  core,  while  F  indicates  the  outer  side  bordering 
on  the  flesh  of  the  fruit.  In  varieties  of  apples  with  smooth  carpels,  the 
inner  lining  of  the  core  is  formed  only  of  such  cell  elements,  as  are  shown 


325 

at  p.  These  are  very  much  elongated,  extraordinarily  thick-walled  cells, 
traversed  by  many,  frequently  branched  canals ;  they  turn  yellow  with 
chloriodid  of  zinc.  Single  layers  of  such  cells  may  cross  one  another.  Ac- 
cordingly, besides  such  cells  seen  in  full  length  at  p,  the  same  horizontal 
section  also  exhibits  parts  of  elements  in  cross-section  q.  It  is  evident  that, 
because  of  the  close  arrangement  of  the  cells  on  the  one  hand  and  because 
of  their  very  strong  walls  on  the  other  hand,  a  very  great  firmness  is  ob- 
tained in  the  core  tissue,  increased  by  the  transverse  course  of  the  cells.  It 
is  evident  further,  that  in  fruits  with  a  larger  calyx  depression,  through 
which  fungi  may  grow  easily  into  the  core,  the  spread  of  fungi,  which  pro- 
duce decay,  is  limited  by  the  parchment-like,  solid  carpels. 


Fig.  44. 


Rupturing  of  the  papery  carjei  oi  the  apple,  due  to  the  excrescence  tis 
of  a  Avoolly  strealv.      (Orig.) 


This  protection  from  internal  decay  is  destroyed  by  the  woolly  streaks 
(Fig.  43  W)  for  they  consist  of  very  loose  tissue,  which  breaks  through  the 
solid  walls. 

We  see  in  Fig.  44  that  these  woolly  streaks  are  formed  of  thick  bunches 
of  cell  rows  elongated  like  threads,  which  differ  strikingly  from  the  sur- 
rounding ones  because  of  their  thinner  walls,  and  very  gradually  pass  over 
into  the  tissue  of  the  fruit  {F),  while  others  are  quite  sharply  and  suddenly 
cut  off  from  the  thick- walled  cells  (/»)  below  the  places  in  the  core  which 
have  remained  membranous.  Only  at  the  base  of  this  bunch  of  threads  do 
short,  schlerenchymatous  cells  {sk),  isolated  or  lying  beside  one  another  in 
mats,  recall  the  elements  {p)  to  be  found  in  the  normal  wall.    Although  these 


326 

thin-walled  cell  rows  approximate  more  nearly  tissue  of  the  fruit  in  form 
and  by  the  blue  coloration  from  chloriodid  of  zinc,  they  still  do  not  corres- 
pond to  it  entirely.  The  difference  consists  chiefly  in  a  wart-like  thickening 
of  the  cell  wall  xv  which  is  most  strongly  developed  in  the  outer  cells  of  the 
thread  bunch,  but  in  the  inner  cells  is  often  only  weakly  indicated  and 
generally  is  not  present  at  all  in  the  schlerenchymatous  elements.  These 
cell  wall  thickenings  which  push  outward  and  look  like  buttons,  show,  with 
the  action  of  chloriodid  of  zinc  either  a  pale  blue  color  or  remain  uncolored, 
or  even  appear  yellow.  The  latter  case  is  found  most  distinctly  in  the  very 
thick-walled  cells  (sk)  in  which  the  whole  membrane  is  also  colored  yellow. 
Fig.  44,  at  the  left,  is  a  more  strongly  magnified  section  from  a  cell  row  of 
the  bunch  filament.  It  is  seen  here  that  the  wart-like  protuberances  of  the 
wall  which  I  would  also  like  to  consider  phenomena  of  the  swelling  of 
various  points  in  a  fine  middle  lamella,  often  have  mushroom  forms  (kn)^. 

Thus  it  should  be  assumed,  that  at  the  time  of  the  chief  swelling  of  the 
fruit,  the  tension  of  the  tissues  in  the  carpel  has  become  so  great,  because 
of  a  sudden,  great  supply  of  water,  that  the  connection  in  the  membranous 
tissues  is  broken  in  stripes  and  loosened  and  the  elements  now  freed  from 
pressure,  and  not  thick-walled,  extend  like  pouches  into  the  hollow  of  the 
core. 

Varieties  inclined  to  have  woolly  streaks  are  especially  easily  exposed 
in  damp  years  to  the  formation  of  moulds,  i.  e.  phenomena  of  decay  in  the 
core.     It  is,  therefore,  advisable  to  use  these  fruits  quickly. 

The  Ring  Disease  of  Hyacinth  Bulbs. 

This  disease  is  very  serious  for  growers  of  hyacinth  bulbs.  It  manifests 
itself  by  the  browning  and  loosening  up  of  a  scale  in  the  midst  of  healthy 
bulb  layers.  The  decomposition  of  the  tissue  progresses  from  the  neck  of 
the  bulb  downwards  into  the  bulb  centre.  If  it  reaches  the  latter,  the  bulb 
is  as  good  as  lost.  The  disease  is  often  transmitted  to  the  bulblets.  All  the 
diseased  parts  become  covered  with  Penicillium,  which  here  has  actually 
taken  on  a  parasitic  character.  The  reason  for  the  extremely  rapid  spread 
of  the  fungus  is  to  be  found  in  the  change  of  the  substratum  which  proves 
unusually  favorable  for  it.  Analyses  show  especially  that  the  fresh,  healthy 
substance  of  the  ring-diseased  bulb  possesses  more  sugar  than  that  of  healthy 
specimens.  The  former  resemble  younger  scales  in  contrast  to  the  older 
ones.  Since  now  a  reduction  of  the  sugar  takes  place  with  the  increased 
ripeness  of  the  bulbs,  we  shall  have  to  conclude  from  the  greater  amount 
of  sugar  that  diseased  bulbs  are  less  ripe. 

In  fact  it  may  now  be  proved  that  by  their  cultural  methods  our  bulb- 
growers  often  run  the  risk  of  harvesting  unripe  bulbs.  In  taking  up  the 
bulbs,  the  grower  sometimes  does  not  wait  until  the  leaves  have  completely 
dried  up  in  summer.    This  holds  good  primarily  where  the  hyacinths  serve 

1  The  same  or  similar  phenomena  have  been  observed  very  recently  by  various 
scientists.  I  found  them  also  in  the  hair-like  cells,  clothing  the  interior  of  beets 
which  had  become  hollow;  in  the  leaf  parenchyma  cells  of  fallen  oat  plants,  etc. 


327 

as  decorative  plants  in  gardens  and  public  places.  There  a  bed  of  old 
flowers  and  slowly  yellowing  leaves  is  very  unsightly.  Consequently  the 
bulbs  are  lifted  and  let  ripen  in  another  place.  The  resulting  great  injury 
to  the  root  prematurely  checks  the  vegetative  growth  of  the  bulbs.  The 
leaves  dry  before  they  have  lived  out  their  life  and  their  bases,  i.  e.  the 
scales  of  the  bulbs,  remain  immature  and  rich  in  sugar,  thereby  forming  the 
desired  centre  for  convenient  infection  by  the  fungus. 

In  the  large  field-grown  commercial  bulbs,  the  supply  of  fertilizer 
enters  into  the  question,  since  it  is  desirable  to  produce  very  strong  bulbs 
in  the  shortest  possible  time.  The  fertilizer  so  lengthens  the  time  of  growth 
that  many  varieties  have  not  finished  growth  at  the  fixed  time  of  harvest. 
The  leaves,  still  green,  then  possess  in  every  case  unique  scales  and  during 
the  storage  of  the  harvested  bulbs  on  the  "bulb  floors,"  up  to  the  time  of  the 
autumn  sales,  Penicillium  has  ample  time  fo  attack  the  scales,  which  remain 
rich  in  sugar,  and  to  destroy  them.  It  is  a  matter  of  course  that  varieties 
ripening  especially  late  will  exhibit  this  bad  condition  and  the  growers, 
therefore,  speak  of  "ring  diseased  races." 

The  testing  of  the  bulbs  is  accomplished  by  cutting  superficially  through 
the  tip  of  the  neck  during  the  dormant  period.  If  the  cross-section  shows 
a  brown  ring  between  the  white  scales  of  the  bulbs,  these  bulbs  should  not 
be  sold. 

Stock  suffering  from  the  ring  disease  can  be  cured  by  putting  the  bulbs 
in  sandy  soils,  not  freshly  manured,  with  a  deep  lying  ground  water  level, 
where,  with  scarcity  of  nutriment  and  moisture,  they  can  ripen  early. 

The  fact  still  remains  to  be  mentioned  that  a  phenomenon  has  been  con- 
fused with  the  real  ring  disease,  which  is  very  similar  to  it  judging  from  its 
habit  of  growth\  The  cause  is  known  to  be  a  nematode  {Tylenchus 
Hyacinthi  Pr.)  which  can  wander  into  the  scales  from  the  leaves.  In  this 
disease,  however,  a  gall-like  distension  of  the  cells  takes  place,  also  the 
formation  of  cork  w^alls  like  little  islands  and  other  differences,  as  has  been 
described  more  in  detail  in  the  second  edition  of  our  manual. 

Springing  of  the  Bark. 

In  illustrating  the  ruptured  bean  plant  (Fig.  42),  we  noticed  that  a 
soft  tissue  mass  had  protruded  through  the  gaping  split  in  the  cracked  stem. 
This  is  the  new  formation  of  bark  tissue,  which  may  be  considered  a  re- 
action of  the  organ  to  the  wound  stimulus  and  the  decreased  tension.  Other 
cases,  however,  occur  in  which  matters  are  reversed,  viz.,  that  the  increase 
of  bark  tissue  is  the  primary  process  and  the  splitting,  the  secondary  one. 
Such  an  increase  in  growth  can  arise  from  different  causes.  Hartig-  con- 
siders one  of  these  to  be  the  increase  in  size  caused  by  a  sudden  isolation 
of  forest  trees.     He  describes  cases  of  hornbeams  in  a  beech  grove,  where, 

1  Journal  de  la  Soc.  nat.  et  centrale  d'Horticulture  de  France.  April,  1881. 
Sorauer,  Zur  Klarung  der  Frage  tiber  die  Ringelkrankheit  der  Hyacinthen.  Wiener 
illustrierte  Garlenzeitung,   1882.     April  number,  p.   177. 

2  Hartig-,  R.,  Das  Zerspringen  der  Hainbuchenrinde  nach  plotzlicher  Zuwachs- 
steigerung.     Untersuch.  forstbot.  Inst.     Vol.  Ill,  p.   141. 


328 


after  isolation, — "the  breast  high  growth,  measuring  1.2  sq.  cm.  in  cross- 
section,  in  a  few  years  increased  in  cross-section  growth  to  13.7  cm.  ann- 
ually \"  The  cork  was  split  thereby  in  numerous  places  and  resulted  in  a 
rupturing,  indeed,  in  places  it  lifted  the  bark  body  from  the  wood-cyUnder. 
Hartig  found  similar  conditions  in  oaks  and  explained  this  by  a  greater 
soil  activity,  resulting  from  the  isolation  and  increased  action  of  light'-. 

I^henomena  of  tliis  kind  may  be  found  also  in  other  trees,  especially  in 
])arks  and  gardens. 

Shedding  of  the  Bark. 

Hartig  describes  a  case  in  which  the  splitting  of  the  bark  is  due  to  an 

increase  in  the  normal 
growth.  I  observed  a 
splitting  and  shedding 
of  the  bark  from  an  ab- 
normal cell  -  elongation 
in  the  bark  parenchyma. 
In  1904,  I  found  in  an 
a\cnue  of  elms  a  num- 
ber of  trees  standing 
side  by  side  at  the  bases 
of  which  a  great  many 
pieces  were  perhaps  as 
long  as  one's  hand. 
Upon  closer  investiga- 
tion, loosely  hanging 
strips  of  bark  25  to  50 
cm.  long  were  found  on 
llie  lower  end  of  the 
trunk,  which  could  easily 
be  removed.  The  trunk, 
thus  exposed,  was  cov- 
ered with  greenish  tis- 
sue in  spots  which 
proved  to  be  new  for- 
mations of  bark.  The 
loosened  pieces  of  bark 
(Fig.  45),  exhibited  on 
t!ie  inner  side  flat,  light  brown  cushions  irregularly  distributed  and  differing 
in  size  and  thickness.  Having  a  spongy  consistency,  they  easily  gave  way 
to  the  pressure  of  a  finger-nail.  Here  and  there,  between  them  could  be 
seen  crater-like,  harder,  small  protuberences.  The  upper  surface  of  the 
cushion  was  smooth  ;  it  was  rough  and  sometimes  woolly  in  places  because 
of  prominent,  hair-like  processes.     The  part  of  the  Itark  remaining  on  the 


.hion-like, 


of    a    fallen    piece 
protruding-    tissue 


of    elm 
islands. 


1    Lehrbuch   der  Prtanzenkrankh,   1900,   p.    261. 
3    Unters.  Vol.  I,  1880,  p.  45. 


329 


Iree  appeared  a  yellowish  green  and  juicy.    It  consisted  of  bark  parenchyma, 
which  had  originated  from  a  healthy  cambium. 

The  subjoined  Fig.  46 


t.. 


pictures  the  bark  about  \.o 
be  shed.  At  h  is  shown 
the  old  wood;  at  nh  the 
last  produced  new  wood ; 
g  indicates  ducts ;  c  the 
cambium.  Next  this  lies 
the  normal,  young  bark 
which  gradually  passes  sp. 
over  towards  the  outside 
into  the  broken  older  bark. 
In  reality  the  extent  of 
loosened  older  bark  is 
much  greater  in  proportion 
to  the  normal  young  bark 
than  is  shown  in  the  draw- 
ing, because  of  lack  of 
space.  The  normal  inner 
bark  has  a  very  regular 
structure,  in  which  layers 
of  porous  bark  parenchyma 
alternate  regularly  with 
flat  bands  of  slender  cells 
(/)  which  might  be  differ- 
entiated as  "wedge-cells." 
These  slender  cell  bands 
would  correspond  to  the 
"pressure  wedges"  men- 
tioned in  connection  witli 
the  tan  disease.  The  cells 
forming  these  wedges  ap- 
pear in  longitudinal  section 
as  long  as  in  cross-section, 
nearly  colorless,  with  pe- 
culiar, wide-meshed  wall 
thickenings,  looking  like 
irregular  wedges.  The 
parenchyma  lying  between 
every  two  such  thin,  slen- 
der bands  of  wedge  cells  is 
proportionately  large-celled,  porous  and  rich  in  starch.  Deposited  in  it 
are  large,  hard  bast  bundles,  {h)  with  the  rows  of  calcium  oxalate  crystals 
accompanying  it  (0)  and  the  cells  {si)  containing  mucilage. 


TTlSt 

Fig'.  46.     Elm  bark  with  barlv  excrescence.     (Orig.) 


330 

These  alternating  tissue  layers  are  separated  by  broad  curved  medul- 
lary rays  (mst)  which  even  in  the  entirely  healthy  bark  can  exhibit  a  wavy 
course,  but  in  the  diseased  bark  may  often  be  displaced  and  take  a  hori- 
zontal course.  The  sharp  curvature  is  caused  by  the  spreading  apart  of  the 
parenchyma  cells  which,  containing  chlorophyll  and  lying  between  the  slen- 
der bands  of  wedge  cells,  elongate  into  pouches,  and  for  a  long  time  contain 
a  great  deal  of  starch.  They  also  press  outward  the  hard  bast  bundles  and 
the  rows  of  oxalate  crystals.  This  great  layer  of  separation  is  covered  by  a 
plate  cork  layer  extending  irregularly  into  the  tissue  and  often  accompanied 
by  full  cork  (J)  and  the  suberized  bark  tissue  cut  off  by  it  which  belonged 
to  the  earlier  period  of  growth  (k).  The  cork  layer  often  curves  spherically 
into  the  pouch-like  spongy  tissue  (sp)  and  forms  the  hard,  crater-like  points 
on  the  under  side  of  the  loosened  bark  scale,  which  were  mentioned  at  the 
beginning  of  this  description.  The  process  of  loosening  the  bark  tatters  is 
completed  on  the  boundary  between  the  hard  tissue  of  the  suberized  cortex 
of  the  previous  year,  and  the  soft  pouch-like  parenchyma.  The  upper  sur- 
face of  the  separating  cushions  appears  woolly  and  rough,  or  smooth, 
according  to  whether  the  pouch-like  parenchyma  clings  more  or  less  strongly 
to  the  separating  surface. 

In  the  elongation  of  the  parenchyma  these  out-pushings  differ  from  the 
tan  disease  in  which  cork  excrescences  are  concerned  essentially. 

von  Tubeuf  ^  describes  a  case  of  the  Weymuth  pine  very  similar  to  that 
on  Ulmus,  only  no  shedding  of  the  bark  strips  could  be  observed  because 
of  the  smoothness  of  the  bark.  The  pine  was  diseased  and  covered  with 
cushions  of  Xanthoria  parietina.  Among  these  lichens  were  found  blister- 
like processes,  of  which  part  appeared  to  be  split  and  were  produced  by  a 
distention  of  the  bark  tissue.  The  resin  ducts  were  enlarged,  the  deeper 
bark  parenchyma  cells  elongated  into  pouches  and  poor  in  chlorophyll. 

von  Tubeuf's  statement  that  he  had  produced  very  similar  knob-like 
processes  on  a  branch  by  wrapping  it  with  cotton  wadding  which  was  kept 
constantly  moist,  warrants  the  assumption  that,  in  the  cases  above  described, 
w^e  perceive  the  action  of  a  local  excess  of  water. 

The  same  kind  of  processes  as  these  in  the  bark  have  been  observed 
on  roots  also.  Some  years  ago  a  serious  disease  of  the  grapevine  was  re- 
ported from  near  Lindau".  Its  effects  were  similar  to  those  caused  by  the 
rust  fungus,  but  it  could  not  be  proved  to  be  of  parasitic  origin.  The  part 
of  the  trunk  beneath  the  soil  and  the  older  roots  exhibited  tears  i  to  3 
cm.  long  from  which  protruded  calluses,  white  at  first  but  later  turning  a 
chocolate  brown.  The  lateral  roots  near  these  calluses  died.  The  calluses 
consisted  of  bark  parenchyma  cells  abnormally  lengthened  radially  and 
scarcely  connected  any  longer.  The  American  varieties,  scattered  among 
the  diseased  European  vines,  were   found  to  be  unaffected.     As  is  well- 


1  V.    Tubeuf,    Intumescenzenbildung    der   Baumrinde    unter    Flechten.      Naturw. 
Zeitschr.    f.    Land-   u.  Forstwirtsch.    1906,   p.   60. 

2  Kellermann   im    Jahresber.    d.    Sonderausschusses    f.    Pflanzenschutz.     Arb.    d. 
Deutsch.  Landw.-Ges.  1892-93. 


331 

known,  the  extremely  luxuriantly  growing  American  vines  consume  much 
greater  amounts  of  water. 

Tissue  warts  of  this  kind  are  much  more  abundant  than  is  generally 
assumed  and  occur  also  on  decorative  plants\  They  are  reactions  of  the 
plant  body  to  a  wound  stimulus  or  internal  disturbances  of  equilibrium  in 
the  supply  of  water  and  nutritive  substances. 

Watersprouts. 

By  the  term  watersprouts,  watershoots,  or  suckers,  are  understood  ex- 
ceedingly vigorous  foliage  shoots  with  long  internodes,  which  grow  up 
perpendicularly  from  old  branches  or  trunks.  Often  trunks  covered  with 
lichens  are  distinguished  by  abundant  sucker  formation.  Since  the  suckers 
grow  up  into  the  crown  of  the  tree,  they  produce  wood,  and,  indeed,  un- 
fruitful wood,  at  the  very  places  which  it  is  desirable  to  keep  free  from 
branches  in  order  that  sufficient  light  and  air  may  reach  the  inner  part  of 
<-he  crown.  It  is  not  advisable,  however,  to  remove  the  suckers,  if  the 
cause  of  their  formation  is  not  removed  at  the  same  time.  In  many  cases 
the  cause  may  be  found  in  an  impervious  subsoil.  The  roots  of  the  vigorous 
tree  reach  this  impenetrable  layer  sooner  or  later,  which  not  infrequently  is 
y  vein  of  closely  cemented  sand  containing  iron.  The  absorption  of  food 
stufifs  is  limited  by  this,  the  tree  forms  only  short  shoots  and  smaller  leaves, 
but  still  bears  fruit.  In  a  warm  and  damp  spring,  when  all  trees  make  a 
strong  foliage  growth,  the  energy  of  the  weakened  tree  also  appears  to  be 
increased  by  the  favorable  vegetative  conditions.  The  strong  upward  force 
of  the  water  causes  the  formation  of  adventitious  buds  or  stimulates  dor- 
mant buds,  especially  those  not  too  far  distant  from  the  central  trunk,  since 
the  upward  force  of  the  water  and  the  nutrition  is  much  more  energetic  in 
a  perpendicular  direction  than  in  the  more  inclined  position.  Gardeners 
know  how  to  turn  this  to  use  in  growing  plants  on  trellises.  The  horizontal 
branches  on  one  side  of  the  mam  trunk,  which  are  weaker  than  the  corres- 
ponding ones  on  the  other  side,  are  held  in  a  perpendicular  position  for  a 
year.  This  treatment  results  in  a  much  greater  and  more  rapid  growth 
and  development.  With  the  production  of  water  shoots  a  gradually  in- 
creasing inequality  in  nutrition  sets  in,  at  the  expense  of  the  older,  more 
horizontal  branches  which  now  suffer  from  scarcity  of  nourishment.  This 
explains  the  death  of  the  tip  twigs  of  older  lateral  branches  which  begins 
with  the  appearance  of  the  water  shoots.  One  part  of  the  tree  starves  when 
some  other  part  develops  very  luxuriantly. 

As  has  been  said,  it  is  scarcely  advisable  to  remove  the  water  sprouts 
during  such  a  disturbance  in  the  equilibrium  of  nutrition,  rather,  it  is  more 
advantageous  in  older  trees  to  graft  them  with  valuable  varieties  and,  at 
the  same  time,  to  saw  ofif  a  part  of  the  older  branches,  so  that  the  tree  is 
thus  rejuvenated.     In  places  where  the  sub-soil  cannot  be  opened  up  easily 


Sorauer,  P.,  tjber  Rosenkrankeiten,  Zeitschr.  f.  Pflanzenkrankh.    1898.    p.  220. 


332 


tlic  evil  can  be  checked  for  a  considcraU'e  number  oi  years  by  using  ferti- 
lizers at  some  distant  from  the  trunk.  The  tree  in  its  endeavors  to  reach 
the  fertihzer  develops  a  new  vigorous  P.ni  system,  ^'oung  trees  can  be 
entirely  cured  by  transplanting. 

It  must  also  be  emphasized  that  the  formation  of  suckers  disappears 
of  itself  from  many  trees  after  a  few  years.  This  is  the  case  where  such 
water  sprouts  have  been  induced  by  an  excessive  pruning  of  the  tree  or  the 
sudden  dressing  of  the  trunks.  In  avenues  of  trees,  or  along  streets  with 
telephone  wires,  and  in  tree  plantations,  through  which  a  street  or  railroad 
line  has  been  cut,  a  strong  development  of  suckers  is  found  on  the  sides 

of  the  trees  toward  the 
street. 

In  sucli  cases  large 
tranches  are  often  sim- 
ply chopped  ofif  on  the 
side  toward  the  street. 
Since  the  root  system 
remains  unimpaired,  it 
pumps  up  just  as  much 
water  as  before  the  tree 
toi)    had    been    reduced. 


l!v      the      removal 


ated    branch    of    Picea 


rhf  oritrinal  baiid-likc  shoot  (/),  in  one  year,  ha.s  developed  llirce  svic 

cessive  stages  wliicli  sprout  out  from  one  another  iJ, .?,  ^}.    (a)  liiid 

scales,     d/z  natural  size.     After  Nobbe.) 


the  branches,  however, 
there  is  less  consumption 
and  consequently  dor- 
mant buds  are  awakened 
which  mature  into  slen- 
der shoots,  becoming 
water  sprouts  whose 
buds  often  sprout  even 
in  the  }ear  of  their  pro- 
duction. Th.  Ilartig' 
has  obser\ed  tliat  these 
premature  shoots  de- 
velop no  basal  buds. 

If  suckers  are  pro- 
duced by  the  sudden  re- 
moval of  large  branches  from  the  crown,  their  formation  may  be  retarded 
by  creating  other  diverting  centers  by  scarification.  In  the  spring  pruning 
of  branches,  scarifying  will,  indeed,  prevent  the  formation  of  the  water 
shoots.  In  the  same  way,  chopping  into  a  vigorous  root  near  the  base  of 
the  trunk  at  the  side  where  the  tree  crown  has  been  greatly  thinned  out. 
will  diecrease  the  supply  of  water  and  prevent  the  sucker  formation. 


Fig-.   IS.     Cross-section  of  the  fasciated  spruce  branch. 

A  through  the  upper  part  of  the  branch;  Ji  throusrh  the  lower  part : 

((/)  bark  with  needle  cushions:  (*)  wood:   (.1 )  pith. 

(Natural  size.     After  Nobbe). 


1  Vollstandige   Naturg-eschichte   d.   forstl.   Kulturpflanzen,   p.    176 


333 
Union  of  Parts. 

We  may  likewise  consider  as  due  to  local  over-nutrition  the  con- 
dition arising  when  a  cylindrical  branch  becomes  broad  and  flattened.  It 
then  looks  as  if  a  number  of  branches  had  grown  together;  nevertheless, 
this  is  only  rarely  the  case,  for  almost  always  only  a  single  branch  is  in- 
volved which,  by  broadening  its  vegetative  point,  no  longer  has  a  vegetative 
cone  at  its  apex,  but  a  comb-like  vegetative  surface'. 

In  the  illustration  of  a  spruce  fasciation  here  given  (Fig.  47)  we  recog- 
nise the  fact  that  the  broadened  axis  is  a  single  unit,  first  by  the  continued 


Fig-.  49.     Fasciation  of  Alnus  glutinosa. 

I'X  Tiatui-alsize.     Aftei  Nolibc). 


Spiral  position  of  the  needles,  especially  at  /  and  2,  and  further  in  the  cross- 
sections  A  and  B  (Fig.  48),  of  which  the  pith  and  wood  form  a  single 
connected,  uniform  surface,  and  do  not  show  any  possible  coalescence  of 
many  single  adjacent  rings,  as  must  be  the  case  where  fasciation  is  produced 
by  the  coalescence  of  many  branches  originally  separated.  This  theor}"^  is 
not  changed  by  a  consideration  of  the  fasciation  of  the  alder  (Fig.  49),  in 
v,'hich,    besides    the    unusually    characteristic    crook-like    bending    of    the 


tJber  Pflanzen-Verbanclerung-.     Referat  in   Bot.   Zeit.    1867,   p.   232. 


334 

branches,  resulting  from  a  one-sided  increase  of  growth,  we  can  also  per- 
ceive the  splitting  of  cylindrical  branches  from  the  band  bodies  which 
occurs  more  frequently  in  deciduous  trees.  Thus  the  material  for  many 
axes,  which  can  be  isolated,  lies  accumulated  in  the  fasciated  stem,  while 
the  stem  itself  is  a  unit. 

We  can  speak  only  hypothetically  as  to  the  production  of  the  fasci- 
ations,  which  are  characterized  as  hypertrophies  by  the  great  increase  of 
the  leaves  and  cords  of  the  leaf  spurs.  An  axis,  which  fasciates  later,  must 
originally  have  suffered  some  arrestment.  We  have  seen  already  in  roots 
held  fast  between  split  rocks  that  pressure  from  two  opposite  sides  may 
give  the  axis  a  band-like  form.  Under  certain  circumstances  such  a  changed 
direction  of  growth  may  continue  if  the  cause  of  arrestment  itself  has  dis- 
appeared. Thus  Treviranus  cites  an  observation  on  the  stem  of  Tccoma 
radicans  which  had  become  band-like  from  pressure  against  the  wall,  but 
still  remained  band-like,  after  it  had  grov.-n  far  out  over  the  wall.  Here 
the  branches,  which  developed  further,  also  became  band-like  in  places. 

Besides  such  lateral  pressure,  in  other  cases  a  transitory  pressure  from 
above  may  also  probably  cause  a  broadening  of  the  vegetative  point  into  a 
vegetative  surface,  and  such  pressure  can  possibly  be  produced  by  the  ab- 
normal behavior  of  the  bud  scales  (delayed  loosening  due  to  resinification, 
dr}'ing,  etc.).  In  case  no  abnormal  increase  of  pressure  occurs,  direct  in- 
juries to  the  vegetive  tip  may  cause  the  increase  of  the  vegetable  points. 

If  the  fasciation  has  once  been  produced,  it  can  be  propagated  by 
cuttings ;  even  under  certain  circumstances  it  can  be  proved  constant  in  the 
seed,  as  is  seen  in  the  favorite  garden  plant,  cock's  comb  (Celosia  crisfata). 
The  capacity  for  fasciation  may  be  presupposed  in  all  plants  and  actually 
obserA'ed  cases  have  been  reported  in  great  numbers  (150)  by  Masters'. 
As  mentioned  already,  the  fasciated  growth  produced  by  a  band-like  fasten- 
ing together  of  isolated  axes,  should  be  distinguished  from  real  fasciation. 
Lopriore-  has  produced  such  cases  artificially  in  roots. 

Compulsory  Tu'isting  (Spiralismus  Mor.). 

A.  Braun''  characterizes  by  the  above  name,  those  malformations  of 
the  stem  which  consist  of  barrel-like  distended  places  in  which  the  grooves, 
extending  down  from  the  leaves  and  representing  the  vascular  bundles  be- 
longing to  them,  exhibit  an  extreme,  spiral  twisting.  At  times  the  barrel- 
like swelling  is  so  great  that  the  stem  splits  in  the  direction  of  the  spiral 
twisting  and  divides  into  a  number  of  spiral  bands  at  these  diseased  places. 
Schimper  has  named  this  disturbance  in  growth  "Strophomania."  The  ma- 
jority of  cases  are  known  in  the  families  of  the  Dipsaceae,  Compositae  and 
the    Rubiaceae.      Single    examples    are    described    also    for    the    Labiates, 


1  Masters.  Veg-etable  Teratology,  1869,  p.  20.     (Compare  Penzis-  and  the  isolated 
cases  in  the  Bot.  Jtihresberichten.) 

2  Lopriore.  G.,  Die  Anatomie   bandartig-er  Wurzeln.     Cit.  Zeitschr.  f.   Pflanzen- 
krankheiten.  1904,  p.   226. 

3  Sitzung-sberichte  naturf.  Freunde  z.  Berlin.     Cit.  Bot.  Zeit.  1873,  p.  11  and  20. 


335 

Scrophulariaceae,  Cruci ferae  and,  among  monocotyledons,  Asparagus, 
Lilium,  Orchis,  Triticum.  etc.,  and  also  in  Equisetum. 

We  think  it  justifiable  to  consider  the  compulsory  torsion  as  a  fasci- 
ation  which  has  swollen  up  like  a  barrel.  The  cases  have  no  agricultural 
significance. 

Difl^ering  from  them  is  the  increased  spiral  twisting  of  normally  con- 
structed woody  trunks,  which  we  trace  to  an  arrestment  of  the  growth  in 
length  (usually  resulting  from  a  lack  of  water  and  nourishment). 

Dropsy  (Oedema). 

a).     In  Small  Fruits. 

Since  the  propagation  of  standard  gooseberries  and  currants  by  budding 
on  vigorous  shoots  of  Rihes  aureum  has  found  wider  distribution,  there  has 
been  a  great  increase  in  the  complaints  of  a  disease  of  the  stock  which  makes 
doubtful  the  success  of  the  budding. 

This  disease  has  been  called  "dropsy"  by  growers  and  consists  in  the 
appearance  of  closed  bark  tumors,  i.  e.  of  bark  swellings  entirely  covered 
by  the  outermost  cork  layers,  or  of  swellings  rupturing  later  (Fig.  ^o  A). 
These  swellings  of  the  bark  are  sometimes  small,  but  they  may  reach  an 
extent  of  several  centimeters.  They  are  formed  either  on  one  side  of  the 
trunk  or  surrounding  it,  spreading  into  one  another.  They  appear  most 
abundantly  on  wood  two  or  more  years  old,  yet  they  can  also  occur  in  great 
numbers  on  branches  one  year  old  and  directly  cause  their  death,  while  the 
wood  of  the  older  branches  mav  become  diseased,  to  be  sure,  but  does  not 
directly  die. 

^^'hen,  as  is  the  custom  at  present,  Ribes  is  'grafted  indoors  in  the 
spring,  rupturing  tumors  are  found  frequently  directly  below  the  place  of 
budding.  In  such  cases  the  bud  does  not  grow.  But  in  extreme  cases  the 
same  kind  of  swellings  may  also  be  found  further  back  from  this  place,  on 
the  trunk  between  every  two  buds,  as  well  as  near  the  buds  or,  rather,  the 
branches  already  developed  from  them.  Cases  are  observed  in  which  the 
base  of  a  shoot  left  standing  on  wood  one  or  two  years  old,  has  swollen 
up  like  a  barrel  and  is  covered  by  loose,  hanging  strips  of  bark.  The  branch 
above  this  place  is  dead. 

As  soon  as  the  bark  layer,  which  forms  the  outer  skin  of  the  branch 
and  covers  this  fresh  swelling,  has  split,  the  swollen  place,  pushing  out  from 
under  it,  exhibits  a  yellowish,  spongy,  soft,  callus-like  tissue-mass  con- 
sisting of  cells,  elongated  to  pouches,  very  poor  in  contents  but  rich  in 
water.  (Fig.  50  i?  s).  This  is  the  former  normal  bark  of  which  the  cells 
beginning  in  the  region  between  every  two  groups  of  bast  cells  (Fig.  $0  B  b) 
have  elongated  extraordinarily  in  the  direction  of  the  trunk's  radius  at  the 
expense  of  their  contents,  otherwise  rich  in  green  coloring  matter.  The}' 
have  partially  separated  from  one  another,  and,  by  their  constantly  in- 
creasing extent,    have   finally   ruptured    the   outermost   oldest  bark   layers 


336 

(Fig.  ^o  B  e  k)  which  no  longer  participate  in  the  changes  and  are  sep- 
arated prematurely  by  the  cork  layers  (k)  from  the  tissue  lying  beneath 
them^ 

The  full  thickness  of  the  bark  is  not  always  attacked  by  the  pouch-like 
elongation  ;  in  very  severe  cases,  however,  even  the  cells  of  the  cambial 
region  are  deformed  (c).  The  wood  is  no  longer  normal.  Instead  of  normal 
mature  wood,  consisting  of  thick-walled,  elongated  wood  cells  and  ducts, 


Fig:.  50.     Dropsy  in    Ribes  aureum.     (Orig.) 


with  cross  walls  broken  through  like  ladders,  a  wood  is  produced,  composed 
of  short,  broad,  comparatively  thin-walled,  parenchymatous  cells  {h  p).  The 
cross-section  (Fig.  50  B)  shows  the  transition  of  the  healthy  side  of  the 
branch  (A'')  into  the  dropsical  side  (W)  ;  h  indicates  the  normal  wood.  At 
the  time  when  the  layer  st  was  produced,  the  disease  manifested  itself  in  the 

1  Compare  Sorauer  in  "Freihoff  s  Deutsche  Gartnerzeitung^'  August  1,  1880,  and 
Goschke  in  Monatsschrift  d.  Ver.  z.  Beford.   d.  Gartenb.   October,   1880,   p.  4.51. 


337 

cambium  and  the  result  was  that,  from  there  down  on  the  diseased  side, 
parenchyma  wood  {h  p)  was  formed  which  at  the  left  ended  in  a  medullary 
ray  {m).  Still  further  towards  the  left,  normal  wood  was  produced  at  the 
same  time.  The  same  difference  is  found  in  the  youngest  bark  parenchyma 
{r  p).  Because  of  the  great  radial  elongation  of  the  cells  on  the  dropsical  side 
(W)  the  hard  bast  cords  {h)  are  pressed  out  like  bows  and  the  cell  rows, 
containing  calcium  oxalate  (o),  which  accompany  the  bast  body,  have  also 
been  correspondingly  misplaced  into  steeply  ascending,  irregular  rows.  At  chl 
are  groups  of  parenchyma  which  have  remained  rich  in  chlorophyll.  It  is 
evident  that  this  loose  structure  of  the  tissue,  rich  in  water,  which  forms 
the  swelling,  has  no  great  permanency.  In  dry  places  and  with  increasing 
dryness  in  the  air,  this  tissue  turns  brown  rapidly,  shrivels,  collapses  and 
forms  a  soft,  brown  mass,  part  of  which  remains  clinging  to  the  wood,  while 
part  sticks  to  the  outer  bark  tatters  which  roll  back  in  times  of  drought  and 
spread  out,  gaping,  from  one  another.  Such  stems  of  such  plants  then 
have  a  rusty  appearance  and  are  best  excluded  from  cultivation.  Because 
of  the  ease  with  which  such  stock  can  be  grown  on  strong  soils,  the  loss 
from  the  disease  would  be  less  important,  if  it  did  not  attack  directly  the 
potted  specimens  which  have  been  budded  and  if  the  number  of  budded 
plants  was  not  considerably  decreased  thereby. 

I  am  not  of  the  opinion,  often  expressed  in  general  practice,  that  an 
over-abundant  feeding  of  the  plant  is  to  blame,  but  I  think  that  an  excess 
of  water  makes  itself  felt  in  some  places  on  the  axis.  If  there  should  be 
an  accumulation  of  plastic  food  material  here  at  the  same  time,  it  would 
manifest  itself  preferably  by  an  abundant  cell  increase.  But  this  is  not  the 
case.  If  the  cells  on  the  healthy  and  on  the  diseased  sides  are  counted,  only 
an  insignificant  preponderance  is  found  on  the  side  attacked.  Accordingly, 
an  abnormal  cell  elongation  is  chiefly  concerned  here. 

This  is  explained  by  the  treatment  of  the  Ribes  stems  during  the 
preparation  for  budding.  In  order  to  obtain  slender  stems,  growing  tall 
rapidly,  the  other  sprouts,  produced  at  the  sides,  must  be  removed  and 
even  the  lateral  branches  on  the  young  stock  must  be  cut  back. 

If  now  the  stock  is  well  rooted,  it  will  grow  rapidly  in  the  greenhouse 
and  the  buds,  scantily  present  because  of  the  earlier  pruning,  are  still  fur- 
ther decreased  by  the  fact  that  the  shoots  developing  from  them  are  cut 
back  or  entirely  removed.  By  cutting  ofif  the  branches,  the  amount  of  water 
forced  up  by  the  water  pressure  is  increased  in  the  main  axis  and  manifests 
itself  in  a  pouch-like  elongation  of  the  younger  bark  cells  and  in  the  forma- 
ion  of  tumor  swellings  which  finally  rupture. 

My  attempts  to  produce  dropsy  by  abundant  watering  and  the  rapid 
forcing  of  well-rooted  specimens  in  the  greenhouse,  together  with  a  con- 
tinued removal  of  the  developing  lateral  shoots,  gave  very  favorable  results. 

The  disease  will  be  prevented  if  the  budded  stock  is  not  forced  too 
rapidly  and  the  sprouts  from  the  bud  are  cutting  back  carefully,  but  not 


338 

entirely  removed.  Maurer^  has  recommended  the  use  of  Ribes  nigrum  in- 
stead of  R.  aureum  for  budding  stock.  However,  I  have  also  known  of 
cases  of  excrescences  on  the  axes  of  the  black  currant,  especially  after  the 
transplanting  of  such  plants  as  tend  to  sterility. 

b).     In  Stone  Fruits. 

It  may  be  foreseen  that,  with  the  present  methods  of  culture,  phenom- 
ena similar  to  those  observed  with  Ribes,  will  also  appear  in  other  vari- 
eties, for  our  fruit  trees  are  becoming  more  and  more  delicate,  due  to  the 
great  increase  in  nutrition  supplied  them.  The  mass  of  the  parenchy- 
matous branch  substance  increases  constantly  in  comparison  with  the 
prosenchymatous  tissues.  Between  unbudded,  wild  stock,  and  budded 
varieties  there  are  considerable  differences.  Direct  measurements  have 
shown  me  that  the  branches  of  the  cultivated  varieties  acquire  a  fleshier 
bark  while  the  wood  ring  decreases  considerably  in  thickness-.  I  have 
called  this  increasing  tendency  of  our  fruit  trees  to  form  soft,  parenchy- 
matous tissues,  storing  up  reserve  substances,  at  the  expense  of  the  breadth 
of  the  wood  ring,  " parenchymatosis." 

In  special  cases  this  change  in  development  acquires  such  extreme  pre- 
ponderance that  diseases  arise.  I  observed  such  diseases  especially  in  the 
fruit  wood  of  pears  which  is  often  shortened  up  to  barrel-like  fleshy  swell- 
ings; growers  call  these  "Fruchtkuchen."  The  morbid  disturbance  con- 
sists either  in  the  shedding  of  the  cork  layers  and  outermost  bark  layers  in 
shield-shaped  pieces  from  the  side  of  the  branch,  thus  showing  a  greenish 
yellow  callus-like  tissue  mass,  or  in  the  uplifting  of  the  bark  itself  in  stiff, 
crumbly  scales,  like  rings  extending  almost  around  the  whole  branch,  with 
similar  changes  in  the  tissues.  In  the  latter  case,  all  the  branches  found 
above  such  a  place  are  dead. 

If  the  diseased  condition  manifests  itself  in  a  less  luxuriantly  developed 
fruit  wood,  which  may  be  distinguished  from  the  "Fruchtkuchen,"  as  fruit 
spears,  a  complete  casting  of  these  twigs  was  often  found  resembling  that 
of  the  normal  dropping  of  the  twigs  observable  every  year  in  poplars.  In 
the  present  abnormal  dropping  in  pears,  the  exposed  surface  was  not  smooth 
but  uneven  and  woolly,  light  colored,  however,  like  the  cross-section  of 
healthy  wood. 

A  cross-section  through  a  place  in  the  branch  which  is  found  in  the 
first  stages  of  the  disease,  shows  that  the  bark  has  developed  strongly  on 
one  side,  especially  within  the  primar}^  bark.  Its  parenchyma  is  thin-walled, 
vesiculated  in  places  or  pouch-like  and  extremely  porous. 

A  comparison  of  the  pith  in  a  branch  which  has  split  and  in  a  healthy  one 
'^f  equal  age  shows  that  the  former  is  one-third  larger  than  the  latter,  while 
the  wood  ring  is  only  one-third  as  wide.  Significant  structural  differences 
are  connected  with   these  misproportions.     While   a  healthy  shoot  shows 


1  Der  Obstgarten,  1879,  p.  182. 

2  Sorauer,    P.    Nachweis   der   Verweichliehung    unserer    Obstbaume 
Kultur.  Zeitschr.  f.  Pflanzenkrankh.    1892,  p.  66, 


339 

normal  libriform  fibres  and  an  abundantly  developed  vascular  system,  the 
wood  of  the  diseased  branch  is  made  up  almost  exclusively  of  parenchy- 
matous thin  cells,  between  which  the  vascular  cords  are  deposited.  In 
normal  trees,  under  certain  circumstances,  the  weakness  of  the  wood  ring 
can  be  compensated  for  by  schlerenchymatous  elements  in  the  bark^. 

The  dropsical  branches  of  pears  differ  from  those  of  Ribes  in  that  the 
wood  body  is  also  involved  in  the  parenchymatosis  and  entirely  broken  up. 
By  the  rounding  up  and  dilation  of  the  wood  cells,  which  have  become  par- 
enchymatous, the  ducts  are  gradually  curved,  displaced  and  finally  torn. 
Just  as  soon  as  the  loosening  process  has  affected  the  whole  extent  of  a 
fruit  spear,  or  a  "Fruchtuchen,"  dropping  follows. 

The  diseased  branches  came  from  trellised  trees  in  a  well  watered 
garden,  richly  fertilized  with  cow-manure. 

Even  if  such  extreme  cases  are  less  frequent,  yet  the  first  stages,  con- 
sisting of  the  widening  and  excrescence  of  the  medullary  rays  and  the  pro- 
cesses of  elongation  in  various  groups  of  bark  cells,  are  often  observed. 

Swellings  on  the  St.  John's  Bread  Tree. 

Swellings  often  appear  as  a  result  of  cell  elongation  and  cell  increase. 
Savastano-  reports  thus,  for  example,  of  the  outgrowths  on  the  branches  of 
Ceratonia  Siliqua.  Conical  outgrowths,  rich  in  tannin,  are  found  at  the 
tips  of  the  flower  stalks,  causing  atrophy  of  the  blossoms.  In  an  earlier 
study^,  he  describes  the  production  of  larger  swellings  on  the  St.  John's 
Bread  tree.  On  normally  developed  fruit  branches,  in  the  beginning  of  the 
disease,  the  fruit  falls  in  the  first  stages  of  development  and  the  remaining 
basal  part  of  the  axial  cone  begins  to  swell.  The  repetition  of  this  process 
in  succeeding  years  produces  a  knotty  swelling  which  can  attain  a  very  con- 
siderable size  and  a  height  of  6  to  lo  cm.  The  bark  of  this  hypertrophied 
tip  of  the  fruit  twig  is  often  seven  times  as  thick  as  that  on  the  normal 
fruiting  wood  and  the  wood  itself  consists  of  ductless  wood  parenchyma. 
In  the  almost  pithy  bark,  the  bast  fibres  have  wider  lumina  and  take  an 
unusual  course.  The  medullary  rays  are  twisted,  the  wood  ring  is  often 
bent.  In  the  parenchyma,  various  cell  groups  with  discolored  walls  and  a 
gummy  content  are  recognizable.  From  the  beginning  of  the  disease,  the 
tannin  content  of  the  swelling  increases,  causing  a  distinct  disturbance  in 
lignification. 

A  case  described  by  Vochting*  in  Kohlrabi  plants  may  be  mentioned 
here.  If  all  the  vegetative  points  were  removed,  the  leaf  cushions  swelled 
to  extensive  structures.  In  the  normal  wood  of  the  axis,  as  in  the  leaf 
cushions,  the  cambium  developed  thin-walled  xylem  elements.     In  similar 


1  Pieters,  A.,  The  influence  of  fruit-bearing  on  the  development  of  mechanical 
tissues  in  some  fruit  trees.     Ann.  of  Bot.     Vol.  10.     London,  1896.     P.   511. 

2  Savastano,    L,.,    Tumori    nei    coni    gemmarii    del   carubo.    Boll.    d.    Society    d. 
Naturalisti  in  Napoli.     1888.     Vol.  H,  p.  247. 

3  Savastano,  L..,  Hypertrophie  des  cones  k  bourgeons  (maladie  de  la  loups)  du 
Caroubier.     Compt.  rend.   12.  Janv.   1885. 

4  Vochting-,  H.,  Zur  experimentcllen  Anatomie,  cit.  Bot.  Jahresb.  1902.  II,  p.  300. 


340 

experiments  with  Helianihus  annuus  Vochting  found  little  tubercles  formed 
on  the  roots.  I  observed  barrel-like  thickenings  of  the  sharply  bent  roots 
of  sweet  cherries. 

The  swellings,  described  by  Warburg'  in  the  branch  canker  of  the  kina 
tree  on  damp  soils,  may  also  represent  such  correlation  phenomena. 

Retrogrkssive  Metamorphosis   (Phyllody). 

If  the  organs  of  a  morphologically  higher  developmental  stage  seem 
transformed  into  those  of  a  lower  one,  we  speak  of  a  retrogressive  meta- 
morphosis. The  change  in  the  blossoming  organs  is  pathologically  of  mo- 
ment only  if  the  sexual  apparatus,  by  changing  into  a  group  of  vegetative 
organs,  loses  the  purpose  for  which  it  was  designed  and  thereby  initiates 
sterility. 

These  cases  are  listed  under  the  group  of  phenomena  caused  by  excess 
of  water  and  nutriment,  in  accordance  with  the  following  theory.  The 
development  of  the  vegetable  organism  depends  upon  two  factors,  the  con- 
stitution of  the  organic  building  materials  and  the  way  in  which  they  are 
utilized.  With  the  assumption  that  the  first  achievement  of  the  organism, — 
assimilation,  i.  e.,  the  formation  of  new  dry  substance, — takes  place  in  a 
normal  way,  the  development  of  the  plant  depends  upon  the  way  in  which 
this  organic  building  material  is  utilized.  In  this  we  recognize  two  directions 
which  we  will  keep  separate  as  the  vegetative  and  the  sexual  generations. 
The  latter  is  initiated  usually  by  the  appearance  in  the  organism  of  an  often 
clearly  recognizable  dormant  period  in  the  production  of  its  vegetative 
apparatus.  As  a  rule,  new  leaves  are  not  formed  at  this  time,  the  apical 
growth  of  the  twigs  stops.  In  place  of  this  the  process  of  the  storage  of 
reserve  building  material  becomes  conspicuous. 

We  find  this  storage  process  initiated  and  favored  by  a  decrease  in 
the  absorption  of  water  with  increasing  light  and  heat.  An  increased  con- 
centration of  the  cell  sap  is  required,  if  the  reserve  substances,  for  ex- 
ample, are  deposited  in  the  form  of  starch.  If  such  a  concentration  cannot 
be  obtained  under  any  circumstances  whatever  and  the  building  substances 
remain  in  a  diluted  form, — for  example,  sugar, — only  a  slight  impetus  is 
necessary  to  start  up  vegetative  activity.  Thus,  a  certain  antagonism  pre- 
vails between  the  two  developmental  phases,  which  we  may  consider  as 
transmissable  adaptations  to  atmospheric  conditions.  After  a  cool  wet 
period  when  the  plant  takes  mineral  substances  from  the  soil  and  through 
the  production  of  the  leaves  causes  the  chlorophyll  apparatus  to  attain  to 
its  richest  possible  development,  a  warmer,  drier  period  follows  which 
makes  possible  the  greatest  amount  of  light.  In  this  period  the  sexual 
organs  are  formed  from  the  finished,  plastic  building  materials  prepared 
in  the  leaves  and  develop  further,  after  a  shorter  or  longer  dormant  period. 

1    Warburg-,    O.,    Beitra^    zur   Kenntnis   ties    Krebses   der   Kinabaume   auf   Java. 
Cit.  Bot.  Centralbl.  1888.     Vol.  XXXVI,  p.  145. 


341 

The  more  the  plastic  material  is  worked  up  by  the  leaves,  the  more 
numerous  and  perfect  are  the  sexual  organs  formed  within  this  dormant 
period.  The  manner  in  which  these  primordial  buds  subsequently  develop 
depends  on  the  nature  of  their  further  nourishment.  If  influences  make 
themselves  felt  which  are  necessary  for  the  maturing  of  the  vegetative 
organs,  foliage  leaves  will  develop  and,  indeed,  either  from  the  newly 
formed  centres  or  from  the  already  existing  primordia  of  the  sexual  gene- 
ration.    Thus  "phyllody"  takes  place. 

From  our  experience  in  horticulture,  we  know  that  an  abundant  supply 
of  nutritive  substances  with  a  simultaneous  increase  in  warmth  and  mois- 
ture, usually  at  the  time  of  a  lesser  light  action,  are  conditions  initiating 
and  favoring  the  process  of  phyllody.  This  becomes  especially  apparent 
in  the  production  of  double  flowers,  in  which  the  stamens  are  transformed 
into  petals. 

Since  this  process  can  become  hereditary,  like  all  changes  in  the  di- 
rection of  growth,  where  conditions  remain  equal,  and  may  be  increased, 
it  is  evident  that  we  will  find  examples  in  which  the  tendency  to  the  retro- 
gression of  the  sexual  organs  into  forms  of  morphologically  lower  develop- 
ment, has  afi'ected  all  parts  of  a  flower,  and  then  the  whole  blossom  turns 
green. 

Of  course,  the  influence  of  the  soil  is  rarely  the  direct  cause  of  phyllody. 
This  is  due  rather  to  definite  combinations  of  all  the  factors  of  growth,  as 
already  mentioned,  and  also  occurs  not  infrequently  as  a  correlation  phe- 
nomenon resulting  from  the  suppression  of  other  processes  of  growth.  Thus 
phyllody  of  individual  flowers  and  inflorescences  is  produced  by  injuries 
to  the  vegetative  axis  and  by  vegetable  and  animal  attacks  (mites).  For 
example,  C.  Kraus^  removed  leaves  from  H elianthus  annuus  plants  of  differ- 
ent ages,  leaving  only  the  bracts  of  the  blossom  head.  In  the  older  plants 
the  bracts  curled  back  and  enlarged  prematurely.  In  the  younger  plants 
25  per  cent,  showed  an  actual  phyllody;  since  the  bracts  assumed,  more  or 
less,  the  form  of  foliage  leaves. 

In  my  freezing  experiments,  I  have  often  observed  that  the  bud  scales 
were  transformed  into  herbaceous,  leaf-like  organs  after  the  apical  portion 
had  been  destroyed  by  frost.  Goebel-  obtained  similar  results  by  removing 
the  leaves  of  young  plants  of  Prunus  Padus,  Aesculus,  Rosa,  Syringa  and 
Quercus,  and  then  putting  the  plants  into  plaster  casts. 

Teratology  has  classified  the  phenomena.  The  simplest  case  is 
"virescence,"  turning  green,  in  which  an  organ  of  the  flower  retains  its 
form  in  all  essentials,  but  becomes  green  in  color.  As  a  rule,  the  organ  be- 
comes fleshier  with  this  appearance  of  the  chlorophyll  coloring  matter.  In 
the  actual  metamorphosis  of  the  floral  organs  into  leaves   (phyllody,  phyl- 


1  Kraus,  C,  Untersuchungen  tiber  kiinstliche  Herbeifuhrung  der  Veiiaubung 
usw.  durch  abnorme  Drucksteigerung.  Forsch.  auf.  d.  Geb.  d.  Agrikulturphysik. 
]880,  p.  32. 

2  Goebel,  Beitrag-e  zur  Morphologie  und  Physiologie  des  Blattes.  Bot.  Zeit. 
1880,  p.   803. 


342 

lomorphosis)  the  organ  also  approaches  the  foUage  leaf  in  form.  Bracts 
become  normal  stem  leaves,  the  sepals  are  replaced  by  actual  foliage  leaves, 
the  petals  become  green  and  fleshy,  the  pistils  become  stamens  (staminody) 
or  the  stamens  and  pistils  assume  the  character  of  petals  or  green,  fleshy 
leaf-like  structures,  as,  for  example,  in  the  double  cherry,  the  double 
Ranunculus,  etc.  In  mignonette,  through  phyllody  of  the  ovules,  little  leafy 
axes  can  be  formed  in  the  urn-like  open  ovule  cases.  In  the  favorite  tub- 
erous Begonias,  I  found  that  the  placentae  had  grown  out  of  the  ovule  cases 
and  the  ovules  carried  over  on  to  petal-like  transformed  branches  of  the 
pistil,  etc. 

There  are  cases  in  which  all  the  parts  of  a  flower  are  transformed  into 
small,  uniformly  green  leaves,  i.  e.,  a  complete  green  flozver  condition 
(chloranthy)  arises.  One  of  the  best  exam.ples  of  this  is  the  green  rose 
{Rosa  chinensis,  Jaqu.),  received  in  its  time  with  great  enthusiasm,  the 
transformation  processes  in  which  have  been  thoroughly  described  by 
Celakowsky\ 

I  would  like  to  introduce  here  also  parthcnogensis,  which  various 
scientists  have  often  proved  recently  to  be  of  constant  occurrence.  Kirchner- 
saw  in  this  an  arrangement  "which,  differing  from  the  much  more  wide- 
spread, spontaneous  self-pollination,  serves  to  assure  the  development  of 
seed,  capable  of  germination,  in  cases  where,  for  any  reason  whatever 
pollination  has  become  uncertain  or  difficult."  Even  those  seed  primordia 
can  be  assumed  to  be  of  a  somatic  character,  in  which,  at  the  time  of  the 
production  of  the  embryo  sacs,  the  reducing  division  is  suppressed  and  the 
egg  cell  retains  a  vegetative  character. 

In  cryptogamic  plants  Apogamy  corresponds  to  the  process  of  phyllody 
in  the  phanerogams.  Instead  of  the  sexual  products,  vegetative  organs 
appear  here,  as  in  Athyrium  Filix  feniina  var.  cristatum^  Aspidium  falcatum 
and  Pteris  cretica.  It  is  said  that  in  the  last  plant,  no  more  female  sexual 
organs  are  formed  at  all,  but  the  young  plant  is  produced  from  a  vegetative 
sprout  exactly  on  the  places  in  the  prothallium,  where  the  archegonia  must 
have  stood'. 

Such  plants  which  "produce  their  young  alive"  (viviparous)  furnish 
abundant  material  for  propagation,  just  as,  for  example,  the  bulblets  of 
many  lilies,  produced  by  the  transformation  of  a  flower. 

The  Barrenness  of  the  Hop. 

A  special  process  of  phyllody,  of  great  agricultural  significance,  is  the 
barrenness,  the  blindness,  the  fool's  head  formation  of  the  hop.  The  names 
designate  only  different  degrees  of  a  malformation  which  begins  with  a 
simple,  abnormal  lengthening  of  the  catkins  and  develops  into  the  formation 

1  Celakowsky,  Beitrage  zur  morphologischen  Deutung  des  Staubgefafses. 
Pringsheims  Jahrb.  1878,  p.  124. 

-•  Kirchner,  O.,  Parthenogenesis  bei  Bliitenpflanzen.  Ber.  d.  Deutsch.  Bot.  Ges. 
1904,  Vol.   XXII.    Generalversamnilungsheft.     Here   also  a  bibliography. 

a  Noll  in   Straszburger's  Lehrbuch    der  Bot.   1894,   p.   243. 


343 

of  flvittering,  dark  green  inflorescences  on   vv'hich  develop   foliage  leaves, 
differing  in  size  and  varying  in  numbers. 


Fig-.  51.     Different  transitional  stages  between  the  normal  hop  catkin 
and  a  leafy  one.     (Orig-.) 

Hop  growers  know  that  the  quality  of  the  hop  decreases  according  to 
the  increased  length  of  the  catkin  and  enlargment  of  the  bracts.  The  de- 
velopment of  the  catkins,  most  advantageous  for  technical  use,  is  a  short. 


344 

compact  form  of  the  whole  inflorescence  and  a  short,  broad  form  and  papery, 
thin  consistency  of  the  bracts,  as  shown  in  the  preceding  Fig.  5 1 .  Xos.  /  and  J. 
Half  of  the  leaves  have  been  removed  in  No.  2,  in  order  to  show  the  short- 
ness of  the  joints  in  the  catkin  spindle.  Nos.  J  and  s/.  show  the  abnormal 
excessive  lengthening  of  the  catkin,  known  among  growers  by  the  name 
"bransche"  hops,  which  must  count  as  the  first  stage  of  phyllody.  Such 
"brausche"  hops  are  coarse,  contain  less  substance,  ripen  somewhat  later  and 
have  more  herbaceous  bracts.  Beginning  with  this  condition,  the  phenom- 
ena of  phyllody  increase  up  to  the  stage  shown  in  No,  5.  The  green  foli- 
aceous  leaves,  which  here  become  visible,  attain  at  times  the  size  of  a  nor- 
mal leaf,  h  is  the  leaf  blade  which  may  be  followed  back  into  the  petiole. 
At  the  base  of  this  petiole  stand  the  two  green  lateral  leaflets  {n,n)  which  in 
the  present  basal  part  of  the  catkin  are  very  small,  but  increase  in  size  up- 
ward. No.  6  is  taken  higher  up  on  the  inflorescence  and  shows  the  lateral 
leaflets  {n,n)  in  a  size  equal  to  the  other  bracts,  while  the  leaf  body  {b)  is 
much  smaller.  The  remaining  bracts  and  protective  leaves  are  seen  at  No.  5. 
Each  one  encloses  a  flower. 

The  scale  leaves,  which  exceed  developmentally  the  other  leaves  and 
are  developed  only  in  the  normal  female  inflorescence  of  the  hop  have  the 
same  bract-like  constitution  as  do  the  protective  leaves,  so  that  the  whole 
catkin  seems  composed  of  uniformly  developed  bracts.  All  the  bracts  are 
short  lived  and  soon  become  dry  skinned,  when  they  lie  over  one  another 
like  tiles. 

The  barrenness  consists,  therefore,  of  the  development  of  the  otherwise 
suppressed  leaf  blade  between  every  two  bract-like  leaves.  Wide  exper- 
ience now  shows  that  damp  years^  and  soils  strongly  manured  with  sub- 
stances containing  nitrogen  cause  the  more  extensive  appearance  of  the 
barrenness.  Frequent  summer  rains,  resulting  in  cloudy  days,  are  often 
injurious,  even  without  directly  producing  the  disease.  The  cells  of  the 
leaf,  as  well  as  the  axis,  then  elongate  and  even  if  favorable  harvest  weather 
occurs,  the  catkins  ripen  only  superficially.  They  are  brought  into  the 
storage  rooms  while  containing  much  more  water  of  vegetation,  thereby 
causing  a  very  rapid  heating  of  the  whole  heap.  Consequently,  even  in  well- 
developed  catkins,  a  rapid  loss  of  the  peculiar  gloss  and  the  light  green 
color  takes  place,  together  with  a  considerable  reduction  in  value  of  the 
whole  harvest  product. 

As  a  remedy  for  the  barrenness,  the  removal  or  checking  of  the  causes 
must  be  attempted,  in  case  these  are  found  in  the  soil  in  the  form  of  excess 
of  water  or  nitrogen.  If  the  cause  is  cloudy,  damp  air,  all  means  should 
be  utilized  which  further  the  greatest  possible  aeration  and  illumination  of 
the  hop-plantation.  If  nitrogen  is  present  in  the  soil  in  excess,  a  subsequent 
fertilization  with  superphosphate  is  advisable. 


1  Beobachtungen  libor  die  Kultur  der  Hopfenpflanze.     Published  by  the  Deut- 
scher  Hopfenbauverein,   Jahrg-.   1879-82. 


345 
Forked  Growth  of  Vines. 

It  may  be  noticed  in  various  localities,  that  different  varieties  of  vines 
assume  a  tendency  to  excessive  branching  and  retain  it  hereditarily.  The 
kind  of  false  ramification  appears  as  a  forking  of  the  vines  and  such  dis- 
eased plants  are  usually  Httle  if  at  all  productive.  Rathay^  published  the 
most  thorough  observations  on  this  subject  and  corroborated  these  state- 
ments in  lower  Austria.  The  wine  growers  there,  who  call  these  branch- 
sick  vines  "Forks,"  or  "Double  tipped/'  state  that  the  forked  formation  may 
commence  in  very  different  places.  The  vines  which  in  adjacent 
groups  •  usually  begin  showing  this  abnormal  direction  of  growth, 
first  develop  scattered  forked  branches  and  in  this  way  present  a  "spurious 
forking"  as  may  be  seen  everywhere  in  luxuriant  vineyards.  This  initial 
stage  of  the  disease  is  not  dangerous,  since  the  plants  frequently  return  to  a 
normal  growth.  The  danger  begins  with  the  spread  of  the  disease  over  the 
whole  plant.  Correlated  with  this  is  the  transmissibility  of  the  disease. 
This  has  been  demonstrated  in  cuttings  and  suckers  of  affected  vines. 

No  cause  of  this  phenomenon  can  be  given  as  yet  with  certainty. 
R.athay  was  convinced  that  parasites  were  not  present.  The  opinions  of 
practical  workers  disagree  greatly.  Some  think  that  exhaustion  of  the  soil 
by  intensive  grape  culture  is  the  cause,  while  others  are  of  the  opinion  that 
a  clogging  of  the  soil  due  to  heavy  rain  storms  or  to  the  working  of  the 
soil  during  and  soon  after  rain  has  an  injurious  effect. 

In  my  opinion  this  disease  is  a  phenomenon  of  turning  green — vires- 
cence — i.  e.,  a  morbid  increase  of  the  vegetative  development. 

Kaserer's-  statements  favor  this  hypothesis.  He  states  that  the  first 
evidences  of  the  disease  are  found  in  the  transformation  of  the  covering 
bract  of  the  tendrils  into  a  small  leaf,  the  most  advanced  stage  in  the  trans- 
formation of  all  the  tendrils  into  leafy  shoots.  In  grape  vines,  the  tendrils 
are  axial  organs,  of  which  the  development  depends  upon  the  amount  and 
constitution  of  the  organic  building  materials  present.  In  younger  vines 
they  become  herbaceous  shoots,  but  in  older  ones  develop  into  inflorescences 
at  the  lower  buds.  If  all  the  tendrils  are  transformed  into  leafy  shoots 
the  vegetative  development  will  predominate,  a  morbid  condition.  The 
building  material  present  is  wrongly  utilized.  The  cell  sap  necessary  for  the 
formation  of  the  sexual  organs  is  not  properly  concentrated.  Thus  far  it 
is  possible  to  agree  with  Krasser",  who  speaks  of  a  diseased  condition  of 
the  protoplasm  in  certain  regions  as  a  cause  of  this  "herbaceousness." 

If  Krasser,  referring  to  the  works  of  Kober  and  Gaunersdorfer  (1901) 
insists  that  no  disturbances  in  conduction  and  no  lack  of  nutritive  sub- 
stances can  be  assumed  as  causes  of  the  "herbaceousness,"  which  represents 


J   Rathay,  Emerich,  tJbcr  die  in  Nieder-Osterreich  als  "Gabler"  oder  "Zwiewip- 
fler"  bekannten  Reben.     Klosterneuburg-,  1883. 

2  Kaserer,   H.,   Uber   die   sog-enannte   Gablerkrankheit   des    Weinstocks,    Mitteil. 
d.  k.  k.  chemisch-physiol.  Versuchsstation  Klosterneuburg",   1902.     Part  6. ' 

3  Krasser,   Fridolin,    tJber  eine   eigentumliche  Erkrankung   der   Weinstocke.   II, 
Jahresb.  d.  Ver.  d.  Vertreter  d.  angewandten  Botanik.   1905,  p.   73. 


346 

only  a  metamorphosis  of  scattered  buds  into  leaves,  but  that  a  very  local 
affection  of  the  cells  of  some  buds  is  present,  this  does  not  upset  at  all 
our  theory  of  phyllody.  It  is  a  matter  of  course  that  the  formation  of  each 
organ  takes  place  under  definite  nutritive  conditions.  That  these  change 
constantly  and  are  the  product  of  the  momentary  combination  of  all  the 
factors  of  growth  has  been  emphasized  already  in  the  introductory  chapters 
of  this  edition.  It  is  still  far  from  possible  to  determine  these  combinations. 
.For  the  present,  we  have  only  scattered  observations  on  this  subject,— that, 
for  example,  an  excess  of  potassium  and  nitrogen  in  relation  to  the  con- 
sumption of  the  other  nutritive  substances  one-sidedly  increases  the  vege- 
tative activity  at  the  expense  of  the  sexual  development.  An  excess  of 
water  with  a  relatively  scanty  supply  of  light  can  in  a  similar  way  influence 
the  direction  of  growth.  We  cannot  determine  how  these  disturbances  in 
equilibrium  are  produced  individually  for  the  formation  of  each  organ, 
whether  momentary  arrestments  in  the  absorption  or  transportation  of  the 
nutritive  substances  form  the  cause. 

We  can,  therefore,  state  only  very  generally  that  phyllody  is  produced 
by  a  preponderance  of  the  direction  of  growth  producing  green  leaves  as 
against  the  mode  of  growth  favoring  the  sexual  organs.  The  so-called 
"changelings"  or  spurious  forkings,  are  plants  which  are  still  partially 
fruitful.  Among  the  conditions  favoring  the  tendency  to  phyllody,  Kaserer 
cites  unfavorable  positions  on  which  drainage  water  collects  from  higher 
lying  ground.  Healthy  plants  set  out  in  a  group  of  affected  plants  are  said 
to  fork  rapidly.    Superphosphate  seems  to  favor  a  return  to  fruitfulness. 

We  consider  the  replacement  of  diseased  plants  by  healthy  ones  of 
varieties  which  withstand  a  more  abundant  supply  of  water  and  heavier 
soils  to  be  the  most  advisable  mode  of  procedure.  The  so-called  aggregations 
of  forked  plants  might  be  improved  by  drainage  and  the  addition  of  sand 
together  with  that  of  calcium  phosphate. 

Falling  of  the  Leaves. 

The  falling  of  the  leaves,  the  normal  result  of  age^  is  of  pathological 
significance  only  because,  under  certain  circumstances,  it  can  appear 
prematurely.  -   . 

The  causes  which  may  lead  to  such  premature  dropping  of  organs 
are  of  different  kinds,  and  extremes  of  weather  may  give  rise  to  it.  Ac- 
cordingly, the  phenomena  could  be  treated  in  different  sections  of  this  book. 
Nevertheless,  we  prefer  to  consider  here  the  processes  of  loosening  as  a 
whole,  because  they  are  connected  with  changes  in  the  tissues,  in  which  in- 
creases of  turgor  occur  decisively,  after  the  organs,  for  any  cause  whatever, 
have  become  functionally  weak.  In  regard  to  the  falling  of  the  leaves,  for 
example,  Wiesner-  differentiates  the   falling  of  the  leaves  into  a  summer 


1  Dingier,  H.,  Versuche  und  Gedanken  zum  herbstlichen  Laubfall.  Ber.  d. 
Deutschen  Bot.  Ges.  VoL  XXIII   (1905),  p.  463. 

-'  Wiesner,  Jul.,  Ber.  d.  Deutschen  Bot.  Ges.  Vol.  XXII  (1904),  p.  64,  316,  501. 
Vol.  XXIII.  p.  49. 


347 

falling,  falling  due  to  growth,  falling  due  to  heat  and  falling  due  to  frost. 
Pfeffer^  gives  us  an  insight  into  the  diversity  of  the  causes.  "Such  a  hasten- 
ing of  the  leaf-fall  is  brought  about,  for  example,  by  insufficient  illum- 
ination, also  by  an  insufficient  water  provision  and  by  too  high  a  temperature. 
Not  infrequently,  however,  a  premature  shedding  of  the  leaves  is  caused 
especially  by  the  sudden  change  of  external  conditions,  which  for  perti- 
nent reasons  concern  first  of  all  the  older  leaves."  As  examples  of  the 
injurious  influence  of  a  sudden  change  in  the  amount  of  transpiration, 
Pfefi^er  cites  the  sudden  loss  of  leaves  in  plants  as  soon  as  they  are  brought 
from  the  moist  greenhouse  air  into  a  dry  room.  Sharp  changes  of  temper- 
ature, illumination,  etc.,  can  act  in  the  same  way. 

V.  MohF  has  studied  the  anatomical  processes  very  thoroughly. 

The  shedding  of  leaves  is  accomplished  by  the  formation  of  a  trans- 
verse parenchyma  layer  at  the  base  of  the  petiole,  as  a  rule  within  the  leaf 
cushion,  and,  in  fact,  usually  where  the  cork  of  the  bark  passes  over  into 
the  epidermis  of  the  petiole,  and  in  the  interior  of  the  petiole  tissue,  which 
is  produced  by  a  special  cell  division.  The  cells  of  this  layer  separate  from 
one  another  in  one  plane. 

V.  Mohl  calls  the  zone  in  which  the  layer  of  separation  is  formed,  the 
"round-celled  layer,"  because  it  consists  of  very  short  parenchymatous 
tissue,  which  toward  the  leaf  body  gradually  passes  over  into  the  elongated 
cells  of  the  petiole,  but  is  sharply  defined  on  the  side  toward  the  bark  of 
the  twig. 

In  very  many  cases,  a  cork  layer  formed  of  plate-like 'cork  cells,  sep- 
arates the  green  bark  of  the  branch,  rich  in  chlorophyll  and  starch,  from  this 
short-celled  parenchyma  of  the  round-celled  layer  of  the  leaf  cushion  which 
usually  contains  no  starch,  and  very  little  cholorophyll  and  turns  brown 
at  the  base  at  the  time  of  leaf  fall.  Schacht^  considers  this  cork  sheet, 
which,  at  the  sides,  passes  over  into  the  inner  cork  layers  of  the  bark,  to  be 
the  cause  of  the  shedding  of  the  leaves.  In  fact,  it  may  be  assumed  that  if 
a  cork  layer  be  shoved  in  between  the  tissue  of  the  bark  and  that  of  the 
petioles,  the  food  supply  of  the  leaf  is  impoverished  and  the  leaf  gradually 
goes  to  pieces.  Nevertheless,  the  cork  layer  is  not  the  cause  of  the  leaf 
fall,  for  V.  Mohl  has  shown  that  it  is  not  formed  in  many  plants  which 
cast  their  leaves.  Thus,  for  example,  no  cork  layer  can  be  found  in  ferns 
with  deciduous  fronds  (Polypodium,  Davallia)  further,  in  Gingko  biloba, 
Fagus  sihatica,  some  varieties  of  oak,  Ulmus  campestris,  Morus  alba,  Frax- 
inus  excelsior,  Syringa  vidgaris,  Atropa  Belladonna,  Liriodendron  tulipifera, 
etc.  On  the  other  hand,  the  cork  layer  is  formed  in  Populus  canadensis  and 
r.  dilafofa,  Alnus  glutinosa,  fuglans  nigra.  Daphne  Mezereum,  Sambucus 
racemosa.  Viburnum  Lantana,  Lonicera  alpigena,  Vitis  vinifera,  Ampe- 
lopsis  quinque folia,  Aesculus  macrostachya,  Pavia  rubra  and  P.  lutea,  Acer 


1   Pfeffer,  Pflanzenphysiolog-ie.    II  Edition,  Vol.  2  (1904),  p.  278. 
-    V.    Mohl,    tJber   die    anatomischen    Veranderungen    des    Blattgelenkes,    welche 
das  Abf alien  der  Blatter  herbeifiihren.  Bot.  Zeit.  1860,  Nos.   1  and  2. 
•i    Schacht,  Anatoniie  and  Physiologie,  II,   136. 


348 

plafanoides,  Primus  Padus,  Robinia  Pscndacacia.  The  cork  layer  should, 
therefore,  be  considered  only  as  a  protective  layer  for  the  bark  tissue  ex- 
posed by  the  falling  of  the  leaf,  often  developed  before  the  leaf  has  fallen. 

The  real  layer  of  separation,  in  fact,  is  formed  above  the  cork  layer 
in  the  almost  isodiametric  parenchyma  of  the  round-celled  layer,  not  in  the 
brown- walled  portion  bordering  directly  on  the  cork,  but  in  the  adjacent 
healthy  portion,  of  which  the  walls  are  light  colored.  There,  shortly  before 
the  leaves  fall,  a  zone  is  found  running  obliquely  in  front  of  the  bud  toward 
the  outer  side  of  the  petiole  and  composed  of  young,  delicate  walled  cells  with 
intercellular  spaces  containing  less  air.  Small  starch  grains  are  found  in 
these  cells  which  otherwise  do  not  occur  in  the  enlarged  end  of  the  petiole. 
In  this  newly  formed  tissue-zone,  the  cells  separate  from  one  another  with- 
out tearing,  but  by  rounding  ofif.  as  Tnmann^  has  observed.  One  part  re- 
mains attached  to  the  petiole  as  it  breaks  ofif,  the  other  to  the  leaf  scar 
where  it  soon  dries  up.  The  leaf-fall,  accordingly,  is  a  z'ital  act,  not  a  me- 
chanical one.  Before  the  leaf  falls,  vascular  bundles  take  no  part  in  the 
changes  undergone  by  the  cell  tissue  of  the  swollen  end  of  the  petiole.  These 
extend  through  the  round  celled  layer  and  the  cork  layer  without  changing 
their  organization,  even  without  turning  brown.  The  cleavage  in  these 
*"'kes  place  in  a  purely  mechanical  way  after  the  split  has  extended  through 
the  parenchymatous  tissue. 

In  many  plants  (Nuphar,  many  monocotyledons,  herbaceous  ferns')  in 
which  there  is  no  cork  formation  on  the  leaf  scar,  its  outer  dried  cell  layers 
i>ass  over  directly  into  the  healthy  bark  parenchyma  and  are  thrown  off 
during  later  development. 

V.  Bretfeld'"*  arrives  at  the  conclusion  tliat  the  process  of  abscission  of  the 
leaves  is  the  same  in  monocotyledons  and  dicotyledons,  only  the  shutting  ofif 
of  the  abscission  surface  dififers  in  dififerent  genera.  An  essential  difiference 
lies,  however,  in  the  time  of  the  formation  of  the  tissue  zone  in  which  the 
separating  layer  is  produced.  \\^hile  in  dicotyledons,  the  process  of  ab- 
scission is  the  product  of  living  activity,  taking  place  shortly  before  the 
leaves  fall,  this  process  in  the  tree-like  monocotyledons,  orchids  and 
Aroideae  is  exhibited  as  an  act  [^rcpared  by  the  primordia  of  a  definite 
layer  and  advancing  with  the  general  tissue  dififerentiation. 

The  loss  of  leaves  occurring  in  conservatory  plants  of  the  her- 
baceous and  bushy  Begonias,  of  Cistus  species  and  many  Mytaceae  and 
Leguminoseae  from  New  Holland  must  be  mentioned  in  discussing  leaf 
fall  due  to  an  excess  of  water.  The  upward  force  of  the  sap  is  increased 
excessively  by  an  abundant  watering  of  the  plants  at  the  time  of  minimalleaf 
activity.  The  cleavage  surfaces  of  the  falling  leaves  at  times  are  very 
mealy,  due  to  the  loosened  cells  of  the  abscission  surface. 


1  Bot.   Zeit.    1850,  p.  198. 

2  V.  Mohl,  tJber  den  Vernarbungsproze.ss  bei  der  Pflanze.  Bot.  Zeit.  1849,  p.  64.5. 
p.   645. 

3  V.    Bretfeld,    tJber   den   Ablosung-sprozess    saftig-er   Pflanzenorganc    Bot.    Zeit. 
1860,   p.   273. 


349 

Leaf  Casting  Diseases. 

The  leaf  casting  diseases  form  the  most  significant  case  of  premature 
dropping  of  the  leaves.  We  speak  here  in  the  plural,  although  it  is  custo- 
mary generally  to  call  a  sudden  dropping  of  the  needles  of  young  pines 
"leaf  casting."  All  plants  can  "cast  their  leaves"  which  are  capable 
in  any  way  of  pushing  off  their  dying  leaf  apparatus.  The  only  concern, 
then,  is  wliether  the  leaf  body  in  its  entirety  suddenly  becomes  functionally 
weakened,  or  even  functionless.  It  is  only  because  it  appears  so  uncom- 
monly abundantly  among  pines  and  is  accompanied  by  severe  results  that 
the  dropping  of  the  pine  needles  is  cited  especially  often  for  "Leaf  Casting." 

This  form  of  disease  manifests  itself  most  frequently  and  severely  in 
seedlings  two  to  four  years  old,  the  needles  of  which  suddenly  become 
I'rownish-yellow  or  brownish-red  in  the  spring  and  fall  after  a  short  time. 
The  considerable  spread  of  this  phenomenon  dates  only  from  the  general 
change  in  the  cultural  methods ;  instead  of  sowing  the  seed  and  of  the 
Femel  management,  the  raising  of  plants  in  seed  beds  has  been  introduced. 

Since  that  time  it  has  been  observed  that  in  the  months  from  March  to 
May.  often  within  a  few  days,  great  areas  of  seedling  plants  look  as  if  they 
had  been  burned.  In  this,  however,  it  can  be  noticed  that  young  plants 
protected  by  a  not  ver\'  close  conifer  forest,  or  one  of  mixed  trees,  or,  in 
nurseries  protected  by  trees  of  an  earlier  seeding,  do  not  cast  their  needles, 
while  exposed  areas  in  the  open  or  in  enclosed  places  are  extraordinarily  at- 
tacked by  the  disease.  Specimens  with  pruned  roots  suffer  more  than  those 
with  long,  vigorous  ones,  while  plants  on  wet  soil  suffer  most  intensely. 
Mountain  plantations  are  less  attacked  than  those  on  plains  and  a  northern 
exposure  seems  to  be  almost  entirely  spared,  while  a  southern  or  western 
one  suffers  greatly. 

The  disease  does  not  appear  every  year,  but  generally  only  after  wet, 
cold  winters  with  but  little  snow,  and  alternating  sharp  frosts.  The  plants 
cast  their  needles  most  extensively  if  dry  springs,  March  and  April,  are 
distinguished  by  bright  warm  days  followed  by  cold  nights.  Often  the 
phenomenon  occurs  in  stripes  or  spots.  It  has  been  obsen^ed  further,  that 
plants  protected  from  the  noonday  sun  by  neighboring  woods,  etc.,  general- 
ly did  not  become  diseased.  Plants  in  seed  beds,  which  were  left  covered 
until  after  the  time  of  spring  frosts,  did  not  cast  their  needles  while  ad- 
jacent, unprotected  seedlings  did  so.  Seedlings  grown  between  older 
covered  plants  or  between  broom  plants,  even  those  protected  by  high  grass, 
did  not  develop  the  disease,  while  others  where  the  broom  plants  had  been 
dug  out  in  the  spring  were  attacked. 

Ebermayer^  in  explanation  of  these  facts,  states  that  observations  of  a 
forestr}^  experimental  station,  made  for  several  years,  showed  that  in  March 
and  April  the  soil  temperature  down  to  1^4  meters  was  scarcely  more  than 


1  Ebermayer,  Die  physikalischen  Einwirkungen  des  Waldes  auf  Luft  und 
Boden  etc.  Resultate  der  forstl.  Versuchsstat.  in  Bayern.  Aschaffenburg-,  1873. 
Vol.  I,  p.  251. 


350 

5  degrees  C,  while  the  air  temperature  in  the  shade  not  infrequently  was 
higher  than  19  to  22  degrees  C.  Such  differences  in  temperature  between 
the  air  and  the  soil  result  directly  in  the  excessive  transpiration  of  the  aerial 
parts  of  the  plant,  while  the  roots  kept  in  a  state  of  inactivity  because  of  the 
cold  soil,  are  incapable  of  taking  up  the  soil  water,  or  not  to  the  amount 
necessary  to  replace  the  aerial  loss.  Thus  the  young  pines  dry  up  even 
when  the  soil  is  abundantly  wet. 

The  greater  the  difference  between  the  soil  and  the  air  temperatures  in 
direct  sunlight,  the  more  abundant  and  devastating  is  the  leaf  casting.  On 
the  other  hand,  the  more  frequently  conditions  arise  which  raise  the  soil 
temperature,  such  as  warm  spring  rains,  or  which  prevent  a  greater  lowering 
of  it,  i.  e.  masses  of  long  unmelted  snow  or  of  mulch,  the  less  the  disease 
appears.  This  lessening  of  the  disease  will  take  place  also  if  the  temper- 
ature of  the  air  and  the  intensity  of  the  sunlight  are  decreased  as,  for  ex- 
ample, by  a  very  cloudy  sky,  by  a  position  on  northern  slopes,  or  under 
the  protection  of  larger  trees,  high  grasses  or  bushes,  or  by  the  artificial 
screening  of  the  seed  beds  during  the  day. 

That  older  plants  suffer  less  often  from  leaf  casting  is  explained,  in  the 
first  place,  by  the  more  strongly  developed  wood  which  in  all  plants  may  be 
considered  as  a  water  reservoir;  in  the  second  place,  by  a  more  abundantly 
developed,  deeper  reaching  root  system,  which  possesses  more  organs  for 
absorption  in  its  greater  number  of  fibrous  roots. 

Holzner^  has  raised  an  objection  to  this  theor}^  In  leaf  casting,  dis- 
coloration appears  within  2  to  3  days,  while,  in  an  actual  process  of  dr}'ing, 
the  pine  needles  redden  only  gradually.  He  considers  the  cause  a  direct 
effect  of  frost.  It  is  a  well  established  fact  that  frost  will  also  cause  leaf 
casting.  Baudisch-  protected  seedlings  by  a  brush  covering  one  meter  deep 
above  the  surface  of  the  soil.  The  plants  which  had  remained  healthy  until 
the  protection  had  been  removed  then  suffered  from  the  April  frosts. 

Many  authors  ascribe  an  injurious  influence  to  autumn  frosts^.  The 
theory  most  generally  accepted  at  present  considers  the  disease  to  be  para- 
sitic and,  accordingly,  recommends  that  it  be  treated  with  fungicides.  Ac- 
cording to  V.  Tubeuf's*  experiments,  it  cannot  be  doubted  that  there  are 
also  cases  of  parasitic  leaf  casting"'.  However,  the  fact  must  be  taken 
into  consideration,  that  the  fungi  of  leaf  casting  are  present  in  abundance 
on  older  pines,  firs,  spruces  and  larches,  without  calling  forth  the  specific 
phenomena.  Therefore,  unless  some  conditions  especially  favorable  for  the 
much  dreaded  juvenile  disease  are  present,  it  cannot  become  epidemic.  . 


1  Holzner,  Georg.  Die  Beobachtungen  iiber  die  Schiitte  der  Kiefer  oder  Fohre 
und  die  Wintei-farbung-  immergruner  Gewachse.  Freising,  1877.  Here  bibliography 
of  145  studies  on  leaf  casting. 

1!    Centralbl.  f.  d.  ges.  Forstwesen  VII,  1881,  p.  362. 

•■!  Alers  in  Centralbl.  f.  d.  ges.  Forstw.  1878,  p.  132.  Nordlinger  ibid  p.  389. 
Dammes  and  others,  .Tahrbuch  d.  schles.  Forstvereins  1878,  p.  40  ff. 

4  V.  Tubeuf,  Studien  iiber  die  Schiittekrankheit  der  Kiefer.  Arb.  d.  Biolog.  Abt. 
am  Kais.  Gesundhcitsamt.    Part  II,  1901. 

■•    Cf.  Vol.  II,  p.  268. 


EDGAR  TULLIS 

351 

All  these  statements  as  to  the  factors  causing  leaf  casting  agree  in 
maintaining  that  the  needles  fall  because  they  have  become  weakened 
functionally  or  still  are  normally  weak  as  a  result  of  the  winter's  rest. 
Moreover,  the  abscission  process  depends  upon  the  development  of  the  cleav- 
age layer  which  presupposes  living  activity  and  an  increased  turgor.  Thus, 
there  arises  an  antagonism ;  the  leaf  organ  is  not  at  the  time  in  a  condition 
to  function  as  a  normal  center  of  attraction  and  consumption.  Because  of 
its  anatomical  structure  the  basal  part  above  the  region  of  the  subsequent 
cleavage  can  be  excited  and  it  is  prematurely  brought  to  the  development 
of  this  cleavage  layer  by  the  increase  in  turgor,  which  arises  in  the  spring 
due  to  exposure  to  the  sun,  or  has  been  retained  from  the  previous  year, 
and  finds  no  equalizaion  since  even  the  inactive  lamina  of  the  leaf  do  not 
take  up  the  water  from  it.  This  disturbance  in  the  equilibrium  of  the  turgor 
distribution  is  the  cause  of  all  premature  dropping  of  the  leaves. 

In  the  special  case  of  the  pine  leaf  casting  I  think  that  the  contrasts 
described  by  Ebermayer  and,  indeed,  the  sharp  contrasts,  represent  the 
most  frequent  cause  of  the  disease.  Only  in  explaining  it,  I  differ  from  him 
in  so  far  that  I  accept  as  cause  the  winter's  inactivity,  evident  also  in  the 
constitution  of  the  chloroplasts,  instead  of  the  excessively  increased  evap- 
oration from  the  needles.  Only  the  base  of  the  needle  is  excited  and  de- 
velops the  cleavage  laver,  which,  as  will  be  mentioned  under  petals,  can. 
under  certain  circumstances,  be  produced  in  an  extremely  short  time.  I  am 
of  the  opinion  that  the  needle  does  not  become  dried  out,  but  is  put  out  of 
action  by  the  cleavage  layer.  I  would  like  to  assume  from  the  absolute 
scanty  elimination  of  water  by  pines  in  winter,  that  a  drying  of  the  needles 
resulting  from  an  excessively  increased  evaporation,  is  not  the  cause  of  the 
discoloration  and  falling  of  the  needles.  An  experiment  in  a  water  culture 
of  one  year  old  seedlings  showed  me  that  a  pine  ceased  its  evaporation  on 
the  17th  of  November  despite  following  days  with  temperatures  of  +  3.  4-  7' 
9  degrees  C.  Up  to  the  22nd  of  December  they  did  not  evaporate  one  gram 
more  of  water,  although  the  root  stood  in  water\  It  can,  therefore,  scarcely 
be  assumed  that  the  spring  temperature  can,  in  a  few  days,  cause  a  great  loss 
of  moisture,  more  particularly  as  the  pine  is  a  tree  species  which  evap- 
orates the  least  of  alP. 

Since  the  dr}-ing  of  the  needles  does  not  seem  to  me  to  be  the  cause  of 
leaf  casting,  but  rather  a  lack  of  equallization  in  the  water  supply,  resulting 
from  the  sharp  contrast  between  the  needle  surface,  weakly  assimilative, 
and  its  base,  already  active,  I  would  like  to  believe  the  best  preventative 
method  to  be  the  avoidance  of  such  sharp  contrasts :  I,  therefore,  add  the 
proposals  made  by  Ebermayer : — 

A.  Increase  in  soil  temperature  :  (i)  due  to  the  prevention  of  too  great 
cooling  during  the  winter  by  means  of  leaf,  brush  or  moss  coverings;   (2) 


1   Sorauer,    Studien    iiber  Verdunstung-.    Forschungen   auf   d.    Gebiete   der  Agri- 
kulturphysik.  Vol.  Ill,  Parts  4  &   5,  p.  10. 
"  V.  Hohnel,  loc.   cit.  Vol.  II,  p.  411. 


352 

by  draining  wet  soils;  (3)  by  loosening  and  mixing  heavy  soils  with  earths 
rich  in  humus,  so  that  the  warmth  of  the  air  can  penetrate  more  easily. 

B.  Lessening  of  sharp  contrasts  by  shading:  (i)  by  brushing  the  seed 
beds  with  evergreen  boughs,  w^hich  should  not  be  removed  on  warm  days ; 
(2)  by  making  the  seed  beds  in  places  which  are  protected  on  the  south  by 
tracts  of  trees, 

"In  the  restoration  of  pine  woods,  on  the  wliole,  the  most  radical  means 
consists  in  a  return  from  the  extensive  clearing  system  to  a  plan  of  seeding, 
such  that  the  young  plants  have  tlie  necessary  protection  from  the  direct 
sunlight  in  the  overhead  wood  protection,  but  can  still  obtain  as  much  light 
as  is  necessary  for  their  vigorous  development.  The  same  end  is  attained 
by  a  slender  fringe  of  trees  running  from  N.  E.  to  S.  W.,  which  are  much 
used  at  present  in  the  restoration  of  the  pine  tracts.  In  the  cultivation  of 
extensive  clearings  the  shading  can  be  obtained  by  a  shelter  growth  of  such 
plants  as  are  favored  by  the  habitat, — for  example,  by  birches,  etc.,  or  by 
previous  spruce  plantations." 

"In  cases,  where  no  shelter  growth  can  be  arranged  because  of 
local  conditions,  the  planting  of  seedlings  is  preferable  (yearling  plants  with 
a  good  root  system  seem  best  suited  for  this),  yet  the  first  two  cultural 
methods  will  much  more  surely  attain  the  desired  goal." 

Finally  it  is  well  to  emphasize  that  every  attention  should  be  given  to 
obtaining  a  good  root  system; — accordingly,  too  thick  seeding,  heavy,  un- 
broken soil,  considerable  injury  in  transplanting  and  the  like  are  to  be 
avoided. 

A  leaf  casting  occurs  also  in  older  trees.  The  older  needle  bunches  of 
plants  standing  on  moor-soils  in  misty  depressions,  or  found  in  localities 
subject  to  extreme  frost,  fall  prematurely.  But,  in  the  autumn,  these  hang 
to  the  trees,  turning  yellow  or  drying  up,  and  are  thus  distinguished  from 
the  seedlings  specifically  diseased  with  leaf  casting.  On  heavy  soils  the 
pine  always  dies  easily^. 

Leaf-Fall  in  House  Plants. 

Among  the  most  delicate  of  the  house  plants  belong  the  azaleas,  be- 
cause, as  a  rule,  they  suddenly  drop  their  leaves  in  summer  or  in  the 
autumn;  the  broom-like  little  tree  then  at  best  develops  only  a  few  pitiful 
flowers.  Here  too  are  concerned  sharp  contrasts  occurring  suddenly.  Either 
the  plants  (usually  set  in  moor  soil)  in  summer  are  left  too  dry,  and  later 
watered  very  abundantly,  or  they  are  brought  too  suddenly  into  the  warm 
house  in  the  autumn.  In  both  cases,  the  leaves  are  weak  functionally  and 
then  their  functioning  is  increasingly  stimulated  by  the  increased  upward 
pressure  of  the  water.  If  the  transition  is  brought  about  gradually,  the  inac- 
tive leaf  surfaces  would  have  time  to  resume  their  normal  action  by  a  general 
slow  increase  in  their  turgidity  and  there  would  be  no  resultant  injury. 


1   Runnebaum,  A..  Das  Absterlien  iind  die  Bewirtschaftuner  drr  Kiefer  im  S^an- 
genholzalter  usw.    Zeitschr.  f.  Forst-  u.  Jagdwesen,  1892,  p.  43. 


353 

But,  with  the  sudden  upward  pressure  of  the  water,  the  basal  region  alone  is 
stimulated,  thus  causing  the  development  of  the  cleavage  layer. 

In  foliage  Begonias,  rubber  plants,  camelias  and  many  others,  the 
leaves  begin  to  drop  in  the  autumn  and  winter.  Here,  the  leaf  is  in  a 
natural,  dormant  state.  Abundant  watering  in  a  warm  room  causes  an  up- 
ward current  of  water  which  the  leaves  cannot  utili/e. 

Here  are  briefly  a  few  of  my  own  observations.  A  Begonia  fuchsioi- 
des  which  had  been  forced  through  the  winter  in  a  warmer  room,  was 
brought  at  the  end  of  March  into  an  unheated,  but  sunny  room.  Within  a  few 
days  it  dropped  all  its  leaves  except  the  youngest  ones.  Libonia  florihiinda, 
which  had  been  kept  very  cold,  was  suddenly  brought  into  a  greenhouse  in 
December  for  forcing.  The  plants  dropped  all  the  older  leaves,  while 
plants  remaining  in  the  cold  retained  theirs.  Some  specimens  of  a  double 
white  fuchsia  were  brought  into  the  house  in  the  autumn  in  order  to  get 
early  shoots  for  cuttings.  Other  specimens  of  the  same  variety  were  left 
in  the  cellar  until  the  beginning  of  March.  At  this  time  the  tips  of  all  the 
plants  were  set  as  cuttings  in  a  bench  with  25  degrees  C.  soil  heat.  After  a  few 
days  the  cuttings,  from  the  plants  in  the  cellar,  lost  their  leaves  up  to  the 
very  tips,  while  the  others  had  not  even  lost  the  leaf  at  the  cut  surface.  The 
tips  of  one  branch,  taken  a  few  days  later  from  a  cellar  plant,  were  placed 
in  sand  in  the  cellar,  without  any  especial  care  and  were  found  in  May  to 
have  rooted,  while  the  tips  from  the  cellar  plants  had  gone  to  pieces  in  the 
warm  case. 

For  house  plants  it  may  be  recommended  as  a  fundamental  principle 
that  the  plants  should  be  subjected  gradually  to  other  vegetative  conditions, 
and  the  dormant  period,  upon  which  every  vegetative  plant  enters,  should 
not  be  interrupted  by  an  increase  in  the  supply  of  heat  and  moisture. 

The  Dropping  of  the  Flowering  Organs. 

This  process  takes  place  in  the  same  way  as  that  of  the  leaves\  The 
composite  axes  of  the  inflorescences  in  Aesculus  and  Pavia  are  known  to 
separate  into  their  individual  parts,  which  loosen  from  one  another  with 
smooth  cleavage  surfaces.  In  the  same  way,  if  many  fruits  are  set,  a  num- 
ber of  half-grown  ones  are  often  abscissed  to  a  joint  in  the  fruit  stem. 
The  staminate  blossoms  of  the  Cucurbitaceae  are  abscissed  at  the  cleavage 
layer  formed  on  the  boundary  between  pedicel  and  blossom,  those  of 
Ricinus  communis  in  a  line  of  separation,  produced  at  a  joint  lying  in  the 
lower  part  of  the  peduncle.  The  hermaphrodite  blossoms  of  Hemerocallis 
fulva  and  H.  flava,  left  unfertilized,  are  abscissed  by  a  cleavage  layer  ex- 
tending under  the  base  of  the  blossom  through  the  upper  part  of  the  ped- 
uncle. The  cells  of  the  cleavage  surface  round  up  and  separate  from  one 
another. 


1  V.  Mohl,  H.,  ijber  den  Ablosung-Siprozess  saftiger  Pflanzenorgane  Bot.  Zeit.  1860. 
p.  273. 


354 

In  the  same  way  a  fully  developed  cleavage  layer  is  found  in  the  sepals 
of  Papavcr  somniferum,  Liriodendron  iulipifera,  at  the  time  they  fall;  in 
the  falling  parts  of  the  calyx  of  Mirabilis  Jalapa,  Datura  Stramonium;  in 
ihe  petals  of  Rosa  canina,  Papaver;  in  the  single  corolla  of  Lonicera  Capri- 
folium,  Rhododendron  ponticum,  Datura  Stramonium;  in  the  stamens  of 
Liliiim  hulbiferum  and  L.  Martagon,  Dictamnus  Fraxinella,  Liriodendron ; 
in  the  stigma  of  Lonicera  Caprifolium,  Mirabilis  Jalapa  and  Liliiim 
Martagon. 

In  the  majority  of  cases,  the  cells  of  the  abscission  layer  contain  no 
starch,  or  at  least  no  more  than  does  the  surrounding  tissue,  while,  in  the 
leaves  and  thick  sepals  and  petals  of  Liriodendron  abundant  starch  is  pres- 
ent. This  lack  of  reser\e  nutriment  is  explained  by  the  rapid  formation  of 
the  cleavage  layer  in  the  blossoms,  for  which  the  momentarily  transportable 
nutritive  substance  is  sufficient.  In  the  sepals  of  Papaver  somniferum  the 
cleavage  layer  is  produced  in  a  single  night,  in  the  petals  of  single  roses, 
in  the  hours  of  an  afternoon.  While  cell  increase  seems  to  occur  in  the 
cleavage  layer  of  leaves,  it  can  hardly  take  place  in  the  petals.  The  pro- 
cesses there  visible  consist  only  of  a  more  abundant  protoplasm,  an  in- 
creased porosity  and  mutual  separation,  due  to  a  rounding  up  of  the  cells, 
and,  at  times,  a  pouch-like  enlargement  of  the  cells,  whereby  the  cleavage 
layer  looks  velvety.  The  appearance  of  the  cleavage  layer  is  delayed  as  the 
organs  are  better  nourished. 

The  Shelling  of  the  Grape  Blossom. 

By  the  term  "shelling"  or  "falling"  the  winegrower  means  the  dropping 
of  blossoms  soon  after  blooming.  In  some  regions  the  phenomenon  returns 
annually  while,  in  other  localities,  it  appears  only  in  isolated  years,  as,  for 
example,  in  those  when  wet,  cold  weather  destroys  the  blossoms.  Accord- 
ing to  Miiller-Thurgau's^  investigations,  with  a  low  temperature  at  the 
time  of  blossoming,  the  cells  of  the  stigmas  were  beginning  to  turn  brown 
even  before  the  blossom  sheaths  fell,  which  indicated  death  or  at  least 
an  extensive  retarding  of  the  process  of  pollination.  Actually,  on  such 
stigmas  the  pollen  grains  did  not  develop  pollen  tubes  at  all,  or  only 
poorly.  The  dropping  of  the  petal  cap  took  place  ver)'  slowly  or  was  en- 
tirely suppressed.  The  ovule  cases  of  such  blossoms  remained  for  some 
time,  often  actually  for  a  long  time,  but  they  scarcely  enlarged  at  all.  How- 
ever, since,  according  to  Miiller's  discoveries,  ringing  of  the  vines  is  usually 
beneficial,  the  low  temperature  cannot  be  the  direct  cause  of  the  incompleted 
act  of  pollination  and  the  failure  to  mature  the  seed.  The  dull,  cool  weather 
during  blossoming  is  especially  favorable  for  the  growth  of  leafy  shoots, 
which,  on  this  account,  require  the  material  stored  up  for  the  development 
of  the  inflorescence,  so  that  the  nutrition  is  not  sufficient  for  the  blossoms. 
Such  a  starving  of  the  blossom  cluster  and,  consequently,  a  more  or  less 


1  Miiller-Thurgau,    t)ber    das    Abfallen    der    Rebenbliiten    und    die    Ent.stehuns 
kernloser  Traubenbeeren.    Der  Weinbau,  1883,  No.  22, 


355 

extensive  shelling  of  the  blossoms  will  occur  also  with  weather  favorable 
for  blooming,  if  abundant  nitrogen  is  present  in  the  soil,  or  if  virgin  soil 
with  an  abundant  supply  of  nutrients  and  water  is  used  for  the  cultivation 
of  grapes,  when  the  luxuriant  development  of  the  vegetative  organs  limits 
the  further  development  of  the  sexual  apparatus. 

In  fact,  Miiller  gives  examples  of  such  cases  and,  at  the  same  time, 
states  his  experience,  viz.,  that  sometimes  fertilization  has  helped  over- 
come the  evil,  and  sometimes  a  long  incision  in  the  vine  accomplishes  the 
same  end. 

Miiller  also  ascribes  to  the  same  causes  the  appearance  of  seedless 
grapes  on  the  bunch,  which,  as  a  rule,  is  correlative  with  a  partial  shelling. 
The  seedless  grapes  are  larger  than  the  unpoUinated  seeded  ones  which,  at 
times,  remain  on  the  bunch  even  until  autumn.  The  seedless  ones,  however, 
are  not  as  large  as  normal,  seed  bearing  grapes,  although,  like  them,  they 
color  and  become  sweet.  Indeed,  it  is  evident  that  they  ripen  earlier  and 
become  sweeter  than  the  grapes  with  matured  seeds. 

Since  the  seed  primordia  in  the  seedless  grapes  do  not  seem  much 
larger  than  at  the  time  of  blossoming,  it  must  be  assumed  that  some  dis- 
turbance had  taken  place  at  that  time.  It  is  probable  that,  in  such  cases, 
pollinization  had  taken  place,  but  that  either  a  temporary  lack  of  suit- 
able nutritive  substances,  or  some  other  disturbance,  prevented  the  further 
development  of  the  &gg  cell.  The  stimulus,  exercised  by  pollination  on  the 
walls  of  the  ovule  cases  is  present  and  the  grape  consequently  develops. 
Since,  however,  it  does  not  need  to  use  up  any  of  the  nutritive  substances 
flowing  towards  it  in  maturing  the  seeds,  this  grape  at  first  exceeds  develop- 
mentally  the  grapes  containing  seeds.  Weighing  seedless  and  seeded  grapes 
proves  that  the  seed,  in  maturing,  functions  as  a  centre  of  attraction  for 
material.  Miiller-Thurgau^  found  that  the  weight  of  the  fruit  flesh  of  too 
berries  of  Riesling  was 

Seedless       With  i  Seed       With  2  Seeds       Normal,  with  4  Seeds 
25.0  g  58.2  g  77.2  g  112.  g 

As  examples  of  the  differences  in  the  material  development,  the  results 
of  an  experiment  by  Miiller  with  Riesling  may  be  cited  here. 
1000  berries  on  the  25th  of  September  showed 

Seedless   a  weight  of  208.9  g>       sugar  10.63%,       acid  18.2% 

Containing  seeds   ...a  weight  of  846.0  g,       sugar     9.77%,       acid  24.2% 
On  the  1 2th  of  October 

Seedless  a  weight  of  231.0  g,       sugar     14.7%,       acid  11.0% 

Containing  seeds  ....a  weight  of  898.7  g,       sugar     12.3%,       acid  15.7% 

In  regard  to  the  effect  of  ringing,  an  experiment  showed  that  the  non- 
ringed  vines  bore  only  unfertilized  grapes,  which  fell  soon,  while  the  bear- 

1  Muller-Thurgrau,  Einfluss  der  Kerne  auf  die  Ausbilding  des  Fruchtfleisches  bei 
Traubenbeeren  und  Kernobst.  II.  Jahresbericht  d.  Versuchsstat.  Wadensvveil 
Zurich,  1893,  p.  52. 


356 

ing  vines,  which  were  ringed  shortly  before  blossoming,  furnished  com- 
paratively long  bunches  with  an  extremely  large  number  of  seedless  berries, 
between  which  were  found  only  scattered  normal  ones. 

This  formation  of  seedless  grapes  is  a  great  injury,  under  our  present 
conditions,  since  the  prematurely  ripe  grapes  shrivel  before  the  general 
vintage  until  all  the  juice  is  lost,  and  drop  off  or  decay;  they,  therefore,  are 
wasted.  If,  on  the  other  hand,  this  degeneration  is  increased,  it  may  be 
termed  an  advantage.  Probably  our  currants  and  Sultana  raisins,  among 
which  only  scattered  berries  with  seeds  are  found,  are  the  products  of 
plants  in  which  a  seedless  condition  of  the  berries  has  become  the  rule. 
In  other  localities,  cuttings  of  the  currant  grape  are  said  to  bear  grapes 
with  seeds. 

Eger^  gives  some  advice  well  worth  considering.  He  studied  the  in- 
dividuality of  different  varieties  of  grapes  from  many  points  of  view  and 
found  that  certain  plants  of  the  same  variety  always  ripen  their  berries 
earlier  and  that  many,  under  otherwise  similar  conditions,  show  a  lesser 
tendency  to  the  falling  of  the  bloom,  which,  especially  in  Riesling,  is  very 
considerable.  Accordingly,  in  each  nursery  and  vineyard  those  individuals 
should  be  labelled  which  are  notable  each  year  because  of  their  favorable 
development,  and  only  from  these  should  cuttings  be  chosen  for  propagation. 

Other  processes  are  found  in  our  stone  fruit  trees  when  grown  for 
trade.  If  the  wood  is  thinned  too  much,  i.e.  too  many  leaf  branches  are 
cut  away,  in  order  to  furnish  light  for  the  blossoms  and  young  fruit,  the 
buds,  blossoms  and  young  fruit  may  be  dropped.  By  the  sudden  decrease 
of  the  evaporating  leaf  surfaces,  an  increased  root  pressure  sets  in  for  the 
other  organs,  which  cannot  take  up  the  increased  amount  of  water.  Cleav- 
age of  the  abscission  layer  results.  The  dropping  of  the  organs  can  natural- 
ly be  initiated  by  other  causes". 

The  Shedding  of  the  Young  Flower  Clusters  of  Hyacinths. 

Many  shipments  of  hyacinth  bulbs  from  different  growers  have  shown 
me  that  the  shedding  of  complete  but  undeveloped  flower  clusters  is  not  of 
rare  occurrence.  The  uncolored,  otherwise  perfectly  healthy  flower  clusters, 
still  rather  short,  may  be  Hfted  from  entirely  healthy  bulbs  with  fully  de- 
veloped, often  excessively  elongated  foliage.  In  the  very  luxuriant  variety 
Baron  Van  Thuyll  (originated  in  Holland)  I  found  yellowish  areas  on 
otherwise  normally  developed  leaves  and  these  areas  were  slightly  swollen, 
even  split  here  and  there.  The  flow-er  clusters  were  strong,  perfectly 
healthy,  perhaps  8  cm.  in  length,  with  an  equally  long,  perfectly  healthy, 
almost  colorless  stalk. 

The  stalk  had  separated  from  the  base  of  the  bulb  and  the  cells  of  the 
former  were  found  to  be  swelled  up  more  or  less  ascus-like.    This  swelling 


1  Eger,  E.,  Untersuchungen  tiber  die  Methoden  der  Schadlingsbekampfung- 
und  uber  neue  Vorschlage  zu  Kulturmafsregeln  fiir  den  Weinbau,  Berlin,  P.  Parey, 
1905,  p.  63. 

^    The  Dropping  of  the  Buds  of  Peaches.  Gard.  Chron.  XIII,  1893,  p.  574. 


357 

could  be  traced  back  from  the  place  of  cleavage,  to  varying  depths.  The 
pro-cambial  cells  of  the  firo-vascular  bundles  were  broadened  like 
bladders. 

The  ducts  thus  exposed  were  simply  broken  off  and,  like  the  other  ex- 
posed surfaces,  had  absolutely  uncolored  walls  at  first. 

The  separation  begins  to  show  itself  in  the  rounding  up  and  bending 
outward  of  scattered  cells  in  the  basal  tissue  of  the  flower  stalk,  usually  at 
a  short  distance  from  the  base  of  the  bulb.  Simultaneous  with  the  begin- 
ning of  this  convexity  a  swelling  of  the  membranes  of  these  cells  appears 
at  the  side  where  the  curvature  sets  in.  It  is  the  striated  middle  lamella  of 
the  cell  walls  which  swells.  Also,  the  swelling  does  not  take  place  uni- 
formly in  the  whole  membranous  layer,  but  in  some  places  to  a  greater  de- 
gree than  in  others,  hence  the  swollen,  stripe-like  areas  have  a  knotted 
course,  in  places  showing  constrictions. 

A  bead-like  irregular  condition  of  the  outer  surface  of  the  cell  walls 
in  the  cells  lying  next  the  cleavage  surface  seems  worthy  of  attention.  The 
hemispherical,  to  nipple-shaped  swellings  correspond  to  those  in  the  woolly 
stripes  in  the  apple  core  and  take  on  a  pure  golden  yellow  color  with  chlo- 
riodid  of  zinc  while  the  rest  of  the  membrane  becomes  intensely  blue.  This 
disturbance  sets  in  if,  when  growth  starts,  the  hyacinths  bulbs  are  given 
at  first  too  great  warmth  and  too  copious  watering.  The  flower  cluster, 
not  yet  beginning  to  elongate,  cannot  utilize  or  absorb  the  water  brought  to 
it  by  the  increased  root  pressure.  Thus  an  excess  of  water  is  accumulated 
at  the  base  of  the  flower  stalk,  whose  cells  elongate  and  weaken  their 
connection. 

A  slower  forcing  of  the  hyacinth  might  prevent  this  condition. 

Twig  Abscission. 

The  small  branches  which,  usually,  together  with  their  fully  developed 
foliage,  are  cut  off  from  the  main  axis  by  some  organic  process  may  be 
called  abscissed  twigs.  This  abscission  takes  place  chiefly  in  the  autumn, 
yet  it  has  been  observed  in  summer  (July)  and  as  in  leaf  casting  we 
must  take  into  consideration  different  causes  for  the  same  phenomenon. 
All  trees  do  not  show  this  peculiarity  and  even  those  in  which  it  appears 
do  not  shed  their  branches  every  year\  nor  do  all  of  them  do  so.  Young, 
vigorous  trees  often  do  not  shed,  while  older  specimens,  or  those  standing 
on  poor  soil,  in  the  autumn  cover  the  ground  underneath  them  with  branches. 

The  poplars-  furnish  the  best  known  example.  Their  branches,  often 
meters  long,  with  their  swollen,  hemispherically  rounded  joint-like  abscission 
surfaces,  smooth  and  shining  like  velvet  in  damp  weather,  show  most  clearly 
that  the  branch  is  not  loosened  by  a  forcible  tearing  of  its  component  parts, 
but  by  a  separation  of  certain  tissue  zones  preceded  by  internal  organic 
processes. 


1  Borkhausen,  Forstbotanik  I,  p.  294. 

-  K.  Muller,  Hal.,  Der  Pflanzenstaat,  p.  532,  gives  an  illustration  of  this. 


358 

The  abscissed  branches  of  oaks'  should  be  mentioned.  In  spruces 
except  for  the  twigs  frequently  found  bitten  off  by  squirrels-,  there  are 
probably  no  actual  abscissed  twigs. 

Further,  this  phyllocladia,  or  loosening  of  the  branches,  has  been  ob- 
served in  Xylophylla  and  Phyllocladus^,  in  all  Dammara  species  and 
especially  in  Dammara  australis,  according  to  A.  Braun,  in  several  Podo- 
carpus  species,  in  Guajaceae,  Piperaceae,  many  bushy  Acanthaceae,  in 
Laurus  Camphora,  Crassula  arborescens,  Portulacaria  afra,  Taxodium 
distichum*,  in  Tilia"  in  UUnus  pendula,  Evonymus,  Prunns  Padus,  Erica, 
Salix"*,  etc. 

The  trees  partially  owe  their  characteristic  habit  of  growth  to  these 
abscissed  twigs.  But  the  process  of  freeing  varies  according  to  the  habitat, 
weather  and  other  agencies.  Thus  Rose,  for  example,  emphasizes  that, 
with  continued  drought,  the  branches  fall  more  abundantly;  in  the  majority 
of  cases,  side  shoots  are  dropped,  but  many  plants  lose  their  tips  as  well. 
The  last  case  is  observed  most  frequently  in  young  trees  grown  on  fertile 
soil.  Nordlinger"  emphasizes  that  predominantly  the  weakly  grown 
branches  are  the  ones  shed. 

Just  as  we  find  the  leaves  falling  in  summer,  we  also  tind  a  summer 
abscission  of  the  branches.  Gymnocladus,  Catalpa  bignonioides,  Gleditschia, 
Tilia  and  especially  Ailanthus  glandidosa  exhibit  the  same  formation  of  an 
abscission  layer  and  the  separation  of  the  cells  from  one  another  as  found 
in  the  case  of  fallen  leaves.  In  young  shoots  of  Ailanthus  it  may  be  ob- 
served that,  besides  the  parenchyma,  even  the  still  unlignifted  cells  of  the 
vascular  bundles  are  involved  in  the  formation  of  the  cleavage  layer.  No 
cork  is  developed  at  this  time  either  near  the  abscission  or  in  the  upper 
surface  of  the  bark  of  the  branch.  Hence  we  often  find  it  affirmed  that  the 
process  of  abscission  does  not  depend  upon  the  formation  of  a  cork  layer 
and  that  this  cork  layer  is  to  be  considered  only  as  a  protective  layer  for 
the  free-lying  parenchyma  appearing  sometimes  earlier  (before  the  cleav- 
age), sometimes  later. 

We  owe  very  extensive  investigations  of  twig  abscission  to  v.  Hohnel', 
who  has  included  conifers  especially  in  the  scope  of  his  work,  and  has  come 
to  the  conclusion  that,  in  them,  one  cannot  speak  of  any  twig  abscission, 


1  Th.  Hartig,  Naturgeschichte  d.  Forstl.  Kulturpflanzen,  p.  119.  Pfeil,  Deutsche 
Holzzucht,  1860,  p.  136.  Wigand,  Der  Baum,  1854,  p.  67.  Schacht,  Der  Baum,  1853. 
p.  305.     Lehrbuch  d.  Anatomic  usw.,  1859,  II,  p.  19. 

2  Ratzeburg,  Waldverderbnis,  I,  1866,  p.  219  (Plate  28,  Fig.  3).  Compare  Beling 
and  further  Roth  (tJber  Absprunge  bei  Fichten),  Bot.  Jahresbericht  von  Just,  II, 
p.  968,  971,  and  v.  Hohnel,  Bot.  Jahresb.  VI,  Gonnermann,  tJber  die  Abbisse  der 
Tannen  and  Fichten.  Bot.  Zeit.  von  v.  Mohl  and  Schlechtendal,  1865,  No.  34.  RosSi, 
Bot.  Zeit.  1865,  No.  41. 

a  v.  Mohl,  tJber  den  Ablosungsprozess  saftiger  Pflanzenorgane  Bot.  Zeit.  1860, 
p.  274  and  275. 

4  Rose,   tlber  die  "Absprunge"  der  Baume.  Bot.  Zeit.  1865,  p.  109   (No.  14). 

5  V.  Mohl,  tJber  den  Ablosungsprozess  saftiger  Pflanzenorgane  Bot.  Zeit.  1860, 
p.   274  and  275. 

0    Nordlinger,  Deutsche  Forstbotanik.  1874,  I,  p.  199. 

"  V.  Hohnel,  tJVjer  den  Ablosungsvorgang  der  Zweige  einiger  Holzgewachse  und 
seine  anatomischen  Ursachen.  Mitteilungen  aus  dem  forstlichen  Versuchswesen 
Oesterreichs  von  v.  Seckendorff,  III,  1878,  p.  255.  Weitere  Untersuchungen  iiber  den 
Ablosungsvorgang  von  verholzten  Zweigen.  Bot.  Centralbl.   1880,   p.   177. 


359 

so  long  as  the  shedding  of  Uving,  fresh  and  sappy  branches  is  meant  by  it. 
In  conifers,  the  branch  to  be  shed  first  dies  on  the  trunk,  becoming  yellow 
or  brown ;  it  is  shed  in  the  usual  way  only  after  death,  and  a  cork  layer  is 
always  formed ;  in  this  process,  the  wood  breaks  off  at  a  definite  place. 
The  abscissed  twigs  of  deciduous  trees  are  shed  in  a  living  and  sappy  con- 
dition by  means  of  a  parenchyma  zone  traversing  the  thick  wood  but  with- 
out the  assistance  of  a  cork  layer. 

The  age  of  normally  abscissed  twigs  varies  greatly.  In  Taxodium  they 
are  always  one  year  old;  in  Pinus  strobus,  always  three  years  old;  in  Finns 
Larcicio,  2  to  y  year  old ;  in  Pinus  silvestris,  2  to  6  years  old ;  in  Thuja 
occidentalis,  3  to  11  years  old.  It  was  stated  at  the  outset  that  spruces  and 
firs  are  said  not  to  shed  their  branches.  Nevertheless,  I  remember  once 
having  seen  fresh  spruce  shoots  with  a  dismembered  surface  resembling 
an  articulation. 

In  deciduous  trees,  it  can  be  seen  clearly  that  the  twigs  usually  shed 
are  those  grown  from  lateral  buds  or  adventitious  eyes  which  are  often 
weakly,  and  have  grown  only  to  short  shoots.  Only  in  poplars  and  willows 
and  seldom  in  oaks  are  long  shoots  abundantly  shed,  and  then  only  older 
ones  (branches  up  to  6  years  old).  In  rare  cases  the.  process  is  observed 
also  in  Pnimis  Padus  and  Evonymiis  europaea,  while  in  other  trees  usually 
one  year  old  shoots  alone  are  shed. 

Worthy  of  our  attention  is  v.  Hohnel's  observation  that  the  wood  of 
Thuja  occidentalis  is  weaker  where  the  constriction  will  appear  later,  than 
at  any  other  place.  At  the  place  which  will  later  be  the  cleavage  surface, 
ihe  wood  is  greatly  constricted.  The  parenchyma  cells  of  the  bark  enlarge 
so  that  a  considerable  loosening  is  produced.  In  Thuja  orientalis  the  fleshy 
branch  cushion  is  lacking,  and  no  regular  shedding  is  found.  Meehan^ 
found  in  Ampelopsis  quinque folia  that  the  basal  internode  remains  stationary 
and,  in  the  following  year,  produces  new  shoots,  which  in  turn  disarticulate 
with  the  occurrence  of  colder  weather. 

The  law  formulated  for  leaf  casting  may  be  applied  to  abscissed 
twigs : — the  centre  of  consumption,  which  here  is  the  twig,  for  some  reason, 
no  longer  forms  the  normal  centre  of  attraction  for  the  undiminished  flow 
of  water  and  an  excess  of  water  accumulates  accordingly  in  the  basal  zone 
which  is  still  capable  of  reaction,  and  anatomically  differently  constructed. 
Either  the  branches,  from  the  beginning,  have  been  more  weakly  set,  or, 
because  of  an  unfavorable  habitat  they  do  not  develop  so  far  or,  in  great 
summer  drought,  they  have  become  prematurely  ripe  or  they  are  rendered 
incapable  of  action  by  cold,  etc.  In  a  weak  organ,  the  relative  excess  of 
water  makes  itself  felt  first  at  the  base.  If  this  organ  develops,  from  the 
start,  with  the  presence  of  a  large  water  supply,  no  shedding  takes  place. 
Wet  years  exhibit  little  if  any  twig  abscission.  The  theory  held  by  fores- 
ters, that  years  with  much  twig  abscission  initiate  good  seed  years,  has  its 


1  Meehan,   On  disarticulating  branches  in  Ampelopsis.     From   "Proceed,  of  the 
Americ.  Acad,  of  Philadelphia."     Part  I,  1S80,  im  Bot.  Centralbl.  1880,  p.   1005. 


36o 

foundation  in  the  fact  that  these  are  dry  years,  favoring  the  maturing  of  the 
blossom  buds. 

Even  if  twig  abscission  is  of  httle  practical  importance  in  forestry, 
it  is,  however,  of  horticultural  importance  as  a  symptom.  Especially  in 
the  autumn  the  stem  parts  of  many  greenhouse  plants  are  abscissed,  as  in 
the  bushy  Begonias,  Melastomaceae,  Acanthaceae,  etc.  They  are  positive 
indications  of  excess  of  water,  and  the  only  means  of  prevention  is  to  keep 
the  plants  dry. 

b.     Increase  of  Food  Concentration. 

Among  the  phenomena  of  disease  to  be  discussed  in  this  section,  those 
must  be  considered  in  which  an  excess  of  water  in  the  plant  becomes  mani- 
fest locally.  In  this  the  root  activity  is  not  necessarily  increased,  the  accum- 
ulation of  water  is  produced  rather  by  a  depression  of  the  transpiratory 
activity  of  the  leaves.  Increase  in  turgor  must  set  in  in  various  organs,  or 
parts  of  organs,  by  increased  water  supply,  as  has  been  proved  artificially  in 
severed  leaves.  Consequently,  the  fact  remains  to  be  considered  here  that 
the  humidity  of  the  air  often  co-operates  decisively.  Conversely,  in  other 
cases,  in  which  an  excess  of  nutrients  is  involved,  attention  should  be  called 
to  the  fact  that  this  excess  does  not  always  presuppose  an  absolute  accum- 
ulation in  the  soil,  but  also  occurs  when  the  solvent,  i.  e.,  the  water,  is 
temporarily  present  in  too  small  an  amount,  thereby  producing  an  injuriously 
high  concentration  of  the  soil  solution. 

The  demands  made  upon  the  soil  solution  by  each  species  seem  to  dift'er 
according  to  the  different  cjuantitative  proportions  in  which  the  various 
nutrients  and  other  factors  of  growth  participate  in  the  production  of  one 
gram  of  dry  weight  of  a  species.  In  plants,  for  example,  which  require 
much  potassium  or  nitrogen  to  produce  their  substance,  a  high  percentage 
solution  of  these  substances  will  be  necessary  for  the  root.  The  plants  do 
not  die,  if  the  desired  high  concentration  is  not  afforded  them,  but  they 
change  their  mode  of  growth.  They  then  require,  as  already  proved,  much 
more  water  just  as  if  they  must  strive  to  obtain  the  necessary  quantity  of 
a  certain  nutrient  by  an  increased  absorption  of  the  more  dilute  solution. 
In  spite  of  the  large  quantity  of  water  and  substances  otherwise  offered, 
the  production  as  a  whole  is  small.  A  similar  cessation  of  growth  is  found, 
if  the  plants  are  placed  in  a  too  concentrated  soil  solution.  The  absorption 
of  water  is  relatively  scanty;  the  amount  of  ash,  however,  large  and  the 
production  in  dry  weight  small.  The  excess  then  is  taken  up  but  not  uti- 
lized, the  mineral  substances  are  simply  deposited  in  the  plant  and  may 
partially  be  leached  out  again  by  water.  In  water  cultures  with  a  high 
concentration  of  nutrients  the  short,  gnarled  root  hairs  are  sometimes  per- 
ceptibly covered  with  crystalline  scales.  Thus,  for  example,  accumulations 
of  saltpetre  may  take  place  in  the  plant  if  an  excess  of  potassium  nitrate  is 
given.     Emmerling\  by  means  of  experiments,  explains  very  acceptably 

1  Emmerling-,  A.,  Beitrage  zur  Kenntnis  der  chemischen  Vorg-ange  in  der 
Pflanze.     Landwirtsch.   Versuchsstationen,  Vol.  XXX,  Part  2,  1884,  p.  109, 


36i 

the  processes  taking  place.  He  shows  that,  exactly  as  with  the  use  of  cal- 
cium nitrate,  potassium  nitrate  is  decomposed  by  oxalic  acid,  even  in  very 
dilute  solutions,  in  such  a  way  that  potassium  oxalate  and  free  nitric  acid 
are  produced,  while  oxalic  acid  does  not  act  strongly  on  calcium  carbonate, 
since  it  only  coats  it  with  an  impervious,  thin  layer  of  calcium  oxalate.  If 
now  the  saltpetre  in  the  soil  is  relatively  great  in  proportion  to  the  acid 
which  a  plant  species  can  form,  the  saltpetre  will  be  taken  up,  to  be  sure, 
but  will  be  decomposed  only  proportionately  to  the  oxalic  acid  present,  and 
the  free  nitric  acid  is  used  in  the  formation  of  the  proteins;  the  remaining 
saltpetre  is  deposited  unchanged  in.  the  plant. 

In  our  cultivated  plants  the  law  certainly  holds  good,  that  they  all  re- 
quire the  same  nutrients  but  in  different  concentrations,  and  also  that  their 
capacity  for  enduring  the  accumulation  of  various  substances  is  decisive 
for  the  success  of  the  cultures.  It  should  not  be  forgotten  here,  that  neither 
the  absolute  amount  of  nutrients,  which  is  borne  without  any  injury,  nor 
also  the  quantity  of  any  nutrient  proved  to  be  the  best  (optimum)  for  pro- 
duction, represents  absolutely  fixed  amounts  for  any  definite  plant.  Rather, 
it  should  be  assumed  that  the  need  for  any  definite  nutrient  changes  con- 
stantly according  to  the  combination  in  which  the  other  vegetative  factors 
are  present  at  the  moment.  Thus,  there  is  always  a  relative  optimum  and 
maximum  for  each  vegetative  factor.  The  mode  of  production  and  the 
product, — viz.,  the  plant  body, — change  according  to  the  momentary  com- 
bination of  the  vegetative  factors ; — thus  morphological,  anatomical,  and 
chemical  analyses  give  different  values  for  each  individual. 

Each  change  in  concentration  in  the  same  nutrient  mixture  changes  the 
method  of  growth  and  directly  manifests  itself,  under  certain  circumstances, 
in  the  behavior  of  the  root  hairs,  as  stated  by  Stieler\  He  found  in  the 
growing  root  hair,  with  each  change  in  the  solution,  a  change  (thickening) 
of  the  membrane  at  the  end  of  the  root  hair; — under  certain  circumstances, 
in  fact,  a  cessation  of  growth  occurs.  In  aqueous  solutions  of  the  electro- 
lytes, the  root  hairs  in  many  plants  form  vesicular,  irregular  widenings,  and 
can  even  crack  open  at  the  tip  or  (rarely)  laterally.  The  non-electrolytes 
exercise  an  injurious  influence,  only  if  they  have  a  poisonous  effect  or  are 
present  in  too  high  a  concentration,  which  causes  plasmolysis.  The  ob- 
servation that  concentrated  magnesium  compounds  can  be  proved  to  act 
directly  poisonously,  is  especially  noteworthy.  This  cannot  be  observed 
for  other  nutritive  salts  even  with  high  concentration. 

These  investigations  confirm  my  own  observations,  viz.,  that,  in  a 
highly  concentrated  nutrient  solution,  "gnarled  or  distended"  root  hairs 
appear,  and  thereby  indicate  that  the  plant  has  had  to  combat  difficulties  in 
absorbing  its  food. 

In  regard  to  varieties  of  grain,  the  experiments  indicate  that  oats,  for 
example,  can  suffer  from  the  amounts  of  nutrients  wdiich,  for  wheat,  make 


1   Stieler,  G.,  tJber  das  Verhalten  der  Wurzelharchen   gegen    Losungen,   Disser- 
tation. Kiel  1903.    Cit.  Bot.  Centralbl.  v.  Lotsy  1904,  No.  47,  p.  541. 


362 

possible  only  a  full  production.  Thus  oats  often  fail  on  parcels  of  land, 
which  have  gradually  been  too  heavily  fertilized.  Measurements  of  the 
amount  of  transpiration  show  that  in  concentrated  solutions,  the  plant  needs 
less  water,  for  the  production  of  one  gram  dry  weight,  than  it  does  in  very 
dilute  ones.  From  this  it  is  evident  that,  up  to  a  certain  degree,  fertilizing 
signifies  a  saving  of  water\ 

The  structure  and  size  of  the  root  system  is  changed  gradually  by  con- 
centration, corresponding  to  the  change  in  the  root  hair,  already  mentioned. 
Schwarz's-  experiments  with  pines  demonstrated  this  very  well.  He  found 
a  gradual  decrease  in  the  extent  of  the  roots  of  conifers  with  an  increase 
of  the  nutrient  content  of  the  soil,  as  had  already  been  determined  for 
other  plants.  Here  the  relation  between  the  aerial  and  underground  axes 
was  changed.  While,  in  unfertilized  sand,  the  weight  of  the  root  system  of 
the  pine  seedlings  was  greater  than  that  of  the  aerial  parts,  with  an  abun- 
dant supply  of  nutritive  salts  the  weight  of  the  root  system  amounted  to 
only  one-fifth  that  of  the  aerial  axis. 

Even  in  cabbage  plants,  which  have  been  gradually  accustomed  by  cul- 
tivation to  the  highest  admissible  concentrations,  an  over-nutrition  finally 
takes  place  and  with  it  a  retrogression  in  production.  Thus  kohlrabi  plants 
were  found  to  be  especially  susceptible  to  large  additions  of  phosphorus, 
while  they  require  high  nitrogen  and  potassium  fertilization,  together  with  a 
corresponding  addition  of  calcium^. 

Changes  in  Meadows. 

The  method  of  improving  sour  and  sandy  meadows  by  fertilization, 
depends  essentially  on  an  increase  of  the  nutrient  concentration.  The  acid- 
loving  grasses,  or  those  of  sterile  soil,  which  withstand  only  weakly  con- 
centrated solutions,  then  disappear  and  our  good  fodder  grasses,  demand- 
ing higher  nutrient  content  and  producing  more  nutritive  substance  are 
established.  Very  instructive  experiments  on  permanent  meadows  are 
found  in  Lawes  and  Gilbert*.  We  w^ill  cite  from  them  only  one  example, 
in  order  to  show  that  those  different  grass  species  gradually  prevail  in  those 
nutrient  solutions,  of  which  they  can  endure  a  higher  concentration.  With 
the  stated  fertilizers,  the  percentages  of  the  various  grass  species  in  100 
hay  plants  were  found  as  given  in  the  following  table. 

From  this  table  of  grasses,  we  see  how  the  rapidly  spreading  Festuca 
duriuscula  disappears  on  sterile  sandy  soil,  if  the  concentration  of  the  ni- 
trate solutions  and  the  mineral  substances  increase  simultaneously.  Agrostls 
julgaris  and  Anthoxanthum  odoratnm  behave  similarly,  while,  conversely, 


1  Sorauer,  P.,  tJbef  Mifsernten  bei  Hafer.  Oesterr.  Landwirtsch  Wochenblatt. 
Nos.  2,  3.  1888. 

2  Schwarz,  F.,  t)ber  den  Einfluss  des  Wasser-  und  Nahrstoffgehaltes  des  Sand- 
bodens  auf  die  Wurzelentwicklung  von  Pinus  silvestris  im  ersten  Jahr.  Zeitschr.  f. 
Forst-u  Jagdwesen.    January,   1892. 

3  Otto,  R.,  Vegetationsversuche  mit  Kohlrabi  etc.     Gartenflora,  1902,  p.   393. 

4  From  "Journal  of  the  Royal  Agric.  Soc.  of  England"  and  "Proceedings  of  the 
Royal  Hort.  Soc.  1870,"  cit.  in  Biedermann's  Centralbl.   1876,    II,  p.   405. 


3^3 

the  heavy  feeding  plants  of  our  sewage  disposal  fields,  Dactylis  (jlomerata 
and  Poa  trivialis,  during  the  five  years  over  which  the  experiments  extended 
(the  results  are  given  in  the  table),  became  more  and  more  abundantly 
established  on  the  parcels  of  land  strongly  fertilized  with  nitrogen,  and 
crowded  out  the  others.  The  grass  of  village  streets,  Bronius  mollis,  ap- 
peared in  high  percentages  only  when  stable  manure  had  been  used,  while 
Loliuni  perenne  and  Holcus  lanatus  were  present  everywhere,  to  be  sure, 
yet  spread  but  little  where  stable  manure  was  abundantly  used. 

>.      'ji         "^  r  c         Stable- Manure 


Species  of  Gras.ses  ^^         "5'S-         'S-r         .5  2^        u^~  5  S;^ 

>  ■-         -2  ^  Z  zr'       •Sol'  <  <•- 

Festuca  duriuscula    I3-04  21.42  12.00  2.98  0.79  0.22  0.19 

A(irostis  vulgaris 8.62  21.29  2.76  11.55  9-15  ^-3^  ^-'■/^ 

Folium  perenne   8.62  3.39  3.03  11.89  ^•^-'  2.59  2.73 

Holcus  lanatus    4.97  9.68  4.86  11.06  8.82  2.17  2.01 

Dactylis  glomerata    1.76  2.2y  2.79  5.04  23.58  4.85  16.86 

Poa  trivialis 1. 50  1.61  5.77  12.00  15.47  27.43  29.34 

Bromus  mollis   0.08  0.15  0.63  2.21  0.93  9.64  12.53 

Anihoxanthum   odoratum.   3.29  2.41  0.80  0.49  o.io  0.19  0.06 

Among  other  interesting  observations  of  these  authors  is  the  one  that 
the  parcels  of  meadow  land,  which  had  remained  unfertilized,  exhibited 
great  diversity  in  the  families  and  species  growing  on  them.  The  grass  was 
short,  stemless,  and,  at  the  time  for  cutting,  comparatively  very  green.  With 
mineral  fertilizers,  the  Leguminoseae  gained  the  upper  hand,  while,  in  the 
Gramineae,  which,  however,  showed  no  especial  prevailing  genus,  the  tend- 
ency to  the  development  of  blossoms  was  mere  decided  than  on  unfertilized 
land.  Conversely,  ammonium  salts,  given  alone  without  other  fertilizers, 
almost  excluded  the  Leguminoseae,  and  the  Gramineae,  therefore,  predomi- 
nated. Festuca  and  Agrostis  reached  their  highest  percentage,  and  Rumex, 
Carum  and  Achillea  throve  luxuriantly. 

If  Chile  saltpetre  alone  were  used,  the  efifect  in  general  was  the  same  as 
with  ammonium  salts  ;  nevertheless,  among  the  grasses,  Alopecurus  pratensis 
was  especially  prevalent ;  and  a  predominating  tendency  to  leaf  production 
also  became  noticeable  in  contrast  to  the  development  of  the  flower  stems. 
Besides  the  somewhat  better  developing  Leguminoseae,  there  was  a  lux- 
uriant development  of  the  little  useful  Plantago,  Centurea,  Ranunculus  and 
Taraxacum. 

The  highest  yield  and  the  best  development  of  the  grasses  was  found 
with  stable  manure  to  which  some  fertilizer  containing  nitrogen  had  been 

1   By  mineral  fertilizers,  the  authors  mean  a  mixture  of  super-phosphate  with 
potassium,  sodium  and  magnesium  sulfates. 


364 

added.  The  Leguminoseae  and  other  plants  disappeared,  having  been  over- 
grown by  the  grasses  which  then  ripen  more  easily  than  if  they  have  only 
a  nitrogen  supply.  Stable  manure  alone  also  yielded  a  considerable  har- 
vest of  Bromus  mollis  and  Poa  trivialis  especially,  with  fewer  Legumi- 
noseae, but  it  left  much  to  be  desired  in  the  fineness  and  uniformtiy  of 
the  hay. 

If  mossy  meadows  are  brought  under  cultivation,  the  moss  cannot  en- 
dure a  concentrated  nutrient  solution,  or,  at  least,  a  high  concentration  of 
various  nutrient  salts  which  require  still  closer  examination.  This  explains 
the  disappearance  of  moss  from  meadows  after  they  have  been  fertilized 
with  potassium.  The  same  behavior  is  found  for  the  horsetail  (Equisetum) 
which  is  said  to  disappear  absolutely  after  the  use  of  calcium  chlorid,  and 
seems,  on  this  account,  to  be  especially  sensitive  to  high  calcium  concen- 
tration. 

In  contrast  to  the  extreme  impoverishment  of  the  meadows,  manifested 
by  a  mossy  vegetation,  stands  the  over-powerful  development  of  grass  on 
the  so-called  rankly  growing  places.  There  is  an  abundant  nitrogen  fertili- 
zation from  the  excretions  of  animals  and  its  results  are  shown  by  a  more 
luxuriant  blade  development..  According  to  Weiske^,  the  plants  had  nearly 
twice  as  much  protein  but  possibly  %  less  of  substances  free  from  nitrogen, 
than  the  neighboring  plants  which  had  not  been  over-fertilized.  Accord- 
ingly, the  ash  of  the  former  contained  more  alkalis,  magnesium  and  sulfuric 
acid.  The  plants  on  such  rankly  growing  places,  despite  their  greater 
volume,  remained  in  an  immature  condition.  With  a  greater  spread  of  such 
over-fertilized  places,  these  plants  would  become  more  injurious  than  bene- 
ficial.   In  this  they  resemble  the  condition  on  the  sewage  disposal  beds. 

Sewage  Disposal  Beds. 

The  increased  use  of  sewage  disposal  beds  near  large  cities  requires 
special  discussion  of  the  injuries  unavoidable  in  this  practice.  Ehrenberg- 
has  recently  published  his  experiences  in  regard  to  the  Berlin  sewage  beds. 

Aside  from  the  notably  increased  development  of  Plasmodiophora 
Brassicae,  due  to  the  rapidly  repeated  cultivation  of  species  of  cabbages, 
he  reported  also  injuries  due  to  animal  parasites.  Most  of  all  occurred 
the  extraordinary  increase  of  Silpha  atrata,  whereby  great  areas  of  beets 
were  completely  destroyed.  The  parasites  found  over-abundant  nourish- 
ment in  the  decomposing  organic  substances  of  the  liquid  sewage  and,  in 
the  dams  and  canals,  lurking  places  where  they  were  protected  from  cold 
and  enemies.  The  great  supply  of  nutrients  also  attracted  the  crows  from 
long  distances  to  the  sewage  beds  on  which  seeds,  as,  for  example,  maize 
and  wheat,  were  uprooted  in  whole  rows.     Rats  were  another  pest. 

In  addition  to  the  damage  done  by  animal  and  plant  forms,  the  wind 
caused  more  damage  here  than  on  other  fields.     On  the  Berlin  sewage  beds 


1  Annalen  d.  Lnndwirtsch.   1871.     Wochonblatt,  p.  310. 

2  Ehrenberg-,  Paul,      Einig-e  Beobachtung-en  iiber  Pflanzenbeschadigungcn  durcli 
Siniljauchenberieselunp:.     Zeitschr.    f.    Pflanzenkrankh.    1906. 


365 

a  large  number  of  fruit  trees  in  full  leaf  were  blown  down,  in  spite  of 
strong  stakes,  because  the  earth,  which  was  wet  through,  did  not  support 
the  roots  sufficiently.  This  was  especially  noticeable  if  a  part  of  the  field, 
with  the  surrounding  avenues  of  fruit  trees,  was  flooded  with  liquid  sewage. 

Sugar  and  fodder  beets,  carrots  and  similar  roots  irrigated  during 
the  growing  season,  could  not  withstand  liquid  sewage  about  their  crowns 
for  any  length  of  time.  In  a  few  hours  the  leaves  began  to  zvilt  and  towards 
evening  the  petioles  became  limp.  Grains,  grass,  legumes  and  other  plants 
withrut  fleshy  roots  did  not  react  in  this  way.  Probably  the  wilting  is 
physiological  since  the  scanty  root  fibers  present  on  each  fleshy  root  cannot 
draw  enough  water  from  the  highly  concentrated  soil  solution  to  make 
good  the  loss  from  evaporation.  If  the  concentration  of  the  soil  solution 
was  decreased  by  the  absorption  of  the  soil,  the  wilting  disappeared. 

To  avoid  this,  dams  one  meter  wide  were  built,  or  the  roots  were  hilled 
up  as  they  grew  and  irrigated  in  the  furrows  thus  produced. 

Attention  has  been  called  in  another  place  to  the  change  in  the  growth 
of  grasses.  On  the  Berlin  sewage  beds,  Lolium  italicum  abounds  and  often 
is  entirely  killed  if  irrigated  in  winter. 

The  softness  of  the  grass,  indicated  by  its  easy  decay,  is  also  caused 
chiefly  by  an  excess  of  nitrogen.  On  an  average,  in  the  years  1900  to  1902, 
a  hectare  of  the  Berlin  sewage  land  received  800  to  1200  kg.'  Nitrogen^ 
In  spite  of  the  very  sparse  seeding  and  the  widely  separated  planting  the 
over- fed  grain  plants  are  usually  inclined  to  lodge.  I  had  an  opportunity 
to  study  the  process  taking  place  in  this  lodging  of  oats  on  the  Berlin  sew- 
age beds-.  In  this,  a  peculiar  softening  of  the  leaf  tissue,  due  to  bacteria, 
was  noticeable.  Regarding  the  behavior  of  young  seedlings  with  over- 
fertilization,  I  observed  in  barley,  that,  in  comparison  with  the  normally 
nourished  plants,  over-fertilized  ones  became  a  darker  green,  but  were  back- 
ward in  growth.  Then  the  tips  of  the  leaves  bore  greyish  yellow  spots  and 
finally  turned  entirely  grey;  at  this  time  a  number  of  seedlings  lodged.  Soon 
after  lodging,  the  part  of  the  stalk  above  the  bend  began  to  dry.  But  while 
plants  normally  drying  finally  assume  a  straw  color,  only  the  lower  leaves 
in  this  case  became  straw-colored  and  the  upper  ones  dried  to  a  hay  green 
color.  Of  importance  here  is  also  the  diseasing  of  the  vascular  bundles 
ind  the  great  predisposition  of  the  plants  to  attacks  of  fungi"*. 

Besides  the  well-known  delay  in  the  ripening  of  grain  on  sewage 
fields.  Ehrenberg  also  mentions  the  change  in  the  proportion  between  the 
yield  in  straw  and  grain.  In  irrigated  oats  the  proportion  of  grain  to  straw 
was  as  I  :3.33,  in  non-irrigated,  as  i  :2.88. 

Such  a  "luxurious  growth  of  straw"  gradually  becomes  typical,  for 
seven  newly  grown  varieties  of  barley  gave  an  average  proportion  of  grain 


1  Backhaus,  Landwirtschaftl.  Ver.suche  auf  den  Rieselg-iitern  der  Stadt  Berlin 
im  .Jahre  1914. 

"  Soiauei-,  P.,  Beitrag  zur  analomischen  Analyse  rauchbeschadig-ter  Pflanzen. 
Landw.  Jahrbiicher  von  Thiel.,  1904,  p.  593. 

■■!  Loc.   cit.    p.    646. 


366 

to  straw  of  i  :i.75,  while  varieties  grown  for  a  long  time  on  sewage  beds, 
showed  I  :2.88.  Wheat  and  rye  behaved  similarly.  The  amount  to  which 
ripening  can  be  retarded  in  extreme  cases,  was  found  for  red  mountain 
wheat,  which,  sown  on  April  19th,  ripened  on  irrigated  fields  on  the  13th 
of  September,  but  on  non-irrigated,  on  August  24th.  Tliere  was  then  a 
difference   of   20   days. 

Mention  is  made  in  another  place  of  the  disadvantageous  effect  of 
chlorin  compounds  on  the  starch  content  of  potatoes,  and  on  other  plants. 

The  "coatin;/  with  ooze  and  mud"  is  the  most  important  injury  in  sew- 
age disposal  beds.  Liquid  sewage  contains,  besides  great  quantities  of 
sodium  chlorid  and  other  salts,  many  organic  substances  especially  pieces  of 
paper,  coffee  grounds  and  the  like.  Six  investigations  of  Berlin  sewage  in 
1902,  gave  on  an  average : 

Organic  Substances   0.030  per  cent. 

Potassium    0.006  per  cent. 

Sodium     0.022  per  cent. 

Sulfuric  acid 0.006  per  cent. 

Chlorin     0.020  per  cent. 

The  pieces  of  paper  and  the  organic  substances  dry  up  on  the  beds 
into  tough,  thin,  flat  cakes,  decomposing  only  with  difficulty  because  of 
their  fatty  content.  Soaked  with  salts  and  organic  substances,,  these  form 
the  ooze,  which  acts  detrimentally  to  the  soil.  The  high  content  in  salts  will 
easily  cause  a  leaching  of  the  calcium  through  an  exchange  of  bases. 

Analyses^  prove  that,  on  sewage  beds  covered  with  ooze,  calcium  is 
actually  carried  off.     The  calcium  content  amounted  in 

upper  surface  sub-soil 

Normal  soil    0.153  per  cent.         0.031   per  cent. 

The  same  soil,  but  covered  with  ooze. 0.122  per  cent.         0.048  per  cent. 

An  application  of  calcium  is,  therefore,  desirable  in  soils  covered  with  ooze, 
since  its  action  improves  the  soil  physically. 

The  disposal  of  the  above  mentioned  papery  flat  cakes,  which  ma\ 
choke  young  plants,  especially  grasses,  will  have  to  be  undertaken  first  of 
all  by  harrowing,  tearing  and  removing  the  rags.  Nevertheless,  in  planting 
the  fields,  great  quantities  get  on  to  the  soil  and  have  an  injurious  effect. 
The  enrichment  in  organic  substances,  due  to  the  ooze,  may  be  recognized 
from  the  loss  when  heated : 

Normal  soil  contained   (in  a  friable  condition) ...  1.994  per  cent. 
The  same  soil,  covered  with  ooze 2.418  per  cent. 

Vegetative  experiments  in  pots  showed  that  an  admixture  of  ooze  always 
arrested  growth,  and  an  addition  of  quick  lime  did  not  overcome  this  re- 
tardation. The  arrestment  in  development  did  not  show  itself  in  the  ap- 
pearance of  positive  symptoms  of  disease,  but  only  in  the  delayed  sprouting 

1   Backhaus,  loc.  cit.  p.   69  and   p.  114. 


3^7 

of  the  seed  and  general  depression  in  growth.  The  explanation  of  the  phe- 
nomenon should  be  sought  in  the  physical  domain.  The  ooze  which  is  very 
impervious  to  water  and  air, 
because  of  its  closely  cemented 
particles  and  its  fatty  content 
arrests  the  spread  of  the  roots 
and  greatly  prevents  the  rise  and 
fall  of  the  water. 


The   Scurvy   Disease. 

Among  the  many  forms  of 
disease,  of  which  the  causes 
are  not  satisfactorily  explained, 
scurvy  should  be  included  under 
the  diseases  due  to  material  ex- 
cess. The  reason  for  this  is  the 
frequent  observation  that  after 
the  addition  of  substances  tend- 
ing to  increase  the  alkalinity  of 
a  soil,  scurvy  usually  appears  in 
increased  amounts. 

Scurvy  or  "scab"  consists 
of  flatly  spread,  cork  colored 
bark-like  spots  formed  on  the 
fleshy  under- 
ground root, 
or  storage  tu- 
ber. As  long 
as  such  a  bark- 
like cleft  re- 
mains super- 
ficial the  dis- 
ease is  called 
"surface  scur- 
vy." If,  on  the 
other  hand,  the 
injured  places 
deepen  rapid- 
ly becoming 
grooves  or 
holes,  the  dis- 
ease is  called 
"deep  scurvy." 
In    certain 

cases  warty  outgrowths  appear  on  the  wounded  surface,  and  this  condition 
has  been  distinguished  as  "knotted  scurvy." 


Fig-.    52. 


Carrot    diseased    with    deep    scurvy,    seen    from    the 
most  diseased  side  of  the  root. 


Fig.  A.  /,  /'  find  t-.  vascular  bundle  ring's  arranged  in  terraces:  g.  holes  in  the 
tissue  with  tinder-like  eilt;es;  k.  tnl'erons  parenchyma  outgrowths  on  the  carrot 
head,  which  may  be  iiidiiMlnl  as  i)u-  o\  irjrowtli  ti-^'^iie  of  the  scurvy  wound:  s, 
initial  stages  of  the  s>  m  \  \  w  liii  li  t  \ti  ii>l  d^  .w  iiwaid  along  the  root  groove  (IV) : 
r,  outer  edge  of  the  scui\\  Imllcw:  .,  it-,  ikii>cst  pail;  big.  /?.  Cross-section  of 
the  carrot  near  the  center  of  tlie  deep  scurvy  U  )  .■  Vascular  bundle  rings  destroyed 
by  tlie  scurvy  i,  i'-  and  t^  which  extend  outward  like  terraces  from  the  deepest 
part  of  the  wound;  /  shows  the  poor  formation  of  the  outer  vascular  rings. 


368 

Besides  sugar  and  fodder  beets,  potatoes  sufifer  most  frequently :  also 
roots  of  the  Umbelliferae,  such  as  celery,  carrots,  parsley,  etc.;  more  rarely 
the  fleshy  roots  of  cabbage  plants.  This  condition  is  characterized  by  the 
destruction  of  the  cork  layers.  For  some  time  they  are  replaced  again  and 
again  by  the  underlying  tissues.  Fig.  52  illustrates  a  sugar  beet  suffering  from 
"zonal  deep  scurvy"  or  "girdle  scun-y,"  the  worst  form  of  this  disease. 
The  beet  is  7  to  8  cm.  thick  at  its  head,  but  is  circular  only  at  the  top ;  while 
en  both  sides  where  the  roots  grow,  there  is  a  considerable  flattening  which 
disappears  again  toward  the  lower  end.  The  flattened  sides  are  depressed 
like  troughs  and  the  centre  of  the  trough  is  possibly  6  cm.  away  from  the 
cut  surface  at  the  head  of  the  beet.  The  inner  surface  of  the  trough  is 
wavy  because,  around  the  very  deep  centre,  the  different  layers  of  the  beet 
flesh  rise  like  terraces  aboxe  one  another  towards  the  outer  edge  in  more  or 
less  clearly  defined  zones. 

The  consistency  of  the  tissue  at  the  edges  of  the  trough  is  tindery, 
scurvy-like,  i.  c.  fissured  and  the  fissures  traversed  by  tube-like  passages, 
which  initiate  a  fibrous  decomposition  of  the  substance.  The  passage-like 
fissures  are  lined  with  brown,  corked,  jagged  pieces  of  tissue,  whose  sur- 
faces show  a  peculiarly  grainy  decomposition.  In  spite  of  the  deep  decom- 
position at  the  place  attacked,  we  find  that  the  beet  retains  the  ability  to 
react,  for  the  edges  of  the  various  rings  of  vascular  bundles,  because  of  a 
new  cell  ff)rmati()n.  curve  out  like  ramparts  after  the  injury. 

That  the  growth  of  the  beet  at  the  scurvy  places  may  previously  have 
been  somewhat  arrested  is  evident  from  the  fact  that,  on  the  injured  side  of 
the  beet  as  well  as  on  the  opposite  side,  the  different  tissue  rings  are  smaller 
than  on  the  other  sides.  If  cross-sections  of  the  diseased  plants  are  treated 
with  sulfuric  acid,  it  is  found  that  beneath  the  brown,  dry,  gradually  de- 
composing tissue  layers,  which  have  turned  to  cork,  the  intercellular  sub- 
stance of  the  apparently  healthy  root  flesh  assumes  a  yellowish,  wine-red  to 
bright  carmine  tone.  Often  some  duct  groups  also  seem  to  be  provided  with 
solid  balls,  or  stoppers,  which  assume  the  same  color  when  treated  with 
sulfuric  acid.  Later  the  intercellular  substance  is  found  to  be  broken  up 
and  finally  begins  to  decompose  into  a  grainy  slime.  To  the  naked  eye  the 
whole  process  seems  a  form  of  dry  decomposition. 

As  already  mentioned,  this  form  of  scurvy  which  extends  so  deep  into 
the  flesh  of  the  beet,  is  less  frequent.  We  usually  find  much  flatter,  bark- 
like fissures,  occurring  in  circular  areas,  and  often  showing  that  they  have 
appeared  in  a  rather  early  developmental  stage  of  the  beet,  but  later  have 
stopped  spreading.  It  is  worth  noting  that,  in  the  zonal  deep  scurvy,  the 
head  of  the  beet  does  not  seem  to  be  attacked,  but  the  disease  becomes 
visible  first  at  a  certain  distance  below  this,  in  the  soil.  In  too  deeply 
planted  beets  the  first  traces  of  scurvy  are  often  found  at  the  base  of  the 
petioles.  Ver\^  similar  phenomena  are  noticed  also  in  potatoes,  carrots,  etc. 
In  potatoes,  it  has  been  observed  that  the  scurvy  formation  extends  out 
from  the  lenticels.    If  we  examine  such  a  lenticel,  we  perceive  without  difli- 


PART  V. 


MANUAL 


OF 


PLANT  Diseases 

BY 

PROF.  DR.  PAUL  SORAUER 


Third  Edition—Prof.  Dr.  Sorauer 

In  Collaboration  with 

Prof.  Dr.  G.  Lindau        And       Dr.  L.  Reh 

Private  Decent  at  the  University  Assistant  in  the  Museum  of  Natural  History 

of  Berlin  in  Hamburg 


TRANSLATED  BY  FRANCES  DORRANCE 


Volume  I 
NON-PARASITIC  DISEASES 

BY 

PROF.  DR.  PAUL  SORAUER 

BERLIN 


WITH  208  ILLUSTRATIONS  IN  THE  TEXT 


Copyrighted,  1916 

By 

FRANCES  DORRANCE 


THK    RECORD    PRESS 
"Wilkes-Barre,   Pa. 


3^59 

cully  how  fit  a  point  it  is  for  parasitic  attack.  Here,  under  the  skhi, 
formed  of  plate-like  cork  cells  (k)  (in  the  subjoined  Fig.  53),  we  find  the 
first  stages  of  lenticel  formation  beneath  the  stomata  in  the  form  of  irregu- 
lar cells,  poor  in  contents  (a).  Since  this  cell  formation  extends  further 
and  further  backwards  and  the  cells  first  formed  take  up  water,  swell  and 
rupture  the  corky  cortex,  a  lenticel  is  produced  which  now  gives  rise  to 
scurvy.  From  it  the  loosened  cork  cells  (/)  push  out  in  the  form  of  a 
whitist,  moist  meal.  These  cells  decay,  and  the  process  of  decay  is  con- 
tinued further  inward  so  that  the  close  pressed,  still  connected  rows  of 
immature  cork  cells  (v)  must  be  sought  deeper  and  deeper  in  the  interior 
of  the  tissue.  Here  the  starch  (^0  disappears  from  the  tissue  surrounding 
the  cork  cells.     Continued  moisture  will  develop  very  similar  conditions  in 


Fig.  53.     Identical  formation  on  the  potato  sliin. 


other  underground  parts  of  plants.  In  this  process  the  cork  mantel,  which 
has  previously  acted  as  a  protection,  is  seriously  loosened  and  broken  apart. 
The  scurvy  disease  has  recently  been  considered  to  be  parasitic  and 
usually  is  described  as  due  to  bacteria.  Therefore,  it  is  also  treated  in  the 
second  volume  of  this  manuaP.  But  there  it  is  emphasized,  that  the  cause 
is  ascribed  to  very  different  organisms,  by  some,  to  bacteria,  and  by  some 
to  fungi.  On  the  one  hand,  it  is  stated  that  these  organisms  should  be  con- 
sidered as  wound  parasites,  which  cannot  attack  the  uninjured  cork  layer 
(Kriiger),  while,  on  the  other  hand,  inoculation  experiments  on  immature 
organs  have  been  carried  out  successfully  under  special  circumstances. 
(Bolley).  It  must  also  be  added  here  that  a  great  many  practical  experi- 
ments have  determined  beyond  question  that,  as  already  mentioned,  certain 
substances  contained  in  the  soils  favor  scurvy.     This  explains  the  possible 


1  See  Beet  scurvy,  p.  46  and  Potato  scab,  p.  75. 


370 

connection  of  the  scurxy  disease  with  parasitic  organisms,  which,  ne\er- 
theless,  are  not  specific  scurvy  organisms.  It  is  much  more  probahle  that, 
in  beet  soils,  saprophytic  species,  which  are  generally  present,  are  able,  be- 
cause of  definite  changes  in  the  composition  of  the  soil,  to  attack  weakened, 
old  beets,  or  tender  young  ones.  The  fact  that  the  healthy  vascular  bundle 
rings  are  more  slender  where  scurvy  began,  i.  e.,  their  growth  in  breadth  has 
been  retarded,  proves  that  the  beet  has  undergone  arrestment  during  the 
time  of  the  scurvy  disease. 

Supported  by  Bolley's  inoculation  experiments'  which  ])rove  that  beet 
scurxy  and  potato  scab  are  due  to  similar  causes,  we  will  t;)ke  up  the  main 
question,  viz..  what  conditions  have  been  determined  practically  as  favoring 
or  causing  scurvy.  It  is  well  known  among  agriculturalists  that  marling  the 
field  results  most  frec|uently  in  an  attack  of  potato  scab.  The  yellow  marl, 
which  contains  magnetic  oxid  (Fe.,  O^)  is  said  to  be  the  most  dangerous. 
Frank  has  conducted  cultural  experiments'-  to  determine  the  problem. 
.Scurvy  is  produced  on  unsterilized  soil,  but  not  on  sterilized,  even 
when  loamy  marl  is  added  tf)  it.  As  sliown  by  ','xperiencc.  meadow 
ore.  street  sweepings,  sewer  muck,  fresh  animal  manure,  liciuid  manure  and 
Chilean  saltpetre  all  favor  scurvv.  which  fact  enforces  the  decision,  that  (//' 
alkaline  reaction  affords  the  most  favorable  conditions  for  the  development 
of  scurvy  f)rganisms.  Bolley'  also  arrives  at  this  conclusion.  His  experi- 
ments show  that  the  scurvy  bacteria  which  he  used  develop  most  rapidly  on 
neutral  or  basic  nutrient  soils.  T-Vank's  comparative  experiments  ])ro\c 
that  moisture  acts  favorably,  and  Bolley  emphasizes  the  observation  tint 
light,  sandy  soils,  as  a  rule,  yield  smooth  tubers.  Frank's  results  seem  to 
contradict  the  observation  that  a  good  deal  of  scurvy  can  lie  found  in  some 
places  in  hot,  dry  years. 

These  apparent  contradictions  are  explained  by  Thaxter's  investi- 
gations*. He  distinguishes  between  organisms  causing  the  deep  scurvy  and 
those  causing  superficial  forms  and  empliasizcs  his  conclusion  that  a  i-'c-utral 
reaction  seemed  most  favorable  for  the  organisin  which  lie  cultivatei. 
Slight  alkalinity,  however,  like  slight  acidity,  seemed  to  have  a  retarding 
effect.  In  his  experiments  young  tubers  were  attacked  at  any  place,  older 
ones  on  wounded  surfaces  and  especiallv  on  lenticels,  while  nearly  ripe 
tubers  were  entirely  free. 

All  scurvy  organisms,  therefore,  do  not  seem  to  require  the  same  C(M1- 
ditions.  In  common,  how'ever,  they  prefer  lenticels  and  young  organs  with 
a  delicate  cork  covering.  In  beets,  the  places  where  the  rootlets  arise  are 
especially  suitable  as  points  of  attack  for  the  micro-organisms.  These 
places  become  very  much  broken  in  wet  soils,  and  this  fact  explains  the 
assertion  that  moisture  favors  the  development  of  scurvy  diseases.     Wet, 

1  Bolley,  H.  I^.,  A.  disease  of  beet.s.  identical  with  deep  seal)  of  potalfies.  Gov. 
Agric.  Exp.  Stat.  f.  North  Dakota.     Bull.  4,  1891. 

-  KamiJfbuch  segen  die   Sohadlinge   unserer  Feldfriichte.     1897,   p.   177. 

3  Zeitschr.  f.  Pflanzenkiankh.  1901.  p.  43. 

•t  Thaxter,  Roland,  The  Potato  Scab.  Fourteenth  Annual  Report  of  the  Con- 
necticut Agric.   Exp.  Stat.  1890. 


371 

heavy  soils  are  aerated  with  difficulty  and  if  substances  are  present  in  the 
soil,  which  require  large  amounts  of  oxygen,  they  take  it  from  the  living 
plant  when  a  sufficient  amount  is  not  found  in  the  soil.  Refuse,  sewage, 
animal  manure,  ferrous  oxid  compounds,  etc.,  must  be  considered  as  sub- 
stances which  require  a  great  deal  of  oxygen.  We  find  examples  where  a 
piece  of  land  fertilized  \\  ith  stable  manure  yielded  scabby  potatoes,  while 
unfertilized  land  surrounding  it  yielded  a  crop  free  from  scurvy ^ 

However,  in  the  decomi)osition  of  sewage  and  other  animal  refuse, 
injurious  sulfur  compounds  are  produced  in  the  soil,  which  will  naturally 
act  poisonously  on  the  root  system  and  yet  favor  certain  groups  of  bacteria. 
As  soon  as  such  processes  set  in,  the  scurvy  bacteria,  wdiich  prefer  neutral 
or  alkaline  soil,  will  thrive. 

Such  conditions  may  also  be  produced  in  clay  soils  in  times  of  intensive 
heat  and  drought ;  or  they  can  be  brought  about  by  the  addition  of  marl 
containing  iron.  In  this  way  might  be  explained  the  appearance  and  often 
the  annual  repetition  of  the  scurvy,  which  may  appear  after  marling  but 
does  not  always  set  in.  All  the  above  named  factors  favoring  scurvy 
can  actually  develop  it  in  certain  cases  and  not  in  others.  The  good 
effect  of  lime,  already  observed  in  many  cultural  experiments-,  may  be 
explained  by  its  characteristic  flocculating  action  in  heavy  soil,  with  a  conse- 
quent improvement  in  physical  texture.  The  soil  becomes  warmer,  more 
porous,  more  easily  aerated,  while  the  animal  manure  is  more  protected 
from  unfavorable  decomposition.  The  easily  aerated  sandy  soils,  which  do 
not  long  contain  highly  concentrated  soil  solutions,  are  usually  free  from 
scurvy.  Therefore,  the  various  substances,  said  to  favor  scurvy,  arc  not 
injurious  in  themselves  but  only  in  certain  combinations,  which  direct  soil 
decomposition  into  unhealthy  channels. 

A\'e  have  been  led  to  the  point  of  view  here  expressed  by  our  own 
experiments",  which  were  intended  to  answ'er  the  question,  as  to  whether 
scurvy  can  be  retained  constantly  in  the  soil  and  can  spread  there.  The 
result  was  negative.  In  the  two  successive  experimental  years  not  only  the 
tubers  obtained  from  healthy  seed,  but,  with  a  very  few  exceptions,  even 
those  originating  from  scabby  potatoes  were  healthy.  Thus  it  is  clear  that 
the  condition  of  the  seed  does  not  necessarily  determine  that  the  scab  dis- 
ease will  be  present  in  open  land,  and  so  the  much  recommended  steriliza- 
tion is  unnecessary.  The  recommendations  for  combatting  the  disease  must 
be  based  on  a  change  in  the  constitution  of  the  soil  and  especially  on  the 
avoidance  of  substances  which  favor  scurvy.  In  regard  to  the  oft-asserted 
injuriousness  of  lime,  my  experiments  have  proved  that  tubers,  some  of 
which  were  brought  directly  in  contact  with  the  lime,  remained  perfectly 
smooth  skinned  and  healthy.     Recently,   substances  have  been  introduced 


1  Arb.  d.  D.  Landw.-Ges.  Jahresbericht  d.  Sonderausschusses  f.  Pflanzen- 
schutz  1904. 

-  Kriiger,  Fr.,  Untersuchungen  iiber  den  Gurtelschorf  der  Zuckerruben.  Zeit- 
schrift  d.  Ver.  d.  Deutsch.  Zuckerindustrie.     Nov.  1904. 

3  Zeitschr.   f.   Pflanzenkrankh.   1899,   p.  182. 


372 

into  trade  which  arc  said  to  increase  tlie  reaction  of  the  soil  (for  example, 
snlfarin). 

In  connection  with  scur\  y  diseases  of  edible  roots,  we  would  like  to 
call  attention  also  to  similar  phenomena  on  smooth  barked  young  trees, 
which  have  not  as  yet  been  studied.  Lindens,  elms,  oaks,  etc.,  on  certain 
kinds  of  soil  (i.  e.  moor-soil)  had  round,  rough  splits  in  the  bark,  which 
increased  greatly  in  extent  adjacent  to  the  adventitious  buds  or  shoots. 
This  bark  sciirz'y  is  frequent  near  large  cities,  where  the  base  of  the  tree  is 
exposed  to  debris  of  all  kinds. 

Another  phenomenon  found  in  barley  and  wheat,  which  should  be  in- 
cluded in  this  group,  is  "spotted  necrosis,"  i.  e..  the  appearance  of  deep, 
dark  reddish  brown,  dying  spots  at  the  tip  and  along  the  edge  of  the  grain 
leaves.  I^p  to  the  present,  T  have  found  the  disease  most  extensively  in 
heavy,  clayey,  or  moor  soil,  w^hich  had  had  abundant  potassium  fertilization 
and  also  in  regions  with  a  deposit  of  ashes. 

Progressive  Metamorphosis. 

While,  in  tlie  cases  already  discussed  in  this  chapter,  we  have  empha- 
sized as  the  common  characteristic  of  all  the  phenomena,  the  influence  of 
unsuitable  concentrations  of  the  soil  solution,  because  of  which  tlie  i)lant 
suffers,  we  will  now  consider  the  cases  in  which  the  plastic  building  sub- 
stances have  been  increased  out  of  proportion  to  their  utilization.  Here.  too. 
an  excessive  supply  of  nutrients  in  the  soil  does  not  give  rise  necessarilv  to 
this  condition,  but,  for  various  reasons,  a  disturbance  in  the  equilil)rium  in 
the  formative  direction  of  the  individual  may  occur,  that  is  to  say,  a  chamjc 
in  the  utilization  of  the  plastic  food  materials. 

Examples  of  this  are  those  phenomena  grouped  under  progressive 
metamorphosis,  such  as  the  transformation  of  leaf  organs  into  a  morpho- 
logically higher  developmental  form.  Teratology  classifies  such  transfor- 
mations under  the  heads  "petalody''  and  "pistillody,"  i.  e.,  cases  in  which 
the  calyx  bracts  become  petal-like,  or  parts  of  the  corolla  assume  the  char- 
acter of  the  stamens,  or  the  organs  actually  belonging  to  the  androe- 
cium  circle  are  changed  into  carpels.  Numerous  examples  of  ])eta- 
lody  are  furnished  by  the  cultivated  forms  of  our  Primulae  and  Ranunculi. 
We  find  the  best  instances  of  pistillody  in  the  poppy  (Papaver  somni- 
ferum).  In  this  plant,  as  in  the  different  varieties  of  cabbage,  long  con- 
tinued cultivation  has  so  disturbed  the  morphological  rules,  that  the  organs 
tend  to  transformation.  A  most  interesting  case  may  be  found  in  the  poppy 
heads  which,  at  the  base,  bear  a  circle  of  many  small.  Avoody  primordia  of 
smaller  heads  (stamens  which  have  been  changed  into  carpels).  In  double 
tuberous  Begonias,  tulips  and  other  Tiliaceae,  specimens  are  found  in  which 
the  stamens  have  been  transformed  into  carpels  with  seed  primordia.  Re- 
lated to  this  are  the  phenomena  of  the  "cone  malady"  in  conifers,  especially 
in  pines,  as  illustrated  in  Fig.  54. 


373 


In  the  majority  of 
cases,  the  cones  at  the  base 
of  an  annual  shoot  He  close 
together  and  remain  small- 
er than  normal  ones,  but 
yield  seeds  capable  of  ger- 
mination. The  production 
of  such  cones,  instead  of 
staminate  flowers,  points 
to  a  local  excess  of  con- 
centrated, plastic  food  ma- 
terial. Borggreve^  has  made 
a  corroborative  observa- 
tion. He  found,  the  year 
after  transplanting  several 
spruces,  possibly  15  years 
old,  in  the  Botanical  Gar- 
dens at  Bonn,  that  the 
terminal  shoot  had  been 
transformed  into  a  pistil- 
late inflorescence. 

If  an  excess  of  plastic 
building  substances  partici- 
pates in  this,  so  that  the 
various  leaf  members  of  a 
blossom  retain  their  form, 
but  the  axis  is  lengthened, 
we  speak  of  the  disunion 
of  parts  of  the  blossom 
normally  united  as  aposta- 
sis.  The  calyx,  for  ex- 
ample, then  appears  sepa- 
rated from  the  corolla  by 
a  long  internode,  the  cor- 
olla in  turn  from  the 
stamens,  etc. 

The  most  perfect  form 
of  over-nutrition  of  the 
blossoms  is  found  in  the 
so-called  "Rose-Kings,"  i. 
e.,  in  the  roses  in  which  a 
new  blossom  springs  from 
the  center  of  an  older  one, 


1  Forstliche  Blatter  1880. 
Vol.  17,  p.  245. 


Fig-.  54. 


Cone  disease  in  the  Scotch  pine. 
(After  Nobbe.) 


374 

or  new  blossoms  appear  laterally.  We  term  such  cases  proliferous  shoot 
development  ( proliferation).  Unusual  buds  arise  inside  of  one  blossom 
or  of  one  inflorescence. 


Fig.   55.     Spi-outing:  pear.s. 

Such  buds  sometimes  de\elop  into  blossoms,  sometimes  into  leafy 
shoots.  If  such  an  adventitious  bud  stands  in  the  centre  of  a  blossom,  so 
that  the  axis  of  the  flower  appears  to  end  in  it  and  can  be  continued  only 
by  the  development  of  this  bud,  we  call  such  a  proliferation  diaphysis.  If, 
on  the  other  hand,  the  adventitious  bud  appears  in  the  axil  of  any  member 
of  the  inflorescence,  or  the  bracts,  the  formatixe  variation  bears  the  name 


375 


of  axiliary  proliferation,  the  appearance  of  buds  within  the 
flower  (ecblastesis).  Sprouts  in  the  centre  of  the  blossoms 
are  more  frequent  than  those  in  the  axils,  a  circumstance 
probably  connected  with  the  fact,  that  all  shoots,  which  form 
the  direct  continuation  of  the  erect  axis,  obtain  water  and 
nutrition  more  easily  than  do  lateral  branches.  In  favor  of 
this  is  also  the  very  rare  occurrence  of  proliferations  in 
flowers  which  stand  isolated  in  the  axils  of  leaves. 

The  doubling  of  hlossoDis  in  the  Compositae  consists,  as 
is  well-known,  mostly  in  the  change  of  the  normally  tubular 
labiate  flowers  into  brightly  colored  ligulate  flowers  (ray 
florets).  Proliferation  in  the  Compositae  has  often  been  ob- 
served, when,  instead  of  the  separate  florets,  a  whole  head  is 
produced  at  the  base  of  the  inflorescence.  Thus  Magnus^ 
reports  specimens  of  Bellis  percnnis  which  had  numerous, 
stemmed  secondary  heads  around  the  edge  of  its  heads.  The 
same  phenomenon  has  been  observed  at  times  on  Crepis 
biennis,  L.  as  well  as  on  Cirsium  arvense  Scop.  Everywhere 
the  individual  florets  were  so  developed  that  they  had  a  more 
or  less  long  stemmed  axis,  often  provided  with  dry,  mem.- 
braneous  leaflets  and  crowned  by  a  small  but  perfect  flower 
head.  In  fact,  on  the  edge  of  each  secondary  head,  tertiary 
heads  and  even  heads  of  later  orders  may  develop. 

Similarly  sprouts  from  phanerogamic  fruits  are  not  rare. 
The  best  known  examples  are  found  in  our  pomaceous  fruits 
and.  of  these,  more  often  in  pears  than  in  apples.  We  give 
in  Fig.  55  an  illustration  of  sprouting  pears,  in  which  one  or 
more  secondary  fruits  develop  on  the  primary  fruit.  This 
phenomenon  may  be  explained  by  considering  the  fruits  of 
our  pomaceous  fruit  as  twigs,  of  which  the  bark  has  developed 
extraordinarily.  Usually,  the  tip  of  the  twig  ends  in  the 
carpels.  These  develop  into  a  core  and  bear  the  seeds  inside 
this  core.  The  bark  of  the  twig  swells,  depressing  more  and 
more  the  terminal  blossom  above  the  seed  primordia  and  be- 
comes the  flesh  of  the  fruit  by  material  changes  and  cell- 
elongation.  As  in  the  proliferation  of  the  rose,  a  pear  blossom 
may  also  develop  a  secondar\^  blossom  in  its  centre,  in  which 
the  small  axillary  crown  between  the  embryonic  carpels 
elongates ;  the  carpels  are  pressed  apart,  or  do  not  develop  at 
all.  This  secondary  blossom  matures  into  a  twig,  sprouting 
from  the  firts  pear.  This  develops  a  blossom  at  its  tip  or, 
without  it,  swells  out  like  a  top,  thus  producing  a  second  pear 
on  the  first  one.     If  these  twigs  do  not  develop  sexual  organs. 


itzungsber 
28.  Nov. 


Bot.    Ver.    d.    Pro  v.    Brandenburg    XXI.     1879. 


Fig.  56. 
Larch  cone 

with  growth 
of  the  axis 
continued. 

f After  Nobbe.) 


376 

the  monstrous  pears  have  no  core.  If  the  proUferous  axis  of  the  fruit 
divides,  lateral,  smaller  pears  sprout  around  the  central  one. 

In  apples,  the  ability  to  sprout  often  extends  only  to  some  branches  of 
the  vascular  bundles  in  the  fruit.  Then  a  knot  swells  out  at  the  side  and 
can  increase  to  a  small  secondary  fruit.  If  the  lateral  sprout  develops  and 
produces  an  actual  bud,  we  find  two  cores  lying  diagonally  above  one 
another.  This  case  bears  great  resemblance  to  double  fruits  which  arise 
from  the  union  of  two  separated,  laterally  placed  embryonic  flowers.  A 
simple  case  is  the  development  of  a  dormant  leaf  bud  on  the  unthickencd 
part  of  the  fruit,  i.  e.,  the  stem. 

In  conifers,  proliferation  is  found  in  the  continued  growth  of  the  cone 
axis  into  a  needled  branch;  this  may  be  found  most  often  in  larches   (see 

i^'ig-  56). 

Among  the  phenomena  in  which  an  excess  of  plastic  food  material  is 
manifest,  belongs  also  the  occurrence  of  leaves  at  places  on  the  axis  which 
normally  should  be  leafless,  Chorisis,  and  the  increase  of  the  leaf  organs 
in  a  node  {Doubling,  Dedoublenient)  as  also  the  multiphcation  of  parts  of 
a  compound  leaf  (Pleophylly).  The  most  common  example  of  the  last 
case  is  the  four-leafed  clover.  Tammes',  in  a  recent  study  of  this  case, 
mentions  that  De  Vries,  by  continued  selection,  has  created  a  race,  the  in- 
dividuals of  which  possess  four  to  seven  leaves.  This  is  also  a  very  good 
example  of  the  way  in  which  phenomena  of  over-nutrition,  once  produced 
accidentally,  may  become  hereditary.  We  referred  to  this  point  also  in 
treating  of  fasciation.  In  the  clover,  individual  veins  and  even  the  mid- 
rib seem  more  vigorous  and  are  divided,  at  times  extending  even  into  the 
petiole.  Then  each  part  of  the  divided  petiole  bears  leaflets  at  its  tip. 
Pleophylly  also  deceases  on  the  branches  of  the  second,  third  and  fourth 
order  in  which  the  supply  of  nutrients  decreases  in  contrast  to  the  first 
produced,  vigorous  axes.  We  find  less  striking  examples  in  all  plants. 
Leaves  which  display  especially  strongly  developed  leaf  surfaces  and  then 
a  forking  of  the  different  veins  are  found  everywhere  on  the  branches 
most  favorably  located  for  the  supply  of  nutrition. 

Such  luxuriantly  developed  forms  are  found  most  often  in  the  so-called 
sprouting  of  the  stock,  i.  e.  sprouts  growing  from  dormant  and  adventitious 
buds  on  the  stumps  of  felled  trees  (for  example,  Populus  and  Morus). 
The  size  proportions  usually  far  exceed  the  average  and  the  leaf  forms 
often  vary  from  the  type,  even  to  unrecognizable  forms.  In  these  cases  the 
newly  produced  shoots  have  the  whole  store  of  reserve  substance  of  the 
tree  stump  at  their  disposal,  which  causes  their  enormously  increased 
growth. 

As  related  phenomena  we  will  also  name  here  the  witches-broom  which 
we  may  pronounce  a  "twig-malady."  The  accumulation  of  the  plastic  food 
material  in  various  places  in  the  branch,  which  gradually  seeks  utilization 


1  Tammes.  Tine,  Ein  Beitrag  zur  Kenntnis  von  Trifolium  pratense  quinquefolium 
de  Vries,  Bot.  Zeit.  1904,  Part  XI,  p.  211. 


377 

in  a  proleptic  bunched  formation  of  branches  may  be  produced,  in  the  ma- 
jority of  cases,  by  parasitic  stimulation.  As  a  rule,  the  abnormally  formed 
axes  deviate  structurally  from  normal  ones^. 

Further,  there  belongs  here  retrogression  to  the  juvenile  form-  in  trees 
which  sprout  vigorously  after  great  injury.  The  so-called  rosette  shoots, 
as  shown  for  a  pine  in  Fig.  57,  result  from  local  over-nutrition,  due  to  the 
fact  that  the  trees  have  previously  suffered  very  great  loss  of  foliage 
(usually  from  the  attacks  of  caterpillars).  The  mobilized  building  sub- 
stances, which  have  thus  lost  their  province  of  nutrition,  now  stream  toward 
the  dormant  buds,  lying  between  the  normal  clusters  of  needles  or  more 
clearly  recognizable  in  the  form  of  weak  whirls,  and  cause  them  to  sprout. 
Instead  of  clusters  of  needles,  simple  broad,  sword-like  needles  with  serrate 
edges  are  then  produced.  In  their  axils,  as  shown  in  the  figure,  the  normal 
short  shoots  (clusters  of  needles)  may 
again  be  formed. 

If  we  consider  these  cases  as  a  whole, 
we  perceive  at  once  a  feature  common  to 
all.  It  is  the  excessive  presence  of  build- 
ing material  in  one  part  of  the  axis.  In- 
deed, by  over-nutrition,  organic  sub- 
stances, actually  newly  formed  by  the 
leaf  apparatus,  are  placed  at  the  disposal 
of  a  part  of  the  axis,  or  an  accumulation 
of    the    structural    material    is    produced  pjg..  57.    Rosette  shoot  of  a 

locally   since   the   mobilized   reserve   sub-  Scotch  pine. 

stance  does  not  find  its  normal  utilization  ,„  ,Heaxns  of  the  simple  sword-like  needles 
due     to     some     injury    such     as     attacks     of        r/eedle.r'mn'larKecU     Uffer  R^TTZEHrRlu 

caterpillers,  pruning,  storms,  etc.     If  this 

excessive  material  reaches  the  existing  primordial  organ,  it  becomes 
manifest  in  the  increased  development  of  the  normal  form,  or,  within  the 
compass  of  progressive  metamorphosis,  of  other  organic  forms.  If  the 
structural  substances  reach  a  vegetative  point,  additional  organs  are  formed. 
Each  vegetative  point  is  always  the  product  of  the  food  at  its  command.  It 
retains  its  distinctive  morphology  only  as  long  as  the  nutritive  process  re- 
mains the  usual  one.  If  the  amount  of  structural  material  is  increased,  the 
vegetative  point  forms  additional  primordial  organs,  thus  changing  the  laws 
of  the  leaf  arrangement,  determined  by  heredity.  New  normal,  vegetative 
points  may  develop  in  the  form  of  buds.  There  are,  therefore,  no  steadfast 
characteristics  in  an  organism  and  cultivation  constantly  changes  the  in- 
herited structural  type. 


1  Compare  Zang-,  Wilh.,  Untersuch.  iiber  die  Entstehung-  des  Kiefernhexen- 
besens.  Ber.  d.  Kgl.  Lehranstalt  f.  Weinbau  usw.  Geisenheim  1905,  p.  235.  Abun- 
dant material  has  been  furnished  recently  in  the  Naturwiss.  Zeitschr.  f.  Land-  u. 
Forstwirtschaft. 

2  Diels,  L.,  Jugendformen  und  Bliitenreife  im  Pflanzenreich.  Berlin  1906. 
Gebr.  Borntrager. 


3/8 
Prkssuri-;  of  thi:  Buds  (Bi.astomania  A.  I'.k.). 

In  the  preceding  section  the  so-called  "sprouting  of  the  stock"  lias  been 
considered.  The  phenomena  are  observable  everywhere  where  large  trunks 
of  poplars,  oaks,  beeches,  chestnuts,  etc.,  have  been  felled.  On  the  cut  sur- 
face of  the  stump  a  callus  arises  from  the  cambial  zone  and  numerous  ad- 
ventitious buds  are  formed  on  this.  The  various  processes  of  propagation 
by  "leaf -cuttings"  of  Begonias,  Ciesnerias,  etc.,  show  that  new  buds  may  be 
produced  on  the  cut  surfaces  of  herbaceous  stems  and  leaves.  The  peculi- 
arity of  "viviparity"  should  be  presupposed  as  equally  well-known,  i.  e.,  the 
development  of  new  vegetative  buds  from  an  uninjured  leaf  blade  during 
the  normal  course  of  development  {Asplenium,  Bryophyllurn,  etc.).  Fre- 
(|uently  observed,  but  abnormal  cases,  are  similar  formations  of  buds  in 
Cardaminc  pratensis,  Drosera  interynedia,  Arabis  pumila,  etc.  Duchartre 
found  small  leafy  shoots  growing  out  nf  leaves  of  Solamiin  Lycopersicum. 
liraun  observed  such  excessive  formation  of  adventitious  buds  on  the  leaves 
and  especially  f)n  the  stems  of  the  cultivated  forms  of  Calliopsis  tinctoria. 
Vox  example,  he  could  count  about  300  on  a  piece  of  stem  possibly  20  cm. 
long'.  Similar  cases  have  also  been  observed  on  other  plants'-,  and  I  found 
specimens  of  Pelargonium  zonalc  and  F.  peltatum  with  disc-like,  fleshy 
outgrowths  at  the  base  of  the  stem  which  were  entirely  covered  with  little 
buds.  Individual,  more  vigorous  specimens  developed  to  such  a  point  that 
even  very  small  leaves  could  be  distinguished;  the  majority  of  the  buds 
died  because  of  mutual  pressure.  A  similar  fleshy  cushion  was  formed  by 
a  Dahlia  7'ariabilis  tuber  which  had  been  forced  in  a  propagating  case,  in 
order  to  develop  new  eyes  from  the  base  of  the  stem.  The  shoots  were  cut 
off  immediately  for  use  as  cuttings,  whereupon  the  growing  stumps  de- 
veloped new  lateral  shoots  from  their  basal  buds,  which  became  more  and 
more  numerous  but  increasingly  weaker.  In  this  way  a  herbaceous  goitre 
ipiarl  was  produced. 

The  Goitre  Gxarl  of  Treks. 

\\  ith  the  rarely  occurring  bud  accumulation  in  herbaceous  plants, 
abo\e  mentioned,  there  is  naturally  connected  a  formation  of  goitre  gnarls 
in  trees,  which,  with  few  exceptions,  are  produced  when  the  growth  in 
length  of  normal  branch  buds  is  prevented,  thus  inducing  the  sprouting  of 
new  lateral  buds  in  their  stead.  The  shoots  from  such  buds  stand  closer, 
the  nearer  they  are  to  the  base  of  the  branch  from  which  they  arise,  because 
the  internodes  are  shortest  there.  I  f  the  tip  growth  of  such  shoot  primor- 
dia  is  limited  by  injury,  or  some  other  cause,  such  as  mutual  pressure,  they 
again  develop  lateral  shoots. 

The  illustration  from  a  trunk  of  Acer  campestre  in  Fig.  58  gives  a 
fine  example  of  a  goitre  gnarl.     After  the  noticeably  thick  l)ark  had  been 


1  Braun.  A.,  t)ber  abnorme  Bildung  von  Adventivknospen  am  krautartigen 
Stengel  von  Calliopsis  tinctoria,  Dec.  Verh.  d.  Bot.  Ver.  d.  Frov.  Brandenburg,  XII, 
p.   151. 

-   Magnus,  I'.,  Verh.  d.  Rot.  Ver.  d.  Prov.  Brandenburg,  XII,   p.  161. 


379 


Fig.  58.     Peeled,  gnarled  growth  of  the  maple. 


38o 

removed,  the  wood  showed  the  spike-like  processes  of  the  dead  bud  cones. 
The  surface  view  is  given  at  a;  at  b  the  cross-section  of  the  spike-Uke  wood 
cones  with  the  medullar}'  parenchyma  indicated  by  the  darker  inner  circles. 
Similar  structures  appear  in  very  different  tree  genera  and  at  will  in 
places  on  the  aerial  axis  as  well  as  in  the  buds  of  the  root  stock, — but  here 
more  rarely.  The  places  exposed  by  the  removal  of  branches  are  especially 
preferred.  Here  the  latent  and  adventitious  buds,  accumulated  at  the  base 
of  the  branch,  begin  to  develop  into  small   shoots.     The  wood  elements, 


Fig.   60. 
C'ros.s-section    through    a   g-narl    cushion. 


Fig.  59.     Formation  of  gnarls  on 

the  branches  of   Malus   sinensis. 

(After  Kissa.) 


It  is  seen  that  the  central  part  of  the  indiviclual  sj: 
the  iriiarl  is  produced  1)\-  a  broadeningr  of  tlu-  niii 
ra.\  of  tile  branch  axis.     (After  KisSA.) 


arising  from  the  cambium  of  the  trunk,  take  a  serpentine  course  around  the 
bud  cones,  because  they  are  prevented  by  them  from  extending  through  the 
cambium.  The  plastic  food  material  is,  therefore,  not  conducted  so  readily 
towards  the  base  of  the  trunk.  But  the  economy  of  the  tree  suffers  little, 
as  the  gnarled  swelling  usually  occurs  on  one  side  of  the  axis,  so  that  the 
opposite  side  lies  free  and  remains  constantly  accessible  for  normal 
nutrition. 

Nevertheless,  normal  branch  primordia  may  not  always  be  assumed  as 
the  points  of  departure  of  gnarl  formation.  There  are  also  cases  in  which 
the  spikes  of  the  gnarl  arise  from  excrescences  of  the  medullary  rays.     One 


38i 


such  case  is  treated  in  a  study  by  Kissa^  on  gnaii  formation  in  Malus 
sinensis,  which  he  conducted  under  my  direction.  Fig.  59  shows  a  branch 
of  gnarl  cushions,  which  have  sprouted  chiefly  from  the  parenchymatous 
base  of  a  small  fruit  shoot. 

In  cross-section,  it  is  seen  that  the  conical  spikes  represent  wood 
cylinders,  of  which  the  central  tissues  have  arisen  from  broadened  medul- 
lary rays.  This  kind  of  medullary  ray  (Fig.  60)  is  either  primary  or  is 
produced  only  in  a  later  annual  ring.  The  wood  layer  of  the  spike  is  a 
continuation  of  the  wood  ring  of  the  mother  branch.  As  in  a  normal 
lateral  axis,  the  spike  of  the 
gnarl  is  covered  by  its  own 
bark  and  has  also  a  well  de- 
veloped cambial  layer.  Just 
like  a  normal  branch,  the  spike 
of  the  gnarl  ramifies  (Fig.  60 
hm')  and  lengthens  by  apical 
growth.  But  not  one  of  these 
axes  at  any  time  bears  the 
primordia  of  leaves  or  buds. 

The  dififerentiation  of  the 
tissue  of  the  spike  of  the  gnarl 
takes  place  in  the  very  first 
developmental  stages  inside  the 
bark  of  the  mother  branch, 
which  at  first  appears  to  be 
only  swollen.  This  swelling  is 
produced  from  the  upward 
forcing  of  the  bark  by  a  num- 
ber of  especially  strongly  de- 
veloped medullary  rays,  pro- 
vided with  meristcmatic  tips. 
By  the  further  apical  growth 
of  these  structures,  the  bark  of 
the  mother  branch  is  finally 
ruptured  and  the  spikes  of  the 

gnarl,  covered  with  their  own  bark,  now  appear  as  independent  structures. 
But  growth  in  length  soon  ends  since  the  bark  cap  and  the  underlying 
meristcmatic  layer  dry  up.  Instead  of  an  apical  growth,  a  basal,  lateral 
sprouting  now  takes  place  in  the  dift'erent  gnarl  spikes  in  the  interior  of 
the  mother  branch. 

In  Fig.  60,  the  cross-section  of  a  branch  covered  with  gnarls,  we  see 
that  the  medullary  rays  forming  the  pith  of  the  spikes  are  mostly  primary, 
and,  therefore,  arise  from  the  pith  of  the  mother  branch,    sp  indicates  the 


61.     Longitudinal   section   through   the 
spikes  of  a  gnarl.      (After  Kissa.) 


1  Kissa,   N.    W.,    Kropfmaserbiklun^-   bei    Pirus    Malus    sinensis.      Zeitschr.    fiir 
Pflanzenkrankh.  1900,  p.  129. 


spike;  ;;/,  pith;  h,  wood;  r,  l^ark  ;  c,  cambium;  uist,  medullary  rays  of  the 
mother  branch  ;  hm,  wood  layer;  rm,  bark  layer  of  the  spike;  n,  meristematic 
cap  of  the  si)ike;  hm' ,  rm' ,  wood  and  bark  of  the  lateral  sprouts  of  the 
gnarl  cone;  h' .  second  annual  ring;  h" ,  third  annual  ring. 

b'ig.  ()i   is  a  highly  magnified  longitudinal  section  thro\igh  a  si)ike  of  a 
gnarl  lying  within  the  bark  of  the  mother  branch.     Fh,  indicates  the  phel- 
logen  :  k,  tlie  cork  layer ;  Fc\  tlie  collenchymatically  thickened  cells ;  Pr,  the 
I)arcncliynia  of  the  ])rimary  bark  of  the  mother  branch,  of  which  the  inner- 
most   layers   begin   to   be   tilled    with    starch;   St, 
starch  ;  .\hp,  dead  layer  of  parenchyma   cells  of 
the  primary  branch  bark;  M,  meristematic  tip  of 
tlu-  spike;  ./,  cells  of  the  wood  layer  of  the  gnarl 
cone    with    their    pores    d'ar);    c,    cambium;    B, 
bark  of  the  spike. 

Therefore,  the  cone  mantel  (Abp),  composed 
of  the  shaded  cells,  forms  the  boundary  between 
the  spike  primordia  and  the  mother  bark  of  the 
twig  and  may  be  clearly  recognized  as  the  axial 
cylinder,  since  the  wood  layer  (A)  is  covered 
v\  ith  its  own  bark  tissue  ( B)  while,  between  both, 
tlie  cambial  zone  (c)  becomes  recognizable.  The 
wood  r}lin(ler  is  composed  chiefly  of  very  porous 
]iai-enchymalous  wood  (For).  The  bark  tissue 
abounds  in  <tarch.  The  young  spike  is  lengthened 
b\  [hv  apical  growth  of  its  meristematic  cap,  and 
graduall}-  compresses  the  adjoining  cells  of  the 
mother  bark  into  a  yellowish  layer  (Abp).  Above 
iliis  dead  cell  layer,  the  mother  bark  is  still  per- 
fectly healthy  and  dies  only  if  ruptured  by  the 
gnarl  cone. 

In  tlie  above  statements,  we  ha\e  i)aid  special 
attention  to  the  structure  of  ihe  completed  gnarl 
cone,  and  will  now  turn  to  the  processes  of 
broadening  the  medullary  rays,  which  initiate  the 
formation  of  the  gnarl  cone.  I  have  studied  one 
such  case  in  Ribes  nigrum'^. 
l"'ig.  ()2  h  shows  the  accumulated  beady  gnarls,  up  to  one  millimetre  in 
height,  which  lie  side  by  side,  or  partially  over-lapping.  In  the  cross-section, 
Fig.  63,  is  seen  the  radiation  of  the  wood  ring  of  the  branch,  in  fan-like 
or  feathery  subdivisions,  into  the  body  of  the  gnarl  which  in  this  case  is 
not  conical,  as  in  Mains  sinensis,  but  resembles  a  spherical  wart. 

Fig.  63  gives  at  B  the  longitudinal  section,  at  A  the  cross-section  of  a 
gnarl  wart.  D  is  the  normal  Jixis  of  the  branch  w^ith  its  pith  body  (w)  and 
wood  ring  (//),  which  now  seems  cleft  by  the  excrescent  medullary  rays 


Fig-.  62.  Bead-like  for- 
mation of  gnarls  in  tlie 
black  currant. 


1   Sorauer,  F.,  Krebs  an   Ribes  nigrum.     Zeitschr.  f.  Pflanzenkiankh.  1891,  p.  77. 


383 


(nisi).  These  medullary  rays  form  the  point  of  departure  for  tlie  fan-like 
gnarl  formations  (sp)  which,  in  later  development,  display  a  central  wood 
body  (kh)  and  a  distant  bark  layer  (r). 

A  cross-section  through  the  branch  at  such  a  warty  place  shows  (Fig. 
64)  that  the  wart  represents  a  conical 
outgrowth  (k)  of  the  inner  bark, 
which  has  ruptured  the  outer  bark- 
layers,  but  is  still  coAered  by  them, 
like  lips  (/).  The  edges  of  the  lips 
are  dead,  and  a  mycelium  is  usually 
fo\md  in  the  depressions.  This  grows 
f)ut  into  the  outer,  browned  and  dying 
or  already  dead  cells  of  the  primary 
gnarl  cone  (p).  If  we  trace  back  the 
excrescent  tissue  which,  towards  its 
base,  possesses  a  wood  layer  com- 
posed of  slender,  reticulately  thicken- 
ed vascular  cells,  passing  over  into 
the  normal  wood  ring,  it  is  found 
to  be  only  a  simple  outgrowth  of  a  medullary  ray. 

Fig.  64  illustrates  an  advanced  stage  of  the  medullary  ray  outgrowth 
of  a  branch  at  the  end  of  the  first  year  (the  year  of  its  production)  ;  the 
left   side   still   shov.s   the   normal  bark   structure;   at  ak   are  the   suberized 


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Ci-oss-seetion  throug'h  a  part 
twig    covered    with    gnarls. 


Fig.  64.     Cross-section  througli  the  bark  of  the  black  currant;    healthy  tissue 
at  the  left;   at  the  right  a  continued  outgrowth  of  the  medullary  rays. 


remnants  of  the  outermost  bark  layers  shed  in  the  course  of  the  year  of  its 
production,  which  contain  scattered  crystals  of  calcium  oxalate.  These 
remnants  are  still  connected  in  places  with  the  discolored,  uninjured  cork 
lamellae  (gk)  which  enclose  the  twig,  like  a  firm,  uniform  girdle.     Below 


384 


the  cork  layer  lie  the  collenchymatically  thickened  bark  layers  (c  o)  ;  these 
border  on  the  parenchyma  containing  the  chlorophyll  (chl)  which  is  seen 
separated  into  zones  by  tangential  calcium  oxalate  bands  (o,  o\  o').  The 
normal  bark  of  the  healthy  branches  also  not  infrequently  has  tangential 
cavities  along  these  bands  of  crystals,  produced  by  the  tearing  of  the  cells 
which  remain  thin-walled  and  contain  small  deposits  of  calcium  oxalate,  so 
that  some  of  the  crystals  appear  to  be  lying  free  near  the  edges  of  the 
cavities. 

In  the  autumn  of  the  first  year,  the  phloem  rays  may  be  seen  to  extend 
as  far  as  the  first  oxalate  band  (o).  Adjacant  to  these  rays,  as  is  usually 
the  case  in  our  woody  plants,  the  cambial  zone  (c)  curves  outward  over 
the  wood,  and  then  in  again,  like  a  bow.    This  shows  that  the  medullary  ray 

assists  in  the  radial  extension  of  the  axis, 
just  as  the  pith  cylinder  itself  causes  the 
longitudinal  stretching. 

On  an  average  the  normal  medullary 
ray  (ui)  retains,  inside  the  bark,  the 
number  of  cells  last  formed  in  the  wood 
and  its  extension  in  the  bark  then  depends 
only  on  the  greater  distension  of  the  in- 
dividual cells.  Near  the  excrescence, 
however,  medullary  rays  are  often  found 
of  which  the  cells  have  increased  in 
number  (;;?')  but  have  kept  essentially 
their  radial,  normal  elongation.  An  ex- 
traordinary cell  increase  finally  takes 
place  in  the  ray  of  the  excrescence  and  the 
cambial  zone  curves  abruptly  outward. 
This  is  best  seen  in  the  comparatively  few  cases  in  which  the  medullary 
rays  begin  with  the  formation  luiilaterally  of  excrescent  tissue,  as  shown  in 
Fig.  65.  In  this  figure  m  indicates  the  cells  of  the  medullary  ray  within  the 
wood ;  c  the  cambial  zone  which  at  the  right  side  rises  towards  the  wood 
(h)  and  sinks  back  at  the  left  side  over  the  wood;  nr  is  the  normal  side  of 
the  bark  ray,  which  pushes  against  the  thick-walled  bark  parenchyma  (/>) 
and,  in  caustic  potash,  is  clearly  differentiated  from  its  surrounding  tissue 
by  its  yellower  color.  At  0  are  indicated  the  very  thin-walled  small  cell 
rows  containing  calcium  oxalate;  here,  near  the  cambial  zone,  the  walls  of 
these  cells  show  a  peculiar  granular  consistency  as  an  indication  of  their 
approaching  decomposition.  Such  a  granular,  slimy  decomposition  of  these 
cell  bands  and  the  movement  of  the  calcium  deposits  to  the  edges 
of  the  cavities  thus  produced  is  also  found  in  the  normal  bark.  On 
the  excrescent  side  (wr)  of  the  bark  ray,  of  which,  the  cells  turn  a  still 
darker  yellow  after  treatment  with  caustic  potash,  than  do  those  of 
the  normal  side,  and  not  infrequently  display  a  distinct  knot-like  swell- 
ing of  the  walls,  the  cambial  zone  turns  abruptly  outward   {c')   and  indi- 


Fig-.  65.     Meilulhiry  ray  in  the  first 
.stajies  of  the  gnarl  formation. 


385 

cates  that  it  will  curve  outward  like  a  cap  in  the  mature  tissue  of 
the  excrescence. 

This  conical  elevation  of  the  cambial  zone  is  visible  in  Fig.  64  wc. 
It  forms  also  an  apical  region,  which,  however,  does  not  lie  at  the  outermost 
tip  of  the  excrescence  but  always  remains  covered  by  bark  tissue,  which 
dies  from  the  outside  inward  until  it  reaches  the  meristematic  tip  of  the 
excrescence  cone. 

The  apical  as  well  as  the  basal  region  of  the  meristematic  zone  of  the 
gnarl  cone  begins  to  develop  shoots  in  the  following  year.  Successful 
sections,  showing  the  full  course  of  a  medullar}^  ray,  demonstrate  that  the 
formation  of  the  secondary  axes  takes  place  repeatedly  in  the  same  way  in 
which  the  priman,^  gnarl  cone  was  produced, — viz.,  by  the  outgrowth  of 
part  of  the  medullary  ray  extending  through  the  bark. 

If  the  structure  of  the  internodes  is  traced  from  the  spot  already 
recognizable  as  the  primordium  of  a  gnarl  towards  the  younger  parts  of 
the  branch,  a  lack  of  uniformity  in  the  structure  of  the  medullary  rays  is 
seen  in  the  very  weakly  developed  wood  ring  of  the  axis.  At  the  base  of 
the  buds  of  the  current  year  in  which  the  immature  wood  cylinder  has  only 
the  spiral  ducts  of  the  pith  crown  and  a  few  libriform  fibres,  together  with 
scattered,  reticulated  or  porous  ducts,  medullary  rays  may  be  found  here 
and  there  which  vary  from  the  other  rays  in  the  somewhat  greater  width 
of  the  cells,  the  somewhat  stronger  refractive  power  of  the  cell  walls,  the 
distinct  straight  course  and  the  further  continuation  in  the  bark.  It  is 
noteworthy  here  that  the  end  of  the  phloem  ray  extending  furthermost 
into  the  bark,  unlike  the  other  phloem  rays,  is  not  more  slender  than  those 
liehind  it.  but  broader,  in  fact,  the  broadest  of  all  the  cells  composing  the 
ray.  While,  therefore,  the  normal  medullary  rays  are  conical,  this  one  has 
turned  its  broadest  base  toward  the  periphery.  This  is  the  same  tendency 
in  growth,  found  in  the  older  stages,  which  appear  as  distinct  excrescence 
rays.  Such  a  differentiation  in  the  earliest  stage  shows  how  this  goitre 
gnarl  formation  is  prepared  in  the  first  juvenile  phases  of  the  axis. 

Besides  the  excrescences  of  the  medullary  rays,  there  are  still  other 
factors  which  distend  the  bark  during  the  encysting  of  diseased  tissue 
centres.  We  will  return  to  these  points  in  the  section  on  the  "tuber  gnarls" 
which  are  best  treated  under  the  processes  of  wound  heaUng. 

I  had  an  opportunity  to  obsen^e  in  Primus  Pad  us  the  formation  of 
goitre  gnarls,  which  branch  like  witches  broom,  and  have  found  similar 
structures  on  gooseberries^  I  also  found  warty  gnarls,  similar  to  those 
described  in  Ribes,  in  Cydonia  vulgaris^.  On  gooseberry  bushes  near  com- 
post heaps,  I  could  later  determine  gnarl  structures  in  a  form  similar  to  those 
in  the  black  currant^  In  a  case  in  the  red  cherry  currant,  of  which  I  heard 
only  recently,  long  leafy  shoots  which  had  no  mature  buds  on  their  leaf 


1  Jahresbericht    des    Sonderausschusses   fiir   Pflanzenschutz.      Arb.    d.    Deutsch. 
L.andw.-Ges.  1898,  p.  145. 

2  Ibid.  1899,  p.  188. 

3  Ibid.  1900,  p.  213. 


386 

axes,  developed  from  a  goitre-like  gnarl-knot.  At  the  places  where  the  pith 
bridge  in  the  branch  node  otherwise  leads  to  the  bud,  either  no  meristematic 
layer  was  found  or  it  remained  covered  by  a  bark  cap  and  developed  into 
a  small  gnarl  spike.  Instead  of  the  apical  bud,  I  found  accumulations  of 
spike  primordia  which,  in  the  following  year,  became  actual  goitre  gnarls 
from  which  sprouted  weak,  leafy  branches,  as  in  Acer  and  Tilia. 

So  far  as  may  be  concluded  from  their  description,  the  remarkable 
"cylindrical  gnarls"  (chichi,  nipple)  on  Gingko  Biloba  may  also  be  in- 
cluded under  the  goitre  gnarls.  According  to  Kenjiro  Fujii^  these  chichi 
or  nipples  are  found  to  be  cylindrical  or  spherical  excrescences  which,  as  a 
rule,  grow  down  perpendicularly  from  older  branches.  Their  size  varies 
from  the  length  of  a  finger  to  2  meters,  with  a  thickness  of  30  cm.  They 
resemble  normal  branches,  on  which  all  foliage  is  lacking.  Having  reached 
the  soil,  they  strike  root  and  then  are  able  to  develop  leaves.  Similar  for- 
mations are  said  to  occur  on  the  roots. 

I  have  given  a  more  thorough  description  to  this  form  of  the  goitre 
gnarl  formation,  in  which  normal  embryonic  buds  do  not  participate,  be- 
cause it  demonstrates  the  importance  of  the  medullary  ray  tissue  in  a  way 
which,  as  yet.  has  not  received  the  slightest  consideration.  Frank-  cites 
references,  deserving  attention,  and  also  describes  earlier  observations  on 
gnarl  structures.  In  this,  however,  the  chief  concern  is  the  explanation 
of  the  wavy  course  of  the  wood  fibres  in  gnarled  wood.  We  lay  the  chief 
weight  on  the  causes,  which  lead  to  the  broadening  of  the  medullary  rays. 
The  form  of  goitre  gnarl,  last  described,  is  only  the  extreme  of  a  tendency 
to  an  excrescence  of  the  medullary  rays,  which  may  lead  to  certain  canker 
swellings.  In  them,  however,  processes  are  involved  which  are  caused  by 
wounds,  while  here  we  can  ascertain  internal  disturbances  in  the  equilibrium 
of  the  processes  of  growth,  but  no  external  ones. 

We  are  concerned  with  local  increases  of  pressure  and  turgor  con- 
ditions brought  about  by  the  form  of  nutrition.  Kny's^  investigations  in  this 
connection,  give  us  the  desired  proof.  He  found,  in  the  action  of  mechani- 
cal pressure,  that,  in  the  meristematic  cells  of  the  medullary  rays,  the  di- 
vision walls  take  a  different  direction  and  produce  two-rowed  medullary 
rays.  In  this  instance,  the  results  of  mechanical  pressure  from  outside, 
must,  according  to  our  conception  of  the  matter,  be  affected  also  by  the 
mutual  pressure  of  the  tissues  upon  one  another,  caused  by  increase  in 
turgor.  Since,  however,  turgor, — a  sufficient  water  supply  being  pre- 
supposed,— depends  on  the  constitution  of  the  cell  contents,  on  the  abundant 
presence  of  compounds  which  attract  water,  each  increased  supply  of  plastic 
food  xnaterial  will  give  rise  to  an  increase  in  turgor  and  a  change  of  the 
existing  pressure  conditions  in  the  different  tissue  forms. 


1  Kenjiro    Fujii,    On    tho    nature    and    orig-in    of   so-called   "chichi"    (nipple)    of 
Gingko  biloba.     Bot.  Magazine.     Vol.  TX.  No.  105. 

2  Frank,  A.  B.,  Die  Krankheiten  der  Pflanzen.     2d  ed.,  Part  1,  p.   82. 

3  Kny,   L...    iiher  den   Einfluss   von   Druck   und   Zug   usw.      Pringsheim.s    .Jahrb. 
f.  wiss.  Bot.     1901.     Vol.  XXXVII,  p.  55. 


387 

Such  an  increased  supply  of  plastic  food  material  is  present,  if  some 
disturbance  in  the  normal  economy  of  the  plant  arises,  due  to  the  removal 
of  certain  centers  of  consumption.  Goitre  gnarl  formation  arises  from  the 
removal  of  branches  necessitated  by  trimming  the  trunks  and  various  other 
kinds  of  pruning,  ^^'e  find  striking  examples  of  this  in  lindens,  poplars, 
maples,  etc.,  planted  along  streets ;  in  an  ever-increasing  accumulation  of 
buds  at  the  places  where  branches  have  been  removed.  If  such  gnarl  accum- 
uations  occur  at  especially  preferred  places,  well  suited  for  the  work  of 
assimilation,  some  shoots  from  these  gnarls  gain  the  upperhand  and  ap- 
proximate water  sprouts. 

c.     Effect  of  an  Excess  of  Nitrogen. 

As  seen  already,  a  disturbance  in  the  formal  development  of  the  plant 
body  by  a  local  accumulation  of  the  prepared  building  materials  is,  to  be 
sure,  of  interest  scientifically  but  has  no  great  disadvantage  agriculturally. 
Indeed,  we  actually  find  that  the  cultivation  of  such  formal  variations,  as 
doubled  flowers,  is  often  intentionally  increased.  The  conditions  are  very 
different,  however,  if  the  material  processes  are  unequally  affected  by  the 
raw  materials.  Here  the  question  of  fertilization  comes  primarily  under 
consideration  and  disturbances  are  especially  involved  which  are  produced 
by  an  excess  of  nitrogen  and  an  unequal  increase  of  the  supply  of  potassium. 

We  have  already  mentioned  the  fact  that  the  soil  will  be  injuriously 
influenced  physically  by  an  over-abundant  supply  of  soluble  fertilizing  salts. 
Even  if  the  salts  keep  the  soil  damper,  as  long  as  sufficient  atmospheric 
precipitation  is  present,  yet  they  form  a  constant  menace  for  the  plants  in 
time  of  drought,  because  a  too  highly  concentrated  soil  solution  may  easily 
be  produced,  making  more  difficult  the  passage  of  the  water  into  the  plant 
roots^.  This  cannot  fail  to  have  some  effect  on  the  development  of  the 
plant.  Gerneck's^  work  throws  some  light  on  this  subject.  He  observed  in 
Triticum  that  root  hairs  were  formed  more  abundantly  if  Ca(NO:;)o  was 
added  than  if  KNO,  was  used.  In  feeding  with  nitrates,  the  blades  and 
ears  developed  late,  while,  with  chlorid  and  phosphate  fertilization,  they 
appeared  early.  With  the  latter  method,  the  root  cells  appeared  to  be  more 
thickened  than  with  the  former,  in  which  the  epidermal  cells  and  the  leaf 
schlerenchyma  were  also  the  least  lignified. 

We  will  now  discuss  a  few  special  cases. 

Over-Fertilized  Seed. 

The  erroneous  theory  that  plants  can  be  brought  to  unbounded  per- 
fection by  abundant  fertilization  has  given  rise  to  an  endeavor  to  give  seeds 
additional  help  by  fertilizing  them  at  the  time  of  sowing.  The  seeds  were 
either  "candied,"  i.  e.  coated  with  a  crust  of  nutrients,  or  they  were  soaked 

1  "Wollny,  K,  ITntersuchungen  liber  den  Einfluss  der  Salze  auf  die  Boden- 
feuchtigkeit.  Vierteljahrsschr.  d.  Bayer.  Landwirtschaftsrates  1899.  Supplement 
p.  437. 

-  Gerneck,  R.,  tjber  die  Bedeutung-  anorg-anischer  Salze  fur  die  Entwicklung 
und  den  Bau  der  hoheren  Pflanzen.  Gottinger  Dissertation,  cit.  Just,  Bot.  Jahresber. 
1902,  II,  p.  301. 


in  more  or  less  concentrated  nutrient  solutions.  The  discovery  was  then 
made  immediately,  that  such  treatment  assistance  is  often  useless,  and  some- 
times injurious. 

Fertilization  experiments  with  beets,  made  by  Fremy  and  Deherain. 
throw  some  light  on  this  point.  They  proved  that  ammonium  sulfate  and 
potassium  salts  have  an  injurious  efifect  on  the  germinative  process,  and 
they  also  found  that  germination  failed  entirely,  even  with  a  concentration 
of  0.2  per  cent.  The  results  of  soaking  experiments  made  by  Tautphous^ 
with  beans,  peas,  maize,  rape,  rye  and  wheat  proved  that  seeds  soaked  in 
distilled  water  germinated  best  of  all  and  that  the  capacity  for  germination 
was  the  more  reduced,  the  more  concentrated  the  solutions  (potassium  chlo- 
rid,  sodium  chlorid,  (commercial)  sodium  nitrate,  potassium  iulfate,  potas- 
sium phosphate  and  calcium  nitrate  in  a  solution  of  0.5  to  5  per  cent.).  Rape 
germinated  in  a  2  per  cent,  solution  almost  as  well  as  in  distilled  water, 
while  the  other  seeds  were  considerably  impaired,  even  in  a  0.5  per  cent, 
solution.  The  development  of  the  seedlings  was  considerably  more  lux- 
uriant in  a  3  per  cent,  sodium  chlorid  solution  than  in  distilled  water. 

Fleischer-  reports  on  an  experiment  made  in  East  Prussia,  in  fertiliz- 
ing potato  seed  with  kainit  and  superphosphates ;  a  considerable  number 
did  not  sprout  and  at  the  time  of  harvesting  were  found  unchanged  in  the 
soil.  The  analysis  of  these  tubers  gave  a  content  of  pure  ash  nearly  twice 
as  great  as  the  average  values  given  in  A\'olflf's  ash  analyses.  In  a  thousand 
parts  of  dry  weight  the  ungerminated  tubers,  compared  with  normal  ones, 
contained  potassium  in  the  proportion  of  37  to  22.  While  the  calcium  con- 
tent was  almost  the  same  in  the  diseased  and  normal  tubers,  the  magnesium 
was  apparently  twice  as  great  in  the  former;  the  phosphoric  acid  almost 
double,  and  the  chlorin  content  thirteen  times  as  great  as  in  the  normal 
tubers.  The  sulfuric  acid  also  increased  to  four  times  the  amount  in  one 
thousand  parts  of  dry  weight,  so  that  it  is  evident  that  exactly  the  elements 
of  the  kainit  (potassium,  sodium,  magnesia,  sulfuric  acid  and  chlorin)  had 
undergone  an  unusual  increase  in  the  ash  of  the  unsprouted  tubers.  In  the 
present  case,  the  fertilizer  was  applied  in  the  spring  directly  before  the 
potatoes  were  planted,  not  sometime  previous  to  planting,  as  prescribed  in 
the  directions  for  the  use  of  kainit. 

In  Fittbogen's"  field  experiments  ^^  ith  oats,  which  had  been  mixed  in 
a  gruel  of  superphosphate  before  sowing,  the  plot  sown  with  candied  seed 
yielded  less  than  did  that  with  unfertilized  seed.  If,  on  the  other  hand,  the 
superphosphate  was  diluted  with  sawdust,  the  yield  was  the  heaviest  of  all. 
Probably  the  sulfuric  acid  hydrate  which  often  appears,  together  witli 
phosphoric  acid  hydrate,  also  acts  injuriously  in  direct  contact  with  the 
superphosphate.     Briigmann"*  also  reports  on  the  injurious  action  of  fcr- 


1  T.iutphous.  v..  Die  Keimune:  der  Samcn  bei  verschiedener  Besrhaffcnheit 
deraelben.     rit.  P.ot.  Jahi-esber.  1876.  II.  p.  117. 

-  Beobachtung-en  liber  den  srhadlichen  Einfliifs  der  Kainit-  und  Superphosphat- 
diing-ung-  auf  die  Keimfahig-keit  der  Kartoffeln.    Biedermann's  Centralbl.  1880,  p.  765. 

3  Deutsche  landwirt.schaftl.  Presse  1877,  No.  81. 

4  Hannover'sche  landwirtsch,  Zeit.  1881,  No,  12. 


389 

tiliers  made  sokxble  by  sulfuric  acid.     This  action  was  very  evident  in  dry 
springs,  and,  in  fact,  on  wheat  as  well  as  on  other  cultivated  plants. 

In  seeds,  the  injurious  effect  of  the  "candying"  will  be  the  less  felt  the 
longer  the  seed  lies  in  the  soil,  before  sprouting,  for  then  frequent  rains  can 
wash  more  of  the  fertilizing  salt  into  the  surrounding  soil.  This  has  been 
demonstrated  in  earlier  experiments  in  Salzmunde\ 

Over-Fertilized  Beets. 

Common  experience  with  present  intensive  beet  cultivation,  shows 
that  an  increased  nitrogen  supply  increases  the  harvest  in  bulk,  but  reduces 
the  sugar  content.  For  this  reason  we  will  give  only  one  proof  that  shows 
the  importance  of  the  form  in  which  the  nitrogen  is  applied.  PagnouF 
analyzed  three  beets,  of  which  the  first  (H)  had  been  w^atered  several  times 
with  a  solution  of  (commercial)  nitrate  of  soda;  the  second  (J)  with 
ammonium  sulfate ;  while  the  third  (K)  represented  a  normal  beet,  har- 
vested at  the  same  time. 

H.  J.  K. 

The  harvest  weight  amounted  to  4i45g        26'/og  7^5S 

Density  of  the  sap  amounted  to  1.026  1.040  1.046 

Percentage  of   sugar  in  the  beet 

substance  amounted  to    3.9  6.3  8.3 

CO2,  and  Chloral  alkalies  in  100 
parts  beet  substance  amounted 

to 1.991  0,924         0.814 

The  amount  of  these  in  100  parts 

sugar  is 28.0  14.6  9.8 

It  is  evidenr  that  with  nitrogen  fertilization  the  amount  of  fresh  sub- 
stance harvested  has  increased  three  and  a  half  to  five  times  that  obtained 
with  normal  cultivation,  but  the  sugar  percentage  has  fallen  to  one-half. 
The  comparison  of  the  effect  of  the  nitric  nitrogen  with  that  of  am- 
moniacal  nitrogen  is  especially  interesting.  Mention  was  made  above  that 
the  latter  gives  rise  to  a  considerably  greater  ammonium  content  in  the  beet 
substance. 

Mtiller-Thurgau's  recent  experiments"  show  that  the  nitrogen  fertilized 
plants  have  a  heightened  respiration,  which  may  well  be  the  result  of  a 
heightened  conversion  of  cane  sugar  into  the  directly  reducing  sugar.  On 
an  average  every  6  beets  contained 

Sugar,  directly  reducing,      Cane  sugar 
Beets  rich  in  nitrogen       0.34  per  cent.  8.27  per  cent. 

Beets  poorer  in  nitrogen     0.04  per  cent.  14-39  P^r  cent. 

An  idea  of  the  processes  which  are  initiated  by  a  superabundant  nitro- 
gen supply  may  be  obtained  from  the  statements  of  Pfeiffer-Wendessen*, 

1  Jahresber.  f.  Agrikulturchemie  1863,  p.  60. 
-  Annales  agronomiciues  1876,  p.  321. 

3  s.  tJberdiingte  Kartoffeln.  p.  390. 

4  Bericht    liber    die    Generalversammlung    d.    landwirtschaftl.    Centralver.    f.    d. 
Herzogtum  Braunschweig.      Blatter  f.   Zuclverriibenbau   1896,   No.   8. 


390 

who  is  of  the  opinion  that  in  any  case  the  nitrogen  is  transformed  into 
proteins,  which,  in  combination  with  calcium,  are  decomposed  into  asparagin, 
glutamin  and  corresponding  organic  salts.  These  form  soluble  salts  with 
calcium,  which  in  turn  are  found  again  in  the  sugar  extractives,  etc. 
Schultze  also  characterizes  the  incompletely  utilized,  intermediary  nitrogen 
compounds  as  essential  constituents  of  the  syrup  which  impair  the  crystal- 
lization of  the  sugar.  In  the  plant  itself,  as  in  sugar  manufacture,  the  com- 
pounds here  named  may  retard  the  precipitation  of  the  sugar,  and  thus 
explain  the  condition  of  unripeness  and  of  small  sugar  content  in  the  over- 
manured  beets.  Besides  the  delay  in  ripening,  the  beets  do  not  keep  well 
when  stored  in  piles.  Phosphoric  acid  improves  the  quality;  the  juice  of 
beets,  which  had  been  over- fertilized  with  phosphoric  acid  and  badly 
polarized,  contained  the  fewest  elements  which  prevent  the  crystallization 
of  the  sugar. 

Good  and  i>ad  experimental  results  have  been  obtained  from  top 
dressing  chiefly  with  Chile  saltpetre.  This  condition  is  observed  in  almost 
all  experiments.  Besides  the  quantity  used,  the  result  depends  also  on  the 
way  in  which  the  plant  utilizes  the  fertilizer.  This  dilifers  greatly  according 
to  the  variety,  the  density  of  the  soil,  the  way  it  is  worked,  the  locality  and 
the  weather.  Reference  should  be  made  to  Kuntze-Delitsch's^  observations 
on  top  dressing.  He  found  that  the  soil  easily  forms  a  crust,  causing  the 
young  beets  to  die  in  spots  because  of  a  lack  of  oxygen,  while  the  older 
ones  develop  poorly.  In  any  case,  fertilization  with  Chile  saltpetre  should 
be  followed  immediately  by  harrowing-. 

Opinions  differ  as  to  the  advisability  of  using  nitrogen  fertilizers  with 
seed  beets.  While  it  is  asserted  by  some  that  the  quality  of  the  strain  de- 
clines, Wilfarth%  on  the  strength  of  his  experiments,  contradicts  this 
statement. 

Over-Fertilized  Potatoes. 

The  effects  of  over- fertilizing  potatoes  with  nitrogenous  fertilizers  are 
the  same  as  lor  beets.  Miiller-Thurgau's*  results  show  for  both  that  an 
abundant  nitrogen  fertilization  causes  a  stronger  leaf  development  with  a 
greater  chlorophyll  content.  At  the  same  time,  the  formation  of  starch  is 
impeded;  the  starch  is  more  rapidly  dissolved  in  the  leaves,  and  smaller 
quantities  are  stored.  The  organs  show  a  greater  glycose  content,  the  re- 
serve substances  are  more  rapidly  dissolved,  the  nitrogen  compounds  are 
more  extensively  transformed,  while  respiration  is  heightened  and  growth 
increased. 

A  poorer  keeping  quality  of  the  tubers  is  correlative  with  a  lesser  supply 
of   reserve  substances   and   their   more  rapid  consumption  in   respiration. 


1  cit.   Zeitschr.   f.  Pflanzenkrankh.   1896,  p.   310. 

2  The  action  of  the  perchlorate  in  the  use  of  Chile  saltpetre  will  be  discussed 
under  the  section  on  Injurious  gases  and  liquids. 

•i  Wilfarth,  H.,  Wirkt  eine  iStickstoftdungung-  der  Samenriiben  schadlich  usw. 
Zeitschr.  d.  Ver.  Deutsch.  Zuckerindustrie.     Vol.   50,  Fart  528,  p.  59. 

*  MuUer-Thurgau,  Dritter  Jahresbericht  des  pllanzenphysiol.  Laboratoriums  d. 
Versuchsstat.  Wadensweil.     Zurich  1894,  p.  52. 


391 

But  an  excess  of  nitrogen  directly  promotes  decay,  while  that  of  calcium 
phosphate  has  an  opposite  effect.  I  planted  in  sandy  soil,  in  alternating 
rows,  pieces  of  healthy  tubers  from  three  varieties  as  different  as  possible 
and  also  pieces  from  tubers  suffering  from  hlack  dry  rot^.  This  field  was 
divided  into  two  halves  absolutely  similarly  planted,  of  which  one  was  given 
large  amounts  of  Chile  saltpetre  on  all  the  rows,  the  other  Thomas  slag. 
In  the  healthy  seed,  in  the  half  fertilized  with  Chile  saltpetre,  the  tubers 
sprouted  very  imperfectly  while  almost  all  the  diseased  seed  had  decayed. 
The  results  obtained  in  the  plot  fertilized  with  Thomas  slag  were  directly 
opposite.     There  the  diseased  seed  yielded  very  uniform  healthy  plants. 

In  the  last  named  plot,  plants  from  health}'-  and  diseased  seed  of  all 
varieties  developed  shorter  shoots  with  more  highly  colored  foliage.  They 
ripened  more  rapidly  and  the  han-est  was  nearly  twice  as  large  as  from 
the  plot  fertilized  with  Chile  saltpetre-. 

With  this  might  be  associated  also  the  phenomenon  well-known  in 
practical  circles  as  iron  spottedness  or  the  multi-colored  condition  of  pota- 
toes. Tubers  outwardly  normal  have  brown  or  brownish-gray  places  in 
their  tissue  in  the  fresh  cross-section.  In  this,  the  rest  of  the  flesh  can  be 
perfectly  healthy  and  remain  white,  or,  exposed  to  the  air,  may  quickly 
assume  a  rusty  red  color.  The  spots  originally  discolored  have  brown, 
dead  cell  walls  and  many  still  contain  starch.  Often,  and,  in  fact,  when 
the  cut  surface  subsequently  turns  red  in  the  air,  only  traces  of  starch  may 
be  found  in  the  diseased  centres,  but  sugar  is  found  instead. 

While  some  observers  think  the  iron  spottedness  must  be  traced  to  an 
abundance  of  acid  iron  compounds  in  the  soil,  others  are  inclined  to  be- 
lieve dampness  to  be  the  cause.  Many  discoveries  show,  however,  that 
heavy  fertilization  with  stable  manure  caused  the  iron-spotted  condition  in 
certain  varieties,  which,  in  the  same  year,  with  chemical  fertilization,  re- 
mained healthy^.  Tubers  which  turn  red,  when  cut,  are  found  most  fre- 
quently where  an  abundant  nitrogen  fertilization  is  used.  Hence  one  is 
justified  in  considering  a  multi-colored  condition  of  the  flesh  to  be  an  indi- 
cation of  nitrogen  over-fertilization.  Tubers  with  iron  spots,  as  a  rule, 
yield  healthy  plants  in  the  following  year. 

Chile  Saltpetre  W^ith  Woody  Plants. 

Janorschke*  has  investigated  the  phenomena  of  nitrogen  fertilization 
without  the  addition  of  calcium  and  phosphoric  acid.  He  found  that  plants 
with  multi-colored  leaves  became  greener  for  the  first  year  or  two.  In 
dwarf  fruits  the  branches  continued  to  grow  almost  without  interruption 
until  August  and  even  later,  which  thus  prevented  the  setting  of  the  blossom 
buds.  Attention  should  also  be  called  to  the  fact  that  the  effect  of  the  fertilizer 


1  Zeitschr.  f.  Pflanzenkrankh.   1894,  p.  12G,  und  1895,  p.  98. 

2  Zeitsch.   d.   Landwirtschaftskammer  f.    d.   Prov.   Schlesien   1899. 

3  s.   Jahresbei'jchte   des    Sonderausschusses   fiir   Pflanzenschutz,   herausgegetaen 
I.  Deutsch.  Landw.-Ges. 

4  Zeitschr.    d.   Landwirtschaftskammer   f.    Schlesien   1898,    No.    34. 


392 

on  trees  does  net  make  itself  felt  until  the  year  following  its  application, 
but  then  has  a  continuous  action  up  to  the  third  year.  From  my  own  ex- 
periments, in  which  sewage  was  used,  I  consider  the  increased  tendency  of 
the  fruit  to  decay,  especially  when  it  begins  at  the  core,  as  well  as  the  greater 
susceptibility  to  frost,  to  be  the  effect  of  a  one-sided,  excessive  nitrogen 
fertilization.  Calcium  phosphate  counteracts  this  evil.  Experiments  with 
apple  trees,  abundantly  fertilized  with  saltpetre,  showed  that  the  fertilized 
trees  suffered  more  from  aphids  than  did  unfertilized  trees\ 

The  foliage  of  Ailanthus  glandulosa  growing  in  well-fertiUzed  positions 
became  yellow  and  the  branches  blighted.  On  the  cut  surfaces  of  fresh 
branches  Peniciliium  developed  abundantly.  The  sugar  content  of  the 
tissue  at  this  place  was  very  great. 

In  orange  plantations,  fertilized  trees  tended  to  gummosis  and  the  dis- 
ease called  "Die-back"  in  Florida  is  traced  directly  to  over-feeding  with 
organic  nitrogenous  compounds.  These  orange  trees  are  said  also  to  be 
more  susceptible  to  insect  attacks". 

Over-Fertilization  of  Vegetables  and  Other  Field  Crops. 

Although  our  vegetables,  as  a  whole,  in  their  present  form,  are  the 
product  of  a  high  degree  of  cultivation,  and  have  adjusted  themselves  to 
abundant  fertilization,  we  still  often  find  cases  of  disease  due  to  over- 
fertilization,  especially  where  sexvage  has  been  used.  There  is  a  perceptible 
increase  of  the  easily  oxidizable  substances  which  turn  brown  in  the  air. 
In  this  case,  the  walls  of  the  ducts  turn  brown  and,  not  infrequently,  some 
of  the  ducts  are  filled  with  an  inky  fluid.  Bacterial  decay  occurs  frequently 
in  over- fertilized  plants.  Peas  and  other  Leguminoseae  withstand  least  of 
all  an  excess  of  nitrogen  while  increased  adaptation  is  found  in  some  Um- 
belli ferae,  as  celery  for  example.  But  even  here  the  favorable  amount  is 
often  exceeded  in  sewage  bed  cultivation.  If  the  cut  surface  of  fleshy 
root  tubers  becomes  rusty,  the  tubers  as  a  rule  have  lost  in  flavor.  The 
more  advanced  stage,  frequently  found  in  vegetables  shown  in  the  markets 
of-  large  cities,  consists  of  an  increased  sponginess  of  the  tissue  and  a  greater 
brown  spottedncss.  Such  conditions  and  the  bacterial  decay,  connected 
with  them,  manifest  themselves  in  cabbage  plants  accustomed  to  nutrient 
solutions  of  the  highest  concentration.  Under  such  conditions  it  is  ad- 
visable to  add  calcium  phosphate  and  to  cultivate  continuously. 

Owing  to  the  increased  use  of  rhubarb  stalks  as  a  spring  sauce,  the 
plants  are  being  cultivated  on  sewage  beds.  In  such  plantations  I  observed 
cases  where  the  unusually  thick  stems  were  absolutely  insipid.-  Thus  a 
scanty  production,  or  a  complete  consumption  of  the  organic  acids,  is  con- 
nected with  over- fertilization.    In  my  opinion  this  regression  in  the  amount 


1  Fiinfter  Jahresber.  d.  Grofsherzogl.   Obstbuuschule  zu  Friedberg  i.  d.  W. 

2  Webber,   H.,   Fertilization    of  the   soil,   etc.     Yearbook   U.    S.   Depart.    Agric. 
for  1894.     Washington  1895,  p.  193. 


393 

of  acid  associated  unth  an  excess  of  nitrogen  may  also  be  sought  elsewhere 
and  may  be  the  cause  of  the  rapid  appearance  of  bacterial  decay^ 

In  the  Cucurbitaceae  (cucumbers  and  melons)  a  concentration  of  the 
nutrient  solution,  not  dangerous  in  itself,  can  act  injuriously  if  the  temper- 
ature is  continuously  too  low.  In  this  case  gum  appears  most  abundantly 
on  the  iruit  and  connected  with  it  a  blackening  of  the  ducts  is  also  noticed. 

In  tobacco  culture,  an  excess  of  nitrogen  manifests  itself  in  coarser 
leaves  and  a  larger  nicotine  content^. 

Mention  has  been  made  of  the  fact  that  sewage  fertilization  of  grain 
may  cause  lodging  and  sterility. 

Excessive  Nitrogen  Fertilization  for  Decorative  Plants. 

Very  numerous  cases  of  this  may  be  found.  Besides  fertilization  with 
sewage  and  Chile  saltpetre,  or  ammonium  sulfate,  horn  shavings  are  ex- 
tensively used,  especially  for  garden  plants.  Naturally  we  can  cite  only  a 
few  examples.  1  gave  a  few  plants  of  Begonia  semperflorens  an  excess  of 
ammonium  sulfate.  Four  days  after  fertilization  the  young  shoots  became 
discolored  at  the  base  and  began  to  drop.  The  edges  of  the  leaves  began 
to  show  dirty  green  areas  which  later  became  brown  and  dried  up.  These 
were  connected  with  the  healthy  tissue  at  the  centre  of  the  leaf  by 
a  more  transparent  transitional  zone.  In  the  sun,  the  wilting  became  more 
rapid.  The  pith  and  bark  were  found  to  be  filled  with  masses  of  calcium 
oxalate ;  the  individual  crystals  were  not  as  sharp  as  those  in  healthy  speci- 
mens but  more  rounded  like  tubers.  No  starch  was  present  in  the  diseased 
tissues  and  the  chloroplastids  were  reduced  to  small  angular  grains. 
The  ducts  were  frequently  filled  with  a  brown,  granular  content.  The  cell 
walls  of  all  the  tissues  were  brown.  The  contents  of  the  epidermal  cells  of 
the  leaves  were  brown  and  granular.  Before  the  decomposition  of  the 
chlorophyll  grains,  brown  drops  were  often  found  in  the  contents  of  the 
mesophyll  cells. 

In  Begonias,  as  well  as  in  Pelargonium  sonale,  the  leaves  discolor  and 
fall  off  easily  wnen  dried.  I  found  an  unusual  number  of  calcium  oxalate 
crystals  in  the  pith  and  young  bark  of  the  axes  of  diseased  plants.  The 
stems  of  the  Pelargoniums  contained  in  general  fewer  and  smaller  starch 
grains.  They  were  almost  entirely  lacking  in  the  bark  parenchyma,  while, 
in  the  over-fertilized  plants,  they  were  present  in  abundance. 

This  is  an  example  of  the  same  phenomenon  observed  in  potatoes  and 
beets, — i.  e.,  a  poverty  in  carbohydrates. 

A  slight  fertilization  with  Chile  saltpetre,  given  to  freshly  rooted  Pelar- 
gonium cuttings  at  first  caused  a  very  luxuriant  growth.  Later,  because  of 
frequent  repetition,  the  effects  became  serious; — the  leaves  drooped,  and 
brown  decayed  areas  appeared  on  the  stem  just  above  the  leaf  bud.  In  a 
a  short  time  these  spots  encircled  the  entire  stem.    Then  the  leaves  fell  and 


1  See  Action  of  oxalic  acid,  p.  361. 

2  Schellmann,  W.,  Der  Tabak  und  seine   Nahrungsanspriiche.     "Der  Pflanzer." 
Herausg.  Usambara-Post  1905,   No.   5. 


394 

the  whole  aerial  axis  died  back  to  a  short  stump.  New,  weak  shoots  then 
began  to  sprout.  We  have  cited  this  example,  in  order  to  show  that  the 
effect  of  over-fertilization,  although  it  takes  place  through  the  soil,  does  not 
make  itself  felt  at  first  at  the  base  of  the  axes  but  on  the  peripheral  organs, 
the  leaves. 

In  comparative  experiments  with  Fuchsia  cuttings ^  a  continued  fer- 
tilization with  small  amounts  of  ammonium  sulfate  resulted  in  a  noticeable 
increase  in  growth  and  an  enlargement  of  the  leaves.  The  epidermal  cells 
of  the  leaves  had  thinner  walls  and  the  wood  ring  of  the  branches  made  a 
weaker  development.  The  starch  content  was  smaller,  the  chlorophyll  con- 
tent larger,  the  period  of  growth  lengthened.  When  the  fuchsias  were 
protected  from  autumnal  frosts,  by  being  brought  into  a  greenhouse,  they 
had  time  to  ripen  normally,  and  the  differences  as  compared  with  unfer- 
tilized plants  disappeared.  The  fertilized  ones  had  rather  the  advantage 
in  a  greater  growth.  Here  we  have  a  result  such  as  is  evident  in  growing 
fodder  beets.  The  addition  of  large  amounts  of  nitrogen  retards  the  ripen- 
ing process.  If  the  plants  can  reach  maturity  before  frost,  so  that  the  leaves 
ripen  normally,  we  obtain  the  desired  results  from  fertilization,  i.  e.,  the 
production  of  greater  amounts  of  material,  with  a  normal  supply  of  reserve 
substances.  But,  as  a  rule,  the  climatic  conditions  prevent  the  termination 
of  growth  and  winter  finds  the  organs  in  an  immature  condition. 

The  disadvantage  of  harvesting  insufficiently  matured  plants  has  been 
emphasized  under  "agricultural  crops,"  Such  plants  have  a  greater  tendency 
to  decay. 

The  same  results  were  obtained  with  comparative  fertilization  experi- 
ments with  Erica.  The  red  blossoming  varieties  developed  less  vividly  red 
or  almost  bluish  red  blossoms  in  the  series  of  experiments  with  a  one-sided 
nitrogen  fertilization ;  their  habit  of  growth  was  more  drooping  and  the 
blossoms  set  less  abundantly.  The  fertilized  specimens  suffered  so  greatly 
from  Botrytis  cinerea  in  winter  that  most  of  them  died,  while  unfertilized 
plants  of  the  same  varieties  from  the  same  place  came  through  the  winter 
uninjured.  Bluth-  carried  out  an  experiment  which  showed  the  eft'ect  of 
a  highly  concentrated  solution  of  all  the  nutrient  substances.  The  Ericas, 
in  the  second  year  of  cultivation,  were  given  continued  supplies  of  a  one- 
tenth  per  cent,  solution  of  Wagner's  nutrient  salt.  After  ten  to  twelve  days  the 
leaves  became  a  darker  color  and  their  growth  stronger,  but  the  plants 
showed  a  greater  sensitiveness  to  the  action  of  the  sun  and  drought,  in  com- 
parison with  many  hundreds  of  unfertihzed  specimens  of  the  same  variety. 
The  new  lateral  shoots  of  certain  tender  varieties  (£.  hiemalis,  E.  congesta, 
etc.)  developed  a  drooping  and  often  curved  habit  of  growth.  Hard 
needled  varieties  {E.  hlanda,  E.  niediterranea,  E.  verticillata,  E.  mammosa) 
retained  their  erect  habit  of  growth  but  the  buds  set  in  a  strikingly  small 


1  Sorauer,    P.,    Einfluss    einseitiger    Stickstoffdiingung-.      Zeitschr.    f.    Pflanzen- 
krankheiten  1897,  p.  287. 

2  Zeitschr.  f,  Pflanzenkrankh.  1895,  p.  186. 


395 

number,  or  not  at  all,  while  the  branches  continued  growth.  Here  too,  for 
the  most  part,  the  fertilized  plants  died  during  the  winter  from  Botrytis. 
In  other  fertilization  experiments,  made  with  horn  shavings  on  Ericas, 
there  was  a  luxuriant  leaf  development  at  the  expense  of  the  blossom  buds, 
but  the  fertilized  plants,  during  the  winter,  showed  no  greater  weakness. 

From  the  many  instances  which  have  come  to  my  notice,  I  must  state 
the  frequent  "failure  of  forced  Lilies-of-the-V alley,"  as  due  to  an  excessive 
nitrogen  fertilization.  Chile  saltpetre  and  ammonium  sulfate  are  often 
used  when  the  plants  are  grown  for  two  years  out  of  doors. 

The  plants  grow  more  luxuriantly  and  their  very  strong  (mostly  blue- 
tipped)  "pips"  (bud-cones)  deceive  the  buyer;  the  formation  of  the  in- 
florescences., however,  is  weak.  Such  plants  force  with  great  difficulty  and 
frequently  bear  flower  clusters  in  which  some  buds  do  not  mature.  Com- 
parative experiments  made  by  Koopmann^  showed  very  interesting  differ- 
•ences  in  forcing.  When  kainit  was  used  as  a  fertilizer  in  growing  the 
plants,  the  flower  clusters  developed  first  and  the  leaves  followed  very 
slowly, — on  the  other  hand,  when  ammonia  was  used  the  leaf  growth  was 
so  luxuriant  that  the  flower  clusters  were  entirely  hidden  by  the  leaves.  In 
general,  potassium  may  be  recommended  as  a  fertilizer  for  Lilies-of-the- 
Valley. 

A  further  injurious  effect  could  be  determined  for  Roses.  I  have  be- 
fore me  observations  showing  that  tea  roses,  among  others,  Marechal  Niel 
and  Nyphetos,  grown  indoors,  drop  their  buds  after  heavy  fertilization,  or 
decay  at  the  point  where  the  calyx  passes  over  into  the  stem.  When  dis- 
eased plants  had  been  repotted  in  a  sandy  soil  poor  in  nutrients,  normal 
blossoms  developed  in  the  following  year.  I  observed  similar  phenomena 
of  deca}^  in  Bourbon  and  Remontant  roses  in  the  open  after  sewage  fertiliza- 
tion.   Here,  an  application  of  g}"psum  gradually  decreased  the  disease. 

In  other  garden  plants,  even  in  ivy,  I  had  opportunity  to  observe  phe- 
nomena of  decay  after  an  excess  of  nitrogen  (usually  in  the  foi"m  of  sewage 
fertilizers,  liquid  manure,  Chile  saltpetre  and  ammonium  sulfate).  In  the 
majority  of  cases,  I  have  recommended  transplanting  the  plants  into  pure 
sand  or  a  very  sandy  leaf  loam  for  a  year  and  have  tried  it  myself  repeatedly 
with  good  results. 

Leaf  Curl  of  the  Potato. 

W^e  will  include  here  this  disease  so  well-known  to  potato  growers  and 
so  often  studied  scientifically;  the  causes  of  which,  however,  are  still  un- 
known. The  reason  for  considering  leaf  curl  here  is  the  deduction  from 
my  observations  that  diseased  shoots  show  characteristic  evidences  of  one- 
sided nitrogen  fertilization.  Direct  results  are  not  involved  here,  only  the 
after  effects  in  the  following  year.  The  parent  tuber  is  either  immature  in 
a  few  eyes,  or  entirely  so.  In  the  following  year  a  diseased  condition  de- 
velops in  all  of  the  shoots  or  only  in  some  of  them.     This  limitation  of  the 


1  Zeitschr.   f.   Pflanzenkrankh.   1894,   p.   314. 


396 

attack  is  to  be  emphasized,  because,  at  times,  up  to  the  present,  observers 
have  emphasized  especially  that  all  the  stems  on  a  tuber  become  diseased, 
i,  e.  that  the  cause  of  the  disease  must  lie  in  the  whole  tuber,  while  my 
observations  have  shown  beyond  question  that  the  diseased  condition  may 
be  limited  to  a  few  eyes. 

According  to  Kiihn',  the  disease  appeared  as  an  epidemic  first  in  1770 
in  England  and  in  1776  in  Germany,  causing  extraordinary  losses.  The 
first  symptom  is  the  discoloration  of  the  leaves  which  no  longer  have  the 
fresh  appearance  of  healthy  plants.  The  main  leaf  stem  is  usually  found 
bent  downward  or  completely  rolled  up;  the  various  leaflets  are  folded, 
curled  here  and  there  and  covered  with  brown,  usually  longish  spots.  The 
latter  extend  as  far  as  the  main  rib  of  the  leaf  and  finally  to  the  stem.  At 
first  only  the  superficial  cells  are  brown,  later  the  disease  extends  deeper 
into  the  tissue,  even  to  the  pith  of  the  stem.  This  changes  the  consistency 
of  the  stem  from  a  normal  flexibility  to  a  glassy  brittleness.  In  addition, ' 
according  to  Schacht,  sugar  is  found  very  abundantly  in  the  diseased  cells-. 
If  such  plants  live  until  harvest  time,  they  either  set  no  tubers  at  all  or  only 
a  very  few. 

In  the  earlier  literature,  very  different  causes  (including  parasitic 
fungi)  are  given,  as  shown  by  reference  to  the  previous  edition  of  this 
manual.  Newer  theories  may  be  found  in  Frank's^  study.  He  distinguishes 
a  number  of  different  forms  of  the  disease  and,  agreeing  with  me,  states 
that  the  very  beginnings  of  the  diseased  condition  do  not  show  any  fungous 
action.  The  cause  of  the  death  of  the  protoplasm  in  the  various  brown 
tissue  centers  is  not  known.  Differing  from  my  observations,  however, 
Frank  emphasizes  "that  all  the  shoots  of  a  plant  became  sick  simul- 
taneously*." 

In  making  more  extensive  cultural  experiments,  using  several  varieties, 
and  directed  especially  to  the  study  of  leaf  curl,  I  found  that  the  phenom- 
ena of  disease  appeared  initially  only  in  one  variety  (Early  Puritan).  The 
diseased  plants,  scattered  among  the  healthy  ones,  made  only  a  third  as 
much  growth  and  showed  the  well-known  characteristics,  especially  the 
breaking  of  the  curled  leaves.  Small  corky  fissures  were  often  found  on  the 
petioles.  The  first  stages  of  the  disease  on  the  stems  were  found  in  one  of 
the  internodes  below  the  surface  of  the  soil,  where  a  blackening  of  the  duct 
walls  could  be  determined.  This  characteristic  can  be  traced  back,  radiating 
more  or  less  deeply  into  the  tuber  which  otherwise  seems  healthy.  This 
shows  that  the  tuber  has  not  carried  the  disease  to  the  shoot  but,  conversely. 
In  the  same  wav,  the  browning  of  the  ducts  radiates  out  from  the  diseased 


1  Kiihn,  Jul.,  Krankheiten  d.  Kulturgewachse.  1858,  p.  200.  —  Ber.  aus.  d. 
physiolog.  Laborat.  d.  landwirtsch.  Institufs  zu  Halle.  1872,  Part  1,  p.  90. 

2  Bericht  an  das  Kgl.  L.andesi3konomiekollegium  liber  die  Kartoffelpflanze  und 
und  deren  Krankheiten.  1854,  p.  11. 

3  Frank,  A.  B.,  Die  pilzparasitiiren  Krankheiten  der  Pflanzen.  Breslau  1896, 
p.  300.  —  Kampfbuch  gegen  die  Schadllnge  unserer  Feldfriichte.  Berlin,  Parey, 
1897,  p.   217. 

4  Kampfbuch  p,  222. 


397 

stem  node  into  the  roots,  produced  at  that  point,  and  may  be  found  in  the 
whole  part  of  the  axis  which  is  still  green,  up  to  the  ribs  of  the  last  leaves. 

Especially  striking  is  the  sap  turgescence  in  the  apparently  perfectly 
healthy  parent  tuber  which  exhibits  some  cells  with  large  unconsumed  starch 
grains.  The  groups  of  cells  containing  the  starch  lie  scattered  in  the  very 
turgescent  parenchyma  of  the  tubers,  which  shows  scarcely  any  traces  of 
solid  cell  contents,  while  the  nuclei  are  large. 

It  is  further  noteworthy  that,  just  as  healthy  and  diseased  shoots  may 
be  produced  from  one  tuber,  the  characteristics  of  disease  on  the  same  stem 
can  often  be  restricted  to  definite  areas.  Healthy  eyes  may  develop  on 
diseased  stems  and  diseased  stems  are  found  in  which  only  half  of  the  vas- 
cular bundle  ring  is  blackened. 

Thus,  like  other  diseases  connected  with  the  discoloration  of  the  ducts, 
leaf  curl  begins  to  manifest  the  first  symptoms  of  disease  at  the  peripher}-. 
The  cuticle  blackens  most  of  all.  The  cell  contents  began  to  change  color 
at  first  to  a  weak  inky  color,  until  the  walls  and  contents  have  become  uni- 
formly brown,  after  which  the  epidermal  cell  collapses. 

Wliere  the  epidermis  borders  on  the  collenchymatous  tissue,  the  dis- 
coloration advances  in  its  walls.  They  become  slightly  yellowish  at  first, 
then  reddish  yellow  (in  some  varieties  a  peculiar  blood  red),  and  finally 
brown.  This  discoloration  of  the  walls,  which  seems  to  spread  rapidly 
tangentially,  recalls  enzymatic  activities. 

The  further  course  of  the  disease  differs  in  the  different  varieties, 
probably  because  the  cell  walls  vary  in  construction,  some  being  more  loose- 
ly built,  others  more  solidly.  In  Early  Puritan  it  was  observed  that  the 
browned  cell  walls  could  be  attacked  by  a  granular  decay,  in  which  small 
rod-like  bacteria  probably  participated.  In  these  cases  the  tissue  disap- 
peared, while  holes  and  depressions  appeared  in  the  bark  tissue  of  the 
stem  and  mycelium  was  found.  In  Early  Puritan  the  depressions  deepened 
to  the  wood  ring  and,  as  the  disease  advanced,  their  pressure  could  be  dem- 
onstrated even  on  the  still  green  tips  of  the  stems.  The  browning  of  the 
ducts,  however,  did  not  proceed  from  them;  it  began  at  the  base  of  the 
stem  and  spread  only  in  the  vascular  system.  At  the  torn  places  processes 
of  healing  often  manifested  themselves  in  the  pouch-like  elongation  of  the 
adjacent,  healthy  bark  parenchyma  cells. 

The  statement  given  above,  that  the  symptoms  of  disease  do  not  uni- 
versally appear  uniformly  relates,  for  example,  to  the  appearance  of  brown 
specks  on  the  uncurled  leaves.  However,  in  the  petioles  of  these  leaves 
there  is  exactly  the  same  pale  inky  filling  of  the  ducts  which,  in  some  cases, 
thickens  to  a  grainy  slime  ;  the  walls  of  the  ducts  also  are  browned. 

The  characteristics  here  described  occur  separately  also  in  other  plants 
with  an  excess  of  nitrogen.  If  these  symptoms  are  compared  with  the  re- 
sults of  earlier  observations,  leaf  curl  may  be  described  as  follows.  The 
diseased  condition  appears  most  luxuriantly  and  abundantly  on  tender  early 
varieties.     The  harvested  tubers   are   immature,  being  distinguished  by  a 


398 

smoother  skin,  a  lower  starch  content  and  a  considerably  higher  potassium 
content.  They  are  also  smaller  in  size  and  have  a  smaller  drj^  weight.  Under 
favorable  conditions,  healthy  plants  may  often  be  grown  from  such  tubers. 

Among  the  characteristics  given,  we  have  emphasized  the  length  of  the 
existence  of  the  parent  tuber,  which  remains  turgid  and  retains  starch, 
because  Hiltner^  has  recently  described  such  a  case  belonging  here  and,  in 
fact,  a  partial  subsequent  enlargement  of  the  parent  tuber.  Different  people 
•have  made  the  same  observations.  In  Hiltner's  case  it  was  also  observed 
that  the  plants  produced  from  the  turgid  tuber  developed  no  tubers  below 
the  soil,  attached  to  the  stolens,  but  bore  them  directly  on  the  lower  inter- 
nodes  of  the  green  stems.  These  stems,  however,  were  only  half  as  long 
as  in  normal  plants  and  bore  leaves,  rolled  together,  which  reminded  Hiltner 
of  leaf  curl.  He  thinks  that  these  processes  are  a  result  of  the  use  of  im- 
mature tubers  for  seed.  These  tubers,  after  developing  the  stem,  had  uti- 
lized in  their  own  further  growth  the  material  obtained  by  the  action  of 
the  leaves.  Naturally  too  little  organic  substance  remains  for  the  tubers  of 
the  current  year. 

If  we  accept  Hiltner's  theory  as  to  the  production  of  tubers  which  re- 
main turgid,  we  can  infer  that  leaf  curl  results  from  the  use  of  unsuitable 
seed.  The  tubers  were  not  sufficiently  matured  in  the  previous  year.  This 
must  also  make  itself  felt  in  the  full  development  of  the  individual  eyes. 
While  the  majority  of  these  had  time  to  develop  normally,  some  may  have 
remained  immature  and  have  retained  this  character  when  sprouting  in  the 
following  year.  This  will  explain  the  fact  that  often  only  isolated  shoots 
are  found  which  show  leaf  curl.  The  characteristic  of  immaturity  is  the 
marked  abundance  of  potassium  and  nitrogen  compounds  with  a  scanty 
deposition  of  carbohydrates  as  reserve  substances.  We  find  such  conditions 
favored  by  the  use  of  fresh  manure  with  early  varieties  and  drought  stops 
the  growth  of  the  tubers  prematurely. 

If  an  over-supply  of  nitrogenous  compounds,  not  normally  utilized, 
determines  the  appearance  of  leaf  curl  in  the  potato,  the  shrivelling  disease 
of  the  mulberry  tree,  and  other  diseases,  to  be  mentioned  under  "Enzymatic 
Diseases,"  then  the  symptoms  of  the  blackening  of  the  ducts  and  rapid 
bacterial  infection,  already  found,  may  be   explained  easily. 

This  theory  is  further  supported  by  a  study  made  by  Appel-,  who,  under 
the  name  "Bacterial-ring  disease,"  describes  the  phenomena  which  often 
suggest  leaf  curl.  He  makes  bacteria  responsible  for  the  ring  disease 
and  "indeed,  as  in  black-leg,  not  one  species  alone  but  a  few  closely  re- 
lated forms."    "These  bacteria  are  undoubtedly  present  normally  in  many 

soils "     Influenced   by   these   statements   I    should    like   to   include 

bacterial  ring  disease  under  those  diseases  in  which  a  constitutional  weak- 
ness in  the  plant  and  not  a  parasite  determines  the  phenomenon  and  favors 


1  Hiltner,  L..,  Zur  Frag-e  des  Abbaues  cler  Kartoffeln.  Prakt.  Bl.  f.  Pflanzcn- 
bau  und  Pflanzenschutz  1905,   Part  12. 

~  Appel,  O.,  Die  Bakterien-Rinskrankheit  der  Kartoffel.  Flugblatt  36  d.  Kais. 
Biolog:.   Anst.   Dahlem.   1906. 


399 

especially  the  spread  of  the  bacterial  infection.  These  conditions  are  simi- 
lar to  those  described  as  leaf  curl,  in  which  I  likewise  have  observed  decom- 
position of  the  tissue  by  bacteria. 

It  thus  seems  that  we  have  before  us  a  whole  group  of  potato  diseases, 
with  the  common  characteristic  that  the  ducts  turn  black.  This  mav  be 
traced  to  the  fact  that  incompletely  consumed  nitrogenous  compounds  make 
their  influence  felt  in  an  insufficient  development  of  the  carbohydrates. 

We  must  seek  to  overcome  this  condition  to  the  best  of  our  ability  by 
fulfilling  the  requirements  for  a  gradual,  complete  ripening  of  the  tubers 
on  the  plant. 

d.     Excess  of  Calcium  and  Magnesium. 

In  addition  to  the  observations  on  the  use  of  lime  as  mentioned  in 
earlier  sections,  we  will  emphasize  here  first  of  all  Orth's^  warning  that  it 
should  be  supplied  to  the  field  in  small,  frequent  doses  rather  than  in  one 
heavy  application. 

Of  course,  an  excess  of  calchun  cannot  be  determined  exactly  by  defi- 
nite figures,  since  the  demand  of  each  plant  and  each  field  is  different.  Also, 
in  adding  the  lime  it  does  not  depend  at  all  on  the  absolute  amount  of  cal- 
cium supplied  but  on  the  proportion  to  the  other  nutrients  of  which  the 
calcium  influences  the  solubility  and  capacity  for  transportation.  Finally, 
the  weather  conditions  at  the  time  the  lime  is  applied  must  be  considered. 

Hoffmann-,  from  his  broad  experience,  has  given  many  warnings  which 
are  of  utmost  value  practically.  Calcium  is  injurious  when  used  in  large 
amounts  on  exhausted  soils.  On  lighter,  active  soils,  poor  in  humus,  during 
dry  springs,  it  loosens  and  dries  the  soil  too  much  and  disturbs  the  bacterial 
action.  If  it  is  used  in  the  form  of  marl,  it  must  first  be  well  decomposed 
in  the  air,  in  order  that  possible  injurious  elements  can  be  oxidized  at  the 
right  time.  Calcium  acts  detrimentally  in  continued  drought,  and  also  with 
stagnant  water  if  it,  in  the  form  of  so-called  "water-lime,"  is  mixed  with  a 
good  amount  of  silicic  acid,  ferric  oxide  and  clay.  In  wet  weather,  it  be- 
comes as  hard  as  cement. 

But  even  under  normal  conditions,  calcium  may  be  detrimental,  ^^'e 
must  not  forget  that,  together  with  the  desired  effect  of  decomposing  organic 
substances,  containing  nitrogen,  and  of  transforming  the  ammonia  produced 
into  calcium  nitrate,  ammoniacal  compounds  are  set  free.  If  ammonium 
nitrate  or  ammonium  sulfate  is  mixed  with  calcium  carbonate  or  phosphate, 
it  produces  the  very  soluble  calcium  chlorid  and  gypsum  and  ammonium 
carbonate  or  phosphate.  In  Wagner's^  experiments  (Darmstadt),  the  loss 
of  nitrogen,  produced  by  the  volitalization  of  ammonia,  was  observed  to  be 
30  per  cent,  of  that  in  a  fertilization  with  nitrate.  The  same  losses  are  pro- 
duced very  easily,  if  the  soil  is  rich  in  calcium  carbonate,  if  the  ammonium 


1  Orth,    A..    Kalk-    und    Mergeldiingung-.      Anleitung-,    im   Auftrage    d.    Deutsch. 
Landw.-Ges.     Berlin  1896. 

2  Hoffmann,  M.,  Diingungsversuche  mit  Kalk.     Arb.  d.  D.  Landw.-Ges.  Part  106. 

3  Zeitschr.   der  Landwirtschaftskammer  f.  d.  Prov,   Schlesien.   1904,   p.   1683. 


40O 

salt  is  only  superficially  worked  in  so  that  the  sun  and  wind  have  abundant 
access  to  it.  Then  the  free  ammonium  carbonate,  produced  by  the  trans- 
formation of  the  fixed  ammonium  sulfate,  can  be  removed  from  the  field 
very  quickly, 

Sandy  soils,  which  at  the  time  are  rich  in  calcium,  are  on  this  account 
not  suited  for  an  ammonia  fertilization,  especially  not  as  a  top  dressing. 
This  explains  why  quick  lime  should  not  be  brought  directly  into  contact 
with  stable  manure  or  other  ammonium  fertilizers. 

Ik'sides  these  reactions,  lime  also  acts  on  phosphoric  acid.  This  action 
must  not  be  underestimated.  The  action  of  the  phosphoric  acid  on  super- 
ph()si>hate.  which  is  soluble  in  water,  is  impaired  by  the  simultaneous  use 

Supeiphosphate 


riiomas   slag 


Stable  manure  and 
g-uano 


Chile  Saltpetre 

Fig-.   GO.     Diagrammatic  representation   of  the  favorable  and   unfavorable   mutual 
relations   of  fertilizers   to   each  other. 


of  lime ;  but  not  so  much  so  as  the  phosphoric  acid  in  Thomas  slag,  soluble 
in  citric  acid.  The  destructive  efifect  of  lime  on  phosphoric  acid  is  greatest 
when  used  with  ground  bone. 

It  may  be  the  place  here  to  refer  to  the  mutual  relation  of  fertilizers  in 
order  to  avoid  using  them  in  such  a  way  as  to  impair  their  action.  Instead 
of  more  lengthy  descriptions  we  will  reprint  a  figure  borrowed  from  the 
"Practical  Advisor  in  Fruit  and  Garden  Culture,"  1906,  No.  17^ 

In  this  diagram,  the  thin  connecting  lines  signify  that  the  various  kinds 
of  fertilizers  may  always  be  mixed  together.  The  fertilizers,  which  appear 
connected  by  double  lines,  may  be  mixed  with  one  another  only  very  shortly 
before  spreading;  while  those  fertilizers  connected  in  the  figure  with  thick 
lines  may  never  be  mixed  together. 


1  "Praktischen  Ratgeber  im  Obst-   und  Gartenbau."     No.  17,  1906. 


40I 

The  poisonous  effects  of  an  excess  of  magnesium  and  the  associated 
theory  given  by  Loew,  as  to  a  definite  quantitative  relation  between  calcium 
and  magnesium  in  the  soil  for  obtaining  good  harvests,  have  been  con- 
sidered already  in  the  section  on  "Lack  of  Calcium"  (p.  301).  Recently 
Loew^  has  supplemented  his  earlier  statements  by  calling  attention  to  the 
fact  that  the  favorable  quantitative  relation  between  calcium  and  mag- 
nesium in  the  soil  cannot  always  be  fixed  by  definite  figures.  It  changes  as 
soon  as  the  two  bases  are  made  accessible  in  different  degrees  for  absorp- 
tion by  the  plant. 

Loew's  theory  is  contradicted  by  experiments  made  by  Meyer-.  The 
emphatic  fact  here  is  that  heavy  additions  of  calcium  as  well  as  of 
magnesium  can  greatly  impair  the  yield.  Naturally  the  various  plant  species 
behave  very  differently  with  the  same  fertilizer.  Given  the  same  quantity 
of  magnesium,  the  grain  and  straw  yield  of  oats  was  lessened,  but  that  of 
rye  was  not  decreased. 

GosseP,  on  the  basis  of  his  own  experiments,  also  considers  Loew's 
point  of  view  to  be  Incorrect,  yet  we  think  it,  nevertheless,  worth  consider- 
ation. Too  much  faith  must  not  be  put  in  definite  figures  because  each 
cultural  experiment  offers  different  conditions.  A  constant  effort  must  be 
made  to  overcome  the  injurious  effects  of  the  magnesium  compounds  when- 
ever brought  into  the  soil  in  great  quantities  in  the  fertilizer.  Qf  first  im- 
portance is  the  great  quantity  of  magnesium  chlorid  spread  on  the  field  with 
the  so-called  "waste  salts"  which  reduces  the  sugar  content  of  beets,  the 
starch  content  of  potatoes,  etc.  An  effort  must  be  made  to  combine  the  non- 
absorbable chlorine  with  a  base,  especially  calcium,  so  that  it  can  be  washed 
easily  into  the  subsoil. 

Finally  attention  must  be  called  to  the  fact  that  the  same  amount  of 
calcium  acts  injuriously  at  one  time  and  beneficially  at  another,  according 
to  whether  it  is  added  in  the  forms  of  calcium  carbonate  or  calcium  sulfate. 
Thus,  for  example,  Suzuki*,  found  in  vegetative  experiments  with  moun- 
tain rice,  that  the  yield  was  considerably  reduced  by  an  excessive  ad- 
dition of  calcium  carbonate  (the  proportion  of  calcium  to  magnesium  was 
as  3:1),  even  if  phosphoric  acid  was  present  in  an  easily  soluble  form.  On 
the  other  hand  the  addition  of  an  equivalent  amount  of  gypsum  caused  an 
unusual  increase  in  the  yield,  especially  of  grain.  From  this  experiment, 
however,  it  is  evident  that  the  injurious  action  of  an  excess  of  calcium  is  not 
always  to  be  sought  in  a  decrease  in  the  looseness  of  the  soil  as  compared 
with  that  found  after  the  use  of  slightly  soluble  phosphoric  compounds,  but 
probably  has  its  foundation  also  in  the  neutralization  of  the  root  acids. 

1  Loew.  O.,  and  Aso,  K..  tJber  verschiedene  Grade  der  Aufnahmefahig-keit  von 
Pflanzennahrstoffen  durch  die  Pflanzen.  Bull.  College  of  Agric.  Tokyo.  Imp.  Univ. 
Vol.  VI.  No.  4,  cit.  Centralbl.  f.  Agrik.-Chemie  1905,  p.  594. 

2  Meyer,  D.,  Untersuchungen  iiber  die  Wirkung-  verschiedener  Kalk-  und 
Magnesiaformen.     Landw.  Jahrbiicher  Vol.  XXXIII,  1904,  p.  371. 

3  Gossel,  Fr.,  Bedeutung-  der  Kalk-  und  Magnesiasalze  fiir  die  Pflanzenernah- 
rung.     Vortrag-  auf  d.  75.  Naturf.  Vers.   (s.  Chemikerz.  1903,  No.  78). 

■i  Suzuki,  S.,  iiher  die  schadliche  "Wirkung  einer  zu  starken  Kalkung-  des 
Bodens.  Bull.  College  of  Agric.  Tokyo,  Imp.  University.  Vol.  VI.  cit.  Centralbl. 
f.  Agrik.-Chem.  1905,  p.  588. 


402 

By  neutralizing  the  acids  of  the  plant  roots  the  available  phosphoric 
acid  will  not  be  so  largely  absorbed.  The  great  difference  between  the 
action  of  calcium  carbonate  and  that  of  gypsum  is  due  to  the  fact  that 
g}'psum  is  taken  up  from  the  soil  only  so  far  as  it  is  soluble  in  water  (i.  e. 
in  the  very  sHghtest  amounts),  while  the  absorption  of  the  carbonate  by  the 
plant  depends  upon  the  carbonic  acid  of  the  root. 

Excess  of  Calcium  With  Grapes. 

Since  the  introduction  of  grapes  grown  on  budded  American  vines 
there  have  been  very  many  complaints  of  Jaundice.  The  disease  is  de- 
scribed usually  as  "Chlorosis" ;  but  according  to  my  conception  it  must  be 
called  "Icterus." 

Of  course,  the  causes  of  the  yellow  condition  of  the  foliage  of  grapes 
may  differ  very  greatly,  as  in  other  plants.  Very  frequently,  root  decay, 
occurring  with  or  without  fungi,  plays  a  role  in  heavy  soils.  Vitis  Riparia 
and  V.  rupcstris,  with  their  w^eaker  root  systems  are  especially  sensitive  to 
such  soils,  while  varieties  with  strong  roots  (Jacquez,  Herbemont,  etc.), 
better  adapt  themselves^.  American  vines,  however,  are  grown  with  great 
difficulty  on  soils  containing  a  great  deal  of  calcium  in  an  easily  foluble  form 
and  not  rich  in  nutrients.  In  France  it  was  possible  to  collect  the  greatest 
amount  of  information  on  this  subject.  Luedecke-  repeats  the  results  of 
soil  investigations  which  the  agricultural  society  of  Cadillac  undertook  in 
1890.  The  soil  which  showed  no  jaundice  of  the  vines  and  that  which 
showed  jaundice  contained 

No  jaundice  jaundice 

Phosphoric  acid  0.07  per  cent.  0.06  per  cent. 

Potassium  0.39  per  cent.  0.37  per  cent. 

Calcium  1.81  per  cent.  18.93  P^^  cent. 

Ferric  oxid  5.90  per  cent.  3.02  per  cent. 

Nitrogen  o.io  per  cent.  o.io  per  cent. 

The  content  of  both  soils  in  nitrogen,  potassium  and  phosphoric  acid, 
therefore,  is  about  equal ;  the  ferric  oxid  percentage  is  high  in  botli,  but 
the  calcium  is  nearly  ten  times  as  great  in  the  soil  producing  jaundice.  Tn 
the  fertilization  experiments  undertaken  with  Chile  saltpetre,  ammonia, 
superphosphate,  potassium  chlorid,  magnesium  sulfate  and  iron  sidfate 
(ferric  sulfate),  only  the  last  gave  any  satisfactory  results.  In  this  ex- 
perimental plot,  the  vines  formed  a  great  many  new  roots.  The  same  re- 
sults were  again  obtained  under  similar  conditions  on  soils  naturally  rich 
in  iron,  in  which,  therefore,  the  favorable  action  of  fertilization  with  iron 
sulfate  cannot  be  ascribed  to  a  previous  lack  of  iron. 


1  Eg-er,  E.,  Untersuchungen  liber  die  Methoden  der  Schadling-sbekampfung- 
usw.     Berlin,  Paul  Parey,  1905. 

-  Luedecke  in  Zeitschr.  f.  d.  landw.  Ver.  d.  Grossherz.  Hessen  1892,  No.  41, 
1893,  No.  2. 


403 

Such  results,  proving  that  jaundice  of  the  grape  is  due  to  a  high  calcium 
content  are  found^  frequently  as  are  also  observations  as  to  the  effectiveness 
of  the  iron  sulfate. 

The  question  now  is,  how  to  explain  the  injurious  effects  of  calcium 
and  the  beneficial  action  of  the  so-called  iron  compounds.  Luedecke  found 
that  the  water  coming  from  the  lime  soils  of  Rhenish  Hessen  has  an  alkaline 
reaction,  and  he  found  that  with  an  addition  of  some  iron  salt  (iron  sulfate 
or  ferric  chlorid),  the  iron  was  precipitated.  He,  therefore,  came  to  the 
conclusion  that,  since  plants  are  able  to  take  up  iron  only  in  a  dissolved 
form,  and  since  the  alkaline  water  prevents  its  solution,  the  grape  vines 
suffer  from  a  lack  of  iron  in  spite  of  the  great  amount  of  it  in  the  soil ;  they, 
therefore,  become  icteric.  Viala  and  Ravaz  noticed  the  injurious  action  of 
lime  in  a  neutralization  of  the  cell  sap  of  the  roots-. 

Until  we  have  the  results  of  further  experiments,  we  must  be  satisfied 
with  the  fact  that  large  amounts  of  easily  soluble  calcium  compounds  will 
produce  icterus  of  the  grape,  and  that  abundant  additions  of  iron  sulfate 
have  often  been  found  to  be  useful  in  combatting  it.  It  is  now  of  the  first 
importance  to  consider  that  the  affinity  of  the  sulfuric  acid  of  the  iron  com- 
pound for  calcium  is  great  and  forms  g>'psum  which,  only  slightly  soluble, 
is  proved  to  be  non-injurious,  or  even  beneficial  to  growth. 

Eger^  cites  Oberlein-Beblenheim's  experimental  results,  showing  that, 
on  rich  soils,  fertilization  with  gypsum  considerably  increases  the  yield. 
Since  the  addition  of  gypsum,  made  at  the  same  time  to  poor  soils,  remains 
absolutely  without  result,  the  favorable  action  of  the  gypsum  may  probably 
he  ascribed  to  its  power  of  loosening  up  the  soil. 

e.     Excess  of  Potassium. 

Reference  has  been  made  already  to  the  danger  to  soil  constitution  of 
a  continued  heavy  potassium  fertilization,  and  in  this  it  was  emphasized 
that  lighter  soils  and  moor  soils  responded  more  favorably  to  the  addition 
of  potassium.  Recently,  however,  Hollrung  has  called  attention  to  another 
disadvantage  of  all  fertilization  with  mineral  salts, — therefore,  of  potassium 
salts  also.  He  refers  to  Hall's  experiments,  showing  an  absolute  change  in 
the  water  conditions  in  the  soils.  Hall  determined  (after  1866)  the  num- 
ber of  days  in  one  year  in  which  drainage  flowed  from  an  unfertilized  field, 
as  contrasted  with  one  constantly  fertilized  with  Chile  saltpetre.  The 
longer  the  drainage  flows,  the  more  water  is  removed  from  the  field.  Al- 
though the  results  fluctuated  in  the  several  periods  of  five  years  each,  which 
he  compared,  yet  as  a  whole  for  the  entire  length  of  time,  they  indicated 
that  in  the  "salted  soils,"  larger  amounts  of  water  had  passed  into  the 
drainage  through  the  subsoil.  This  makes  possible  conclusions  as  to  an 
unfavorable  transformation  of  the  soil. 


1  See  V.   Babo  and  Mach,   Handbuch.  des  Weinbaues   and   der  Kellerwirtschaft 
Eger). 

2  See  Eger. 

3  Ivoc.  cit.  p.  84. 


404 

The  effect  of  potassium  salts  on  tlie  plant  depends  on  the  form  of  the 
fertilizing  salt  and  the  soil  on  which  it  is  used^  The  question  arises  here 
as  to  the  part  played  by  the  accessory  salts  incorporated  in  the  soil  with 
the  addition  of  potassium.  At  present,  kainit  and  the  40  per  cent,  potas- 
sium salt  are  used  more  extensively,  ^^'^ith  kainit,  3^  cwt.  should  be  used 
if  one  desires  to  add  as  much  potassium  as  is  present  in  one  cwt.  of  40 
per  cent,  potassium  salt.  Among  the  accessory  salts  introduced  in  the 
kainit,  sodium  chlorid  i)lays  a  prominent  role.  Besides  this,  magnesium 
sulfate  and  magnesium  chlorid  come  under  consideration.  The  individual 
plants  behave  very  differently  with  sodium  chlorid.  Its  effect  on  sugar 
beets  is  very  good,  but  potatoes  are  very  sensitive  to  it".  The  results  with 
sugar  beets,  however,  are  rather  deceptive.  According  to  Aducco  ard 
Wohltmann's  exj^eriments,  the  amount  of  beet  substance  harvested  is  in- 
creased, but  the  quotient  of  purity  and  the  sugar  content  are  reduced. 

On  account  of  the  accessory  salts,  Schneidewind  and  Ringleben"'  tested 
raw  potassium  salts  with  different  potassium  compounds  as  contrasted  w  ith 
the  highly  concentrated  forms.  It  was  shown  for  a  mixture  of  clover  and 
grass,  and  for  oats,  sugar  beets  and  potatoes,  that  kainit  was  superior  to 
potassium  chlorid  and  potassium  sulfate,  if  sufficient  amounts  of  calcium 
carbonate  were  present.  If  these  were  lacking,  opposite  results  were  ob- 
tained. If  the  slightly  soluble  gypsum  was  used,  instead  of  calcium  car- 
bonate, kainit  proved  to  be  especially  injurious  for  the  mixture  of  clover 
and  grass,  but  less  so  for  oats.  In  potatoes  the  action  was  favorable  if  the 
soils  were  poor  in  potassium.  With  an  increase  of  potassium,  the  effect  of 
excess  became  evident,  i.  e.  the  starch  content  was  lowered.  Szollema'* 
found  that  the  decrease  of  starch,  effected  by  the  chlorid,  which  is  connected 
with  a  greater  abundance  of  water,  was  somewhat  greater  in  the  varieties 
of  potatoes  naturally  rich  in  starch  than  in  those  poor  in  starch. 

When  plants  are  very  sensitive  to  the  chlorine  compounds  of  the  raw 
potassium  salts,  as,  for  example,  kainit,  the  loss  of  potassium  by  its  partial 
leaching  from  the  soil  during  the  autumn  and  winter,  is  really  an  advantage 
in  so  far  as  many  of  the  dangerous  accessory  salts  (sodium  chlorid  and 
magnesium  chlorid),  are  washed  out  at  the  same  time;  therefore,  while 
actually  less  potassium  remains  in  the  soil,  it  becomes  more  effective,  be- 
cause it  is  in  a  purer  form.  This  leaching  of  the  potassium  must  be  taken 
into  consideration  in  soils  with  only  small  amounts  of  calcium  and  other 
such  absorbents,  as,  for  example,  in  light,  sandy,  and  moor  soils'. 

Concerning  the  disadvantageous  effects  of  potassium  fertilization  on 
cultivated  plants,  other  than  those  already  named,  we  will  mention  further 

1  Blatter  fiir  Zuckerriibenbau  1905,  p.   62. 

2  Blatter  fur  Zuckerriibenbau  1905,  p.    89. 

3  Schneidewind,  W.,  and  Rinsleben,  O.,  Die  Wiikunf?  der  Kalirohstoffe  un<l 
der  reinen  Kalisalze  bei  verschiedenen  Kalkformen.  Landwirtsch.  Jahrib.  1904. 
A'ol.  XXXIII,  p.  353. 

■i  Szollema,  D.,  Vber  den  Einfluss  von  Chlor-  und  anderen  in  den  Stassfurter 
Rohsalzen  vorkommenden  Verbindungen  etc.  cit.  Centralbl.  f.  Agrikultur-Chemie 
1901,  p.  516. 

5  Schneidewind.  Auswaschen  des  Kalis  im  Winter.  Zeitschr.  (I.  T>andwirt.schafts- 
kammer  f.  Schlesien  1904,  No.  14,  p.  471. 


405 

the  effect  on  Tobacco  observed  by  Behrens^  His  experiments  showed 
that  the  water  content  of  the  leaves  increased  considerably  if  potassium 
sulfate  was  added  to  stable  manure  and  that  this  hastened  greatly  the  decav 
of  the  leaves  which  dry  with  difficulty  in  the  air.  This  probably  is  con- 
nected with  the  increase  in  turgor  observed  by  Copeland,  which  is  due  to 
potassium  salts  (Potash).  Sodium  salts  (soda)  did  not  show  this  physi- 
ological reaction^. 

The  complaint  of  farmers  that  continued  potassium  fertilization  re- 
duces the  quality  of  pasture  plants  so  that  animals  fed  with  such  hay, 
grow  thin,  should  be  considered  here.  Even  if  the  statement  that  this  ex- 
cessive action  occurs  is  still  contestible,  nevertheless  it  is  true,  that  a  de- 
crease in  flavor  has  been  observed  in  the  hay  from  fields  repeatedly  fertilized 
with  kainit,  or  with  kainit  and  Thomas  slag^. 

The  injuries  appearing  in  different  field  crops  and  fruit  trees  are  gen- 
erally the  result  of  an  unexpedient  use  of  potassium  salts,  a  practice  often 
followed  by  serious  injury*.  These  will  best  be  prevented  by  not  using 
potassium  in  large  amounts  on  heavy  soils,  by  not  spreading  the  salt  with 
the  seed,  by  repeated,  smaller  applications  of  potassium  and  (in  plants 
especially  sensitive  to  chlorine,  as,  for  example,  potatoes)  by  the  use  of  the 
40  per  cent,  potassium  salt,  and  of  other  purified,  highly  concentrated  com- 
pounds, instead  of  the  commercial  salts. 

The  frequent  use  of  potassium  in  small  quantities  is  often  beneficial 
becausq  the  calcium  in  the  soil  water,  containing  carbon  dioxid,  will  be 
more  easily  leached  out  the  more  potassium  salts  are  added  to  the  soil,  since 
the  calcium  is  converted  by  them  into  soluble  compounds.  Hoffman^ 
recommends  the  use  of  a  high  per  cent,  commercial  marl,  where  possible, 
and  its  application  in  at  least  5  to  yj^  double  centner®  per  acre.  If  the 
soil  is  liable  to  become  encrusted  {"he  baked"),  at  least  2^4  double 
centner  of  quick  lime  should  be  turned  under  superficially  in  the  autumn 
and  repeated  possibly  four  years  later. 

f.     Excess  of  Phosphoric  Acid. 

Injuries  due  to  an  excess  of  phosphoric  acid  are  rare.  They  can  only 
be  expected  where  superphosphates  are  used  abundantly,  i.  e.  where  some 
phosphoric  acid,  soluble  in  water,  is  present.  The  phosphoric  acid  of 
Thomas  slag,  soluble  in  citric  acid,  is  less  mobile.  However,  even  the  phos- 
phoric acid,  soluble  in  water,  passes  over  immediately  into  an  insoluble 
form  since  the  di-phosphates  of  calcium,  magnesium,  aluminum  and  iron 
formed  in  the  soil,  are  dissolved  only  very  slowly  by  the  carbon  dioxid  of 


1  Behrens,    J.,    Weitere    Beitrage    zur    Kenntnis    der    Tabakspflanze.      Landw. 
Versuchsstationen  1899,  p.  214. 

2  Bot.  Jahresber.  1897,  I,  p.  72. 

3  Mittellungen  d.  Deutsch.  Landw. -Ges.  vom  11.  Marz  1905. 

■i  Clausen,    Resultate    von    ObstbaumdiJng-ungen.      Landwirtschaftl.    Jahrblicher 
Vol.  XXXIII,  p.  939. 

5  Hoffmann,    M.,    Die    Kalisalze.    Anleitung.      Herau.sg-.    v.    d.    Deutsch.    Landw. 
Gesellsch.    3d  ed.,  1905. 

6  A   double  centnei'  equals  220  lbs. 


4o6 

the  soil  and  the  acid  secretions  of  the  roots.  Injury  from  superphosphates 
is,  therefore,  to  be  feared  even  with  heavy  appUcations  only  on  soils  which 
are  poor  in  calcium,  iron  and  aluminum  carbonates.  There  are  only  a  small 
number  of  experiments  on  this  subject.  The  careful  investigations,  made 
at  the  experimental  station  in  Bernburg,  on  sugar  beets^  fertilized  with  the 
monobasic  calcium  phosphate,  i.  e.,  excess  of  phosphoric  acid  soluble  in 
water,  have  shown  that  the  sugar  content  does  not  decrease  and  also  that 
the  amounts  of  beet  substance  and  non-sugar  have  remained  the  same  as  in 
normally  fertilized  beets. 

So  far  as  my  own  experience  goes,  an  excess  of  phosphoric  acid  may 
manifest  itself  in  a  shortening  of  the  root  system, — the  usual  result  of 
culture  in  all  highly  concentrated  solutions,  and  also  in  shortening  the 
vegetative  period  with  a  premature  ripening  of  the  crop.  The  plants  do  not 
develop  fully,  the  leaves  turn  yellow  prematurely,  and,  accordingly,  the 
yield  is  smaller  than  it  would  otherwise  have  been. 


g- 


Excess  of  Carbo>si  Dioxid. 


Experiments  on  the  effect  of  carbon  dioxid  content  in  the  air  and  soil, 
greatly  in  excess  of  the  normal,  have  led  to  contradictory  results.  While 
some  observers  have  recognized  only  injurious  eft'ects,  others  report  a 
satisfactory  development.  These  apparent  contradictions  may  be  due  to 
the  fact  that  with  carbon  dioxid,  as  with  all  other  nutritive  substances,  the 
effect  depends  upon  how  simultaneous  the  activity  of  all  the  other  growth 
factors  may  be.  The  activity  of  the  plants  is  generally  adjusted  to  the 
small  normal  carbon  dioxid  content  of  the  air'-.  They  sometimes  respond 
to  a  greater  increase  of  carbon  dioxid  by  arresting  growth,  sometimes  by 
increasing  it,  depending  upon  whether  the  carbon  dioxid  increase  occurs 
suddenly,  or  gradually,  and  whether  the  amount  of  light  and  warmth,  water 
and  nutrients  permits  the  individual  utilization  of  the  increased  amount  of 
carbon  dioxid.  Godlewski"  has  substantiated  this  point  of  view  by 
experiment. 

Our  hot  bed  plants  furnish  abundant  proof  of  the  favorable  aff'ect. 
According  to  E.  Demoussy's  investigations*,  this  is  due  not  only  to  an  in- 
creased warmth,  but  actually  also  to  an  increase  of  the  carbon  dioxid  in  the 
air  of  hot  beds,  sometimes  amounting  to  more  than  two  thousandths  parts. 
In  comparative  cultures,  the  air  of  the  hot  bed,  which  after  careful  testing 
showed  no  ammonia,  had  furnished  nearly  three  times  the  harvested  weight 
of  plants  grown  in  ordinary  air  under  otherwise  similar  conditions. 


1   See  lecture  by  H.  Roenier;   cit.  Ulatter  f.  Zuckerriibenbau  1905,  p.  229. 

a  Brown,  F.,  and  Escombe,  F.,  Der  Einfluss  wechselnden  Kohlensauregehaltes 
der  Liuft  auf  den  photosynthetischen  Prozess  der  Blatter  und  auf  den  Wachstums- 
modus  der  Pflanzen.  —  Farmer,  J.,  &  Chandler,  S.,  tJber  den  Einfluss  eines  tJber- 
schusses  von  Kohlensaure  in  der  Luft  auf  die  Foiin  und  den  inneren  Bau  der 
Pflanzen.     Proceed.  R.  Soc.  LXX.     cit.  Centralbl.  f.  Agrik.-Chemie  1903,  p.  586. 

y  s.  Sachs,  Arbeit,  d.  Bot.  Instituts  zu  Wurzburg.     Part  III. 

■t  Compt.  rend,  de  I'Acad.  d.  sciences  1904.  cit.  Centralbl.  f.  Agrik.-Chemie 
1904,   I'art  11,   p,  745. 


407 

The  fact  that  experiments  in  sterilized  soil,  as  contrasted  with  those  in 
non-sterilized  soil,  resulted  in  much  smaller  amounts  of  yield,  is  ascribed 
by  Demoussy  to  the  killing  of  the  micro-organisms  which,  by  their  activity, 
contribute  to  the  decomposition  of  the  carbon  dioxid  production.  It  is  also 
probable  that  the  growth  of  plants  close  to  the  ground  is  favored  by  the 
carbon  dioxid  constantly  given  off  by  the  soil,  since  it  has  often  been  de- 
termined that  air  at  the  surface  of  the  soil  contains  more  than  three  ten 
thousandths  carbon  dioxid. 

In  air  in  which  the  carbon  dioxid  has  a  tension  five  times  above  the 
normal,  a  great  many  different  plants  increased  about  possibly  60  per  cent, 
more  in  weight  than  they  did  in  ordinary  air.  These  also  blossomed  earlier 
and  more  abundantly^. 

If  plants,  which  naturally  behave  differently  according  to  species  and 
individuality,  are  no  longer  able  to  utilize  the  carbon  dioxid  given  them, 
their  life  functions  must  cease.  Kosaroff-  distinguishes  between  a  specific- 
ally injurious  effect,  and  one  due  indirectly  to  the  decrease  of  the  partial 
pressure,  or  rather,  the  removal  of  oxygen.  As  a  result  of  the  depression 
of  the  transpiratory  current,  the  plants  wilt.  Bohm^,  like  Saussure,  ob- 
served that  germination  was  retarded,  in  that  with  an  increase  of  carbon 
dioxid,  the  roots  and  stems  constantly  became  shorter  and  shorter.  The 
chlorophyll  formation  and  assimilation  were  considerably  decreased. 

Neither  can  geotropism  be  perceived  in  articulated  plants  (Gramineae 
Commelinaceae,  etc)  in  a  carbon  dioxid  atmosphere,  nor  may  a  stimulus, 
found  in  the  air,  initiate  any  bending*. 

Finally,  when  carbon  dioxid  begins  to  be  excessive,  the  effect  may  first 
be  beneficial,  then  later  gradually  harmful.  Reference  should  be  made 
here  to  the  experimental  results  obtained  by  Brown  and  Farmer^.  They 
observed  that,  with  an  increased  carbon  dioxid  content  in  the  air,  all  the 
parts  containing  chlorophyll  became  a  darker  green  after  8  to  10  days,  and 
the  starch  content  increased,  but  the  internodes  became  short  and  thick, 
the  leaves  rolled  up  even  to  the  point  of  deformity,  the  flower  buds  dropped, 
or  their  primordia  were  not  formed. 

Such  conditions  as  are  given  in  the  experiment  need  scarcely  ever  be 
feared  in  practice.  Such  cases  occur  most  frequently  in  hot  beds  where  the 
manure,  needed  to  raise  the  temperature  of  the  beds,  sets  free  too  much 
carbon  dioxid.  This  trouble  may  be  overcome  by  proper  ventilation,  (even 
on  frosty  days.) 


1  Demoussy,  E.,  Sur  la  vegetation  dans  des  atmospheres  riches  en  acide  car- 
bonique.     Compt.  rend.  CXXXIX,  p.   883. 

2  Kosaroff,    P.,    Die    Wirkung    der    Kohlensaure    auf    den    Wassertransport    in 
den  Pflanzen.     Bot.  Centralbl.  1900,  Vol.  83,  p.  138. 

3  Sitzungsber.  d.  Wiener  Acad.   1873   vom   24.   Juli. 

4  Kohl,    Die   paratonischen  Wachstumskriinimungen   der   Gelenkpflanzen.     Bot. 
Zeit.  LVni,   1900,   p.   1. 

5  Lioc.  cit. 


SECTION  II. 


INTURIOUS  ATMOSPPIEKIC  IXFLUKXCKS. 


CHAPTER  IV. 


TOO  DRY  AIR. 


Injury  to  Buds. 

Although  in  house  plants,  for  example,  we  have  constantly  met  with  the 
lack  of  sufficient  atmospheric  moisture  as  a  factor  in  the  production  of  the 
phenomena  of  disease,  it  has  as  yet  been  but  very  little  taken  into 
consideration. 

The  direction  in  which  continued  great  scarcity  of  atmospheric  moisture 
makes  itself  felt  may  be  seen  from  the  peculiarities  of  the  xerophytes.  As 
an  example  of  this,  we  will  mention  Grevillius'.  He  found  in  the  plants 
of  a  treeless  lime  plateau  a  thickening  of  the  epidermis  and  its  wax  coating, 
or,  as  a  substitute  for  this,  a  great  increase  of  pubescence.  These  char- 
acteristics are  more  marked  in  leaves  near  the  top  of  the  stem.  The  e[)i- 
dermal  cells,  in  contrast  to  normal  forms,  usually  have  somewhat  smaller 
lumina.  The  palisade  cells  are  broader  and  more  closely  joined  to  one 
another,  the  intercellular  spaces  are  smaller;  the  mechanical  tissues  in  the 
branches  and  petioles  are  better  developed,  the  pith  less ;  it  has  smaller  cells 
but  is  richer  in  starch.  These  changes,  in  fact,  occur  almost  always  in  con- 
nection with  a  great  lack  of  moisture  in  the  soil  whereby  it  is  hard  to  judge 
which  is  due  to  the  dryness  of  the  air  alone  and  which  to  the  excessive 
transpiration  conditioned  by  it.  However,  we  find  various  processes  setting 
in  when,  with  a  sufficient  supply  of  soil  moisture,  the  air  is  constantly  hot 
and  dry ;  these  will  have  to  be  discussed  here.  They  are  in  part  phenomena 
of  arrestment  in  the  life  of  the  buds  or  in  the  conditions  of  germination; 
in  part  disturbances  in  the  mature  leaves  which  lead  to  the  falling  of  the 
leaves  in  summer. 

Two  stages  must  be  noticed  in  the  life  of  the  buds  and  the  develoi^ment 
of  the  young  shoot  after  the  bud  has  unfolded.  If  a  considerable  dry  period 


1  Grevillius,    Morphologisch-anatomische    Studien    lib.    d.    xerophile    Phanero- 
gramen -Vegetation  der  Insel  Oeland.     Englers  Jahrbiicher   1897,  XXIII,  p.  24. 


409 


h> 


sets  in  in  the  early  spring  when,  as  a  rule,  it  is  continued  by  a  persistent 
East  wind,  the  opening  of  the  buds,  dependant  on  the  alternating  action  of 
sunshine  and  rain,  will  be  delayed.  The  gummy  masses 
in  the  bud  scales  of  many  varieties  of  trees,  usually  due 
to  the  gelatination  of  the  tissue,  must  be  softened  by  rain 
to  facilitate  the  development  of  the  buds,  while  the  resin- 
ous and  partially  balsam-like  products  of  this  softening 
in  the  scales,  warmed  by  the  sunshine, 
give  way  at  the  same  time  to  the  pres- 
sure of  the  buds.  In  continued  dry  and 
windy,  spring  weather,  the  buds  unfold 
more  slowly  because  the  necessary 
growth  of  the  inner  side  of  the  scales 
is  prevented  so  that  they  cannot  turn 
back  far  enough. 

In  the  second  kind  of  injury,  the 
young  tip  of  the  shoot,  just  appearing, 
is  suddenly  exposed  to  the  sharp  rays 
of  the  sun  and  to  very  great  evapora- 
tion in  abnormally  dry  air,  after  the 
protecting  scale  has  been  thrown  ofif. 
In  order  to  understand  this  process,  we 
give  a  few  illustrations  from  Griiss^. 

In  Fig.  67  is  shown  the  cross-section 
through  the  bud  covering  of  the  oak  ; 
in  Fig.  68,  one  through  Pinus  Mughus. 
It  is  easy  to  distinguish  the  different 
scales  firmly  overlapping  above  the 
strongly  developed  epidermis  of  the 
outer  side  and,  by  comparing  the 
two  bud  coverings,  the  increase  of 
precautionary  protection  in  the  conifers 
is  found  to  take  place  by  means  of  the 
deposition  of  masses  of  resin  (h).  In 
the  cross-section  of  the  individual  cov- 
ering scales  it  is  noticed  that  their  outer 
or,  later,  under  side  possesses  especially 
strongly  developed  elements.  In  the 
pine,  the  epidermal  cells  have  been  very 
greatly  thickened  sclerenchymatically. 
The  bud  covering  of  the  winter  oak  is 
composed  of  8  separate  scales,  and  its  cell  layers  found  underneath  the  epi- 
dermis are  so  strongly  thickened  that  the  lumina  have  almost  disappeared. 

Pringsheims  Jahrib.  f.  wissen- 


Si 


-ni-nr^/^-) 


Fig-.67. Cross-section  Fig.GS. Cross-section 
through  the  bud  through  the  bud 

covering  of  Quer-  covering  of  Pinus 
cus  sessili  flora,  Mughus,  Scop. 

Sm.   (After  Gruss.)      (After  Gruss.) 


1  Griiss,  J., 
schaftliche  Bot 


Beitrage  zur  Biologie  der  Knospe. 
Vol.  XXIII,   Part  4,  p.   637. 


410 

The  summer  oak,  Qicerciis  peduncidata,  Ehrh.  behaves  somewhat  differently. 
If,  in  the  Spring,  a  basal  growth  increases  the  sclerotic  elements,  the  cover- 
ing scales  show  a  certain  stiffness  and  remain  longer  attached  to  the  growing 
shoot.  They  thus  protect  it  longer  from  the  dangerous  fluctuations  in  tem- 
perature. The  oak  in  the  warmer  Mediterranean  countries,  Quercus  Ilex,  L. 
hardly  shows  the  sclerotic  elements  in  its  scantier  bud  coverings,  and  some- 
times they  are  entirely  lacking.  In  this  we  are  concerned  with  protection 
against  the  summer  drought  period  and  find  it  in  the  hairs,  which  develop 
from  the  epidermis,  and  also  the  cork  layer,  which  develops  from  the  sub- 
epidermal tissue. 

Before  the  leaves  burst  out  from  the  bud,  the  scales,  bent  together  like 
a  roof,  are  simply  small  leaves  reduced  to  stipules,  but  when  the  leaves 
break  out,  the  under  side  grows  further  at  the  base,  while  the  sclerotized 
outer  side  does  not  do  so.  Consequently  the  base  of  the  scale,  drying  from 
the  edges  backward,  become  fleshy,  cushion-like  and,  like  a  prop,  presses 
the  scale  outward.  This  is  the  time  of  danger,  since  even  the  delicate  vege- 
tative cone  is  exposed  to  the  fluctuations  of  temperature,  and  almost  with- 
out protection.  This  explains  the  internal  ruptures  made  by  the  action  of 
the  frost,  sometimes  found  in  the  spring^  and  also  the  phenomena  of 
shrinking  from  drought,  resulting  from  constant  sharp  East  winds. 

No  matter  in  what  way  the  protective  apparatus  of  the  bud  scale  is 
formed  in  the  various  species,  whether  from  sclerotic  cell  layers  or  from 
cork  layers,  layers  of  hair  or  masses  of  resin,  the  fact  holds  good  that  this 
apparatus  develops  differently  in  different  years,  according  to  the  weather 
and  the  amount  of  nutriment  at  the  time  of  its  formation,  and,  accordingly, 
is  of  different  protective  power  in  the  following  spring.  If,  for  example, 
the  summer  has  been  moist  and  cloudy,  the  covering  scales  tend  to  develop- 
ment towards  the  nature  of  the  green  leaf  and  the  cells  become  larger  or 
less  thickened.  In  spring  they  react  more  quickly  to  the  increase  of  turgor 
of  the  tissue  and  separate  from  one  another  more  quickly.  Thus  the  grow- 
ing point  is  exposed  prematurely  to  inclement  spring  weather,  and  so  loses 
too  rapidly  the  protection  against  its  power  of  transpiration. 

This  factor  must  not  be  underestimated,  for  Griiss  reports-  that, 
when  he  removed  the  strongly  developed  outer  scales  from  an  oak 
bud,  he  noticed  that  the  bud  was  destroyed  with  great  regularity,  even 
if  the  temperature  did  not  fall  and  there  was  present  sufficient  moisture. 
Also  the  inner,  more  delicately  walled  coverings  became  dry  since  they  were 
not  accustomed  to  the  increased  transpiration.  Uninjured  buds  kept  under 
similar  conditions  (on  cut  twigs)  developed  further. 

Experiments  with  beech  buds,  from  which  the  whole  covering  had 
been  removed,  showed  that  the  young,  exposed  leaves  kept  fresh  much 
longer  than  those  of  the  oak.  This  is  due  to  the  pubescence  of  the  young 
beech  leaves,  which  protect  them  from  too  great  transpiration  and  the  con- 


See  chapter  on  the  Action  of  Frost. 
Log.   cit.  p.  649. 


411 

sequent  drying.  This  view  is  supported  also  by  the  observation  of  Griiss, 
that,  in  Aesculus  Hippocastanum,  the  young  leaves,  known  to  be  very 
thickly  pubescent,  will  develop  normally  after  the  removal  of  the  bud  cover- 
ing. The  effectiveness  of  the  resin  covering  is  seen  from  an  example  of 
Abies  Pinsapo,  Boiss.  When  the  resin  had  been  removed  from  the  buds 
by  carbon  disulphid,  the}^  dried  up. 

It  may  now  be  asked  how  such  irregularities  in  the  unfolding  of  the 
buds  can  be  combatted  practically. 

The  formation  of  the  bud  covering  cannot  be  influenced  and  the  danger- 
ous fluctuations  in  temperature  and  atmospheric  moisture  in  spring  cannot 
be  controlled.  Nevertheless,  we  think  a  precautionary  measure  might  in- 
deed be  adopted  in  forestration  in  order  to  moderate  the  extremes  of  trans- 
piration. In  the  first  place,  the  soil  should  retain  its  natural  covering  of 
moss  or  litter,  since  in  this  way  the  soil  moisture  is  preserved,  and  a  damp 
atmosphere  made  possible.  Hence  it  might  be  advisable  not  to  clear  away 
all  the  leaves,  etc.  Finally,  however,  and  especially  in  younger  plantations, 
it  might  be  advantageous  to  retain  protective  forests  on  the  side  of  the  tract 
exposed  to  the  strong  spring  sun.  Among  such  protective  trees  the  rapid 
and  loosely  growing  birch  is  especially  useful. 

In  garden  plants,  naturally,  one  can  control  conditions  very  much 
better.  In  this  conne,ction,  attention  should  be  called  for  the  present  only 
to  the  fact  that  one  should  not  attempt  to  replace  the  uniformly  great  loss 
from  transpiration  by  increasing  the  water  at  the  roots.  That  does  not  work 
well  and  plants  are  found  to  dry  up  which  have  an  excess  of  water  at  the 
roots.     The  only  natural  means  is  artificial  shading. 

Defoliation  Due  to  Heat. 

Observation  shows  that  every  year  from  spring  on  the  foliage  falls 
from  our  deciduous  trees.  In  city  planting  this  is  especially  noticable  in 
Acer  Negundo  and  the  slightly  developed  inflorescences  of  the  linden  show 
this  almost  at  once,  sometime  before  the  "linden  blooms."  The  process  is 
less  striking,  but  constantly  present  in  other  deciduous  varieties.  Wiesner^ 
gives  this  constant  dropping  of  separate  yellow  leaves  the  special  name  of 
"the  summer  defoliation"  and  sees  its  cause  in  the  changes  in  the  sun's 
altitude.  I  think  that  other  causes  can  also  operate  here,  for,  while  the 
summer  defoliation  usually  sets  in  predominately  after  the  21st  of  June, 
observations  show  that,  for  example,  according  to  Wiesner's  statements,  in 
Acer  Negundo,  Acer  Calif ornicum.  and  related  species,  the  leaves  first 
formed  may  be  dropped  even  in  May  and  at  the  beginning  of  June. 

As  long  as  this  loss  of  leaves  is  slight  in  comparison  with  the  whole 
foliage  of  the  tree,  it  has  no  pathological  significance.  Experiments  have 
shown  that  it  is  a  perfectly  normal  phenomenon  for  the  leaves  on  a  branch 
to  complete  their  cycle  of  growth  at  different  periods.     Thus  some  would 


1  Wiesner,    Jul.,    tjber    Laubfall    infolge    Sinkens    des    absoluten    Lichtgenusses 
(Sommerlaubfall).     Ber.  d.  D.   Bot.   Ges.    1904,  p.   64. 


412 

fall  earlier,  some  later.  Those  produced  first  in  the  spring  are  weak  in 
their  formation,  being  smaller  and  not  so  brightly  colored;  hence  they  soon 
reach  their  full  development,  when  their  assimilation  is  arrested,  as  the 
stronger  leaves,  produced  later,  cut  off  their  light.  Then  the  tree  frees  itself 
of  the  organs  incapable  of  working. 

However,  the  summer  defoliation  is  to  be  considered  as  a  phenomenon 
of  disease  when  it  becomes  extensive  and  suddenly  attacks  the  well  develop- 
ed foliage  in  full  sunhght.  Late  frosts  and  more  often  a  continued  period 
of  drought,  combined  with  great  heat,  are  among  the  causes  of  summer 
defoliation.  Wiesner  distinguishes  the  latter  form  as  "dcfolialion  due  to 
heat,"  clearly  a  result  primarily  of  excessive  transpiration  with  an  unequal 
decrease  in  the  supply  of  v^^ater  in  the  trunk. 

I  found  examples  of  defoliation  due  to  heat  in  the  trees  planted  along 
the  streets,  especially  among  the  lindens,  in  spite  of  abundant  watering. 
From  this  it  is  evident  that  actually  the  dry  air  with  abundant  sunshine 
should  be  assumed  to  be  the  injurious  factor.  With  deficient  water  supply 
in  the  soil  alone  the  foliage  dies  from  summer  blight  but  usually  remains 
hanging  on  the  tree. 

The  linden,  despite  its  beauty,  is  not  to  be  recommended  as  a  street 
tree  because  of  its  especial  sensitiveness.  The  summer  linden  shows  earlier 
and  more  severe  effects  than  the  winter  linden,  and  after  the  appearance  of 
summer  heat,  almost  without  exception,  is  found  covered  with  the  fine  webs 
of  the  weaving  mite  (Tetranychiis  telarius).  In  many  trees  aphids  occur 
in  immense  quantities.  After  defoliation,  from  which  only  the  tips  of  the 
branches  are  excepted,  there  is  manifest  a  prematurely  dormant  period.  As 
soon  as  the  weather  becomes  cooler  (or  when  the  streets  are  abundantly 
watered  during  the  hot  period)  a  second  growth  appears  in  which  the  de- 
velopment of  lateral  buds  can  push  off  the  hanging  leaves  {defoliation  due 
to  growth,  according  to  Wiesner).  In  wet  autumns  the  wood  of  this  second 
growth  does  not  ripen  properly  and  is  easily  injured  by  the  winter  frosts. 

In  order  to  avoid  these  conditions  it  is  advisable  to  plant  elms  rather 
than  Hndens  along  the  streets.  If  these  conditions  appear  along  avenues  of 
older  trees,  which  cannot  be  replanted,  the  streets  must  be  sprinkled  as 
frequently  as  possible.  Spraying  under  heavy  pressure  in  the  late  evening 
may  prove  to  be  especially  useful.  I  consider  that  consistently  following 
this  measure  will  prove  the  most  effective  prevention  of  vermin  attacks. 

Honey  Dew. 

According  to  observations  made  up  to  the  present,  a  disease  must  be  in- 
cluded here  which  has  often^  been  described  under  the  name  "honey  deii'" 
{Melligo,  Melaeris,  Ros  mellis)  and  which  has  been  traced  to  very  different 
causes.    This  disease  is  characterized  by  the  appearance  of  a  sugary  coating 


1  Saccharogenesis  diabetica;  Ungrer,  "Exanth.  p.  3. — Honning  Dugen,  Fabricius 
Kiobenh.  1774. — Le  Givre,  Adans,  cit.  bei  Seetzen:  Sistematarum  geneialiorum  de 
morbis  plantarum.     Gottingae  1789. 


413 

on  leaves,  blossoms  and  young  twigs  of  woody  and  herbaceous  plants  usually 
covering  the  outer  surface  of  the  organs,  sometimes  as  a  shining  uniform 
varnish,  sometimes  in  the  form  of  yellowish  tough  drops.  Meyen^  relates 
that  for  some  time  the  theory  expressed  by  Pliny  was  accepted,  namely, 
that  the  honey  dew  was  an  actual  falling  from  the  air,  occurring  in  the  dog 
days  especially  and  coating  not  only  the  plants,  but  even  the  clothing  of 
men.  J-  Bauhin  contradicts  this  theory  and  calls  attention  to  the  fact 
that  only  isolated  plants  or  species  in  any  region  become  diseased.  After 
the  excretion  of  a  sweet  sap  from  the  anus  or  the  abdominal  tubes  of  the 
aphids  had  been  observed,  they  were  considered  to  be  the  cause  of  the  dis- 
ease and  at  the  time  it  w'as  observed  that  aphids  and  honey  dew  were  fre- 
quently found  together.  To  this,  however,  was  opposed  first  of  all,  the  fact 
that  the  aphids  usually  occur  on  the  under  side  of  the  leaf,  the  honey  dew, 
chiefly  on  the  upper  side.  However,  this  fact  is  no  very  certain  proof 
since  the  aphids  of  the  under  side  of  the  leaf  can  sprinkle  the  upper  side  of 
the  leaf  lying  next  below.  But  gradually  the  observations  on  honey  dew 
were  increased  on  isolated  outdoor  and  indoor  plants  on  which  no  aphids 
could  be  found  or  upon  which  they  did  not  appear  until  sometime  later. 
Hartig's  observation,  made  in  1834,  is  interesting  in  this  connection.  A 
rose  plant,  which  had  not  been  taken  from  the  house,  secreted  small  drops 
on  the  under  epidermis  of  the  leaves  from  which  the  sugar  was  separated 
in  rhomboidal  or  cubical  crystals.  In  this  the  green  color  of  the  leaves 
changed  to  a  grayish  one,  due  to  the  disappearance  of  the  chlorophyll  in 
the  mesophyll  at  the  secreting  places  and  to  the  appearance  of  clear  drops 
in  the  cells.  Treviranus",  in  the  same  way,  frequently  found  such  sugary 
secretions  in  the  warm,  continuously  dry  air  out  of  doors  as  well  as  in 
greenhouses,  on  white  poplars,  lindens,  orange  trees,  distils  (Carduus 
arctioides)  and  cited  still  older  observations  by  Lobel,  Pena,  Tournefort  et 
al.,  according  to  which  honey  dew  occurs  on  olive  trees,  varieties  of  maple, 
walnuts,  willows,  elms  and  spruces.  He,  and  later  Meyen,  were  convinced 
that  the  drops  containing  sugar  w^ere  secreted  directly  from  the  epidermal 
cells,  to  which  the  former  observers  also  added  that  the  stomata  did  not 
take  part  in  this  secretion.  Further  observations  on  honey  dew  occurring 
in  very  different  plants,  especially  oaks,  were  furnished  later  by  Gasparrini''. 
The  honey  dew  on  the  linden  has  been  chemically  investigated  by 
Boussingault  and  that  on  the  grape  cherry  (Prunus  Padus)  by  Zoller**. 
Boussingault  found  that  the  honey  dew,  collected  at  two  different  times, 
differed  quantitatively  in  regard  to  the  different  substances ;  from  which 
fact  it  is  evident,  that  the  secretion  does  not  always  have  the  same  per- 
centage composition.  But  the  nature  of  the  substance  seems  to  change  also, 
for  although  Boussnigault  found  only  cane  sugar  (48  to  55  per  cent.),  in- 
vert sugar  (28  to  24  per  cent.),  and  dextrin  (22  to  19  per  cent.),  Langlois 

1  Pflanzenpathologie,  1841,  p.   217. 

2  Physiologie  der  Gewachse,  18.38,  Vol.  II,  Part  I,  p.  35-37. 

3  Sopra  la  melata   o  trasudamento   di  aspetto  goommoso   etc.     Bot.   Zeit.   1864, 
p.    324. 

i   Okonom.   Fort.schr.   1S72,  No.   2,  p.   39. 


4M 

also  found  mannit  as  one  constitutent  of  tlie  honey  dew  on  the  linden. 
Czapek^  collected  the  results  of  more  recent  observations.  From  this  it 
may  be  concluded  that  the  composition  of  the  honey  dew  varies  in  different 
plants. 

A  harmony  of  the  theories  as  to  the  causes  of  the  phenomenon  has  not 
been  obtained  as  yet.  While  Biisg^en-  studied  carefully  the  aphid  stings  on 
plants,  he  proved  that  the  animals  secrete  through  the  anus  much  larger 
amounts  of  honey  dew  (the  secretions  of  the  abdominal  tubes  are  waxy) 
than  is  usually  assumed,  and,  on  this  account,  he  concludes  that  real  honey 
dew  depends  only  on  aphids.  Bonnier^  made  some  experiments  which  showed 
an  artificial  production  of  honey  dew  without  the  intervention  of  the 
animals. 

Biisgen  says  the  peculiarities  of  the  cuticle  allow  neither  an  osmosis 
or  distillation  of  sugar  saps  from  the  interior  of  the  cell  nor,  as  Wilson 
assumed,  an  osmotic  withdrawal  of  liquids  through  drops  of  sugar  to  be 
found  on  the  surface  of  the  leaf,  such  as  are  formed  by  the  excretion  of 
the  aphids.  This  statement,  however,  does  not  consider  the  fact  that  the 
smooth  surface  of  the  cuticle  can  become  broken  and  that  secretions  in 
individual  cases  can  find  their  way  through  the  stomata.  Bonnier's  results 
prove  the  later  case.  Leaves  which  had  been  exposed  to  great  differences 
in  temperature  (conifers,  oaks,  maples,  etc.),  showed  under  the  microscope, 
when  examined  by  direct  illumination,  the  formation  of  nectar-like  drops 
from  the  stomata  when  the  light  was  sufficiently  strong. 

My  own  observations  confirm  the  occurrence  of  honey  dew  without  the 
intervention  of  aphids.  In  one  case  I  found  an  abundant  formation  of  honey 
dew  on  the  older  leaves  of  pear  seedlings  grown  in  water  cultures  and 
exposed  to  the  hot  July  sun.  This  observation  showed  that  deficient  soil 
water  was  not  necessarily  a  factor.  I  believe  that  honey  dew  is  produced 
if  there  is  a  sudden  excessive  increase  of  transpiration  in  strongly  function- 
ing active  leaves,  caused  by  a  strong  light  stimulus,  and  brings  about  too 
high  a  concentration  of  the  cell  sap.  If  the  disturbance  continues  beyond 
a  certain  point,  the  leaf  suffers  permanently  and  falls  prematurely.  In 
another  case  the  rain  gradually  washed  the  sugar  coating  away,  which  made 
possible  an  attack  of  the  black  fungi  (sooty  dew).  The  production  of 
honey  dew  is  not  always  dependent  upon  extreme  and  absolutely  high 
temperatures  and  strong  light  stimuli,  but  sudden  great  contrasts  as, 
for  example,  the  sudden  shock  to  an  organism  caused  by  an  intense  morning 
sun  following  a  very  cool  night,  which  had  suppressed  its  activity. 

Shading  would  be  the  best  preventative  measure  and  repeated 
sprinkling  an  effective  remedy. 


1  Czapek,   Fr.,   Biochemie   der  Pflanzen.     Jena.     Gustav  Fischer.     1905,   Vol.  T, 
p.  408. 

2  Biisgen,   M.,   Der  Honigtau.     Biolog.   Studien   an  Pflanzen  u.   Pflanzenlauscn. 
Sond.  Biologisches  Centralbl.  Vol.  XI,  Nos.  7  and  8,  1891. 

3  Bonnier,  G.,   Sur  la  miell^e  des  feuilles.    Compt.  rend.   1S96,  p.   335,  cit.  Zeit- 
RChrift  f.  Pflanzenkrankh.  1896,  p.  347. 


415 

Probably  the  much  dread  Mafuta  disease  of  the  sorghum  millet 
(Andropogon  sorghum)  in  German  East  Africa  belongs  here.  The  word 
Mafuta  means  oil.  Honey-like  excretions  are  found  on  leaves  and  stems. 
These  give  rise  to  a  sooty  coating^.  Other  plants  also  suffer  especially  in 
times  of  drought. 

Heart  Rot  and  Dry  Rot  of  Fodder  and  Sugar  Beets-. 

The  heart  rot  of  the  sugar  beet  should  be  considered  as  a  phenomenon 
usually  related  to  honey  dew.  It  is  found  usually  in  hot  Julys  in  rainless 
periods  and  is  characterized  by  the  death  of  the  heart  leaves.  These  have  not 
grown  to  half  their  norm^al  size.  The  dying  foliage  suddenly  becomes  black. 
In  severe  attacks  the  whole  leaf  area  dies,  but,  as  a  rule,  the  plants  develop 
new  foliage.  In  addition  to  the  affection  of  the  leaves,  the  body  of  the 
beet  is  attacked  by  a  decomposition  or  dry  rot.  The  beet,  near  its  head  end, 
has  spots  which  can  deepen  as  the  tissues  decompose,  and  finally  destroy  the 
beet.  Of  greater  agricultural  significance  in  this  connection  is  the  fact  that 
a  part  of  the  non-reducing  sugar  disappears  from  the  beet  and  another  part 
is  converted  into  reducing  (grape)  sugar^.  If  the  rainy  weather  sets  in  at 
the  right  time,  the  dead  tissue  can  be  thrown  off  through  the  formation  of 
cork. 

If  the  healing  process  does  not  set  in  soon  enough,  so  that  a  long  con- 
tinued autumnal  dampness  can  exercise  its  influence  on  the  decayed  places, 
the  process  of  destruction  of  the  beets,  which  are  poorer  in  sugar,  is  also 
continued  in  the  storage  pits. 

Most  observers  are  incUned  to  seek  the  cause  of  the  trouble  in  fungi, 
since  mycelium  is  often  found  in  the  diseased  heart  leaves*.  Frank 
especially  defended  the  fungi  theory  and  wished  to  make  two  species  re- 
sponsible for  it :  Phoma  Betae,  Frank^  and  Fusarium  beticola,  Frank. 
It  is  certain,  however,  that  the  first  stages  of  the  disease  of  the  heart  leaves 
are  without  fungi  and  bacteria,  and  the  parasites  later,  during  damp  weather, 
occasion  an  advance  in  the  destruction  of  the  tissue.  However,  when  the 
beet  plants  are  healthy,  the  fungi  cannot  attack  them.  Only  when  evapora- 
tion is  sufficiently  increased  and  the  absorption  of  water  sufficiently  de- 
creased do  the  conditions  arise  which  predispose  the  plants  to  attack  by 
fungi. 

Practical  workers  state  that  the  addition  of  lime  also  in  the  form  of 
waste  lime  favors  the  attack  of  the  disease.  We  have  very  instructive 
field  experiments^  along  these  lines  in  which  some  areas  were  limed,  and 
some  not.  Where  lime  was  used,  the  beets  were  diseased,  where  there  was 
none,  the  crop  was  healthy. 

1  Busse,  "W.,  Weitere  Untersuchungen  iiber  die  Mafuta-Krankheit  der  Sorghum- 
Hirse.     Aus  "Tropenpflanzer,"  cit.  Zeitschr.  f.  Pflanzenkrankh.    1902,   p.   82. 

2  See  Vol.  II.   p.   240. 

3  Frank,  A.  B.,  Kampfbuch.    1897,  p.  131. 

4  Prillieux   et   Delacroix,   Complement  a   I'etude  de  la  maladie   du   coeur  de  la 
Betterave.     Bull.   Soc.  mycologique.     VII,   1891,  p.   23. 

5  syn.  Phoma  sphaerosperma,  Rostr.,  Phoma  Betae,  Rostr.,  Phyllosticta  tabifica, 
Prill,  et  Del. 

6  Zeitschr.  f.  Pflanzenkrankh.  1895,  p.  250,  1896,  p.  339. 


4i6 

Also  the  location  itself  has  often  l)een  found  to  favor  the  appearance 
of  tlie  disease,  since  on  field  ridges  with  a  gravelly  underground,  or  declivi- 
ties from  which  the  water  nms  away  (|uickly,  often  only  dry  rotted  beets 
are  produced.  The  different  varieties  are  proved  to  be  susceptible  to 
different  degrees ;  the  Vilmorin  sugar  beet  is  said  to  be  especially  sus- 
ceptible ;  varieties  with  smooth  leaves  spread  flat  on  the  ground  and  long 
roots  should  be  preferred  in  threatened  regions'. 

Sasse-,  as  a  result  of  his  verv'  thorough  field  experiments,  states  that 
xapor  and  deep  cultivation  prevent  the  outbreak  of  dry  rot.  Opinions  vary 
greatly  as  to  the  influence  of  fertilization.  In  my  opinion,  the  variation  is 
explained  by  the  varying  action  of  the  same  fertilizer  on  different  fields, 
and  dependent  on  the  weather.  Fertilizers  making  the  soils  more  porous, 
increasing  their  capacity  for  warmth  and  decreasing  their  power  for  re- 
taining water,  tend  to  favor  the  development  of  dry  rot;  this  can  occur  with 
waste  lime^  The  same  fertilizers  are  satisfactor)^  in  heavy  soils.  Fertiliza- 
tion with  kainit  has  been  most  questioned.  Tt  is  emphasized  that  the  soil 
will  actually  retain  water  better  after  fertilization  with  commercial  manures, 
i.  e.  offer  greater  resistance  to  the  influence  of  drought,  and  yet  not  infre- 
quently where  kainit  fertilization  has  ])ecn  used,  the  first  heart  rot  of  the 
beets  will  be  found. 

Tn  my  opinion  there  is  a  natural  explanation  for  this  phenomenon. 
Kainit  tends  to  develop  leaves  extraordinarily;  hence,  with  a  continued  dry 
period,  the  extensive  leaf  area  withdraws  water  very  quickly  from  the  root 
system,  causing  an  injurious  concentration  of  the  cell  sap.  Analyses  have 
shown  that,  with  a  high  potassium  content  in  the  leaves,  the  dry  rot  appeared 
more  marked,  the  smaller  the  proportion  of  phosphoric  acid  present. 

Therefore,  the  choice  of  land  which  dries  quickly  may  be  a  preventa- 
tive measure  for  this  disease.  When  the  soil  is  light  those  materials,  which 
heat  the  soil  (lime,  separator  ooze )  must  not  be  given  directly  to  the  beets. 
With  the  appearance  of  dangerous  droughts,  one  should  decrease  the  drain- 
age since,  ordinarily,  it  would  not  be  practical  to  always  water  the  crop. 
A  further  condition  should  be  considered,  namely,  whether  the  evaporation 
of  the  plants  can  be  reduced  by  removing  the  older  leaves,  or  by  shading 
with  straw  mulching. 

h'AULTY  Development  of  the  Blossoms. 

Much  oftener  than  is  generally  supposed,  great  atmospheric  dryness 
manifests  itself  in  blossoms,  especially  double  flowers.  If  specimens  of  the 
same  species  with  single  and  with  double  blossoms  in  the  same  position  be 
compared  (fuchsias,  petunias,  tuberous  begonias,  roses,  etc.),  it  will  be 
observed  without  exception  that  the  single  blossoms  develop  more  rapidly 


1  Bartos,    W..    Kinig-e    Beobachtung-en    liber    die    Herz-    und    Trockenfaule,    cit. 
CentralbL  f.   Bakteriologie  1899,   p.   562. 

2  Sasse,    Otto,    Einige    Beobachtiinsen    aus    dem    praktischen    Betriebe    betreffs 
Auftretens  der  Herz-  oder  Trockenfaule.     Zeitschr.  f.  Pflanzenkrankh.  1894,  p.  359. 

3  Richter,  W.,  tjber  die  Beziehungen  des   Scheideschlamms  zum  Auftreten  der 
Herzfaule  der  Ruben.     Zeitschr.  f.  Pflanzenkrankh.  1895,  p.  51. 


417 

and  (|uicklv.  The  slower  and  more  retarded  development  of  double  blocjms 
may  be  traced  to  greater  distribution  of  the  water  and  nutritive  substances 
conveyed  through  the  petioles  over  a  more  considerable  leaf  area.  The  loss 
in  transpiration,  due  to  the  increased  number  of  petals,  is  greater  and  can 
in  no  way  be  replaced  by  supplying  w  ater  to  the  roots.  Consequently,  the 
organs  develop  more  quickly ;  they  become  ripe  prematurely  and  cease 
growing  before  the  blossom  has  been  completely  developed.  On  this  account 
half  open  blossoms  often  fall  where  there  is  great  atmospheric  dryness. 
This  should  not  be  confused  with  the  dropping  of  the  blossoms,  due  to 
excess  of  water.  In  the  latter  case  it  may  often  be  observed  that  both  the 
blossoms  and  peduncles  fall,  ^^^ith  excessive  transpiration  in  a  very  dry 
atmosphere,  the  petals  fall  where  they  join  the  peduncle  after  having 
turned  brown  there. 

AMien,  as  is  often  attempted  in  greenhouses,  an  artificially  moist  atmos- 
phere is  produced  by  abundant  watering  of  entire  plants,  their  condition  is 
improved  only  if  the  flpwer  pots  stand  on  the  soil,  since  the  vaporizing 
dampness  from  the  soil  keeps  the  atmosphere  constantly  moist.  But  if  the 
pots  stand  on  wood,  iron  or  stone,  the  blossoms  shrivel  up  in  spite  of  the 
watering  and  a  Botrytis  growth  is  found  where  the  petals  loosen.  This 
leads  consequently  to  erroneous  conclusions  since  Botrytis  diseases  are 
usually  accompanied  by  great  atmospheric  humidity. 

The  double  staminate  blossoms  of  tuberous  begonias  fall  in  excessively 
dry  air.  and  form  one  of  the  most  striking  examples  of  the  difficulty.  I 
observed  this  often  in  the  dry  summer  of  1904  in  places  which  had  never 
had  direct  sunlight.  That  the  falling  of  the  petals  was  actually  due  to  dry- 
ness of  the  air  was  shown  by  an  experiment  in  which  plants  were  used, 
w-hich  usually  drop  their  blossoms  at  the  time  of  opening.  They  retained 
and  developed  them,  however,  if  placed  over  broad  basins  filled  with  water. 

The  pistillate  blooms  aUvays  mature.  The  first  indication  that  the 
staminate  blossoms  are  going  to  fall  is  that  the  bud  does  not  straighten  up 
but  remains  drooping.  A\'ith  the  hand  lens  a  small  brown  ring  may  be  seen 
at  the  union  of  the  calyx  and  peduncle.  There  the  young  tissue  is  found 
to  be  deep  brown,  its  walls  and  contents  collapsed.  At  the  calyx,  the 
shrivelling  and  tearing  of  the  tissue  forms  large  holes  until  finally  the  petals 
hang  only  by  a  few  shreds  of  tissue.  In  the  indi\'idual  petals,  the  vascular 
bundles  also  seem  deeply  browned  even  at  the  places  which  are  still  not 
discolored  and  apparently  fresh.  This  drying  of  the  base  is  really  a  pre- 
mature end  of  the  life  cycle,  since  the  cell  contains  only  scanty  fllakes  of 
protoplasm.  Near  the  dead  tissue  there  is  an  abnormal  accumulation  of 
asymmetrically  formed,  separate  crystals  of  calcium  oxalate,  as  the  final 
residue  of  the  organic  substances  consumed  in  respiration. 

A  second  kind  of  defective  blossom  development,  resulting  from  dry- 
ness, was  observed  in  the  Uliaceae  and  Amaryllideae.  In  these  instances 
the  perianth  remained  stuck  together  at  the  apices.  Although  the  rest  of  the 
blossom  was  normally  developed  and  colored,  the  tips  of  these  perianths 


4i8 


turned  yellow,  shi\elled  up  and  dried  into  a  mass  which  finally  crumbled. 
The  injury  is  horticulturally  of  significance  only  when  the  blooms  are  forced 
and  large  individual  blossoms  are  desired  as  in  Lilium  aureum.  Lilium  longi- 
florum  and  Hippeastrum  robustum,  Dietr.,  etc. 

In  that  species  which  is  known  among  gardners  as  Amaryllis  Tettaui 
and  is  often  grown  as  a  house  plant  because  it  blooms  freely,  I  observed 
more  carefully  the  mechanics  of  opening  and  incomplete  development  dur- 
ing drought. 

The  three  outer  tips  of  die  brick  red  perianth  begin  to  separate  from 
one  another  at  their  base  on  the  day  before  the  blossoms  are  completely 
opened;  hence  the  large  conical  flower  bud  first  of  all  shows  three  slits. 

The  tips  of  these  three  outer- 
most petals,  however,  remain 
stuck  fast  together  even  if 
the  process  of  separation  from 
one  another  is  so  hastened  by 
the  increased  growth  of  the 
innerside  of  the  perianth  that 
this  is  curved  outward  like  a 
pouch.  In  this  convexity, 
which  becomes  constantly 
greater,  lies  a  great  elasticity 
which  would  be  able  to  sep- 
arate the  gummed  tips  from 
one  another  and,  in  normal 
cases,  actually  does  tear  them 
apart.  The  strength  of  this 
elastic  power,  produced  by 
the  basal  epinasty  of  the 
perianth,  is  demonstrated  if 
the  still  gummed  apices  of  the 
three  tips  are  cut  off  about 
forty-eight  hours  before  the 
normal  time  of  opening.  Then,  within  lo  minutes,  the  individual  tips  have 
separated  1.5  to  2  cm.  from  one  another,  i.  e.  the  corolla  has  begun  to  open. 
The  resistance  offered  to  this  strong  elasticity  arises  from  the  fact  that  the 
green  apices  of  the  three  outermost  tips  are  anchored  to  a  strong  cone  about 
5  cm.  long.  Sometimes  this  cone  is  thimble  shaped.  There  is  a  heavy 
growth  on  the  underside  of  each  tip  which  curves  out  like  a  ridge,  and 
corresponds  with  a  midrib,  making  a  very  fleshy  growth  on  each  tip. 

Fig.  69  shows  three  of  the  perianth  tips,  touching  each  other  with  their 
keel-like  wedges  (a).  These  wedges  contain  no  vascular  bundles.  These 
lie  {§)  frequently  in  groups  of  3  or  4  peripherally  in  the  real  laminal  part. 
The  individual  laminal  halves  at  both  sides  of  the  fleshy  median  ridges  are 
curved  inward  and  touch  the  adjacent  peripheral  tip  with  their  edges  (r)  ; 


Fig.  69.     Cross- section  through  the  apical  region 

of  a    still   closed   blossom  of   Hippeastrum 

robustum.  Explanation  of  the  letters 

in   the    text. 


419 

these  are  green,  while  the  fleshy  cushions  at  the  center  (c),  containing  the 
largest  parenchyma  cells,  seem  colorless.  In  contrast  to  the  abundant  small 
grained  masses  of  starch  in  the  rest  of  the  tissue,  the  cushions  display  only 
a  few  large  starch  grains.  The  epidermis  is  normally  flat  walled  at  the 
outside  of  the  peripheral  tip,  but,  on  the  ventral  side,  at  the  beginning  of 
the  development  of  red  coloring  matter,  shows  a  papillary  outgrowth.  Al- 
though this  grew  out  to  distinct  papillae,  mutually  interlocking,  like 
clogged  wheels,  on  the  cushion-like  raised  places  (a),  it  shows  scarcely 
any  elongation  on  the  flat  laminal  part. 

In  this  close  interlocking  of  the  papillae  of  the  tip  of  one  part  of  the 
perianth  with  those  of  the  others  may  be  seen  the  reason  for  anchoring 
these  tips  so  firmly  together.  An  elastic  strain  loosens  the  tips  since  these 
l^apillae  grow  rapidly  to  conical  hairs,  thus  breaking  the  connection.  In 
the  cavities  (h)  which  the  outer  petals  leave  free,  lie  the  tips  of  the  three 
inner  ones,  whose  epidermis,  however,  develops  papillae  sooner  than  that 
of  the  outer  ones.  The  mutual  resistance  of  the  out-growing  papillae 
favors  the  separation  of  the  inner  tips  of  the  perianth  and,  therefore,  the 
blossoming. 

When  the  atmsophere  is  dry,  the  primordia  of  the  papillae  may  still  be 
found,  but  they  do  not  develop  into  conical  hairs ;  hence  the  tips  of  the 
petals  remain  united  and  gradually  shrivel  up. 

House  Plants. 

The  typical  picture  of  a  house  plant  which  meets  our  eye  shows  brown- 
ing and  drying  leaf  tips.  Where  gas  is  burned,  usually  one  is  inclined  to 
lay  the  blame  on  the  gas.  As  a  fact,  the  dryness  of  the  air  in  the  room  is 
the  cause  and  the  condition  is  as  marked  in  dwellings  where  gas  is  not  used. 
The  fact  that  plants,  especially  the  so-called  foliage  plants,  die  after  the 
tips  become  brown  and  dry,  may  be  explained  as  due,  not  to  the  atmos- 
pheric dryness,  but  to  the  attempts  of  the  grower  to  get  greater  moisture  in 
the  air  by  very  frequent  watering.  However,  the  plants  get  no  benefit  from 
this  increased  supply  of  water.  They  can  use  more  water  and  transpire 
it  only  when  the  tissue  develops  more  abundantly,  resulting  in  a  more 
vigorous  assimilation  and  a  greater  production  of  leaves.  The  dryness  of 
the  air,  however,  inhibits  this  very  development  of  the  leaves. 

When  the  foliage  of  tropical  climates  (m.any  foliage  Begonias,  Hoff- 
mannias,  Ruellias,  Marantes,  etc.),  are  brought  from  the  moist  conservatory 
into  a  room  of  the  same  temperature,  the  development  at  once  ceases.  The 
older  leaves  begin  to  curl  back ;  the  younger  ones  roll  up  their  edges  and 
remain  smaller  than  those  previously  formed.  The  apical  growth  of  the 
shoots  is  retarded ;  all  processes  of  elongation  are  reduced.  It  is  peculiar 
that  with  many  plants  (for  example,  many  bushy  Begonias)  the  blossoms, 
produced  in  dry  air,  either  do  not  open  at  all  or  only  incompletely,  and 
finally  fall  oflf  without  having  become  diseased.  This  process  may  also  be 
observed  out  of  doors.     The  dormant  period  of  the  plant  sets  in   more 


4-'0 

c|uickly,  and,  when  the  new  \egetative  period  Ijegins.  the  de\el()i)nienl  of 
the  buds  is  retarded  and  often  entirely  prevented.  \\  ith  such  actixity  in 
the  parts  above  ground,  the  roots  will  rot  if  given  too  abundant  water. 

Various  methods  have  been  proposed  to  overcome  the  injurious  in- 
fluence of  the  dry  air  in  the  room,  such  as  to  spray  frequently  or  to  cover 
the  plants  at  night  with  damp  cheese  cloth,  etc.  However,  such  methods 
have  not  proved  sufficiently  satisfactory.  I  obtained  best  results  by  using 
Wardian  cases  or  by  setting  the  plants  over  water.  Recently  flower  tables 
have  l)een  used  in  which  the  plant  stands  on  a  zinc  box  filled  with  water, 
the  to])  of  which  has  been  punctured  full  of  holes.  Through  this,  water 
vapor  constantly  rises  between  plants  placed  above  it. 

TTard  Sef.ds  in  the  Lkguminaceae. 

The  hard-shelled  condition  of  T.eguminaceae  seeds,  not  only  those  of 
the  Papilionaceae,  but  also  those  of  the  Mimoscae  and  Caesalpiniaccae,  can 
be  considered  as  a  natural  protection  against  micro-organisms  at  a  time  in 
their  development  when  they  are  most  readily  infested.  All  our  wild  grow- 
ing Papilionaceae  exhibit  the  same  constructive  principle  and  the  hard- 
seeded  condition  becomes  dangerous   only  when   it    ])rcvents   germination. 

This  hard-shelled  condition  arises  from  the  special  thickening  of  the 
palisade  layer  of  the  seed  grain  which,  with  its  cuticle,  forms  the  outer- 
most covering  of  ^the  seed  shell.  These  columnar  palisade  cells,  lying  \ery 
close  to  one  another,  show  in  cross-section  strongly  refractive  cross  lines 
(lu/ht  lines)  of  an  especially  dense  substance.  The  cell  content  contains 
those  substances  which  cause  the  coloring  of  the  seed  shell  and  to  which 
great  importance  is  ascribed  as  substances  protective  against  parasite  at- 
tacks. Next  to  the  palisade  layer,  described  by  Nobbe  as  the  "hard  layer," 
lies,  on  the  under  side,  a  layer  of  so-called  hour-glass  cells,  next  which  are 
thin-walled  cell  layers  wnth  large  intercellular  spaces.  These  cells  function 
especially  in  the  sw^elling  of  seed.  Corresponding  to  the  gluten  layer  in 
grain  seeds,  we  find  in  the  majority  of  Leguminaceae  seed,  with  the  ex- 
ception of  the  Phaseoleae,  Vicieae  and  a  few  other  \arieties,  according  to 
Harz\  the  endosperm  in  the  form  of  a  hard,  horny  matter,  which  becomes 
slimy  when  placed  in  water.  In  the  region  of  the  scar,  palisade  cells  and 
round  hour-glass  cells  usually  appear  in  two  rows. 

In  this  instance  we  follow  Hiltner's  experiments'-,  which  show  that  the 
hard-seeded  condition  preventing  the  rapid  swelling  of  the  seeds,  naturally 
forms  a  protection  against  micro-organisms.  Older  lupine  seeds,  which 
w^ere  not  absolutely  hard-shelled  but  swell  up  only  Avith  difficulty,  were 
soaked  in  water.  The  seeds  which  swelled  each  day  were  laid  separately 
in  the  germinating  box.  This  showed  that  those  lupine  seeds  which  swelled 
most  rapidly  and  hence  were  not  hard-shelled,  almost  always  rotted,  while 


1   Landwirtschuftlielie    Samenkimde. 

-  Hiltner,  I...,  Die  Keimung.sverhiiltni.sse  der  Legumiiiosensamen  und .  ihre 
Beeinflus.sung'  durch  Organismenwirkung.  Arbeiten  d.  Biolog.  Abteil.  f.  I.and-  u. 
Forstwirtsch.  am  Kaiserl.   Gesundheitsamte.     Vol.  Ill,  Part  1.     Berlin  1902. 


421 

the  percentage  of  germination  was  higher  in  those  seeds  where  the  swell- 
ing began  later;  due  to  the  higher  percentage  of  hard  seeds. 

It  was  concluded  from  experiments  with  eight  year  old  clover  seed 
which,  on  account  of  age,  had  already  begun  to  grow  dark,  certain  seeds 
having  become  brown  and  shrivelled,  and  which  was  sorted  according 
to  color,  that  the  grains,  which  still  had  the  appearance  of  completely  fresh 
seed,  gave  the  highest  percentage  of  germination.  Among  the  slightly  dis- 
colored seeds,  the  brown  ones  germinated  least  and  gave  more  than  90  per 
cent,  of  rotted  grains.  Among  these  seeds,  a  much  larger  percentage  of  the 
light-colored  ones  decayed  than  of  tiie  violet  ones.  This  led  to  the  deduction 
that  the  violet  color  of  the  seed  covering  offered  a  protection  against  bac- 
terial attack. 

The  different  percentages  of  hard-shelled  seeds  from  a  given  variety 
over  a  period  of  several  years,  show  the  dependence  of  that  condition  on 
the  weather.  Hiltner,  by  drying  the  seed  artificially  at  a  temperature  of 
35°C.,  or  over  sulfuric  acid,  could  increase  the  percentage  of  hard-shelled 
grain.  This  experiment  showed  the  atmospheric  condition  required  to  pro- 
duce the  undesired  hard-shelled  seeds.  This  condition,  therefore,  resembles 
glassiness  of  grain.  As  the  process  of  drying  during  ripening  is  hastened, 
more  hard-shelled  seeds  might  be  formed. 

In  general  practice,  howe\er,  contradictory  results  are  often  found. 
In  dry  positions  it  was  observed  that  the  seeds  of  lupines,  vetches,  scarlet 
clover  and  the  kidney  vetch  (anthyllis)  (AMndklee),  in  time  become  hard- 
shelled,  while  the  finer  clover  seeds  show  rather  the  reverse.  Hiltner's 
observation  on  artificially  dried  seeds  explains  this  contradiction.  The  in- 
fluence producing  an  increased  toughness  of  the  shell  in  thick-walled  seed 
affects  thin-walled  seeds  as  well,  but  in  them  the  shell  splits,  consequently 
increasing  their  small  capacity  for  swelling;  further  Rodewald  states  that 
cold  can  decrease  the  hard-shelled  condition  of  Leguminaceae  seeds. 

When  one  realizes  that  hard  seeds  can  lie  for  years  in  the  soil  without 
germinating  and  that  those,  even  less  capable  of  swelling,  may  germinate 
so  late  that  they  cause  a  second  growth,  it  will  be  evident  that  the  seed 
grower  must  control  the  formation  of  hard  shells  to  eliminate  them.  In 
the  course  of  years,  many  methods  have  been  recommended.  Thus,  for 
example,  the  seed  should  be  laid  in  a  i  to  2  per  cent,  solution  of  sodium 
carbonate,  to  dissolve  the  silicic  acid  in  the  shell.  Again,  simply  sift  out 
the  hard-shelled  seeds,  since  they  are  all  somewhat  smaller  than  the  normal 
ones  which  will  germinate.  Again,  treating  the  seeds  with  hot  water  has 
sometimes  been  successful,  sometimes  not.  Dipping  in  boiling  water  for 
one  minute  was  injurious,  but  was  beneficial  Avhen  the  seed  was  emersed  for 
five  seconds  only.  This  treatment,  however,  over  so  short  a  time,  cannot 
be  entrusted  to  laborers.  Potassium  permanganate,  dilute  sulfuric  acid,  an 
ammoniacal  solution  of  copper  sulfate,  have  been  as  unsuccessful  as  the 
sodium  solutions.  On  the  other  hand,  Hiltner  found  concentrated  sulfuric 
acid  to  be  successful.     The  sulfuric  acid  injured  onlv  those  seeds  which 


422 

had  been  damaged  in  threshing,  even  if  the  seed  was  left  for  sometime  in 
the  acid.  Frequently,  treatment  with  sulfuric  acid  for  half  an  hour  will  be 
sufficient  if  the  seeds  have  been  thoroughly  wet  by  stirring.  When  the 
treatment  is  completed  the  acid  should  be  thoroughly  washed  off  with  clean 
water  and  then  immediately  with  lime  water  for  at  least  5  to  20  minutes. 
Microscopic  investigations  of  seed  treated  in  this  way  showed  that  (in 
Acacia  Lophanta)  the  sulfuric  acid  had  removed  not  only  the  cuticle  but 
also  the  greater  part  of  the  palisade  cells  and  had  stopped  before  reaching 
the  "light  line."  Yet  the  seeds  could  swell  in  water  only  when  the  acid  had 
penetrated  the  light  line  in  some  places^  Therefore,  this  cell  layer,  present 
in  the  seed  shell  of  all  the  Leguminaceae,  according  to  Mattirolo-,  con- 
sisting of  an  especially  dense  cellulose,  prevents  the  seeds  from  rapid  ab- 
sorption and  elimination  of  water. 

Connected  with  this  innate  hard-seeded  condition  is  the  hardening  of  the 
seed  membrane  during  germination.  With  those  seeds  which,  in  germi- 
nation, pushed  their  cotyledons  above  the  soil,  the  cap-like  seed  shell  is 
gradually  pushed  off,  if  it  has  been  retained  until  the  moisture  is  absorbed 
and  thus  remains  flexible.  But  if  a  hot,  rainless  period  sets  in  suddenly, 
the  cap  dries  on  the  cotyledons,  preventing  their  development,  as  well  as  the 
breaking  of  the  young  stem.  In  case  it  is  not  destroyed,  it  is  twisted  to 
one  side.  Lopriore^  mentions  here  the  germination  of  beans.  I  have  ob- 
served similar  phenomena  in  cucumbers,  pumpkins,  melons  and  the  seeds  of 
stone  fruits.  The  retention  of  the  dry,  stony  shell  shows  itself  most  de- 
structively in  the  seedlings  of  plums,  peaches  and  other  Amygdalaceae. 
SprinkUng  of  the  seed  bed  in  the  evening  is,  therefore,  a  precaution  which 
should  not  be  omitted. 


1  Hiltner  und  Kinzel,  tJber  die  Ursachen  und  die  Beseitigung  der  Keimungs- 
hemmungen  bei  verschiedenen  praktisch  wichtigeren  Samenarten.  Naturwissensch. 
Zeitschr.  f.  L,and-   u.  Forstwirtschaft  1906,  p.  199. 

-'  La  linea  lucida  nelle  cellule  malpighiane  dcgli  integumenti  seminale.  Torino 
1885,  cit.  von  Hiltner  und  Kinzel. 

3  Berichte  d.  Deutch.  Bot.  Ges.  1904,  Part  5,  p.  307. 


CHAPTER  V. 


EXCESSIVE  HUMIDITY. 


The  Mode  of  Growth  With  Continued  Atmospheric  Humidity. 

Older  works  have  called  attention  to  the  fact  that  the  structure  and 
functions  of  individuals  are  altered  by  the  influence  of  a  high  degree  of 
atmospheric  humidity  in  the  same  way  as  by  the  removal  of  light.  Accord- 
ing to  experiments  of  Vesque  and  Viet^,  plants  grown  in  moist  air  have 
longer,  less  branched  roots,  more  delicate  stems,  leaves  with  longer  petioles 
and  smaller  blades.  The  walls  of  the  epidermal  cells  are  less  wavy;  the 
cell  rows  of  the  mesophyll  somewhat  less  numerous  and  without  differ- 
entiation into  palisade  parenchyma.  The  whole  tissue  of  the  leaf  grown 
in  moist  air  is  in  every  respect  more  uniform,  while  in  dry  air  the  dift'erence 
between  palisade  and  spongy  parenchyma  is  clearly  seen.  The  vascular 
bundles  in  the  internodes  are  much  more  developed  in  dry  air.  This  refers 
not  only  to  the  diameter  of  the  whole  bundle,  to  the  number  of  ducts  and 
their  diameter,  but  especially  to  the  hard  bast  fibres  which  may  occur 
abundantly  in  dry  air  and  be  entirely  lacking  in  moist  air.  Duval-Jouve- 
observed  with  grasses  that  dry,  hot  situations  increased  the  development  of 
the  bast  bundles,  while,  in  moist  places,  this  development  is  retarded.  The 
authors  named  quote  Rauwenhoff^,  who  describes  etiolated  plants  in  this 
way.  In  comparative  experiments  with  dry  and  moist  air,  under  light  bell- 
glasses,  as  well  as  shaded  ones,  it  was  found  that,  in  darkness  but  in  dry 
air,  the  plants  were  less  spindling  than  those  grown  in  the  light  in  moist  air, 
from  which  it  is  concluded  that  the  form  of  the  etiolated  plants  is  due  chiefly 
to  deficient  transpiration. 

Brenner^  expresses  the  same  theor}^  In  his  experiments  with  Cras- 
sulae,  he  observed  a  tendency  to  decrease  the  succulency  of  the  leaves  in 
moist  air,  but  to  increase  the  upper  surface.  The  cells  of  the  stems  were 
actually  elongated.     Wiesner^  also  found  that  the  leaves  of  Sempervivum 


1  Vesque  et  Viet,   Influence   du   Milieu   sur  les   vegetaux.     Annales    des   scienc. 
nat.    Sixieme  serie.    Botanique  t,  XII,   1881,  p.  167. 

2  Botan.  Jahresbericht  1875,  p.  432. 

3  Annal.  d.  scienc.  nat.     6  ser.  V,  p.  267. 

4  Brenner,  W.,  Untersuchungen  an  einigen  Fettpflanzen.     Just's  Bot.  Jahresb. 
1900,  p.   306. 

5  Wiesner,     Jul.,     Formveranderungen    von     Pflanzen     bei     Kultur     in     absolut 
feuchten  Raumen.     Ber.  d.  Deutsch.  Bot.  Ges.   1891,  p.  46. 


424 

tcctorum  considcrahly  enlarged  in  an  absolutely  moist  room  and  became 
markedly  epinastic.  The  leaf  rosettes  were  spread  out  because  the  inter- 
nodes  developed  further.  W.  Wollny^  found  that  a  lessened  thorn  de- 
velopment occurs  in  normal  leaves  of  Ulcx  europacus  as  a  result  of  con- 
tinued atmospheric  humidity.  He  also  observed,  however,  that  the  chloro- 
phyll content  decreased  as  the  leaves  increased.  According  to  Eberhardt-, 
the  number  of  chlorophyll  grains  is  decreased  if  the  stems  become  longer 
and  the  leaves  larger.  In  a  later  work'  this  investigator  summarizes  his 
experiments  as  follows;  moist  air  combines  a  reduction  in  the  thickness 
of  leaves  and  stems  with  elongation.  The  formation  of  hairs  is  decreased, 
that  of  blossoms  and  fruit  retarded.  l-Lpidermal,  bark  and  pith  cells  become 
longer,  the  intercellular  spaces  greater,  the  number  of  secretion  canals 
smaller  and  the  development  of  the  ^\•ood  less  noticeable.  A  smaller  pro- 
duction of  lateral  roots  is  noticed. 

E.  Wollny'*  also  mentions  that  the  time  of  blossoming  and  ripening  is 
retarded  and,  by  numerous  experiments,  strengthens  the  easily  foreseen 
conclusion,  viz.,  that  the  evaporation  from  plants  and  soil,  under  otherwise 
equal  circumstances,  is  smaller,  the  greater  the  atmospheric  humidity.  It 
should  be  mentioned  briefly  in  passing  that  in  numerous  cases  abundant 
excretion  of  water  takes  place  in  the  form  of  drops  with  the  reduction  of 
transpiration  and  by  means  of  different  devices  in  the  various  plants''.  We 
ffequently  find  this  in  potted  plants  which  in  the  fall  are  brought  into  un- 
lieated  greenhouses,  when  the  leaves  touch  the  rapidly  cooling  window- 
panes. 

Finally,  I  will  mention  the  results  of  my  own  experiments". 

In  trees  (pear)  the  whole  new  growth  and  also  the  different  individual 
internodes  and  petioles  were;  observed  to  be  shorter  in  dry  air,  and  the  leaf 
blades  more  slender  in  moist  air.  In  grains,  the  growth  from  seed  was 
found  to  be  somewhat  less  in  dry  air;  the  leaf  number  was  also  somewhat 
decreased,  but  the  size  of  the  individual  leaves  was  increased  longitudinally, 
while  somewhat  lessened  in  width.  The  same  change  in  dimensions  was 
also  exhibited  by  the  individual  leaf  cells.  The  influence  of  moist  air 
elongated  the  leaf  sheaths  and  also  the  individual  blades,  as  well  as  the 
roots  themselves,  although  the  plants,  even  those  exposed  to  dry  air,  stood 
in  a  nutrient  solution. 

The  fact  that  the  substance  as  well  as  the  form  of  the  j)lants  will  be 
changed  with  varying  humidity  is  to  be  surmised  as  a  matter  of  course. 
In   fact,  my  experiments  show  that  in  moist  air  a  lesser  amount  of  green 

1  Wollny,  W.,  Untersuchung-en  iiber  den  Einfluss  der  Luftfeuehtiskeit  auf  das 
Wachstum  der  Pflanzen.     Inaugural-Dissertation.     Halle  1898. 

i;  E])ei-hardt,  M.,  Action  de  I'air  sec  et  de  I'air  humide  sur  les  veg-etaux.  Compt. 
rend.  1900,  t.  131,  p.  114. 

3  cit.   Centralbl.  f.  Agrik.-Chem.   1904,  Part  8. 

4  Wollny,  E.,  Untersuchungen  iiber  die  Verdunstung  und  das  Produktions- 
vermugen  der  Kulturpflanzen  bei  veisohiedencm  Feuchtigkeitsgehalt  der  Luft. 
Forsch.  auf  d.  Geb.  d.  Agrikulturphysik  Vol.  XX,   1898,  I'art  5. 

■"'   s.    Hot.    .lahresber.    25.    Jahrg.,    Teil   1,    p.    76.      Abh.    von    Nestler   und    Goebel. 
«  Sorauer.  Studien  Uber  Verdunstung.    For.scli.   aul    d.   del),   d.   Agrikulturphysik, 
Vol.  III.    Part  4-5,  p.  55  ff. 


EDGAR  TULLIS 


425 


matter  was  produced  and  that  of  this  green  matter,  with  plants  in  moist 
air,  a  large  percentage  occurred  in  the  roots.  In  this,  the  aerial  parts  were 
richer  in  water.  It  was  determined  in  regard  to  the  functions,  that  evap- 
oration in  moist  air  is  absolutely  less ;  it  is  less  also,  however,  per  gram  of 
green  and  dry  matter  produced,  i.  e.  the  plant  in  the  production  of  one  gram 
of  material  in  moist  air  needs  less  water  and  this  might  occur  because, 
under  these  circumstances,  it  produces  it  Avith  few  mineral  substances. 

A  further  experiment  with  peas'  shows  that  the  newly  produced  sub- 
stance has  an  actually  lower  percentage  of  ash.  The  increased  amount  of 
water  taken  up  by  the  plant,  because  of  the  strong  evaporation  in  dry  air, 
results  in  the  plant's  taking  up  in  a  given  unit  of  time  only  half  as  con- 
centrated a  solution  as  it  does  with  a  weakened  evaporation,  when  growing 
in  moist  air. 

These  results  explain  sufficiently  why  plants  in  moist  air  frequently 
succumb  more  easily  to  disease  than  plants  grown  in  dry  air.  The  plants 
are  weaker  in  growth,  richer  in  water  and  poorer  in  ash.  Nevertheless,  we 
have  no  insight  into  the  di\  ersity  of  the  organic  elements  in  the  plant  body. 
It  is  very  probable  that  plants  grown  in  moist  air  are  richer  in  sugar, 
poorer  in  starch,  as  well  as  richer  in  asparagin  and  poorer  in  actual  protein. 

Influence  of  Moist  Air  on  Plants  Injured  by  Drought. 

It  has  been  supposed  that  plants  which  have  suffered  from  intense 
drought  can  be  most  cjuickly  restored  to  their  former  activity  if  placed  in 
a  very  moist  atmosphere.  The  following  experiment  shows  the  danger  of 
this  procedure.  Cherry  seedlings,  which  survived  a  long  drought  in  sand 
cultures,  at  once  showed  an  adjustment  to  the  lessened  amount  of  water 
supplied  the  roots.  At  first,  without  change  of  habit  of  growth,  evaporation 
gradually  decreased  until  the  sand  still  contained  possibly  only  4  per  cent, 
of  the  amount  held  when  saturated.  At  this  point  the  plants  began  to  wilt, 
but,  at  the  same  time,  evaporation  ceased  almost  entirely.  For  example, 
at  a  temperature  of  30°C.  and  abundant  sunlight,  a  little  plant  which  had 
formerly  used  daily  about  8  g.  water,  evaporated  only  one  decigram.  After 
adding  considerable  water,  the  plant  gradually  increased  the  amount  of 
evaporation.  If,  on  the  other  hand,  the  drought  continued  too  long,  the 
leaves  dried  backw'ard  beginning  at  the  tips,  showing  no  discoloration. 

If  now,  after  being  wattered,  the  plants  were  brought  into  moist  air 
they  did  not  recover  as  I  had  thought  they  would  at  first.  Those  under 
the  bell  jars  containing  dry  air  had  elevated  the  upper  mature  leaves,  and 
the  partially  dried  bases  of  the  older  leaves  became  turgid  again ;  evapor- 
ation again  set  in  slowly. 

The  gardener  will  find  this  observation  of  practical  use  in  growing 
potted  plants.  Excessively  dry  plants  after  watering  must  not  be  changed 
in  position.  They  must  be  somewhat  shaded  and  they  should  not  be  placed 
in  air  practically  saturated  with  moistm-e,  since  this  will  stoj)  almost  all 
activity. 

1   Loc.  cit.  p.  79. 


426 
Cork  Outgrowths. 

Cork  is  universally  formed  as  normal  tissue.  It  may  increase  abnorm- 
ally, forming  an  excrescence  under  special  circumstances.  Even  the  regular 
formation  of  cork  may  be  observed  in  varying  amounts  in  different  seasons. 
Attention  should  be  given  to  the  usual  bark  pores  with  their  rounded  com- 
plementary cork  cells  separated  by  intercellular  spaces.  These  cells,  show- 
ing for  some  time  a  cellulose  reaction,  are  steadily  reproduced  during  the 
time  of  growth.  In  winter,  when  the  exchange  of  gases  in  the  dormant 
bark  is  at  its  minimum,  the  production  of  the  complementary  tissue  is 
stopped.  In  the  autumn  a  layer  of  normal  cork  is  formed  from  the  cambium 
layer  instead  of  the  roundish  complementary  cork  cells.  With  the  awaken- 
ing of  bark  activity  in  the  spring,  the  cork  cambium  again  forms  comple- 
mentary cork,  rupturing  the  winter  covering  layer  of  the  lenticel,  just  as, 
when  the  first  lenticels  were  formed,  it  had  split  the  epidermis.  The  more 
moist  the  air  becomes,  the  more  frequently  the  elongating  complementary 
cork  cells  which  attract  water  are  formed  on  the  surface  of  the  bark.  The 
longish,  mealy,  white  excrescences,  which  may  be  rubbed  off,  are  well- 
known.  They  occur  on  the  smooth  barked  trunks  of  cherries  and  alders 
in  damp  habitats  when  the  atmospheric  humidity  is  increased  and  the  foliar 
transpiration  decreases. 

At  the  base  of  the  strong  petioles  of  Juglans  regia,  Sambucus  nigra, 
Ailanthus  glandulosa,  Pauloivna  imperialis  and  other  trees,  in  the  autumn, 
structures  may  be  observed  very  similar  to  lenticels,  only  the  cambium  layer 
is  missing  (Stahl)^  Later  research-  has  shown  that  cork  cushions  not  only 
develop  at  the  base  of  the  petiole  but,  in  many  plants,  at  the  veins  of  the 
under  side  of  the  leaf  (Ficiis  siipulata)  and  finally  also  on  the  leaf-blades. 

Now,  although  this  formation  of  cork  on  the  leaf-blade  is  a  phenom- 
enon almost  as  widely  distributed  as  that  on  the  stems  with  which  it  closely 
corresponds  in  structure  and  development,  yet,  in  spite  of  the  wide  distribu- 
tion, there  is  no  pathological  significance  in  these  formations. 

In  these  cork  outgrowths  of  leaves,  two  types  may  be  distinguished'', 
either  the  cork  layer  with  its  dividing  walls  and  its  usually  one-layered 
phellogen  lies  parallel  with  the  leaf  surface  in  the  same  plane, — when  the 
cork  excrescences  are  raised  above  the  surface  of  the  leaf  in  the  form  of 
warts ;  or  the  cork  layer  and  especially  its  phellogen  lies  in  the  form  of  hour- 
glass-like, depressed  zones  in  the  interior  of  the  leaf  and  usually  becomes 
deeper  and  deeper.  Many  plants  have  both  forms  on  the  same  leaf.  In 
contrast  to  the  regularity  of  the  appearance  and  production  of  stem  cork, 
emphasis  should  be  placed  on  the  accidental  appearance  of  cork  excrescence 
on  leaves.  Aside  from  the  fact  that  the  two  above  mentioned  types  can 
begin  on  the  same  leaf,  there  are  also  transitions  between  the  two  types.    In 


1  Stahl,    Entwicklungsgeschichte    und    Anatomie    dcr    Lenticellen.      Bot.    Zeit. 
1873,  No.  36. 

2  Poulsen,  Om  Korkdannelse  paa  Blade.     Kjobenhavn   1S75. 

3  Bachmann,   tlber  Korkwucherungen  auf  Blattern.     Pringsheim's  Jahrb.   1880, 
Vol.  XII,  Part  2,  p.  191. 


427 

fa<jt,  the  cork  outgrowths  can  arise  in  the  same  leaf  in  different  layers  (they 
usually  occur  in  the  sub-epidermal  layer)  and  can  have  a  different  develop- 
mental course  (Bachmann). 

The  external  appearance  of  these  cork  formations  on  leaves,  occurring 
on  gymnosperms,  monocotyledons,  and  dicotyledons,  is  very  different. 
Sometimes  there  are  small  cones,  sometimes  sheets  of  cork,  or  strips  of 
considerable  extent.  At  times  the  cork  excrescences,  however,  lead  to  the 
formation  of  holes  which  penetrate  through  the  whole  leaf  (Ilex,  Zamia, 
Ruscus,  Camellia  axillaris,  Peperomia  obtusifolia.  Eucalyptus  Gunni  and 
E.  Globulus,  etc.).  This  perforation  begins  as  yellowish  points.  In  leaves 
with  large  intercellular  spaces  the  cork  formation  is  preceded  by  a  growth 
of  the  parenchyma  cells,  in  such  a  way  that  the  intercellular  spaces  are  filled 
by  outpushings  of  the  cell  walls.  If  the  cells  with  somewhat  thicker  walls 
in  the  rows  of  cork  cells  are  changed  by  repeated  division,  the  cell  walls 
lose  their  original  thickness.  Frequently  also  the  cork  cells  undergo  a 
subsequent  elongation  after  they  have  split  the  epidermis ;  the  outer  ones 
are  stretched  first. 

In  Zamia  integrifolia,  brown  stripes,  running  parallel  with  the  veins, 
are  found  on  leaflets,  splitting  later  into  pieces  or  tearing  down  the  whole 
length.  These  stripes  are  cork  tissue  which  are  not  produced  sometime 
after  the  leaflets  have  been  torn  and,  thereby,  representing  wound  cork,  but 
are  structures  formed  even  embryonically  in  the  younger  leaf.  Cork  ex- 
crescences appear  on  both  sides  of  the  older  leaves  of  Dammara  robusta, 
but  especially  on  the  upper  side,  remaining  usually  small  and  flat.  When 
young,  they  form  small  round  spots  on  the  green  leaf  surface  and  later  be- 
come brown,  when  they  are  raised  like  little  mounds.  Finally,  the  epidermis 
and  the  immediately  adjacent  cork  layers  rupture.  In  Araucaria  Cunning- 
hami  and  more  rarely  in  A.  Bidwilli,  small  cork  mounds  may  be  found  on 
older  leaves  of  the  previous  year  which  can  coalesce  into  ridges.  In 
Sciadopytis  verticillata  and  Cryptomeria  japonica  small  cork  warts  occur 
at  times  also  on  older  leaves ;  such  structures  may  be  recognized  more  fre- 
quently (but  usually  only  on  the  underside)  on  the  broad  leaves  of  Sequoja 
sempervirens.  In  commercial  horticulture,  small  point-like  cork  warts  in 
Cyclamen  persicum  form  a  blemish  as  do  also  the  chart-like  etchings  on 
the  upper  side  of  leaves  of  Pelargonium  peltatiim  and  in  different  kinds  of 
foliage  Begonias.  These  cork  outgrov/ths  appear,  so  far  as  observed,  only 
in  moist  greenhouses  and  hot  beds. 

Among  the  monocotyledons,  Clivia  Gardeni,  Hook  and  Clivia  nobilis, 
Lindl.,  Pandanus  reflexus,  Dichorisandra  oxypetala,  Billbergia  iridifolia. 
Vanilla  planifolia,  and  other  orchids  exhibit  cork  structures  which  penetrate 
into  the  leaf.  The  cork  excrescences  on  the  leaves  do  not  occur  in  the  same 
amount  in  all  specimens,  nor  to  equal  extent  on  all  the  leaves  of  the  same 
plant,  nor  are  the  appearances  constant  each  year.  It  must  be  concluded 
from  this  that  special  conditions  cause  this  development  of  cork  structures. 
So   far  as  experience  shows,  they  are    due  to  an   excessive   atmospheric 


428 

dampness  with  a  continued  excessive  supply  of  water  at  the  roots  and  a 
decreasing  intensity  of  hght.  An  insight  into  the  production  of  these  phe- 
nomena may  be  found  in  the 

Cork  Disease  or  the  Cacti. 

This  disease,  often  found  in  imported  cacti,  has  become  a  constant 
source  of  anxiety  for  the  European  grower.  It  manifests  itself  in  the 
different  varieties  of  cactus,  in  the  appearance  of  dry,  papery  places.  These 
begin  sometimes  as  raised  yellow  spots,  or  as  spots  remaining  green  and 
looking  somewhat  glassy.  They  widen  out  cither  into  large  cork  colored 
surfaces,  or  become  depressions  which  look  like  the  scars  of  places  injured 
by  biting  insects  or  animals.  My  special  studies  were  first  of  all  with 
Cereus  flagelliformis.     In  severe  cases  the  tips  of  the  stems  still  seemed 


Fig.  70.     Piece  of  the  trunk  of  a  I'hyllooactus  which,  on  its  under  side,  exhibits 

cork  excrescences  in  the  form  of  warts,  while,  on  the  opposite  side,  the 

process  of  i)erforation  is  beRinninff. 

fresh  and  green,  but  at  a  little  distance  back  from  the  tip  a  zone  of  rust 
colored  specks  began,  starting  usually  below  a  thorn  cushion.  The  specks 
gradually  united  into  a  rusty  surface  which  ruptured  here  and  there. 

On  the  healthy  part,  the  outer  epidermal  tissue  consisted  of  two  layers 
of  irregularly  4  to  6  sided  cells  wuth  thickened,  heavily  cutinized  outer  walls. 
Under  this  double  layer  was  a  single  row  of  cells  elongated  tangentially  and 
thickened  like  collenchyma.  Then  came  the  bark  tissue  containing  chloro- 
phyll and  an  abundance  of  crystals  of  calcium  oxalate.  Cork  had  been 
formed  in  the  outer  epidermal  cells  of  the  rust  spots  on  the  stems.  The 
cork  cells  were  wall-like  in  some  places,  irregular  in  others,  like  a  cap  which 
finally  ruptured  on  the  crest,  thus  rupturing  the  outer  w^all  of  the  upper 
epidermal  layer. 

In  other  Cereus  species,  different  sides  of  the  stem  seemed  whitish  and 
dry  in  wide  stretches.  Here  cork  layers  formed  in  the  epidermal  cells  in 
the  angle  of  the  stem;  these  were  raised  like  papillae,  while  on  the  surface 


429 


of  the  stems  they  were  warts.  In  young  spots  a  change  in  the  bark  par- 
enchyma was  noticed.  The  outer  cells  were  no  longer  distinctly  coUenchy- 
matic  and  tangentially  elongated  but  rather  were  broadened  radially,  thin- 
walled,  poor  in  chlorophyll  and  partially  divided.  Because  of  this  structure, 
the  bark  cells  forced  the  cork  tissue  outward,  causing  whitish  blisters  or 
warts. 

In  Opuntia  and  Phyllocactus,  the  second  variety  of  cork  outgrowth  is 
prevalent  and  is  characterized  by  the  formation  of  depressed  places  or  by 
total  perforation.  Fig.  70  of  a  Phyllocactus  illustrates  both  forms  of  cork 
excrescence.  On  the  under  side  we  see  wart-like  convexities,  on  the  upper 
bide  the  beginnings  of  perforation. 

A  cross-section  of  the  fiat  stem  shows  the  fleshy  bark  beyond  the  vas- 
cular l)undle.  In  healthy  places  the 
bark  is  filled  with  starch  (sf)  and  con- 
tains numerous  slime  cells  (s).  cal- 
cium oxalate  crystals  and  glands  ( 0) . 
when  the  wart  begins  to  form,  the  bark 
|)arenchvma,  by  utilizing  the  starch, 
stretches.  di\  ides  and  pushes  out  the 
epidermis.  The  peripheral  tissues  (i) , 
poor  in  contents,  begin  to  die  and  a 
la}'er  of  flat  cork  cells  (/)  separates 
the  dead  tissue  containing  many  inter- 
cellular spaces  filled  with  air  from  the 
still  li\ing  succulent  tissue.  At  this 
point  the  progress  of  the  disease  stops 
and  the  stem  seems  covered  with  dry 
paper-like  spots.  If.  however,  there 
is  no  further  removal  of  starch  nor 
stretching  of  the  bark  parenchyma,  and 
large   particles   die,   the   upper  surface 

of  the  dead  tissue  finally  ruptures,  forming  holes  (/)  which  gradually  be- 
come more  and  more  depressed  v.hile  the  flattened  cork  cells  (t)  are 
constantly  formed,  growing  inward.  At  r  the  bark  changed,  giving  rise  to 
the  cork  formation.  There  the  change  occurred  earliest  and  most  intensively 
and  advanced  rapidly  into  the  interior  of  the  leaf. 

The  process  of  cork  formation  is  in  itself  a  normal  process  in  cacti 
when  the  stems  reach  a  certain  age.  At  the  base  of  older  stems  there  ma}- 
!)e  seen  a  formation  of  bark  as  in  trees.  The  pathological  feature  is  the  for- 
mation of  flat  cork  layers  in  the  younger  parts,  at  the  expense  of  the  bark. 
The  cause  may  be  found  in  the  formation  of  tissue  centers  in  the  bark  m 
which  the  cells  elongate,  while  the  starch  breaks  down  and  the  cell  contents 
are  gradually  impoverished. 

Fig.  71  shows  the  first  change  in  the  tissues,  in  the  formation  of  bark 
types  of  cork  excrescence.     This  illustrates  a  piece  of  bark  from  Phyllo- 


Fig-.     71.     First    stage     of    a    cork 
excrescence   in    Phyllocactus. 


430 

cactus  with  a  spot  differentiated  from  its  healthy  surroundings  by  a  scarcely 
perceptible  yellowish  discoloration  and  a  very  slight  convexity :  e,  indicates 
the  epidermis ;  /,  the  collenchyma-like  thickened  cells ;  o,  the  crystals  of 
calcium  oxalate.  The  change  begins  close  to  the  vessels  (<7)  in  the  delicate 
venation  traversing  the  succulent  parenchyma.  The  darker  spots  in  the 
parenchyma  indicate  the  chloroplasts,  which  are  found  there  either  in  the 
normal  position  along  the  walls,  or  collected  in  large  refractive  drops  of 
cell  contents  (o').  Probably  as  a  result  of  an  accumulation  of  destructive 
enzymes  and  an  increase  in  acid  content,  the  sheath  cells  of  the  vascular 
bundle  {(js^  and  those  even  further  away  {%)  become  poorer  in  contents  and 
elongate,  thus  causing  the  first  evidences  of  disease.  Thus  an  inner  growth 
is  produced  which,  if  it  advances  nearer  to  the  upper  surface,  starts  the  for- 
mation of  cork.  If  the  cells,  extending  further  back  into  the  inner  bark, 
become  impoverished,  more  and  more  cork  will  be  formed.  Since  the  cork 
tissue  cannot  elongate  as  the  organ  growls,  it  must  be  of  necessity  rupture, 
and  thus  forms  superficial  warts  as  the  cork  formation  advances.  Grooves 
are  formed  by  the  strain  of  the  tissues  growing  with  varying  rapidity  and 
these  deepen  until  there  is  a  complete  perforation  as  in  deep  scurvy  of 
potatoes. 

In  order  to  control  or  eradicate  this  important  disease  of  cacti,  the 
water  supply  is  lessened  and  air  is  given  abundantly.  Should  there  be  a 
regular  appearance  of  the  disease  covering  several  years,  the  plants  must 
be  kept  dry  even  to  shrivelling. 

Bitten  or  Perforated  Leaves. 

In  herbaceous  plants,  as  also  in  trees  in  different  localities,  the  leaves 
are  often  strongly  perforated  as  if  some  animal  had  eaten  away  the  tissue 
betw^een  the  veins,  without,  however,  finding  any  animal  on  whom  the 
blame  may  be  laid.  Since  the  injuiy  increases  in  intensity  with  time,  ob- 
servers are  more  eager  to  find  the  cause.  In  extreme  cases  the  injury  is  of 
such  extent  that  the  leaves  appear  like  many  paned  windows,  since  only  the 
network  of  veins  remains  together  wnth  a  slight  margin  of  leaf  parenchyma. 
.Such  leaves  are  often  bent  and  twisted  but  do  not  die  prematurely.  The 
shoots  themselves  show  no  disease  and  frequently  new  sprouts  with  normal 
foliage  develop  in  the  axils  of  these  perforated  leaves. 

The  most  extreme  case  which  I  have  had  opportunity  to  observe  was 
found  in  potatoes.  The  shoots  of  the  plants  at  the  beginning  of  July  bore 
only  perforated  leaves  (see  Fig.  72).  Usually  the  lower  leaves  were  per- 
forated only  in  places,  the  upper  ones  were  split  longitudinally  in  the  areas 
between  the  veins  and  frequently  parts  of  the  edge  were  also  destroyed. 
The  younger  leaves  often  had  a  feathery  appearance  since  the  different 
leaflets  consisted  only  of  the  veins  with  a  very  slender  margin. 

Between  the  perforations  yellowish  points  were  seen  in  the  leaf-blade 
when  held  to  the  light.  These  proved  to  be  the  first  stages  of  the  process  of 
suberization  which  ended  with  the  perforation  of  the  leaf.    The  formation 


431 

of  cork  took  place  in  the  way  described  in  the  preceding  general  section. 
It  was  proved,  however,  to  be  a  secondary  phenomenon.  The  disease  first 
manifested  itself  in  the  pale  green  color  of  the  mesophyll  usually  near  the 
finely  anastomosing  veins.  This  appeared  more  frequently  in  the  palisade 
than  in  the  spong}'  parenchyma.  In  isolated  cases,  instead  of  becoming 
pale,  the  cell  contents  discolored  to  a  brownish  tone  which  was  accom- 
panied by  the  suberization  of  the  walls.  The  epidermis,  in  its  changes, 
followed  the  mesophyll  groups  and  small  dead  tissue  centers  were  produced 
which  did  not  change  any  further. 

In  the  group  of  cells  forming  the  transparent  places  in  the  leaf  because 
of  the  dissolution  of  the  chlorophyll,  an  enlargement  was  seen  on  account 


Fig.  72.     Potato  leaf  perforated  as  a  result  of  a  morbid  formation  of  cork. 


of  which  the  non-participating  epidermis  was  pushed  outward.  A  cork 
formation  now  set  in  among  the  enlarged  mesophyll  cells ;  then  these  places 
broke  out.  By  the  advance  of  these  processes  backward  into  the  flesh  of 
the  leaf,  the  cork  centers  were  depressed  to  complete  perforation.  This 
can  be  understood  easily  since  young  leaves  are  aft'ected.  In  their  growth, 
these  stretch  all  the  tissues ;  since  the  tissues  containing  cork  cannot  stretch 
with  the  other  tissue,  they  must  tear. 

The  process,  therefore,  is,  in  principle,  that  found  on  the  stems  of 
cacti. 

In  other  plants  also,  which  show  perforations  of  the  leaves,  the  im- 
poverishment and  enlargement  of  different  cell  groups  may  be  recognized 
as  the  early  stages  and,  on  this  account,  naturally  belong  to  the  phenomena 


43-' 

which  will  later  be   described  as  intumescences.     The  causes  will  also  be 
taken  up  more  in  detail  then. 

Jn  the  production  of  the  perforations,  individual  nutrition  plays  a 
]jrominent  part ;  for.  in  the  same  place  of  growth,  specimens  which  seem 
almost  eaten  up.  ma\-  be  found  near  plants  which  remain  untouched.  At 
times,  only  isolated  species  suffer.  Thus,  for  example,  I  found  in  groups 
of  different  species  of  maple  only  one  single  vigorously  growing  variety 
which  was  diseased,  among  other  kinds   (leveloi)ing  normally. 

I'"oKMATIO\    OK    (/ORK    OX    FrUITS. 


The  brown,  dull,  not  infrecjuently  scaley  spots  or  lines  on  the  smooth 
outer  surface  of  apj)les  and  pears,  the  so-called  rusty  tracery  is  well-known. 
Some  \arieties  show  the  phenomenon  every  year,  so  that  it  has  been  in- 
cluded in  the  general  description  of  the  species.     They  are  formations  of 

cork,  which,  as  a  rule,  arise  from  the 
stomata.  In  some  years  the  process  be- 
comes abnormal  in  its  appearance,  so  that 
not  only  "the  \arieties  with  rust  spots" 
have  a  i)artial  or  entire  cork-colored  sur- 
face, but  also  the  fruits  of  varieties 
usual  ]>■  remaining  smooth-skinned  are 
affected. 

Injuries  to  the  epidermis  when  the 
fruit  first  swells  are  the  cause  of  this  phe- 
nomenon. In  cases  already  known  to  me 
(apples,  pears,  plums,  grapes),  it  could 
be  proved  that  a  light  late  frost  had  split 
the  cuticle  covering  of  the  young  fruit  in 
innumeral)le  small  tears.  Under  these 
microscopically  small  splits,  the  fruit  at  once  formed  cork  layers. 
In  places  the  epidermal  cells  die  and  remain  together  with  the  first  formed 
cork  layers  as  scales  on  the  rather  didl,  leather  colored  surface  of  the  fruit. 
Whenever  the  corked  places  form  a  contiguous  surface,  the  fruit  in 
development  does  not  swell  uniformly,  with  the  result  that  huge  spUts  show- 
on  the  fruit  itself.  The  spores  of  Monilia  especially  enter  these  places  and 
mummify  the  fruit. 

But  these  phenomena,  in  the  strictest  sense,  do  not  belong  here  They 
are  connected  with  an  excess  of  moisture  only  in  so  far  as  the  splitting 
occurs  the  more  easily,  the  more  quickly  the  swelling  of  the  fruit  takes 
place  with  continued  moisture. 

On  the  other  hand,  I  would  like  to  consider  the  appearance  of  cork  warts 
on  the  stems  of  grapes  as  a  process  which  becomes  noticeable  only  in  moist 
air.  In  Fig.  y^  we  see  two  grapes,  the  stems  of  which  exhibit  a  browned  rough 
surface  due  to  the  appearance  of  many  cork-colored,  closely  distributed  wans. 
The  phenomenon  occurs  before  the  grapes  have  reached  their  normal  size. 


Fis.  73.     Grapes  with  cork  warti 
(W)   on   the  fruit  stem. 


J 


EDGAR  TULLIS 

PART  VI. 


MANUAL 


OF 


PLANT  Diseases 


BY 


PROF.  DR.  PAUL  SORAUER 


Third  Edition --Prof.  Dr.  Sorauer 

In  Collaboration  with 

Prof.  Dr.  G.  Lindau       And       Dr.  L.  Reh 

Private  Docent  at  the  University  Aiii«lant  in  the  Museum  of  Natural  History 

of  Berlin  in  Hamburg 


TRANSLATED  BY  FRANCES  DORRANGE 


Volume  I 
NON-PARASITIG  DISEASES 

BY 

PROF.  DR.  PAUL  SORAUER 

BERLIN 


WITH  208  ILLUSTRATIONS  IN  THE  TEXT 


PART  VI. 


MANUAL 


OF 


Plant  Diseases 

BY 

PROF.  DR.  PAUL  SORAUER 


Third  Edition-Prof.  Dr.  Sorauer 

In  Collaboration  with 

Prof.  Dr.  G.  Lindau        And       Dr.  L.  Reh 

Private  Docent  at  the  University  Assistant  in  the  Museum  of  Natural  History 

of  Berlin  in  Hamburg 


TRANSLATED  BY  FRANCES  DORRANGE 


Volume  I 
NON-PARASITIC  DISEASES 

BY 

PROF.  DR.  PAUL  SORAUER 

BERLIN 


WITH  208  ILLUSTRATIONS  IN  THE  TEXT 


Copyrighted.  1916 

By 

FRANCES  DORRANCE 


THE    RFCORD    PRESS 
Wilkes-Barre,   Pa. 


433 


The  warts  are  developed  most  abundantly  at  the  place  where  the  grapes 
join  the  stem:  large  branches  of  the  clusters  usually  remain  smooth  and, 
as  a  rule,  only  some  grapes  show  the  disease.  This  is  unimportant  in  con- 
tinued dry  weather,  but  with  humidity  makes  for  a  development  of  parasites. 
If  then  a  sharp  dry  period  follows,  some  of  the  very  warted  stems  shrivel 
and  the  grapes  as  well. 

Fig.  74  shows  a  cross-section  through  a  warty  grape  stem  which  exhibits 
the  usual  axillary  structure  and  has  some  strikingly  broad  medullary  rays 
(ms)  which  divide  the  wood  ring  (h).  In  the  bark  we  notice  a  regular 
distribution  of  the  hard  bast  groups  (h)  and  in  front  of  them  the  sieve 
elements  (s)  with  often  thickly  swollen  walls.  At  o  is  indicated  one  of  the 
abundant  crystals  of  calcium  ox- 


^ 


alate.  These  occur  at  times  as 
small  glands,  at  times  as  raphides. 
The  different  stages  of  the  forma- 
tion of  these  corky  warts  are 
shown  at  W.  The  wart-like  ex- 
crescences, which  resemble  len- 
ticels,  are  produced  by  the  radial 
enlargement  of  some  of  the  par- 
enchyma cells  lying  immediately 
beneath  the  epidermis  or  some- 
what deeper ;  and  the  consequent 
outpushing  of  the  outer  skin.  By 
an  increase  of  this  process,  which 
does  not  preclude  the  dividing  of 
the  elongated  cells,  an  accumu- 
lation of  tissue  is  produced  with  a 
corky  covering  which  finally  be- 
comes brown  and  splits.  By  the 
increase  of  the  bark  parenchyma 
and  the  dying  of  the  outermost 
brown  corked  elements  the  large 
warts  are  produced,  the  peripheral  cell  layers  of  which  are  pushed  out  from 
each  other  in  a  saucer-shaped  form.  A  distinct  cork  cambium  is  formed 
connected  with  the  dying  bark  of  the  outermost  layers.  This  constantly 
extends  deeper  into  the  bark  of  the  stem.  If  the  weather  continues  to  be 
cloudy,  warm  and  damp,  or  if  the  grapes  are  too  much  hidden  under  the 
foliage,  the  conditions  are  ideal  for  the  development  of  fungi  among  which 
may  be  noticed  first  of  all  Bofrytis  c'merea. 

The  phenomenon  is  especially  frequent  in  greenhouses,  and  here  the 
close,  moist  atmosphere  must  be  improved  by  ventilation  and  heat  must  be 
provided  at  the  same  time.  If  the  warty  grape  stems  are  found  out  of  doors, 
some  of  the  foliage  above  the  bunches  of  grapes  must  be  removed  and,  after 
each  rain,  the  water  retained  by  the  foliage  carefully  shaken  off. 


.-^ 


Fu 


4.     ('ro^.-^-siiiiuii    il[juug-h   the   warty 
fruit  stem  of  a  grape.      (Orig.) 


434 

As  a  phenomenon  related  to  cork  excrescences,  I  once  observed  wings 
on  young  grape  leaves.  These  appeared  between  the  larger  side  veins  on 
the  leaf  blade  and  were  opposite  each  other  like  lips.  These  outgrowths 
(emergences)  were  a  development  of  the  blade  usually  forming  over  a 
vascular  bundle. 

The  chagrinisation  ((irannlation)  of  the  rose  stem  should  be  cited  here 
in  addition.  As  is  well  known,  standard  roses  are  laid  flat  through  the 
winter  and  covered  with  brush  or  earth.  At  times  in  the  spring  when 
these  are  raised  from  the  soil,  the  young  bark  stems,  which  should  be 
smooth,  are  often  found  covered  with  small  warts,  many  having,  as  a  rule, 
a  pale  or  brownish-red  periphery.  The  warts  are  outgrowths  of  the  lenticel. 
These  begin  below  the  stomata  and  force  the  guard  cells  apart.  Mycelia 
may  be  proved  to  be  present  if  the  peripher}'  is  discolored. 

Yellow  Spots  (Aurigo). 

At  times  the  leaves  of  monocotyledons,  more  than  those  of  dicotyledons, 
are  covered  with  yellow  or  reddish  brown  specks.  This  speckled  condition 
begins  at  the  tip.  The  specks  usually  shade  through  a  pale  green  zone  into 
the  otherwise  normally  green  leaf.  Their  number  may  be  increased,  since, 
as  the  disease  progresses,  small  new  specks  are  formed  between  the  older 
ones.  At  times  the  tissues  afifected  in  the  discoloration  are  forced  out, 
which  shows  a  clear  transition  to  real  intumescences^ 

This  yellow  spotting  occurs  especially  in  greenhouse  and  house  plants. 
and  among  these,  we  find  it  most  frequently  in  Dracacnae,  palms  and  varie- 
ties of  Pandanus. 

To  illustrate  the  formation  of  these  specks  and  show  how.  under  certain 
circumstances,  they  increase  until  the  leaf  is  perforated,  I  will  cite  some 
observations  on  Pandanus  javanicus. 

The  spots  always  begin  in  the  part  of  a  mesophyll  lying  between  two 
veins.  Toward  the  upper  side  of  the  leaf  these  cells  resemble  the  palisade 
parenchyma,  on  the  under  side,  spong}'  parenchyma,  but  in  the  centre  they 
are  very  thin  walled,  approximately  isodiametric,  somewhat  hexagonal, 
filled  with  a  colorless  water}^  content. 

From  the  innermost  colorless  tissue  groups,  the  peripheral  cells,  i.  e.. 
those  bordering  on  the  mesophyll,  containing  chlorophyll,  begin  to  stretch 
excessively  toward  the  side  of  the  least  resistance,  viz.,  toward  the  centre, 
whereby  they  frequently  compress  the  central  cells.  Frequently  the  elon- 
gation takes  place  only  in  the  cells  arranged  directly  upward  and  downward, 
but  not  in  the  lateral  ones  of  the  thin-walled  group,  and  a  peculiar  arrange- 
ment is  thus  produced.  The  central  part  of  the  tissue  then  consists  of  empty 
cells  arranged  radially,  elongated  like  pouches,  which  often  have  become 
thick-walled  by  swelling,  later  browning  and  turning  to  cork.  With 
increasing  intensity,  the  spongy  parenchyma  is  involved  in  this  process  of 
elongation  with  the  dissolving  of  its  chlorophyll  body;  its  contents  disinte- 


1    Vol.  9,  Part  5. 


435 

grate  into  a  brown  granular  substance,  and  in  this  the  yellow  coloration 
becomes  more  intensive.  The  upper  surface  of  the  leaf  is  often  raised  like 
a  wart  when  the  tissue,  rich  in  chlorophyll,  is  drawn  into  the  abnormal 
process  of  elongation. 

Frequently  the  progress  of  the  disease  is  stopped  when  the  elongated 
cells  become  cork,  then  there  are  only  yellow  spots,  recognizable  when 
im.mature,  indeed,  only  when  the  light  falls  through  them.  The  whole 
centre  of  the  disease  may  then  be  separated  from  the  healthy  tissue  by  a 
zone  of  actual  cork  cells.  As  the  disease  advances  in  severity  even  the  cells 
of  the  vascular  bundle  sheath  may  be  afifected  and  show  the  characteristic 
elongation,  brow^ning  and  swelling  until  finally  the  elongating  mesophyll 
cells  rupture  the  epidermis  above  them.  The  processes  already  described 
under  the  phenomenon  of  perforation  now  follow.  Diseases  due  to  fungi 
and  seemingly  similar  in  outward  appearances  may  easily  be  distinguished 
in  Pandanus,  since  in  them  there  is  no  elongation  of  the  cells.  In  Dracaena 
rubra  and  Draco,  the  disease  at  times  only  disintegrates  the  chlorophyll  of 
the  inner  cell  groups ;  here  membranes  are  often  seen  with  bead-like  swollen 
places  extending  into  the  inner  part  of  the  cell.  In  studying  Dracaena 
indivisa,  I  observed  an  abundant  formation  of  sugar  in  those  tissues  in  which 
the  chlorophyll  had  dissolved.  This  sugar  did  not  occur  in  healthy  tissues 
and  disappeared  from  the  diseased  spots  as  soon  as  the  walls  began  to  turn 
brown  and  develop  cork. 

Hence  this  yellow  spotted  condition  seems  in  many  cases  to  be  an 
initial  stage  of  real  intumescence,  in  others,  as  in  the  Dracaena,  it  is  usually 
a  diseased  condition  without  any  sequelae  and  the  temporary  increase  of 
sugar  and  the  bead-like  swellings  of  the  walls  point  to  causes  which  are 
similarly  affective  in  the  over-elongation  of  the  cells.  In  practical  treatment, 
one  should  realize  that  the  plants  exhibiting  aurigo  suffer  from  a  supply  of 
water  which  they  cannot  assimilate.  The  amount  of  water  destroying  the 
equilibrium  need  not  be  greater  than  that  normally  supplied,  but,  being  given 
during  the  dormant  period,  the  plant  cannot  utilize  it  and  the  external  con- 
ditions are  not  such  as  could  stimulate  this  absorption.  The  spots  occur 
with  great  frequency  in  the  autumn  and  winter  when  the  plants  are  brought 
into  a  warm  place.  They  then  have  sufficient  heat,  water  and  mineral 
nutrient  substances,  but  the  light  is  deficient.  Hence  the  one-sided  stimulus 
must  be  removed  and  the  plant  put  in  a  cooler,  dryer  place  where  there  is  as 
much  light  as  possible. 

Intumescences. 

The  knot-like  or  pustule-like  distensions  of  the  tissue  usually  occurring 
in  groups  and  which  I  have  considered  as  "Tntumescentia"  have  not  been 
sufficiently  studied  by  practical  pathologists.  They  are  most  abundant  in 
leaves  but  are  not  rare  on  the  stems.  However,  as  yet.  the  observation  of 
intumescences  on  blossoms  and  fruits  has  been  limited. 

The  consideration  of  a  specific  case  gives  the  best  information  as  to  the 
development  of  such  structures,  the  A'alue  of  which  lies  in  their  symptomatic 


436 

significance.  In  January,  1879,  I  observed  specimens  of  Cassia  tomentosa 
in  a  hothouse.  I  found  the  edges  of  leaflets  on  young  shoots  were  curled 
under.  This  curling  seemed  to  be  due  to  the  increased  growth  of  the  upper 
side,  which  showed  a  pustule-like  convexity.  When  these  convexities  were 
fewer  and  located  along  the  mid-rib,  the  leaflet  was  less  curled.  If  they 
were  scattered  abundantly  and  uniformly  over  the  whole  surface,  the  leaf 
seemed  almost  blistered.  This  cannot  be  said  to  be  actually  blistered,  how- 
ever, because  the  convexity  of  the  upper  side  corresponds  to  no  e(|ually 
great  concavity  of  the  underside. 

The  swelling  is  conical,  having,  at  first,  the  same  color  and  dull  upper 
surface  as  the  rest  of  the  leaf.  Later  the  tip  of  the  cone  becomes  light 
colored,  more  rigid  and  shiny.  Still  later  the  tip  becomes  yellow,  broadens 
and  finally  ruptures  (Fig.  75,  ^e),  if  the  whole  leaflet  has  not  already  turned 


Fig.  75.     lioaf  intumescences   in   Cassia  tomentosa.      (')rig.) 

yellow,  the  swelling  now  seems  depressed  in  the  centre,  tunnel-like,  and 
turns  brown. 

The  phenomenon  is  due  to  a  sporadic  tube-like  outgrowth  of  the  upi)er 
palisade  parenchyma  (p).  The  inner  side  contains  many  chloroplasts  closely 
packed  together  and,  toward  the  spongy  parenchyma,  is  provided  with 
slender,  slit-like  intercellular  spaces  filled  with  air. 

With  the  appearance  of  swelling,  the  chloroplasts  begin  to  disappear 
from  the  tip  of  the  cell  backward,  a  few  of  the  cells  become  elongated ; 
gradually  the  surrounding  tissues  are  involved.  More  and  more  chlorophyll 
is  dissolved  as  the  elongation  advances,  so  that  finally  the  palisade  cells, 
which  have  become  tube-like,  seem  almost  entirely  colorless  or  are  provided 
with  a  few  small  yellowish  grains  scattered  throughout  the  whole  cell  lumen. 
With  this  elongation  of  the  cells  forcing  up  the  epidermis  there  is  a  slight  in- 
crease in  width,  which  presses  the  cells  ver}'  close  against  one  another 
laterally,  with  only  small  intercellular  spaces  in  the  spongy  parenchyma.     As 


437 


soon  as  this  pressure  has  ruptured  the  epidermis  (e)  at  the  highest  point  of 
the  excrescence  (se)  the  ends  of  the  paHsade  parenchyma,  which  are  now 
freed,  swell  up  like  clubs  (kp)  and,  turning  brown,  thicken  their  walls  more 
or  less  farther  back.  The  epidermal  cells  which  are  ruptured,  and  others 
in  the  same  region,  turn  brown  and  partially  collapse. 

The  same  swelling  can  also  occur  on  the  side  of  the  leaf.  In  this  case, 
the  spongy  parenchyma  cells  lying  directly  beneath  the  epidermis,  covered 
with  hairs  (h)  and  otherwise  usually  isodiametric,  become  long  and 
cylindrical. 

In  various  epidermal  cells  of  the  upper  as  well  as  the  lower  side  of  the 
leaf  and  in  many  of  the  parenchyma  cells  which  have  grown  out  like  tubes, 
glycerin    draws    together    in    indi- 
vidual large  glucose  drops  or  many 
small  ones. 

I  found  similar  leaf  distensions 
in  Acacia  longifolia  and  A.  micro- 
botrya  leaves  specked  with  yellow 
and  also  on  those  normally  green. 
Myrmecodia  cchinata  is  an  ex- 
ample of  the  general  appearance  of 
intumescences  with  cork  leaves. 
The  leaves  of  this  plant  usually  de- 
velop intumescences  on  the  lower 
side,  while  the  cork  excrescences 
predominate  on  the  upper  side.  In 
Fig  76  we  perceive  that  actually 
both  of  the  parencyma  layers  lying 
next  to  the  epidermis  participate  in 
the  formation  of  the  delicate  gland- 
like outgrowth  of  the  tissue.  The 
epidermis  (c)  (its  stomata  are  un- 
changed) is  raised  up  and  ruptured 
where  it  joins  the  normal  tissue. 
Strange  to  say,  however,  it  appears 

to  be  still  unbrowned  and  turgescent,  i.  e.,  still  completely  and  sufficiently 
nourished  Hke  the  tube-like  mesophyll  cells  (a).  I  found  that  the  excres- 
cences had  dried  up  and  had  been  cut  oil"  from  the  healthy  parenchyma  by 
the  formation  of  the  layer  of  flattened  cork  cells  at  their  base  {h)  only 
when  the  leaf  was  well  advanced  in  age. 

The  partially  blister-like,  partially  wart-like  cork  excrescences  are  most 
frequently  found  without  intumescences.  They  are  distributed  irregularly 
over  the  whole  leaf  surface  as  rusty,  sometimes  silvery  shining  specks ;  the 
region  of  the  mid-rib  is  most  afifected. 

The  cork  forms  first  within  the  epidermal  cells,  advancing  thence  into 
the  mesophyll,  attacking  at  first  two  adjoining  layers   of  the  hypoderm. 


Fig-.    76.     Piece   of  a  leaf   of    Myrmecodia 
echinata    with   a  cork  wart  breaking-  out 
on    the    upper    side    and    gland-like    intu- 
mescence on  the  under  side.     (Orig.) 


438 

formed  of  four  or  five  rows  of  colorless  cells  with  very  wide  lumina  but 
poor  in  contents  (d).  The  underlying  palisade  parenchyma,  extending  into 
the  hypoderm  in  the  conical-like  buttresses  (e)  is  usually  not  affected,  but, 
like  the  spongy  parenchyma,  poor  in  chlorophyll,  often  exhibits  strongly 
refractive,  often  green  colored  drops  in  its  cells  where  the  cork  is  formed. 

Often  such  corky  masses  ver}^  greatly  resemble  certain  fungous  dis- 
eases as  I  have  had  opportunity  to  observe  in  Pelargonium  sonale. 

The  under  sides  of  the  leaves  were  covered  with  white  cystopus-Iike 
masses,  isolated  or  united  into  large  groups.  These  were  hemispherical 
cork  excrescences,  later  separated  from  one  another  like  fans  and  filled 
with  air.  They  began  with  an  enlargement  of  the  spongy  parenchyma, 
whereby  all  the  intercellular  spaces  were  filled  up.  The  epidermis,  as  a 
rule,  remained  unchanged  while  the  mesophyll  cells  adjoining  it  were  elon- 
gated perpendicularly  and  were  divided  by  cork  walls,  with  a  gradual  loss 
of  chlorophyll.  The  cork  cells  partially  lost  their  parallel  arrangement 
because  of  an  irregular  increase  and  were  much  distended  until  the  epidermis 
ruptured.  The  epidermis,  however,  manifested  its  restraining  influence  by 
pressing  upon  the  cork  cells,  so  that  their  walls  seemed  crumpled.  The 
process  of  elongation  and  suberization  extended  deeper  and  deeper  into  the 
mesophyll  until  at  times  the  excrescence  was  four  times  as  thick  as  the  leaf. 
A  brown,  twisted  mycelium  (possibly  a  Cladisporium)  grew  into  the  stomata 
and  later  into  the  wound  of  the  rupturing  cork  excrescence. 

Grapes  are  especially  susceptible  to  intumescences  and  especially  those 
plants  taken  from  greenhouses  into  the  open  for  early  forcing.  In  addition 
to  the  excrescences  on  the  leaves,  little  knots  were  formed  on  the  stem  of 
the  grapes,  and,  since  the  structure  of  these  differed  from  the  warts  already 
described,  they  may  be  considered  here  more  thoroughly. 

Fig.  yy  is  a  cross-section  through  such  a  knot.  The  vascular  bundles, 
forming  the  wood-ring  of  the  stem,  are  indicated  by  h,  the  pith  by  m;  the 
hard  bast  by  hh ;  the  abnormal  change  in  the  bark  parenchyma  extends  to 
this  point.  This  change  is  characterized  by  a  distension  of  the  parenchyma 
lying  underneath  the  collenchyma-like  elements  and  an  ultimate  elongation, 
the  cells  of  which  have  subsequently  divided.  Because  of  this  over  elon- 
gation the  collenchyma  {c)  is  pressed  together  and,  without  previously 
having  participated  in  the  elongation,  dies  together  with  the  epidermis.  The 
normal  epidermis  may  be  recognized  at  e;  k  indicates  the  cork  zone  formed 
on  the  boundary  of  the  dying  tissue.  The  latter  may  not  always  be  found, 
however.  Often  the  dying  tissue  passes  over  imperceptibly  into  the  very 
thin-walled,  still  living  tissue  w^hich  shows  slight  cork  formation  at  the  place 
of  transition,  eg  indicates  the  normal  collenchyma,  occurring  in  groups  and 
not  in  connected  rings.  The  division  and  over-elongation  of  the  bark 
parenchyma  and  the  absence  of  cork  excrescences  distinguish  these  knot- 
like intumescences  from  the  cork  warts  which,  in  an  immature  stage, 
resemble  them  greatly. 


439 

The  intumescences  on  grape  leaves  have  on  the  under  side  the  form  of 
;land-Uke  elevations  which  often  coalesce  and  are  indicated  on  the  upper 
leaf  surface  by  yellowish  and  at  times  somewhat  raised  places.  They  are 
produced  by  tube-like  outgrowths  of  the  spongy  parenchyma  lying  under 
the  epidermis ;  the  cells  of  this  spongy  parenchyma  are  poor  in  solid  con- 
tents and  closely  pressed  against  one  another  by  the  distension.  With  their 
increasing  over-elongation,  the  epidermis  is  browned  and  ruptured. 

In  the  beginning  only  the  cells  lying  directly  beneath  the  epidermis  are 
affected,  but  usually,  after  the  distension  begins,  the  cell  layer  next  below 
is  attacked  and  it  is  usually  this  which  later  is  most  elongated  and  its  cells 
not  infrequently  divided  by  cross  walls.  The  cells  forming  the  centre  of  the 
swelling  are  the  longest  and  most  slender  and  stand  exactly  perpendicular  to 
the  outer  surface  of  the  leaf,  while  those  laterally  adjacent  are  arranged 


'■A 

Fig.  77.     Part  of  a  knot-like  intume.scence  on  the  stem  of  a  grape.     (Orig.) 

slantingly  like  a  fan,  decreasing  in  length,  increasing  in  width.  The  presence 
of  starch  could  not  be  proved.  In  the  most  extreme  cases  observed,  all  the 
cells  of  the  mesophyll,  up  to  the  palisade  parenchyma  of  the  upper  side,  take 
part  in  this  elongation.  I  did  not  observe,  however,  that  the  palisade 
parenchyma  had  been  attacked. 

These  intumescences  are  not  infrequent  in  vineyards  and  cases  may  be 
found  showing  their  cause  most  clearly.  In  the  course  of  years  material 
has  come  most  abundantly  to  my  hands.  I  quote  from  the  report  of  the 
court  gardener,  Mr.  Rose. 

He  had  a  grape  house  planted  with  14  vines ;  of  these,  six  were  Black 
Hamburgs  (Blauer  Frankenthaler),  one  of  these  was  planted  where  the  hot 
water  pipe  entered.  Therefore,  the  temperature  was  higher  and  the  humid- 
ity very  great. 

This  vine  alone  developed  intumescences  to  such  a  degree  that  the 
under  side  of  the  leaves  seemed  almost  felty.     A  Royal  Muscardine  vine 


440 

was  planted  on  the  opposite  side  of  the  greenhouse.  The  foliage  of  these 
two  plants  became  intertwined  as  they  grew  into  the  upper  part  of  the  house. 
The  Royal  Muscardine  plant  had  no  trace  of  disease. 

These  instances  show  how  differently  varieties  behave  in  the  same 
environment,  and  how  individual  diseases  in  the  same  variety  may  be 
explained. 

In  regard  to  the  different  behavior  of  different  vines,  reference  should 
be  made  to  a  study  by  Fr.  Muth\  who  observed  the  production  of  intu- 
mescences after  spraying  the  leaves  with  copper  compounds,  while,  for  ex- 
ample, the  early  red  Veltliner  and  Muscat  St.  Laurct  show^  no  swelling. 
Morillon  panache,  Madeleine  Angevine  and  the  Blue  Ox-eye  were  very 
greatly  affected. 

In  another  similar  case,  Noack-  found  that  the  disease  decreased  when 
water  was  withheld. 

The  occurrence  above  described  does  not  correspond  with  the  phe- 
nomena found  on  Ampelopsis  hederocca''.  In  this  plant  Tomaschek  found 
bead-like  structures  on  young  branches,  petioles  and  leaf  veins,  and  espe- 
cially on  the  outer  side  of  the  side  leaves.  The  beads  were  very  small  when  the 
illumination  was  insufficient  and  dried  up  in  the  autumn.  They  were  formed 
below  the  stomata  even  in  the  very  young  parts,  since  the  cells  surrounding 
one  cavity  grew  down  into  it  and  forced  up  the  epidermis  by  an  increase 
in  size.  In  the  autumn  and  winter  true  lenticels  with  a  cork  formation  were 
found,  instead  of  these  outgrowths. 


In  addition  to  the  instances  already  described  and  those  to  be  men- 
tioned further  on  of  disease  manifesting  itself  on  greenhouse  plants,  I  will 
now  report  on  the  behavior  of  one  of  the  Gramineae. 

On  the  island  Riigen,  among  vigorously  growing  oats,  plants  were  found 
showing  abnormal  growth.  A  cross-section  of  the  lowest  node,  covered 
with  dirt,  is  illustrated  in  Fig.  78.  The  centre  of  the  node  exhibits  the  well 
known  irregular  course  of  the  vascular  bundles  (g)  and  the  primordia  of 
a  root  (w)  ready  to  break  through  the  distended  bark  of  the  node.  In  this 
bark  covering  r  indicates  the  normally  formed  part,  while  at  r'  the  subepi- 
dermal parenchyma  cells  are  already  beginning  to  elongate  radially.  The 
excessive  elongation  increases  at  j  to  a  decidedly  tube-like  character  and 
afifects  all  layers  of  the  bark  near  the  root  just  coming  through.  This  dis- 
tends the  epidermis  very  greatly,  and,  as  its  cells  do  not  take  part  in  the 
process  of  elongation,  it  finally  begins  to  separate  in  different  places  (c). 
The  leaf  blade  at  rr  shows  an  external  injury  from  grazing  cattle  which 
extends  deep  into  the  node.  The  tissue  is  considerably  browned,  the 
vessels,  as  far  as  the  middle  of  the  node,  are  partially  filled  with  gum.      The 


1  Muth,  Fr.  tJber  die  Beschadigung  der  RebenbUitter  durch  Kupferspritzmittel. 
Mittel.  d.  Deutsch.  Weinbau-Vereins  1906. 

-  Noack,  P^r.,  Eine  Treibhauskrankheit  der  Weinrebe.    Gartenflora  1901,  p.  619. 

3  Tomaschek,  Dber  pathogene  Emergenzen  auf  Ampelopsis  hederacea.  6sterr. 
Bot.  Zeit.  1879,  p.  87. 


441 

facts  warrant  considering  this  injury  the  exciting  agent  in  the  formation  of 
intumescences.  Other  adjacent  blades  which  have  not  been  similarly 
injured,  do  not  develop  the  excrescences.  The  assumption  can  be  very 
easily  made  that,  given  an  abundant  supply  of  water  and  nutritive  sub- 
stances, the  turgescence  in  the  stem  would  be  great,  while  the  evaporation 
from  the  node  covered  wath  soil  would  be  slight  and  an  injury  from  grazing 
cattle  which  would  remove  part  of  the  tissue,  w^ould  so  increase  the  turgor 
that  intumescences  would  be  formed. 

I  had  already  observed  similar  correlation  i)henomena  in  the  action  of 
copper  sprays  on  potato  leaves\  In  vigorously  growing  varieties  a  number 
of  leaves  were  found  injured  by  the  spray;  near  the  dead  spots  in  the  tissue, 
the   intumescences    later   appeared.     Still    other   causes    may   have   similar 


9  .  -g 

Fig-.  78.     Intumescence  on  the  lower  node  of  an  oat  plant. 

results,  since  small  warts  have  been  observed  on  potato  leaves  when  the 
copper  solution  had  not  been  used".  Von  Schrenck^  has  reported  more 
recent  results  in  this  connection.  A  few  days  after  cabbage  plants  in  green- 
houses had  been  sprayed  with  copper  ammonium  carbonate,  pale  knots, 
gradually  becoming  white,  developed  on  the  under  side  of  the  leaves.  They 
proved  to  be  intumescences.  Unsprayed  plants  in  the  same  house  showed 
no  eruptions.  Spraying  with  weak  solutions  of  copper  chlorid,  copper 
acetate,  copper  nitrate  and  copper  sulphate  did  cause  some  distensions.  Von 
Schrenk,  however,  considered  these  intumescences  a  reaction  of  the  leaf 
tissue  to  the  chemical  stimulus  of  the  poisons,  not  correlative  phenomena. 

1  Sorauer,  P.,  Einige  Beobachtungen  bei  der  Anwendung-  von  Kupfermitteln 
geg-en  die  Kartoffelkrankheit.     Zeitschr.  f.  Pflanzenkrankh.  1893,  p.  32. 

^   Masters,  Leaves  of  potatoes  with  warts.     Gard.  Chron.  1878,  I,  p.  802. 

3  Schrenk,  H.  v.,  Intumescences  formed  as  a  result  of  chemical  stimulation. 
Sixteenth  ann.  report  Missouri  Bot.  Gard.  May,  1905. 


442 

Here  belongs  the  case  which  Haberlandt'  describes  in  a  Liane,  Cono- 
cephalus.  He  describes  the  formation  of  compensatory  hydathodes,  after 
the  normal  organs  of  the  leaves  have  been  poisoned.  The  extremely 
abundant  nocturnal  transpiration  takes  place  at  the  base  of  the  shallow 
depressions  on  the  upper  side  of  the  leaf  by  means  of  sharply  differentiated, 
epithemial  hydathodes  with  water  pores  always  lying  over  the  juncture  of 
vascular  bundles.  Where  these  organs  had  been  poisoned  by  painting  the 
It-af   with   a  0.5   per  cent,   alcoliolic  sublimate   solution,  small   knots   were 


Fig.  79.    Stem  of  Lavetera  trimestris 
— with  intumescence.     (Orig.) 


Fig.    SO.     Brancii    of    Acacia    pendulata- 
with  intumescence.     (Orig.) 


Fig.  81. 


Magnified  section  of  Fig. 
(Orig.) 


formed  above  the  vascular  bundles.  Each  morning  large  drops  of  water 
were  found  on  these  places.  These  knots,  which  had  assumed  the  function 
of  the  dead  hydathodes,  seemed  to  be  composed  of  long,  pouch-like  cells,  in 
the  lower  part  divided  by  cross  walls  adjoining  one  another  (without  inter- 
cellular spaces).  The  club-like  swollen  ends  separate  from  one  another 
like  a  brush.  They  have  been  produced  by  the  elongation  of  the  conductive 
narenchyma  cells  and  often  of  the  palisade  cells  and  have  broken  through 
the  epidermis. 


1  Haberlandt  in 
1899,  p.  287. 


•Festchrift  fiir  Schwendener,"  cit.  in  Naturwiss.  Wochenschr. 


443 

Fig.  79  shows  the  habit  of  growth  of  a  piece  of  Lavatera  trimestris 
stem  with  excrescences  due  to  cell  elongation.  Fig.  80  shows  the  rup- 
tured bark  of  Acacia  pcndula,  while  Fig.  81  shows  the  same  much  more 
clearly  because  of  its  magnification. 

In  Malope  grandi flora  and  Lavatera  trimestris,  stems  and  branches 
were  found  bearing  many  long  calluses  on  the  side  exposed  to  the  sun. 
These  were  caused  by  considerable  longitudinal  and  radial  stretching  of  the 
bark  and  wood  cells.  If  the  callus  is  still  young,  the  process  usually  sets  in 
by  a  radial  and  still  more  marked  tangential  stretching,  at  the  level  of  the 
primary  hard  bast  bundles  of  the  parenchyma  cells  containing  chlorophyll 
and  lying  between  two  bundles :  with  this  increase  they  are  pushed  outward 


Fig.  82.     Cross-section  through  a  year  old  branch  of 
intumescence.     (1-433).)      (Orig.) 


ch  of  Acacia  pendula  with 


like  a  bow.  The  mechanical  ring  appears  to  be  broken  because  the  bast 
bundles  are  pressed  far  apart  and  the  collenchyma  layers  less  developed. 
In  large  intumescences  the  broken  places  apparently  extend  deeper  since 
the  wood  also  changes  its  prosenchymatous  elements  and  the  cells  of  its 
medullary  rays  into  a  wide  meshed  parenchyma.  , 

Fig.  82  throws  sufficient  light  on  the  processes  concerned  in  the  forma- 
tion of  the  moss-like  collection  of  intumescences  in  Acacia  pendula;  m 
indicates  the  pith ;  h  the  woodring ;  c  the  cambium ;  b  the  hard  bast  groups ; 
e  the  epidermis ;  .y  the  beginnings  of  elongation  within  the  primary  bark ;  zv 
the  bark  parenchyma  cells  which  have  become  tube-like  and  ascend  in 
spirally  parallel  rows  and,  after  breaking  through  the  epidermis  at  w, 
separate  from  one  another  like  sheaves. 


)   Sorauer,  P.,  tJlier  Intumescenzen.     Ber.  d.  Deutsch.  Bot.  Ges.  1899,  Bd.  XVII, 


444 

When  the  intumescence  is  highly  developed,  the  over-elongation  extends 
backward  to  the  secondary  bark,  stretching  the  cells  of  the  phloem  rays  (q). 
In  fact,  cases  occur  in  which  the  woodring  seems  stimulated  in  those  layers 
last  formed  because  the  outermost  cambial  layers  are  constructed  of  paren- 
chyma wood.  As  on  the  various  kinds  of  Eucalyptus,  the  intumescences 
occur  most  frequently  on  the  side  of  the  branch  turned  toward  the  light, 
and  often  only  then.  After  the  explanation  given  these  cases,  a  more 
thorough  discussion  is  needed  here. 


Fig.    S3.     Blossom.s   of   Cymbidium    Lowi    with    sland-like    intumescence    (a)    on    the 
tops  of  tlic   iiei-iuntli.      (Ori^.) 

Intumescences  occur  most  rarely  on  blossom  organs.  I  observed  one 
such  case  in  Cymbidium  Loivi.  The  blossoms,  normally  large  and  otherwise 
well-developed,  exhibited  on  the  under  side  of  the  perianth,  quince  yellow  or 
yellowish  green,  hemispherical  bosses  (Fig.  83a)  ;  exactly  the  same  struc- 
tures could  be  found  also  on  the  ovaries.  In  an  immature  stage  they  had 
a  smooth  upper  surface,  later  they  cracked  open  in  the  apical  region  and 
became  depressed  like  a  funnel.  In  the  older  knots,  the  depression  advanced 
to  complete  perforation  of  the  perianth  tip.  For  this  reason  the  blossoms 
were  unsalable.     In  Fig.  84,  it  may  be  seen  that  the  cell  layer  found  beneath 


445 

the  epidermis  (?)  of  the  under  side  of  one  part  of  the  perianth  has  devel- 
oped erect,  cIub-Hke  tubes,  at  first  bent  toward  one  another  hke  lopped 
trunks  (s),  which  first  had  been  held  together  by  the  brown-walled,  swollen 
epidermis  not  affected  by  the  stretching.  After  the  epidermis  had  ruptured, 
the  tubes,  which  were  rather  thick  walled,  deep  brown  and  had  lost  their 
contents,  separated  from  one  another  like  sheaves.  The  process  of  the 
over-elongation  gradually  attacks  the  deeper  and  deeper  lying  parts  of  the 
cell  and  finally  advances  even  directly  to  the  upper  epidermis  (zc/).  At  this 
time  the  epidermis  ruptures  and  the  tips  of  the  perianth  tip^  become 
perforated. 

The  first  stages  of  the  intumescences  have  been  studied  in  the  ovaries. 
The  first  symptoms  are  a  localized  change  in 
the  epidermal  cells,  the  walls  of  which  are  yel-  ^ 

lowish  brown,  and  swollen.     These  cells  extend 
over  the  upper  surface.     Beneath  these  places 


Fig.    84.     Cross-section    through    an    intumescence    on    tlie    perianth    of   Cymbidium 
Lowi.     Upper  figure,  young  stage;    lower  figure,  mature  condition.     (Orig.) 

O  upper  side.  ('  under  side,  e  epidermis,  s  (upper  figure)  besrinning  of  elongation  of  the  sub-epidermal  cells, 

J  (lower  figure)  the  rupturing  of  tlie  club-like  over-eloiigited  cells,  g  vascular  bundled.  7ii  av  meed 

condition  of  perforation. 


the  tissue  is  perfectly  colorless,  more  closely  pressed  together  and  filled  more 
abundantly  with  protoplasm  and  oily  looking  drops.  In  some  of  these  places 
a  radial  stretching  has  already  taken  place,  which  increases  up  to  a  diagonal 
inclination  and  cross-division.  The  process  gradually  extends  to  the  sur- 
rounding cells,  especially  to  those  lying  directly  beneath  the  epidermis.  The 
elongating  layer  becomes  strikingly  thick-walled  and  turns  coffee  brown, 
while  the  collapsing,  swollen  epidermis  forms  a  light  yellowish  brown  cap. 
The  discoloration  is  accompanied  by  a  process  of  suberization,  and  to  this 
probably  may  be  ascribed  the  fact  that  the  cells,  becoming  brittle  in  the  still 


1   Sorauer,  P., 
19,  p.  115. 


Intumescences  an  Bliiten.    Ber.  d.  Deutsch.  Bot.  Ges.  1901.     Vol. 


446 


incompletely  developed  organs  affected  ckiring  their  elongation,  rupture  and 
crumble.  This  is  the  beginning  of  the  funnel-like  depression  at  the  tip  of 
the  intumescence. 

Among  fruit  intumescences,  I  have  most  frequently  observed  the  unripe 
pods  of  beans  and  peas  and  noticed  that  many  varieties  of  fungi  infested 
the  pods.  The  fruits,  especially  v\'hen  near  the  surface  of  the  soil,  seemed 
closely  covered  with  warts  and  awakened  the  suspicion  of  a  marked  fungous 
infection,  as  may  be  seen  in  the  pea-pod  shown  in  Fig.  85. 

In  cross-section,  it  may  be  seen  in  different  places,  which  still  seem 
smooth  to  the  naked  eye,  that  some  epidermal  cells  have  already  begun  to 

elongate.  These  often  lie  directly  beside  the 
stomata,  but  without  the  cooperation  of  the 
str)mata  in  jjroducing  intumescences.  Gradu- 
ally the  [)arenchyma  cells  lying  below  be- 
come elongated.  The  elongated  elements  are 
often  divided  by  cross-walls  and  form  warts. 
However,  these  are  first  formed  of  rows  of 
cells  arranged  like  columns.  These  warts 
grow  to  a  height  of  one  millimeter ;  later  they 
become  brown  from  the  dying  of  the  peri- 
pheral layers  and,  after  the  covering  splits, 
the  rows  of  cells  spread  out  like  a  sheaf. 

Fig.  86  shows  the  greatest  development. 
The  normal  wall  of  the  pod  is  shown  at  fr; 
e  indicates  the  epidermis ;  p  layers  of  the 
thick-walled  partially  intersecting  elements 
of  the  inner  parchment-like  fruit  membrane. 
In  the  centre  of  the  outgrowth  (w)  the 
elongated  columnarly  arranged  parenchyma 
cells,  separating  toward  the  outside,  irregu- 
larly like  a  fan,  are  visible.  The  outermost 
peripheral  zones,  shaded  in  the  drawing 
[z,  z).  indicate  the  moribund  tissue.  The 
walls  of  these  collapsed  parenchyma  groups, 
often  shrinking  together  in  curling  tips,  seem 
yellf)w  to  brown  and  give  the  warts  an  earthy  color.  bVom  the  repeated 
splitting  of  the  intumescences,  which  are  often  so  close  to  one  another  that 
only  a  few  normal  epidermal  cells  separate  them,  the  whole  wall  of  the  pod 
obtains  in  places  a  mossy  outer  surface. 

The  parchment-like  inner  wall  of  the  pod  forms  intumescences ;  indeed 
this  is  more  frequently  the  case  than  on  the  outer  wall.  In  some  kinds  of 
peas,  with  very  pithy  pods,  white  tissue  felts  resembling  species  of  mold 
may  be  found  almost  every  year  on  the  firm,  smooth  inner  surface.  In  one 
case  in  the  intumescence  tissue,  I  found  numerous  oospores  which  presum- 
ably had  belonged  to  Peronospora  Viciac. 


Fig.    85.      ]'f"a-i)0(ls    with   glaiui 

like  raised  outer  surface. 

(Orig.) 


447 


From  the  examples  already  cited  it  is  evident  that  the  intumescences 
may  occur  on  all  aerial  organs  of  plants.  They  form  one  link  in  a  chain  of 
phenomena  which  in  part  commonly  occur  together  and  in  part,  in  fact, 
overlap.  We  have  described  the  simplest  disturbances  as  "Aurigo ;"  they 
are  characterized  by  the  impoverishment  of  some  tissue  groups  in  the 
interior  of  the  leaf  with  a  destruction  of  the  chlorophyll  apparatus,  usually 
with  the  formation  of  carotin.  As  the  chlorophyll  disappears  the  cells  are 
apt  to  become  distended.  They  fill  the  intercellular  spaces,  thus  exercising 
pressure  on  the  surroundings ;  they  finally  die  as  the  cell  walls  become 
suberized.  Such  nests  of  over-elongated  cells  are  also  termed  "internal 
intumescences."  In  real  intumescences  the  processes  of  impoverishment 
and  cell  elongation  begin  in  the  peripheral  layers  of  the  organs  and  in  fact 
usually  in  the  sub-epidermal 
cell  layers,  more  rarely  in 
the  epidermis  itself.  The 
process  of  over-elongation 
is  less  impeded  here  and 
frequently  advances  into 
the  more  deeply  lying  tis- 
sue layers,  so  that  we  find 
cases  of  intumescences  be- 
ginning on  the  under  side 
of  the  leaf  and  gradually 
including  the  whole  meso- 
phyll  as  far  as  the  upper 
epidermis.  If  the  forma- 
tion of  cork  sets  in  in  the 
intumescence  tissue,  we  find 
wart-like  or  pitted  cork 
centres  which  can  lead  to 
the  complete  perforation  of  the  leaf. 

On  the  trunk  the  intumescence  manifests  itself  in  the  hypertrophy  of 
the  bark  parenchyma  which,  in  isolated  enclosed  centres,  breaks  out  from 
the  bark  in  the  form  of  warts  with  a  smooth  or  repeatedly  split  outer  sur- 
face. If  the  processes  of  over-elongation  are  not  restricted  to  small  isolated 
centres  but  attack  the  parenchymatous  tissue  in  large,  connected  surfaces,  all 
the  organs  rupture,  causing  the  condition  which  we  have  called  "dropsy." 

Although  the  phenomena  described  here  are  related  structurally,  we 
have  treated  them  separately  because  dififerent  conditions  are  the  dominat- 
ing causes  of  dififerent  outbreaks.  Many  investigations  have  shown  that  an 
atmosphere  heavily  ladened  with  moisture  is  a  decisive  influence  in  causing 
intumescences. 

'J^eferences  to  my  work  and  that  of  other  older  investigators  may  be 
found  in  the  bibliography  of  Kiister's^  "Pathological  Anatomy."     I  will  cite 


Fig. 


86.     Cross-section  through  the  outer  surface  of 
pea-pods  with  intumescences.     (Orig-.) 


1  Kvister,  Ernst,  Pathologische  Anatomie.     Jena  1903.     Gustav  Fischer. 


448 

here  a  few  especially  pertinent  observations.  Some  of  these  consider  the 
question  of  light  on  the  production  of  an  intumescence.  In  this  connection 
Atkinson^  explains  that  increased  turgescence  in  leaves  will  be  produced  by 
repressed  transpiration  if  the  greenhouses  are  poorly  Hghted.  Actually,  in 
many  cases,  I  found  intumescences  in  the  autumn  and  winter,  because  of 
cool,  cloudy  weather,  if  the  greenhouses  had  to  be  heated  after  the  plants  had 
been  brought  in  from  outside.  Trotter-  states  directly  that  half  darkness 
favors  the  formation  of  intumescences.  Steiner''  also  made  the  same 
observation,  but  stated  that  they  will  form  only  in  the  first  days  of  darkness, 
so  that  one  may  conjecture  an  after  effect  of  the  former  acti\  ity  of  the  light. 
This  author  observed  also  in  Ruellia  and  Aphelandra,  that  the  plants  with 
equal  atmospheric  humidity  only  formed  intumescences  for  a  few  weeks 
and  therefore  had  adjusted  themselves  to  the  high  degree  of  moisture.  That 
the  abrupt  transition  from  dry  to  moist  air  is  actually  the  decisive  factor  is 
shown  by  the  renewed  formation  of  intumescences,  when  the  plants,  after 
having  become  adjusted  to  a  dry  atmosphere  for  three  weeks  are  brought 
again  into  moist  air. 

Steiner  found  that  no  intumescences  are  jjroduced  under  water,  as  did 
Kiister''  on  ])()plar  leaves  which  he  had  left  floating  on  water  or  nutrient 
solutions  and  in  darkness  as  well  as  in  light.  Only  when  the  illumination 
was  too  great,  this  process  was  suppressed,  probably  as  a  result  of  increased 
transpiration.  In  contrast  to  this,  A^iala  and  Pacottet",  in  describing  intu- 
mescences on  grape  leaves  in  greenhouses,  said  tlie\-  had  determined  by 
direct  experiment  that  intumescences  are  produced  by  the  action  of  the 
light  in  a  moist  atmosphere.  They  are  produced  only  directly  under  glass. 
The  Missouri  Botanical  Garden  makes  a  similar  report. 

The  most  thorough  experimental  studies  are  Miss  Dale's".  She  ob- 
served with  Hibiscus  vitifolius,  that  the  yellow  and  red  rays  are  especially 
effective  in  producing  intumescences.  Her  experiments  with  potatoes  are 
especially  instructive  in  regard  to  the  action  of  sudden  changes  in  the  vege- 
tative conditions.  The  plants  were  grown  in  a  cold  section  of  a  greenhouse 
and  then  set  in  a  warm  house  at  a  temperature  of  about  2i°C.,  under  a 
brightly  illuminated  bell-glass.  After  48  hours,  the  stem  and  the  upper 
side  of  almost  all  the  leaves  were  covered  with  masses  of  pale  green  raised 
spots.     If  the  plants  were  then  brought  into  dry  air,  the  blisters  shrivelled 


1  Atkinson,  O.  F.,  Oedema  of  the  tomato.  \\\\\\.  C'ornell  Agric.  Exp.  Station 
1893,  No.  53. 

-  Trotter,  A.,  Intuniescence.s  I'os'liari  dj  Ipomea  Batatas.  Annali  di  Botanica 
1904,  No.  1. 

:■•  Steiner,  Rudolf,  Wber  Intumescenzen  bei  Ruelli  formosa  and  Aphelandra 
Porteana.     Ber.  d.  Deutsch.  Bot.  Ges.  1905,  Vol.  23,  p.  lOf). 

4  KUster,  E.,  tjber  experimentell  erzeugte  Intumescenzen.  P.er.  der  Deutsch. 
Bot.  Ges.  1903,  Vol.  21,  p.  452. 

•'  Viala  et  Pacottet,  Sur  les  verrues  des  feuilles  de  la  vif?ne.  Compt.  rend. 
Acad.  d.  sciences  1904,  No.  138. 

I'  Dale,  E.,  Investif?ations  on  the  abnormal  outgrowths  or  intumescences  on 
Hibiscus  vitifolius.  Phil.  Trans.  R.  Soc.  of  London,  ser.  B.  1901,  Vol.  194.— 
Dale,  E.,  Further  experiments  and  histolog-ical  investigations  on  intumescences, 
with  some  observations  on  nuclear  division  in  pathological  tissues.  Phil.  Trans. 
R,  Soc.  of  London  1906,  ser.  B.  Vol.  198. 


449 

up  to  black  spots  or  perforated  the  leaves.  )If  some  leaves  fell,  when  the 
the  plants  were  kept  longer  under  the  moist  conditions,  a  great  cushion  of 
intumescences  was  produced  on  the  leaf  scar  which  displayed  similarity 
to  the  wound  callus.  Older  plants  under  similar  conditions  did  not 
develop  intumescences  as  quickly,  nor  as  abundantly,  while  very  old  leaves 
developed  none.  Pieces  of  leaves,  laid  in  moist  cotton,  after  possibly  two 
days,  were  thickly  covered  with  eruptions.  Quickly  growing  plants  react 
most  easily  to  the  stimulus  of  a  sudden  change  in  the  amount  of  moisture. 

These  observations  support  our  theory  that  the  formation  of  intumes- 
cences is  the  reaction  of  the  organ  to  a  stimulus  due  to  a  sudden  increase 
of  atmospheric  moisture.  Only  the  immature  organ  reacts.  If  older  leaves, 
as  we  observed,  for  example,  with  Solanum  Warscewiczii,  respond  with  a 
formation  of  intumescences  after  having  been  brought  from  the  open  air 
into  a  damp  greenhouse,  these  are  exceptional  cases  of  a  special  excitability 
of  the  species.     Such  cases  occur  in  various  plant  genera. 

My  results  differ  from  those  of  other  investigators,  since  I  always  found 
that  intumescences  invariably  developed  as  the  result  of  an  arrested  assimi- 
lation due  to  an  excess  or  deficiency  of  light.  It  always  manifests  itself, 
however,  in  the  scanty  formation  of  solid  reserve  substances,  usually,  in  fact, 
those  already  formed  become  dissolved.  In  accord  with  Miss  Dale's  assump- 
tion, the  variation  in  assimilation  may  be  connected  with  the  increase  of  the 
oxalic  acid  content  in  the  cells  showing  in  the  abnormal  increase  in  turgor. 
In  the  same  way,  experiments  with  young  leaves  and  pieces  of  leaves  show 
how  the  root  pressure  may  be  eliminated. 

Different  combinations  of  the  vegetative  factors  may  give  rise  to  that 
deficient  assimilation  which  shows  itself  in  the  formation  of  intumescences. 
In  the  greater  number  of  cases  falling  under  my  observation,  I  find  the  cause 
to  be  an  increase  of  heat  and  moisture  given  to  a  plant  naturally  dormant, 
or  being  forced  to  arrest  its  assimilation  from  external  conditions.  The 
following  action  throws  light  on  inhibitory  regulations. 

The  Tubercle  Disease  of  the  Rubber  Plant. 

On  the  under  side  of  the  leaves  are  found  numerous  abundant,  very 
small,  gland  or  tubercle-like,  hemispherical  swellings.  These  are  produced 
by  the  pouch-like  elongation  (Fig.  87,  int)  of  the  cells  of  the  leaf,  which, 
in  a  normal  condition,  have  the  form  and  arrangement  shown  at  the  side  of 
the  picture  marked  ni  and,  therefore,  are  separated  by  larger  or  smaller 
intercellular  spaces  (i).  The  morbidly  elongated  tissue  (int)  on  the  under 
side  of  the  leaf  thus  approaches  the  normal  leaf  pahsade  parenchyma  (/>) 
which  is  provided  with  a  three-fold  epidermis  {e).  Of  these  three  layers, 
the  outermost  is  small-celled  and  provided  with  a  very  thick  layer  of  cuticle. 
The  innermost  cell  layer  of  the  epidermis  displays  more  thin-walled,  com- 
paratively very  broad  cells  (w),  which  form  the  so-called  water-storage, 
protective  layer.     Isolated   cells,   enlarged  like  sacs,   in  this  layer  conceal 


450 

those  peculiar  grape-like  clusters  of  cell  substance  incrusted  with  calcium  (c) 
known  as  cystoliths. 

The  close  structure  of  the  upper  epidermis  of  the  leaf  must  prevent  the 
passage  of  air,  while  the  lower  epidermis  is  well  fitted  for  this  purpose. 
The  spong}^  parenchyma  shows  large  intercellular  spaces  (i),  the  enclosed 
air  in  which  can  pass  out  through  the  air  chambers  under  the  stomata  (a) 
and  the  stomata  (st)  to  the  outside,  making  room  for  the  freshly  entering 
outer  air.  The  conduction  of  water  takes  place  through  the  leaf  veins,  one 
of  which  is  seen  in  section  at  g  and  shows  at  r  the  large  ducts.     The  course 


Fig-.  87.     Cros.s-section  througi 


of  the  rublKM' 


of  organized  building  substances,  produced  in  the  leaf  and  flowing  down 
toward  the  trunk,  is  shown  at  sch,  the  sheath  of  the  vascular  bundle;  k 
indicates  the  place  at  which  the  cells  begin  to  enlarge  because  of  an  excess- 
ively increased  turgor,  thus  filling  the  intercellular  spaces  and  forming, 
therefore,  first  of  all,  "internal  intumescences."  The  excessive  water  con- 
tent manifests  itself  still  more  in  the  peripheral  tissue,  since,  exposed  only 
to  the  pressure  of  the  epidermis,  its  cells  elongate  into  tubes  and,  together 
with  the  epidermis,  can  be  pushed  outward  (int). 

Actually,  therefore,  the  tubercle  disease  of  the  rubber  plant  is  a  regular 
intumescence  which  belongs  to  the  previous  division.     We  have,  however, 


EDGAR  TULLIS 


451 

isolated  this  phenomenon  of  disease,  because  it  has  an  essentially  practical 
significance  in  the  cultivation  of  Fiscus  as  a  market  plant. 

The  disease  occurs  less  often  in  plants  grown  for  sale  than  in  home 
ornamental  plants,  where  it  may  lead  to  a  premature  defoliation.  My  experi- 
ments prove  that  it  is  produced  by  giving  excessive  heat  and  water  to  plants 
when  their  growth  has  stopped  and  their  transpiration  lessened,  thus  stimu- 
lating them  to  renewed  activity.  I  produced  intumescences  by  keeping  a 
rubber  plant  in  a  very  hot  room  and  giving  it  abundant  water  after  it  had 
made  a  vigorous  summer  growth  and  passed  into  the  normal  resting  period, 
instead  of  the  cooler,  drier  environment  which  it  should  naturally  have  had. 
Leaves  fell  immediately,  while  intumescences  were  formed  on  the  younger 
ones.  \Mien  the  plant  was  put  in  a  light,  but  cooler  place,  the  leaves  with 
the  intumescences  remained  on  the  stem  until  the  next  summer,  when  the 
plant  again  grew  nor- 
mally if  somewhat  more 
weakly. 

This  kind  of  disease 
and  its  cure  may  be 
considered  characteris- 
tic. The  intumescences, 
therefore,  are  highly  sig- 
nificant symptoms  of  ab- 
normal turgidity  in  all 
plants.  As  soon  as  they 
show  themselves,  the 
plant  must  be  put  into  a 
light,  cooler  environ- 
ment and  given  a  de- 
creased water  supply. 

The   Skin   Diseases  of       *''§"•  SS.     Hyacinth  bulb  infected  with  the  pustules  of 
^_  the  skin  disease-      (Orig.) 

Hyacinths 

■v  scales  which  have  lost  their  gloss,  d  formation  of  pustles, 
_,  ,     .  ,  /dried  edge,  k  voung-  bulb. 

i  h  1  s  phenomenon 
(Fig.  88)  has  not  been  considered,  although  it  occurs  very  frequently. 
Normally  the  outer  scale  leaves  are  smooth,  firmly  enclose  the  bulb,  and 
usually  extend  up  to  its  neck.  In  this  disease  they  are  short  and  die  back 
from  the  dying  edges.  Often  such  hyacinth  bulbs  crack  open  and  are 
thickly  covered  with  dry  leaves,  especially  near  the  place  torn.  On  the  still 
fleshy  outer  parts  of  the  bulb,  colonies  of  the  blue-green  mold  {Penicillium 
glauciim)  frequently  occur. 

The  leaves  standing  isolated,  or  connected  with  one  another,  are  flat- 
tened on  the  upper  side  and  often  many  boil-like,  swollen,  yellow  places 
appear.  In  the  colored  part  also  of  normally  dried  bulb  scales,  they  almost 
always  show  some  mycelium.  In  cultures  this  is  proved  to  belong  to 
Penicillium.     The  tissue  of  such  diseased  places  differs  from  that  of  normal 


452 

scales  in  its  yellow  ,  uncommonl}-  brittle  walls,  breaking  into  sharply  pointed 
pieces  and  in  the  wide  lumina  of  the  cells,  while  that  of  the  healthy  ones, 
with  their  somewhat  swollen,  thick,  colorless  walls,  ha\e  sunk  together  until 
the  lumen  disappears.  All  traces  of  starch  have  disappeared  from  the 
yellow-walled  tissue,  which  sometimes  traverses  the  scale,  is  suberized,  and 
pushed  up  by  the  subsequently  i)roduced  cork  cells  and  from  the  colorless 
surrounding  tissue. 

After  the  diseased,  dry  bulb  scales  have  been  removed,  one  notices  that 
the  still  perfectly  white,  succulent  scales,  normally  extending  to  the  neck  of 
the  bulb,  have  begun  to  dr}%  beginning  at  the  top.  Here  the  tissue  loses  its 
natural  smoothness  and  turgor,  so  that  gradually  the  scale  has  a  folded 
appearance,  due  to  the  collapse  of  the  cells  which  lie  between  the  more 
prominent  vascular  bundles.  Besides  this,  the  edge  usually  becomes  yel- 
lowish. At  the  same  time,  on  the  deeper  parts  of  the  fleshy,  white  places  in 
the  scales,  glistening  from  turgidity,  appear  small,  longish,  glassy,  trans- 
parent, yellowish  spots,  protruding  shghtly  above  the  upper  surface.     These 


Fig.   89.     Cross-section   tlirougli   a  scale  of  a  hyacinth    infected   witli  skin   disease. 

(Oriff.) 

increase  in  a  few  days  and  almost  at  once  become  more  noticeable  because 
of  the  yellowish  juicy  edge.  Then,  however,  the  change  advances  more 
slowly,  since  the  outpushing  occurs  only  gradually  more  distinctly  and  its 
centre  becomes  whitish  with  a  dry  membrane  and  longitudinal  folds ;  with 
increasing  age,  the  centre  becomes  depressed  and  finally  the  scale  seems 
perforated.  When  treated  with  sulfuric  acid  the  upper  lamellae,  lying 
directly  beneath  the  cuticle  (Fig.  89  /)  of  the  somewhat  thickened  epidermal 
cells,  swell  up  markedly  and  at  limes  mycelium  may  be  found  in  them. 

A  cross-section  through  the  diseased  scale  (Fig.  89)  shows  at  b  an  older 
pustule  and  on  the  left  of  this  a  younger  one.  In  the  discolored  epidermis, 
the  walls  are  swollen  and  this  process  of  swelling  and  suberization  (vk)  m 
the  older  leaves  has  already  advanced  through  the  whole  thickness  of  the 
scale.  Here  the  fleshy,  starchless  parenchyma,  which  at  the  beginning  (p) 
was  found  to  be  still  colorless  and  with  a  normal  arrangement,  has  col- 
lapsed like  cords  and  formed  hardened  places  with  irregular  openings  (s). 

In  the  cells  directly  beneath  the  outpushed  epidermis,  there  are  no  nuclei, 
while  they  are  present  in  the  next  inner  cells,  but  brown  in  color.  In  the 
epidermis,  cork  cells  are  produced,  while  the  parenchyma  lying  beneath  gives 


453 

the  sugar  reaction  with  the  Trommer  test.  In  this  tissue,  rich  in  sugar,  the 
formation  of  cork  advances  and  since  the  corked  cells  do  not  collapse,  they 
rise  gradually  more  and  more  above  the  other  tissue  of  the  bulb  scales,  the 
walls  of  which  retain  their  cellulose  reaction  and  collapse.  Analyses  give 
dry  substance 

Healthy  bulbs.  Diseased  bulbs. 

In  the  outer  scales  34.6  per  cent.  51.82  per  cent,  36.7  per  cent.  55.43  per  cent. 
In  the  inner  scales  22.4       "  33-50       "  32.6       "  40.16       " 

Thus  the  diseased  bulbs  are  richer  in  dry  substance,  which  is  not  strange 
since  the  process  of  drying  of  the  outermost  scales  has  advanced  rather 
further  in  them. 

After  the  removal  of  all  the  brown  colored  scales,  the  sugar  content 
(defined  as  grape  sugar  and  reckoned  on  dry  substance)  is, 

Healthy  bulbs.  Diseased  bulbs. 

In  the  outer  scales 0.71  per  cent.  0.82  per  cent. 

In  the  inner  scales 1.23       "  1.66       " 

That  is,  the  bulbs  are  richer  in  sugar  in  the  inner,  younger  scales  than 
in  the  older  ones,  and  when  diseased  both  the  inner  and  outer  scales  are 
richer  in  sugar  than  those  in  a  healthy  condition. 

We  thus  obtain  the  same  results  as  were  found  in  the  ringing  disease. 
As  a  matter  of  fact,  both  diseases  frequently  occur  simultaneously  and  these 
pustules,  which  may  be  termed  intumescences,  prove  to  be  symptoms  of  a 
scantier  ripening  of  the  bulbs.  This  may  be  found  even  in  very  luxuriantly 
cracked  specimens.  It  is  self  evident  that  Penicillium  grows  rapidly  and 
frequently  on  such  a  medium.  The  skin  disease  therefore  deserves  great 
consideration  as  a  symptom  and  indicates  that  bulbs  should  be  grown  in  a 
sandy  soil  not  too  rich  in  humus  nor  too  damp. 

The  Glassy  Condition  of  Cacti. 

A  diseased  condition  was  observed  in  various  cacti  and  studied  more 
closely  by  me  with  Cereus  nycticalus  Lk.  This  condition  is  characterized  by 
the  appearance  of  glassy  places,  later  becoming  black.  In  the  more  delicate 
Cereus  varieties,  a  greater  extension  of  this  tissue  change  kills  the  part  of 
the  stem  which  lies  above  it.  Death  results  either  through  a  drying  up  of  the 
blackened  tissue,  or  with  the  assistance  of  bacteria,  through  the  appear- 
ance of  a  pulpy  condition,  when  the  outer  skin  may  be  loosened  by  a  slight 
pressure  of  the  fingers.  If  the  centre  of  disease  is  limited  to  one  side  of 
the  stem,  this  may  be  healed,  leaving  deeper  cup-like  wounds. 

The  illustration  on  page  456,  of  the  manner  of  growth,  shows  a  piece 
of  the  stem  of  Cereus  nycticalus  blackened  at  the  upper  end  and  softened 
to  a  pulp.  On  this  softened  part,  a  strip  of  the  outer  skin  has  been  loosened 
by  a  slanting  pressure  of  the  finger.  At  the  base  of  the  piece  of  the  stem 
are  found  healed  wounds  which  extend  to  the  wood  ring  of  the  stem. 


454 

When  examining  badly  diseased  specimens,  it  is  noticed  that  a  number 
of  glassy  places  occur  like  warts  on  the  upper  surface.  The  cross-section 
shows  that  while  the  outer  part  of  the  bark  of  this  piece  of  stem  is  still  dark 
green  and  normally  constructed,  the  underlying  bark  layers  lack  chlorophyll 
and  starch  and  have  greatly  enlarged  cells  which  cause  the  warty  excres- 
cence. In  contrast  to  the  usual  intumescences  in  which  an  elongation  of  the 
sub-epidermal  layers  causes  the  warty  outgrowths  which  often  rupture,  I 
have  termed  the  abnormal  enlargement  of  the  cell  centres  lying  deeply 
depressed  in  the  tissue,  "internal  intumescences."  In  this,  these  phe- 
nomena are  related  to  the  yellow-spotted  condition  described  above.  Here 
the  first  stages  of  the  disease  are  found  in  centres  of  cells  poor  in  content, 
browning  and  turning  to  cork  in  the  midst  of  green  tissue ;  only  in  cacti  the 
stems  are  affected,  while  in  I\indanus  the  changes  are  found  in  the  leaf. 

The  cell  aggregations,  which  usually  increase  only  in  one  direction, 
collapse,  while,  especially  in  the  bark  of  the  cactus,  the  cells  retaining  thin, 
colored  walls,  are  usually  elongated  into  tubes  and  have  a  star-like  arrange- 
ment. From  these  inner  diseased  tissue  centres,  the  process  of  impoverish- 
ment and  over-elongation  of  the  bark  parenchyma  extends  backward  toward 
the  wood-ring  and  laterally  in  the  direction  of  the  bark,  constantly  further 
around  until  a  considerable  part  of  the  stem  is  browned  or  blackened. 
Finally  the  outermost  cell  layers  are  also  attacked  by  the  discoloration 
without  the  usual  appearance  of  any  over-elongation;  rather,  the  stem 
appears  as  black  as  ink,  even  to  the  naked  eye. 

In  the  first  stages  of  this  disease,  while  the  tissue  still  has  a  glassy  appear- 
ance, the  process  of  blackening  occurs  almost  immediately  after  the  sections 
are  made,  indicating  that  even  then  there  are  large  amounts  of  tannic  acid, 
which  unite  with  the  iron  of  the  knife.  Since,  however,  the  discoloration 
follows  when  the  plants  have  been  injured  with  a  horn  knife,  or  with  a 
platinum  spatula,  the  presence  of  a  sensitive  substance  must  be  assumed 
that  rapidly  discolors  in  the  presence  of  the  oxygen  of  the  air.  But 
guaiacum  tinctures  alone,  or  with  hydrogen  peroxide,  do  not  give  a  blue 
coloration.  W'ith  litmus  paper  the  whole  bark  parenchyma  gives  a  sharp 
acid  reaction. 

An  accumulation  of  glucose  may  be  considered  as  a  factor  which  might 
begin  the  over-elongation  of  the  cells ;  for,  after  treating  the  section  with 
the  Trommer  sugar  test,  cuprous  ox  id  is  very  freely  precipitated  in  the 
glassy  tissue  as  a  whole,  and  this  precipitate  is  scantier  toward  the  healthy 
tissue.  The  proportion  of  starch  content  is  the  reverse.  In  the  most  dis- 
eased tissue,  it  is  nil,  while  the  healthier  surrounding  tissue  displays  starch 
abundantly.  The  proportion  of  calcium  oxalate  is  peculiar;  it  occurs  usually 
abundantly  in  the  slime  passages.  In  healthy  green  bark  tissue,  this  calcium 
oxalate  occurs  chiefly  as  raphides,  while  in  the  diseased  parts  it  is  found 
usually  in  short  octahedrons  and  at  times  in  large  cylinders.  Probably 
var}^ing  amounts  of  the  water  of  crystalization  determine  the  form. 


455 

The  upper  figure  in  illustration  90  shows  the  process  of  healing.  It  is 
a  cross-section  through  the  branch  with  a  depressed  wound,  which  may  be 
seen  at  the  base  of  the  picture,  showing  the  habit  of  growth.  M  is  the  pith 
with  its  sHme  cells ;  H,  normal  old  wood ;  R,  bark.  It  is  seen  at  the  wound 
that  the  tissue  atrophy  originally  included  the  whole  bark  {R).  The  wood 
cylinder  (//),  however,  was  not  attacked.  The  edges  of  the  bark  wounds 
{ivr)  died  and  were  separated  by  a  full  cork  layer  {t)  from  the  healthy 
bark  parenchyma  at  the  sides.  In  the  remaining  part  of  the  bark,  a  new 
growth  in  thickness  had  set  in,  which  manifested  itself  by  forming  the 
primordia  of  new  hard  bast  strands  {b').  The  old  hard  bast  near  the  wound 
was  diseased  and  found  shut  in  by  a  cork  envelope. 

The  whole  tissue  zone  (Z^'-&')had  been  formed  anew  subsequently,  and 
indeed  in  those  parts  covered  by  the  bark  by  means  of  a  normal  cambial 
activity,  but  at  the  wound  itself  by  an  increase  of  the  youngest  sapwood. 
For  the  wound  destroyed  the  cambium,  and  accordingly  the  last  formed 
cambial  wood  layer  has  started  a  renewed  increase  of  cells  and  has  formed 
callus-like  tissue.  The  primordia  of  the  vessels,  which  at  the  time  of  the 
deposition  of  the  latest  sap-wood  had  already  become  thick-walled,  have, 
however,  not  taken  part  in  the  increase,  but  have  been  pushed  outward 
passively  by  the  newly  formed  callus.  It  is  seen  in  this,  that  these  primordia 
of  the  vessels  {g'),  which  in  the  cross-section  resemble  the  ducts  {g)  in  the 
normal  wood  {H),  now  occur  isolated  in  the  callus  tissue. 

The  healing  process  becomes  more  exactly  recognizable  in  the  lower 
anatomical  figure  which  represents  a  piece  of  tissue  from  around  the  hole 
in  the  upper  cross-section.  H  again  represents  the  old  wood  with  some 
vessels  {g).  Where  the  elements,  represented  with  thick  walls,  cease,  is 
seen  the  most  depressed  part  of  the  wound.  On  this  remain  the  youngest 
elements  of  the  sap  wood,  which  had  increased  in  size  and  number  after 
the  phenomena  of  decay  had  ceased.  The  immature  sap  wood,  already 
differentiated,  became  imore  porous  and  thin  walled,  and  thus  it  happens 
that  thin-walled  vessels  ig')  may  be  found  again  in  a  delicate  parenchyma 
wood.  All  the  tissue  indicated  by  (n)  has  been  newly  formed,  its  produc- 
tion corresponding  with  the  new  formation  of  bark  on  peeled  trunks.  The 
new  tissue,  developed  from  the  callus,  already  exhibits  some  differentiation. 
This  differentiation  indicates  that  the  stem  is  about  to  form  new  bark  where 
it  was  injured,  for  in  the  region  directly  in  front  of  the  thin-walled  vessels 
{g'),  we  find  the  first  parallel  cell  divisions  indicating  the  formation  of  a 
new  cambial  zone.  Besides  these,  the  primordia  of  secondary  hard  bast  {h') 
may  be  recognized,  to  be  sure,  even  in  parenchymatous  tissue  with  a  plastic 
content  but  not  containing  chloroplasts,  which  later  becomes  normal  bark. 

This  healing  process,  however,  has  only  been  observed  when  the  plant 
had  direct  sunshine  and  fresh  air  in  circulation.  I  have  learned  to  recognize 
the  disease  as  occurring  in  greenhouses  and  indeed  in  those  where  because 
they  contain  plants  from  warmer  climates  the  air  is  enclosed  and  very  moist. 
In  one  special  case,  the  abundant  ventilation  in  the  greenhouse  stopped  the 


457 

Fig.  90.  At  the  right  side  of  the  figure,  indicating  the  manner  of  growth,  is  a 
reduced  piece  of  the  stem  of  Cereus  nycticalus,  which,  blackened  and  softened  at 
the  tip,  shows  a  piece  of  tlie  baric  loosened  by  pressure  of  the  fingers.  On  its  lower 
part  are  found  deep  bowl-like  wounds  which  have  been,  healed-  The  upper  drawing 
of  the  structure  shows  a  cross-section  of  a  bowl-like  wound  which  is  being  healed. 
The  lower  drawing  gives  the  new  structures  and  tissue  differentiations,  which  take 
place  during  the  process  of  healing  the  wounds.     (Orig.) 

M  pith.  H  wood.  R  bark,  s  normally  placed  ducts,  .g-'  di.splaced  duct.s,  b  groups  of  dead,  hard  ba.st  of 
the  outer  bark,  enclo.sed  by  bark,  b^  groups  of  young  hard  bast  of  the  outer  bark,  wr  dead  edge  of  the 
wound  of  the  older  bark  (R).     The  old  tissue  is  separated  from  the  healthy  tissue  by  a  layer  of  plate- 
like cork  cells  (/).     w  and  «  new  bark  differentiated  from  the  wound  callus. 

disease,  while  in  the  following  year,  \\'\\\\  the  new  planting  of  foliage  plants 
and  with  accordingly  increased  humidity  in  the  air,  it  reappeared  to  a  great 
degree.  For  this  reason,  I  would  like  to  consider  the  phenomenon  as  a 
direct  result  of  excessive  humidity. 

Methods  for  checking  this  are  self  evident.  In  one  case,  besides  the 
increased  supply  of  light  and  air,  the  addition  of  plaster  to  the  soil  has 
proved  advantageous. 


We  have  devoted  considerable  space  to  intumescences  and  related 
phenomena  in  order  to  point  to  their  importance.  Greenhouse  plants  are 
chiefly  considered  and  repeated  observations  have  shown  that  most  numer- 
ous diseases  may  be  traced  to  the  act  that  the  natural  dormant  period  of  the 
plant  was  not  considered  and  the  plants  were  stimulated  to  untimely  and 
therefore  abnormal  growth,  by  a  high  degree  of  heat  and  moisture. 


CHAPTER  VI. 


Fog. 

In  temperate  climates,  complaint  is  rarely  heard  of  injuries  from  fog. 
In  the  mountains,  vegetation  has  adjusted  itself  to  the  abundant  precipi- 
tation and  the  attempt  has  been  made  so  far  as  possible  to  overcome  the 
delay  of  ripening  grains  and  of  drying  the  remaining  vegetable  produce  by 
cultural  regulations. 

The  so-called  "fog  holes"  of  the  plains  may  also  be  "frost  holes." 
These  are  distinguished  by  a  vigorous  lichen  growth  on  the  tree  trunks. 

In  warm  regions,  fog  becomes  a  more  important  factor,  causing  damage 
to  plants,  since  it  actually  favors  the  development  of  saprophytic  and 
parasitic  fungi.  We  find  the  greatest  number  of  complaints  in  regions 
where  cotton  is  grown  and  exhaustive  descriptions  have  been  sent  from 
Egypt.  David^  writes  from  the  cotton  experiment  station  at  Zagazig  that 
each  October  morning  in  lower  Egypt,  the  soil  is  covered  by  heavy,  thick 
vapors  or  low  fogs.  The  first  general  result  is  that  the  bolls  do  not  open 
because  the  carpophyles  remain  too  tough.  The  foliage  becomes  covered 
with  red  spots,  ascribed  to  the  action  of  the  sun  on  the  dew  drops,  acting  as 
lenses.  The  cotton  fibres  in  the  bolls  decay  and  lose  their  value  from  the 
action  of  a  black  fungus.  Besides  cotton.  Hibiscus  esculantus  and  H. 
cannabinus  also  suffer;  young  maize  plants  as  well.  The  irrigation  with 
Nile  water,  its  soaking  through  the  land  while  the  soil  is  fallow,  makes  it 
moist,  dense  and  slimy  or  oozy.  This  physical  characteristic  is  the  chief 
factor  which  makes  Egyptian  fogs  more  disastrous  than  the  English  and 
mountain  fogs. 

The  sensitiveness  of  cotton  is  due  to  its  special  soil  and  climate  needs. 
These  are  very  thoroughly  described  in  Oppel's-  special  work.  According 
to  this,  cotton  as  a  low-land  plant  cannot  endure  a  stony  soil  or  any  abrupt 
changes  in  temperature.  In  its  time  of  growth,  lasting  six  months,  it 
requires  i8°  to  20°C.  a  medium  heat  and  abundant  moisture,  but  it  is  found 
to  be  very  sensitive  to  continued  rain.  "A  high  degree  of  atmospheric 
warmth,  a  good  deal  of  soil  warmth,  a  clear  sky  during  the  day  and  abundant 


1  David,  Nebel  und  Krdausdiinstung-en  und  ihr  Einfluss  auf  agyptische  Baum- 
wolle.     Zeitschr.  f.  Pflanzenkrankh.  1897,  p.  143. 

2  Oppel,    Die    Baumwolle    nach    Geschichte,     Anbau,     etc.     Leipzig',     cit.     Bot. 
Jahresber.  1902.  I,  p.  374. 


459 

dew  at  night  are  the  chief  conditions."  After  the  blossoms  open,  dry 
warm  weather  must  prevail  Sandy  soil  is  especially  suitable.  In  soils 
rich  in  humus  the  plant  runs  to  foliage.  Clay  soil  is  absolutely  unsuitable, 
since  it  does  not  let  the  water  percolate  through. 

However,  examples  of  adaptation  to  the  climate  are  known.  Thus, 
V\'ebber  and  Bessey^  report  that  -cotton,  when  carried  from  the  Bahamas  to 
Georgia,  did  not  thrive  at  first,  but  gradually  adjusted  itself  to  the  temper- 
ate climate. 

However,  fogs,  even  of  the  English  variety,  may  become  disastrous, 
especially  near  cities  with  many  factories.  P.  W.  Oliver-,  upon  the  re- 
quest of  the  Royal  Horticultural  Society,  has  published  the  most  extensive 
studies  on  London  fog.  The  most  troublesome  admixture  is  the  smoke, 
the  elements  of  which  coat  not  only  the  plants  but  window  panes,  etc.,  with 
a  sooty  covering.     An  analysis  of  this  sooty  covering  shows : 

carbon   39-00  per  cent. 

hydrocarbons 12.30 

organic  bases 2.00 

sulfuric  acid 4.33 

hydrochloric  acid 1.43 

ammonia   1.37 

Metallic  iron  and  magnetic  oxid 2.63 

Silicate,  iron  oxide  and  other  mineral  substances.  31.24 

The  injuries  to  plants  are  usually  only  phenomena  of  discoloration. 
However,  different  plants  are  more  susceptible ;  hence  the  fog  may  cause 
the  dropping  of  the  leaves.  In  injuries  of  the  first  kind,  leaf  tips  and  edges 
become  brown,  but  the  remaining  leaf  surface  is  still  capable  of  functioning 
(Pteris,  Odontoglossus,  etc.).  The  dropping  of  leaves  with  yellowing  and 
browning,  or  even  without  any  external  signs  of  injury,  is  the  most  frequent 
result.  Sulfuric  acid  is  considered  as  the  cause  of  the  leaf  destruction;  in 
addition,  Oliver  ascribes  as  an  injurious  influence  also  metallic  iron.  In 
deciduous  plants  which  remove  all  the  starch  from  the  leaves  before  they 
fall,  the  most  important  agent  exciting  abnormal  leaf  fall  is  sulfuric  acid. 
Experiments  determining  a  rapidly  reduced  transpiration  show  reactions 
similar  to  these  from  fog,  if  at  the  same  time  the  light  was  decreased.  I 
also  ascribe  the  emptying  of  the  cells  to  the  lack  of  light,  for  with  the  action 
of  the  acid  alone,  I  found  in  my  experiments  that  the  whole  cell  contents 
died  quickly  and  were  deposited  on  the  wall. 

Of  the  tar  compounds,  pyridine  was  found  in  fog  in  especially  large 
amounts.  When  exposed  to  vapors  of  this  substance,  the  leaves  became 
Hmp  and  a  darker  green.  The  cells  were  plasmolyzed;  the  cyptoplasm  in 
the  epidermis  had  turned  brown,  but  the  chlorophyll  did  not  change.     As  a 


1  Yearbook  of  the  Dept.  of  Agriculture,  1899,  p.  463. 

2  Oliver,  F.  W.,  On  the  effects  of  urban  fog  upon  cultivated  plants.  Journ. 
Hortic.  Soc.  Vol.  16,  1893;  cit.  Zeitschr.  f.  Pflanzenkrankh.  1893,  p.  224,  und  Gard. 
Chron.  12,  1892,  p.  21,  594,  648,  etc. 


460 

rule,  wherever  a  brown  coloration  occurred,  tannin  was  found  in  the  cells. 
The  penetration  of  pyridine,  like  that  of  sulfuric  acid,  takes  place  chiefly 
through  the  stomata.  Very  similar  effects  were  found  also,  due  to  sub- 
stances related  to  pyridine,  such  as  picoUne,  lutidine,  nicotine,  thiophene,  etc. 

Phenol  attacks  the  foliage  very  vigorously  in  aqueous  solution  as  also 
in  the  form  of  vapor,  with  strong  plasmolysis  and  a  brown  coloration  of  the 
protoplasm  and  chloroplasts. 

The  blossoms  behaved  very  differently  in  relation  to  fog;  at  times  they 
showed  considerable  difference  in  two  varieties  of  the  genus  and,  in  fact,  in 
different  petals  of  the  same  blossoms.  Tulips,  hyacinths  and  narcissus  were 
very  resistant. 

It  is  interesting  that,  as  a  result  of  the  lack  of  light  connected  with  the 
fog,  whereby  assimilation,  transpiration  and  respiration  are  repressed,  a 
peculiar  yellow-spotted  condition  often  sets  in.  In  this,  there  is  an  accumu- 
lation of  the  acid  content  (because,  with  the  decreased  respiration,  less 
organic  acids  are  burned)  and  an  increase  of  turgescence  connected  with 
this  se>ems  to  lead  to  cell  elongation  in  the  mesophyll  (aurigo). 

Thus,  in  considering  the  effect  of  fogs,  we  have  to  consider  two  injuri- 
ous factors,  the  decreased  light  and  the  action  of  the  poisonous  substances. 
This  becomes  the  more  dangerous  the  greater  the  plant's  need  of  light. 
Plants  adjusted  to  a  lesser  supply  of  light  (ferns)  are  less  sensitive. 

Only  in  greenhouses  can  the  injurious  effect  of  such  fogs  be  lessened, 
and  this  has  been  done  in  England.  Special  purifying  apparatus  is  made 
use  of  (fog  annihilators),  with  which  the  air  entering  the  greenhouse  is 
passed  over  strongly  absorbing  substances  (charcoal).  For  out  of  door 
planting  only  a  choice  of  resistant  species  can  come  under  consideration. 


CHAPTER  VII. 


RAINSTORMS. 

The  injurious  effects  of  beating  rains  on  the  soil  have  already  been 
mentioned.  They  pound  the  upper  surface  down  or  cover  it  with  great 
quantities  of  silt.  The  immediate  result  is  oxygen  starvation  for  the  roots. 
The  mechanical  effect  of  heavy  rains  on  the  plant  itself  is  first  to  be  con- 
sidered. There  are  many  natural  devices  in  plants  which  safeguard  the 
leaves  from  the  beating  and  tearing  effects  of  heavy  rains  or  the  undue 
accumulation  of  water  from  long  continued  gentle  rains.  Stahl^  and 
Jungner-  have  given  a  thorough  presentation  of  these  conditions  and  call 
attention  to  the  formation  of  the  tips  and  to  the  position  and  repeated 
division  of  the  leaf  surface,  etc. 

The  direct  results  of  the  rain  are  a  decrease  of  transpiration  and  a  great 
water  absorption  by  the  roots.  They  have  been  less  considered.  Here  also 
the  swelling  of  the  wood  of  trees  belongs.  Friedrich's  investigations^  show 
that  a  constant  swelling  of  the  tree  trunk  (aside  from  any  direct  growth) 
takes  place  during  the  night  because  with  lessened  transpiration,  the  tree 
swells,  while  in  the  daytime  it  shrinks.  The  differences  will  be  most  marked 
when  the  growth  is  rapid  and  the  wood  swells,  especially  when  rain  comes 
after  considerable  drought.  Bark  and  periderm  are  less  affected.  Growth 
and  swelling  of  the  wood  cylinder  are  regulated  by  the  influence  of  atmos- 
pheric humidity  on  the  tops  of  the  trees. 

It  is  thus  easily  evident  that  smooth  bark  will  crack  in  places  because 
of  the  strong  and  sudden  increase  in  swelling  and  growth.  When  the  soil 
is  rich  and  the  atmospheric  humidity  great,  these  cracks  may  become  open 
wounds,  constantly  increasing  by  bacterial  infection.  Rough  places  then 
arise  on  the  bark  of  the  young  tree  trunks.  These  may  be  observed,  for 
example,  in  lindens,  elms,  ashes,  maples,  etc.,  near  wet  ditches  and  ponds. 

The  influence  of  longer  periods  of  rain  manifests  itself  in  herbaceous 
plants,  even  more  than  in  woody  ones,  by  cracks  in  fruit  and  stems.     Among 


1  Stahl.  B.,  Regenfall  und  Blattgestalt.  Ein  Beitrag-  zur  Pflanzenbiologie. 
Annal.  de  Buitenzorg.;   cit.  Bot.  Jahresber.  1893,  1,  p.  49. 

-  .Jungner,  J.  R.,  Om  regnblad,  daggblad  och  snoblad.  Bot.  Not.;  cit.  Botan. 
Jahresber.  1893,  p.  49. 

3  Freidrich,  Josef,  Uber  den  Einfluss  der  Witterung  auf  den  Baumzuwachs. 
Mitteil.  lib.  d.  forstl.  Versuchswesen  Osterreichs.  Wein  1897,  Part  22. 


462 

our  vegetative  plants,  the  splitting  of  cucumbers  is  most  important.  The 
fruit  suffered  most  of  all,  but  sometimes  the  stems  also  cracked.  Decreased 
temperature,  accompanied  by  continued  rain,  not  infrequently  causes  the 
total  failure  of  harvests,  since  the  cucumbers  often  show  gummosis  and  are 
attacked  by  various  black  fungi. 

Long,  cool  rain}^  periods  also  cause  a  j)remature  leaf  fall,  badly  devel- 
oped heads  in  grain,  a  small  amount  of  sugar  and  starch  in  beets,  tubers,  etc. 

Repeated  showers  have  a  very  disastrous  effect  when  they  fall  on 
blossoming  fruit  trees  and  during  the  setting  of  the  seeds  of  field  crops.  In 
the  first  place,  the  insects,  necessary  for  fertilization,  cannot  fly  about  so 
freely,  and  secondly,  the  anthers  will  not  open  so  well,  nor  will  the  pollen 
grains  stick  so  well  on  the  stigma. 

Nevertheless,  the  theor}'-  that  the  increase  of  bacteria  and  fungi  is 
always  favored  by  periods  of  rain  does  not  hold  absolutely.  Parasitic 
diseases  usually  increase  only  if  tiie  rain  is  accompanied  by  warmth.  On 
the  other  hand,  cold  wet  weather  retards  the  growth  of  the  most  important 
parasites  (rusts,  false  mildew,  etc.). 

In  tropical  regions,  however,  rain  storms  usually  favor  the  development 
of  fungous  diseases  and,  to  give  at  least  one  example,  we  will  mention 
Busse's  observations^  He  found  that  the  Phytophthora  decay  on  the  cocoa 
fruits  was  especialy  marked  in  rainy  years.  The  amount  of  rain  is  not 
decisive  but  rather  the  character  of  the  storm.  Mighty  gusts  of  rain  seem 
to  keep  the  fungus  spores  from  settling  on  the  smooth-shelled  fruit ;  but  the 
softer,  more  frequent  rains,  easily  producing  stagnant  moisture  in  the  de- 
pressions in  tlie  soil  and  in  the  regions  w^here  the  drainage  is  poor,  have 
proved  favorable  for  the  fungi.  Those  regions  suffer  less  to  which  the  fresh 
sea  breezes  or  some  wind  has  unhindered  access. 

Among  cultivated  plants  in  rainy  seasons,  the  wind  is  a  helpful  agent 
in  the  struggle  against  parasites.  This  helpful  agent  has  never  been  suffi- 
ciently credited  for  its  work.  The  tops  of  trees  should  be  freed  of  excessive 
water  by  frequent  shaking.  This  should  be  done  especially  in  closely  planted 
orchards  and  in  warm  rainy  periods. 


1   Busse,  W.,   Reisebericht   der   pflanzenpatholog-ischen   Expedition   d.    kolonial- 
wirtschaftl.  Komitees  nach  Westafrika.     Tropenpflanzer  1905,  p.  25. 


CHAPTER  VIII. 


HAIL. 


All  injuries  from  hail  form  wounds,  with  a  consequent  loss  of  sub- 
stance ;  any  chemical  action  as  a  result  of  the  cold  of  the  hailstones  cannot 
be  demonstrated ;  only  the  mechanical  blow  which  either  tears  away  various 
parts  of  the  tissue  and,  by  drying,  causes  them  to  go  to  pieces,  or  slits  the 
leaves  and  branches  in  knocking  off  more  or  less  large  pieces. 

The  small  piece  of  rye-blade,  which  is  shown  here,  has  been  struck  by 
hail  at  the  points  g,  ::  and  v,  and  shows  the  effects  of  the  blows  of  the  hail 
stones.  In  considering  such  a  section  after  a  hail  storm  which  has  not  been 
severe  enough  to  knock  off  the  leaves,  or  heads,  or  to  break  the  whole  stalk, 
we  find,  as  every  one  knows,  whitish  or  white  spots  on  the  green  striped 
upper  surface.  The  striping  is  produced  by  alternate  dark  green  furrows 
and  lighter  colored  lines.  In  cross-section,  it  is  seen  that  these  furrows 
consist  of  a  soft  bark  parenchyma,  containing  chlorophyll,  while  the  lighter 
colored  stripes  are  composed  of  thick-w^alled  fibre-like  cells  (p).  These 
fibre  strands  stiffen  the  blade.  The  thicker  their  walls  are,  the  more  re- 
sistant the  blade  is  and  the  less  inclined  to  fall.  In  Fig.  91,  the  green 
parts  are  seen  to  be  changed  most.  The  cells  at  g  appear  uninjured ;  at  a 
only  dry  cell  walls  are  found,  which  are  connected  with  one  another  by  a 
scaffolding-like  structure.  Toward  the  centre  of  the  blade,  however,  there 
is  green  living  tissue  (u).  Here,  the  blow  of  the  hailstone  has  not  destroyed 
the  epidermis  (^)  at  all,,  but  has  bruised  the  more  delicate  bark  parenchyma 
underlying  it  so  that  part  of  the  cells  have  died.  Only  a  few  pieces  of  the 
cell  walls  of  the  former  juicy  bark  tissue  remain  and,  at  this  point  the  hail- 
stone has  had  such  force  that  it  has  broken  the  thick-walled,  tough  epidermis 
at  0.  Air  has  entered  through  this  opening  and  this  hail  spot  appears  white 
to  the  naked  eye,  Avhile  at  m  a  greenish  tone  may  still  be  noticed. 

Similarly,  the  loss  of  tissue  will  take  place  in  other  parenchymatous 
parts  of  the  plant  and  the  assimilatory  activity  will  fall  according  to  the 
severity  of  this  loss.  Yet,  this  reduction  of  the  life-activity  may  become  of 
great  influence  only  if  the  hail  storm  sets  in  at  a  time  when  vegetative 
growth  has  stopped  and  the  plant  has  entered  upon  the  reproductive  period, 
when  it  withdraws  the  cytoplastic  substance  from  the  leaves. 


464 

C.  Kraus^  made  his  observations  on  barley  and  describes  the  effect  of 
hail  storms  on  the  grain.  He  found  many  heads  greatly  bent  backward  and 
turned,  since,  after  the  buds  had  been  hit  by  hailstones,  they  were  so  bruised 
that  only  the  furtherest  developed  could  free  their  tips  from  the  outermost 
leaf  sheathing.  Heads  which  had  been  hit  directly  were  retarded  in  their 
whole  development;  the  kernels  were  lighter,  not  uniform  and  often  tipped 
with  black.  The  weight  of  the  heads  was  about  38  per  cent,  of  the  normal, 
that  of  the  grains  about  43  per  cent.  Kraus  found  similar  conditions  in 
two  unbearded  wheats,  in  which,  however,  because  of  the  absence  of  beards, 
the  heads  had  worked  their  way  more  easily  out  of  the  uppermost  leaf  sheath. 
Accordingly  the  weight  of  heads  of  wheat  struck  by  hail  was  only  about 


Fig-,   rtl.     The  effect   of  hail  on  a  blade   of  rye.     (Orig.) 

£■  healthy  Rreeii  tissue,  z  tissue   injured   by  a   hail-stone,  u  adjoining   healthy   tissue,  v  completely 

destroyed   hark   of    the   blade   with   ruptured   outer  membrane   («),   h  parenchyma  of  the  blade,   b 

vascular  buadle.  p  ropes  of  cells  resembling  bast  fibres. 


24  and  15  per  cent,  and  the  weight  of  the  grains  about  2-]  and  17  per  cent, 
less  than  normal. 

When  the  hail  storm  occurs  early  in  the  year,  i.  e.,  perhaps  in  May, 
many  shorter  green  glades  bent  at  the  base  are  found  later  between  the 
ripening,  ujtright  ones  covered  with  hail  spots.  The  hailstone  had  probably 
bent  the  plant  and  the  blade  required  more  time  to  straighten  and  this  had 
delayed  ripening. 

WHieat  seems  to  be  the  most  robust.  I  observed  after  a  hail  storm  in 
June,  1905,  that  rye  blades  showed  the  injuries  represented  in  Fig.  91,  while 
in  the  corresponding  cell  groups  of  the  wheat,  the  inner  tissue  was  split  by 


1   Kraus,    C,    Wirkung    von    Hagelschltigen.     Deutsche    Landwirtschaftl.Presse 
1899,  Nos.  14-15. 


465 


only  one  tear  or  was  not  injured.     The  epidermis  was  not  torn,  but  only  the 
walls  and  contents  were  browned. 

The  heads  were  broken  in  a  very  charac- 
teristic way.  Fig.  92  shows  a  slight  breaking, 
with  the  axis  making  an  obtuse  angle  (h).  In 
the  more  severely  injured  heads,  the  axis  was 
bent  two  or  three  times,  and  where  bent  was 
almost  bare. 

Fig.  93  shows  the  construction  of  the  axis 
where  bent :  g,  ducts ;  2,  torn  parenchyma ;  i', 
a  vascular  bundle,  which  has  been  killed. 
Laterally  from  this,  at  br,  the  tissue  as  a  whole 
was  a  deep  brown.  Where  other  heads  had 
been  hit  the  epidermis  was  torn  open ;  the 
bordering  tissue  had  collapsed,  fallen  to  pieces 
and  turned  brown.  Some  vascular  bundles 
were  found  to  be  almost  entirely  isolated,  since 
the  torn  or  disintegrated  parenchyma  had 
cracked  ofT.  This  might  be  a  result  of  ten- 
sion, since  later  the  still  green  heads  continued 
their  growth.  The  injuries  vary  very  greatly 
according  to  the  way  the  hailstones  strike. 
Kraus's  observation  shows  that  after  the  hail- 
stone had  struck  the  head  before  it  had  become 
rid  of  the  leaf  sheath,  the  beards  remained 
where  they  were.  Therefore,  the  head  ap- 
peared bent  like  a  bow.  The  injuries  usually 
were  at  the  points  where  the  young  heads  are 
attached  rather  than  in  the  internodes  of  the 
axes. 

Oats  will  endure  severe  injuries  if  the 
panicles  are  still  enclosed  in  the  upper  leaf 
sheath  when  the  hail  storm  strikes  them.  Per- 
fectly sterile  heads  may  be  produced  and  the 
injury  to  the  plants  resembles  that  of  thrip  so 
much  as  to  lead  to  confusion.  In  some  years 
I  have  often  found  twisted  barley  heads  due 
to  the  sucking  of  thrip.  PuppeU  has  often 
studied  the  effect  of  mechanical  blows  and  his 
illustrations  are  very  helpful.  For  example, 
with  a  heavy  smooth  roller,  he  flattened  a  field 
of  young  winter  rye  which  had  not  yet  formed 
a  blade.  When  the  heads  began  to  develop, 
they  were  deformed  exactly  as  if  they  had  been  injured  by  hail. 

1  Puppel,  Max,  Hagel-  und  Insektenschadeu.    40  plates  from  original  photogr 


Fig.  92.    Head  of  wheat  broken 

by  hail.  The  grains  have  fallen 

at  the  broken  place,  leaving  it 

bare.     (Orig.) 


iphs. 


466 

Wheat,  hit  by  hail  on  the  4th  of  June,  was  peculiarly  injured.  Besides 
the  well  known  hail  wounds,  plants  were  found  scattered  throughout  the 
field  with  a  green  appearance  and  almost  empty  heads.  In  July,  the  kernels 
present  were  still  green  and  milky.  The  heads,  as  a  whole  appeared  a  light 
leather-brown,  due  to  the  discoloring  of  almost  all  the  glumes.  Among 
these  were  found  short,  fresh  green  tips  which  belonged  to  the  sprouted 
small  heads.  These  contained  six  to  eight  blossom  primordia,  not  one  of 
which  had  developed,  and  the  uppermost  showed  only  the  beginnings  of  the 
anthers.  The  glumes  were  lancet-like,  dark  green  and  as  soft  as  any 
herbaceous  growth,  so  that  a  distinct  transition  to  a  foliage  character  was 
recognizable.  In  one  case  young  plants  had  actually  sprouted  out  of  the 
base  of  some  small  heads. 

Behrens^  observed  similar  conditions  in  hops  after  a  hail  storm  occur- 
ring on  the  first  of  July.     Four  weeks  later  the  blossoming  catkins  opened 


Fig. 


Cross-section  through  the  stalk  of  the  wheat  head  of  th( 
at  the  place  broken  by  hail   (h).     (Orig  ) 


•vious  figure, 


and  contained  only  leaflets.  The  author's  experiments  connect  this  trans- 
formation of  the  inflorescence  actually  with  the  destruction  of  the  leaves 
by  hail.  On  vines  from  which  the  leaves  had  been  stripped,  the  so-called 
brausche  hops  grcAV  (see  p.  344),  while  on  the  stems  on  the  same  place 
which  had  not  been  stripped,  catkins  developed  normally. 

In  potatoes,  it  has  been  observed  that  injuries  due  to  hail  reduce  the 
starch  content  of  the  tubers-.  Injury  to  the  pods  may  seriously  afifect  rape. 
It  is  a  matter  of  course  that,  in  all  cultivated  herbaceous  plants,  the  destruc- 
tion of  the  leaf  must  afifect  the  yield — even  to  the  loss  of  the  harvest.  // 
would  be  a  mistake  to  remove  foliage  injured  by  hail.  Experiments  with 
cabbage  plants  showed  that  better  heads  were  obtained  when  the  injured 
foliage  had  been  left  than  when  it  had  been  removed. 

1  Zeitschr.  f.  Pflanzenkrankh.  1896,  p.  111. 

2  Jahresber.  d.  Sonderausschusses  f.  Pflanschutz  1903,  p.  94. 


467 


Internal  injuries  in  juicy  fruits,  caused  by  hail,  are  interesting.  Fig. 
94  shows  a  cross-section  of  a  tomato  fruit  skin  struck  by  hail.  We  notice 
at  the  left,  the  actual  place  hit,  a  hard,  dry  dark-brown  excrescence, 
the  blow  of  the  hailstone  did  not  destroy  the  epidermis  (e).  The  more 
tender  sub-epidermal  tissue  was  fatally  bruised  and  consequently  turned 
brown  and  dried  (t).  As  a  result  of  the  further  process  of  swelling,  the 
tissue  of  the  still  unripe  fruit  is  torn  and  transformed  to  a  hard  cyst. 

Besides  this  injury,  which  is  most  strikingly  noticeable,  however,  a 
second  hard  place  is  found  in  the  juicy  flesh  of  the  fruit  surrounding  a 
vascular  bundle   ((/).     The  hardness  of  the  tissue  arises  here  because  of 


Fig-.  94.     Cross-section  throug-li  the  fruit  wall  of  a  tomato  strucli  by  hail.     (Orig-.) 

e  epidermis  of  the  outside  of  the  fruit,  />'  epidermis  of  the  inside  of  the  fruit  wall.  7i'  dead  edge  of  the  wound 
cut  oiT  from  the  living  tissue  by  plate  cork  W,  r  cells  elongated  radially  and  in  part  forming  dividing  walls, 
in  normal  cells  of  the  fruit  flesh. /the  beginning  of  the  formation  of  plate  cork,  g  vascular  bundle,  /t  vas- 
cular bundle  sheath,  «  division  of  the  cells  which  are  over-elongated  radially  to  form  a  vascular  bundle. 
k  zone  of  cork  tissue,  s/  starch,  z  collapsed  cells  with  swollen  cork  walls. 


suberization,  which  has  affected  the  whole  spot  after  the  cells  had  begun  to 
elongate  and  divide  freely  in  the  vicinity  of  the  bundles.  This  has  probably 
been  initiated  by  the  change  in  a  ring-like  zone  (s)  at  a  definite  distance 
from  the  vascular  bundle  due  to  the  blow  from  the  hailstone  or  its  after 
effect.  Some  of  the  cells  have  collapsed  from  the  swelling  and  suberization 
of  the  walls ;  in  other  cells,  the  walls  have  only  swelled,  while  the  walls  of 
the  adjacent  cells  have  only  been  suberized.  When  the  hail  fell,  the  fruit 
was  still  green  and  rich  in  starch  and,  during  suberization,  the  starch  was 
retained  in  the  irritated  tissue  zone,  while,  during  the  ripening,  it  has  disap- 
peared from  the  rest  of  the  fruit  flesh.  On  this  account,  we  see  a  ring 
drawn  about  the  vascular  bundle,  composed  of  deep  brown  tissue  filled  with 
starch  (st). 


468 

Because  these  cells  die  and  partially  collapse,  they  make  possible  the 
elongation  of  the  cells  lying  directly  about  the  vascular  bundle  and  rich  in 
water.  They  have  elongated  in  an  approximately  radial  direction,  begin- 
ning at  the  sheath  of  the  vascular  bundle  (h)  and  have  divided  by  parallel 
cross-walls  (w).  Besides  the  actual  place  of  injury,  the  parenchyma  of 
the  fruit  wall  has  also  participated  in  the  radial  elongation  (r)  and  only 
the  inner  flesh  remains  normal.  On  the  boundary  between  the  normal  and 
the  over-elongated  tissue  a  formation  of  flat  cork  (/)  began  at  the  time  of 
the  observation.  Joining  the  corked  internal  spot,  this  forms  a  consistent 
tough  mass. 

vSimilar  cork  places  are  met  with  in  pomes,  such  as  apples.  Here,  too, 
the  blow  from  hail  often  causes  no  open  wounds,  especially  in  unripe  fruit. 
We  find  only  depressed  places,  which  later  turn  practically  brown.  The 
depression  is  produced  by  the  bruising  of  the  parenchyma  of  the  apple  skin, 
lying  under  the  epidermis  which  has  not  been  injured,  and.  as  a  result  of 
which,  it  has  dried  and  split,  usually  in  radial  cracks.  Here,  as  in  the 
tomato,  the  starch  has  been  retained  in  the  corked  tissue,  adjacent  to  the 
hail  wound,  in  case  the  apple  was  still  green  when  struck  by  the  hail.  In 
this  case,  irregular  zones  of  cork  cells  in  the  form  of  an  hour  glass  are 
often  developed  later,  which  cut  ofif  the  whole  internal  hail  wound  from  the 
healthy  flesh  of  the  fruit. 

Most  significant  are  the  bark  injuries  due  to  hail,  which,  in  themselves, 
as  a  rule,  are  of  slight  extent,  but  represent  considerable  damage  because 
of  their  frequency.  So  far  as  I  have  had  opportunity  of  observing  these 
injuries  in  fruit  trees,  I  have  found  that  the  disturbance  in  the  tissue  has 
not  been  confined  simply  to  the  bruised  place  but  has  also  spread  laterally. 
In  hail  wounds  on  the  one  year  old  twigs  of  the  current  year,  on  which  they 
cause  relatively  the  most  considerable  injury,  the  disturbance  spreads  later- 
ally from  the  actual  place  of  injury  in  the  form  of  a  softening  of  the  bark. 
As  a  result  of  this  wc  see,  in  cross-section,  stripes  of  parenchyma  extending 
from  the  dead  zone  outward,  and  usually  filled  with  starch,  pushing  into 
the  normal  wood  and  softening  it.  It  thus  acquires  brittle  and  crumbly 
properties,  which  may  be  of  special  importance  in  those  trees  whose  twigs 
are  used  as  tying  and  braiding  materials  (willows  and  birch).  Wounds,  due 
to  hail,  may  often  be  distinguished  from  the  injuries  due  to  frost  by  their 
position  in  the  annual  ring.  Since  hail  usually  occurs  in  the  hot  season,  the 
wounds  lie  near  the  end  of  the  annual  ring,  while  frost  injuries  appear  in 
the  spring  wood.  It  is  striking  that  beneath  the  places  hit  by  hail  in  the 
twig  of  the  current  year's  growth,  upon  which  frost  cannot  have  acted  at 
all,  one  finds  at  times  in  the  radius  of  the  wounded  place,  that  the  pith  is 
browned  and  the  spiral  vessels  greatly  discolored,  since  the  wood  of  the 
vascular  bundle,  lying  between  the  injury  and  the  pith  crown,  is  healthy. 
The  only  possible  conclusion  is  that  the  disturbance  extends  back  toward 
the  pitli  through  the  medullary  rays. 


469 

Often  hail  wounds  may  be  distinguished  from  frost  wounds  because 
straight  lined  normal  wood,  with  numerous  vessels,  very  soon  appears  again, 
while,  when  the  frost  cracks  heal,  broad  zones  of  parenchymatous  wood 
may  be  found,  due  to  the  great  extension  of  the  adjacent  edges.  When  the 
hail  injury  is  slight,  the  bark  is  not  uniformly  destroyed,  and  the  cambium 
continues  growing  with  many  gaps. 

When  bark  has  been  injured  it  peels  at  this  point  very  unevenly  and 
unsatisfactorily  from  the  wood.  This  has  an  economic  effect,  since,  when 
oak  is  grown  for  the  commercial  use  of  the  bark,  the  shoots,  struck  by  hail, 
peel  very  "unsatisfactorily. 

Often  hail  wounds  provide  openings  for  other  diseases.  If  wet  weather 
prevails  for  some  time  after  the  hail  storm,  decomposition  frequently  sets 
in,  due  to  attacks  of  fungi,  etc.  In  the  Amygdalaceae  an  exudation  of  gum 
may  set  in.  .Such  secondary  diseases  may  later  destroy  the  branches.  If 
this  dying  back  extends  to  tlie  top  shoots  of  young  trees,  deformed  tops  or, 
in  seedlings,  crippled  trunks  are  of  frequent  occurrence. 

In  fruit  nurseries,  after  a  severe  hail  storm  which  has  greatly  injured 
the  smooth  barked  trunks,  these  trunks  should  be  pruned  back  almost  to  the 
bud,  thus  renewing  the  stem.  When  the  tops  of  older  trees  have  been  badly 
broken  and  deformed  by  hailstones,  it  is  advisable  to  try  to  reform  the  top 
by  severe  pruning  in  the  following  spring.  Ordinarily,  the  power  of  regen- 
eration is  so  great  in  trees  that  hail  wounds  heal  over  easily,  but  when  large 
pieces  have  been  torn  from  smooth  barked  trees  by  the  incessant  beating  of 
hailstones,  it  will  be  necessary  to  hasten  the  closing  of  the  wound  by  using 
some  tree  salve.  \\'hcn  the  roughened  surfaces  of  the  hail  bruise  have  been 
made  smooth  by  cutting  with  a  sharp  knife,  they  will  heal  more  easily. 
Then  a  mixture  of  loam  and  cow-manure,  free  from  straw,  with  ashes  or 
powdered  slate  kneaded  into  the  form  of  a  salve,  should  be  used. 

With  the  present  mania  of  wishing  to  cure  everything  by  manuring  the 
soil,  it  is  not  surprising  that,  even  in  extensive  injuries,  as  from  storms  and 
hail,  with  a  loss  of  substance,  fertilizers  will  be  applied  at  once.  We  would 
caution  against  the  use  of  this ;  even  on  poor  soil,  fertilizers  should  be  used 
only  when  the  tree  has  already  made  new  growth.  Large  wounds  which 
will  take  some  time  for  healing,  are  best  closed  by  painting  with  tree-wax, 
which  flows  when  cold,  i.  e.,  with  a  mixture  of  resin,  which  thus  prevents 
the  entrance  of  water.     It  is  cheaper  to  coat  the  wound  with  coal  tar. 

In  connection  with  fruit  trees  and  grapevines,  Miiller-Thurgau  empha- 
sizes our  warning  in  regard  to  retaining  the  foliage  in  vegetative  plants 
which  has  been  injured  by  haiP. 

In  growing  grapes,  a  certain  hard  flavor  is  mentioned".  This  is  sup- 
posedly the  result  of  a  fungous  infection  of  the  places  when  hail  has  injured 
the  grapes.     These  grapes  should  be  cut  out,  though  the  work  is  very  tire- 

1   Miiller-Thurgau,    Beobachtungen    liber    Hagelschaden    an    Obst))aumen    und 
Reben.  VII.  Jahre.sber.  d.  Versuchsstation  zu  Wadenswell. 

-   Chronique  agricole  du  Canton  de  Vaud  vom  10  August,  1S95. 


4/0 

some.  The  broken  cluster  closes  again  completely  as  the  grapes  left  grow  so 
much  the  larger.  If  the  injured  vine  is  to  be  pruned,  this  should  be  begun, 
at  the  earliest,  a  week  after  the  hail  storm  in  order  to  see  how  far  the  plants 
have  recovered.  In  pruning,  as  much  growth  of  the  current  year  as  possible 
should  be  left.  It  is  especially  important  not  to  force  prematurely  lower 
eyes  which  promise  fruit.  By  using  precaution'  at  least  twice  as  many  eyes 
are  left  on  the  vine  above  the  real  fruiting  eyes  as  are  needed  in  the  follow- 
ing year. 

The  method  of  spreading  nets  of  galvanized  iron  wire  over  the  vines, 
said  to  be  customary  in  Piedmont,  should  be  recommended  for  further  test- 
ing, as  a  means  of  protecting  the  vines  from  injury-. 

Recently  many  experiments  have  been  tried  with  "cannonading  against 
hail."  Nolibois^  developed  the  theory  of  this  method.  The  water  vapors 
arising  from  the  soil  are  condensed  into  clouds,  the  moist  dense  layers  lying 
lowest.  When  these  lower  layers  are  greatly  condensed  by  the  radiation  of 
the  soil,  the  layers  directly  above  them  are  cooled  greatly,  occasionally  below 
zero.  Any  shock  is  now  sufificient  to  bring  the  overcooled  mist  to  freezing 
and  precipitation.  If  the  process  is  continued,  there  is  a  constant  weakening 
of  the  cold  action  in  the  upper  cloud  layers,  resulting  finally  in  rain. 

According  to  this  theory,  declivities  would  be  more  exposed  to  hail  than 
lowlands ;  lime  or  sandy  soil  more  than  moist  alluvial  soil ;  bare  soil  more 
than  forests;  land  more  than  lakes  or  the  ocean.  If  superimposed  cloud 
layers  could  mingle  one  with  another  so  that  the  temperature  is  more  equal- 
ized, and  over-cooling  hindered,  the  formation  of  hail  might  be  prevented. 
Attempts  are  now  being  made  to  produce  such  movement  of  the  layers  of 
the  air  adjacent  to  the  clouds,  by  the  explosion  of  cannon. 

Another  theory  based  on  the  production  of  whirlwinds  resulting  from 
the  mingling  of  cold  air  from  the  mountain  with  the  hot,  rising  stream  of 
the  valley*,  likewise  recommends  cannonading  against  hail.  In  Italy  numer- 
ous shooting  stations  have  already  been  formed,  yet  the  reports  are  very 
contradictory.  More  favorable  reports  on  the  cannonading  of  the  air  have 
been  sent  from  France^ 


1  Ungarische  Weinzeitung  1896,  No.  34. 

2  Rho,  G.,  Le  reti  metalliche  a  dife.sa  dellc  viti  dalla  grasnuola.  Bollet.  d. 
Soc.  dei  Viticoltori.     Roma  1892;   cit.  Zeitschr.  f.  Pflanzenkrankh.  1894,  p.  168. 

a  Nolibois,  P.,  Th^orie  de  la  formation  de  la  grele;  cit.  Hollrungs  Jahresber. 
f.  Pflanzenkrankh.  1904,  p.  73. 

•*  Bordiga,  O.,  Grandine  e  sari.  Atti  del  R.  Istituto  d'incorraggiamento,  Napoli, 
Vol.  II,  5  Sen 

6   Praktische  Blatter  f.  Pflanzenschutz,  herausg.  von  Hiltner,  1905,  No.  11, 


CHAPTER  IX. 


WIND. 


Among  the  sudden  effects  of  severe  wind  are  the  injuries  known  as 
"uprooting  of  trees  by  wind"  and  "breaking  of  tree  trunks  by  wind."  In 
the  first,  the  trunks  of  the  trees  are  thrown  over  to  one  side,  taking  the  root 
systems  with  them.  In  the  second,  which  is  economically  more  injurious, 
the  trunk  is  broken  off. 

The  action  of  the  storm  depends  upon  the  variety  of  the  trees,  the 
stiffness  of  the  individual  trunk  and  its  location.  In  regard  to  the  variety, 
it  may  be  remarked  that  tough  wooded  genera,  like  birch,  spruce,  hornbean 
and  redbeech  are  more  often  overthrown  than  broken.  Pines  and  oaks 
break  more  easily.  The  kind  of  break  also  differs  with  the  genus.  It 
seems  as  if  pines  break  off  shorter,  while  the  oak  splinters  and  the  brittle 
acacia  often  shows  deep  clefts  on  the  stump,  extending  downward  from  the 
broken  surface.  In  regard  to  the  individual  firmness  of  the  trunk  in  the 
same  variety,  it  is  evident  that  trees,  rotten  at  the  core,  break  most  easily. 
The  individual  structure  of  the  tree  top.  which  forms  the  chief  point  attacked 
in  the  lever  represented  by  the  trunk,  is  likewise  of  importance.  The 
position  and  the  local  conditions  influencing  the  structure  of  the  root  system, 
essentially  under  consideration  here,  are  of  the  most  extensive  influence.  In 
deep  soil,  those  trees  will  endure  more  wind  which  have  not  been  trans- 
planted, since  in  transplanting  the  tap  root  has  been  cut  off  to  make  the 
moving  easier.  In  shallow  soil,  the  advantage  of  the  tap  root  is  lost  and 
the  development  of  the  top  becomes  the  important  factor.  The  higher  the 
branching  begins  on  the  otherwise  smooth  trunk,  the  higher  is  the  centre  of 
gravity,  and  the  more  liable  the  tree  is  to  be  uprooted  or  broken.  Pyra- 
midal crowns  are  therefore  probably  better  than  those  of  a  dense  spherical 
form.  There  are  naturally  exceptions  to  the  rule;  the  more  exposed  the 
location  of  the  tree,  the  greater  the  danger  of  injury.  On  mountain  slopes 
it  is  often  noticed  that  injury  due  to  storms,  especially  in  uprooting  the 
trees,  is  far  less  extensive  on  the  windy  side  than  on  slopes  on  which  the 
storm  passes  downward.  Further,  whole  groups  will  be  overthrown  often 
in  the  centre  of  an  uniformly  old  tract  of  trees.  This  may  be  explained  by 
the  fact  that  the  wind,  in  blowing  upward,  is  more  uneven  and  can  effect 
only  a  small  part  of  the  crown  of  one  tree  because  another  standing  lower 


4/2 

down  on  the  declivity  is  directly  in  front  of  it.  This  rising  of  the  tree  tops 
in  tiers  can  often  be  perceived  in  forested  level  costal  regions.  Only,  here 
the  terracing  of  the  tree  tops  is  not  produced  by  inequalities  of  the  soil  and 
trunks  equally  tall,  but  by  a  different  height  of  the  trunks,  on  level  soil.  It 
is  noticed  that  where  coast  winds  strike  the  trees,  the  outer  trees  do  not 
grow  tall,  but  are  kept  down  like  shrubs.  Only  at  some  distance  behind 
these,  and  increasing  with  the  distance,  do  they  grow  to  the  height  of  forest 
trees.  Whirlwinds  will  overthrow  whole  groups  of  trees  in  the  centre  of 
an  uniform  tract.  A  different  natural  form  of  wind  protection  is  men- 
tioned by  Schiibeler^  (see  p.  253)  for  spruce  families,  from  the  Gudbrands- 
dai,  at  an  elevation  above  sea-level  where  the  spruces  approach  their  height 
limit.  The  trees  are  usually  arranged  in  rows  in  exposed  places,  and  in  fact 
in  such  a  way  that  the  main  trunk  stands  at  the  side  turned  toward  the  pre- 
vailing wind,  while  the  branch  suckers  form  a  pretty  straight  line  behind  ihe 
parent  tree.  Therefore,  only  where  this  parent  tree  keeps  off  the  wind  is  it 
possible  for  the  young  sucker  trees  to  grow  up. 

In  the  tropics  the  cultivation  of  cocoa  is  often  affected  by  the  wind 
storms.  Aside  from  the  indirect  losses  from  overthrow^n  shading  trees,  the 
wind  also  directly  tears  apart  the  forkings  of  the  main  branches.  Accord- 
ing to  L.  Kindt's  reports,  an  attempt  has  been  made  to  produce  tall  tree 
trunks  from  the  remains  of  the  bush  forms,  injured  by  the  wind,  by  letting 
one  of  the  many  water  sprouts  grow  up  and  then  forcing  it,  by  topping,  to 
form  branches.  This  process  has  been  found  partially  advantageous,  but 
has  been  entirely  abandoned  by  Kindt  upon  his  own  experience.  He  found 
that  in  such  an  artificial  formation  of  the  trunks,  contrary  to  the  nature  of 
the  tree,  only  scanty,  weakly  leaved  crowns  formed  of  short  horizontal 
branches  are  produced  in  which  fruits,  ripening  prematurely,  are  found  only 
on  the  trunks.  The  yield  is  not  satisfactory  quantitatively  and  ciualitatively, 
not  only  in  the  first  year,  but  also  in  subsequent  years. 

The  duration  and  time  of  the  storm,  as  well  as  the  prevailing  weather, 
should  be  taken  into  consideration.  In  rainy  periods,  the  softened  soil 
gives  way  more  easily  and  predisposes  toward  the  uprooting  of  trees  by 
wind  (see  Sewage  Fields),  while  a  spring  storm  on  frozen  soil  finds  the 
trees  more  firmly  anchored  and,  w^ith  increasing  strength,  causes  more 
windbreaks. 

Aside  from  these  gross  injuries  occurring  at  once,  however,  those 
should  also  be  recorded  which  do  not  destroy  the  existence  of  the  individual 
but  only  weaken  it  temporarily  or  permanently. 

Among  wind  damages  belongs  an  inclined  position  of  the  trunks.  The 
most  striking  and  frequent  phenomena  are  offered  by  street  trees,  especially 
where  gutters  run  along  both  sides  of  the  avenue  or  highway.  The  striking 
discovery  may  be  made  here,  that  if  the  street  runs  perpendicularly  to  the 
prevailing  direction  of  the  wind  (with  us  usually  a  west  wind),  the  most 
exposed  rows  of  trees  have  comparatively  erect  trunks,  while  those  on  the 


1  Schiibeler,  Die  Pflanzenwelt  Norwegens.     Christiania  1873-75,  p.  163. 


473 

other  side  are  more  or  less  bent,  overhanging  the  gutter  and  often  exhibiting 
a  curved  growth.  The  inequality  of  the  root  support  is  evident  from  this. 
On  the  windy  side  of  such  a  street,  where  the  wind  first  strikes  the  surface 
of  the  gutter,  the  root  system  has  developed  differently ;  on  this  side,  the 
roots  cannot  extend  as  far  but  are  strongly  fastened  wnthin  the  street  dam. 
The  wind  pressure  finds  in  this  support  a  sufficiently  strong  counterbalance  ; 
on  the  other  side  of  the  street,  the  conditions  are  reversed ;  here,  to  be  sure, 


Fig.  95, 


Two  wind  bent  and  broken  spruces;  the  tree  on  the  left  has  two  witches' 
brooms  and  three  secondary  tips.     (After  Klein.) 


the  roots  are  better  developed  in  the  street  itself,  than  on  the  side  toward  the 
gutter,  and  form  the  anchoring  apparatus  which  counteracts  the  strain  of 
the  bending  trunk.  The  propping  side  of  the  roots  lies  tow^ard  the  gutter 
and,  being  weakly  developed,  causes  the  tree  to  incline  toward  this  direction. 
It  seems,  therefore,  that  the  tap  root  planted  at  an  angle  against  the  direction 
of  the  wind  will  form  the  most  effective  protection  of  fruit  trees.  Guy  wires 
attached  on  the  windward  side  are  more  commonly  used,  and  serve  also  to 
relieve  the  strain  of  the  tree,  but  may  well  be  considered  less  useful. 


474 

This  "sabre"  or  curved  growth  is  explained  by  the  annual  bending  by 
the  wind  when  the  shoots  are  forming  in  the  spring  and  summer.  The  tip  of 
the  trunk,  continuing  its  growth  at  this  time,  tends  always  to  maintain  the 
perpendicular  position  and  bends  only  as  the  tree  is  quickly  blown  toward 
the  horizontal.  All  that  has  been  said  here,  in  reference  to  the  main  axis, 
refers  also  to  all  branches  which,  in  windy  positions,  actually  produce  a 
one-sided,  flag-like  top. 

The  flag-like  character  results  from  branches  bending  away  from  the 
wnid  (with  us  toward  the  east)  and  from  the  scanty  branching,  with  a 
considerably  longer  main  shoot,  while  the  branches  growing  against  the 
wmd  remain  shorter  and  at  times  die  back. 

Ludwig  Klein^  gives  very  instructive  examples  in  two  spruces  from 
the  pastures  above  the  road  Haldenwirthshaus-Wiedenereck.  The  trees  on 
the  windy  side  had  lost  their  branches  almost  entirely,  as  if  one-half  of  the 
top  had  been  cut  off  with  scissors  (the  pninivKj  action  of  the  wind).  This 
is  ascribed  by  Klein  to  the  drying  action  of  the  wind.  To  the  eft'ect  of  the 
wind  is  added  an  api)reciably  greater  warmth  and  consequently  increased 
transpiration. 

In  fruit  trees,  the  flag-like  tops  often  bear  fruit  only  on  their  outer 
edges,  since  the  interior  growth  is  too  dense.  When  the  trunk  has  been  con- 
siderably bent  from  the  perpendicular,  a  great  difference  in  nutrition  shows 
itself  between  the  upper  and  under  side  of  the  branch  in  the  production  of 
a  more  luxuriant  foliage  on  the  upper  half.  The  attraction  of  the  luxuriant 
wood  shoots  for  the  raw  food  substances  from  the  soil,  brought  from  the 
roots,  increases  in  proportion  to  their  (le\elopment.  The  more  they  utilize 
this  solution,  the  more  is  lost  for  the  horizontal  part  of  the  tree  top,  and 
consequently  some  branches  are  pressed  downward  and  begin  to  die,  while 
the  new  leaf  axes  shoot  upward  in  the  perpendicular  and  form  water  sprouts. 
Thus  is  caused  a  sterility  of  many  years  duration.  In  various  forest  planta- 
tions near  the  coast,  this  one-sided  development  of  the  crown  is  also  notice- 
able. The  drying  of  the  branches  at  any  rate  may  be  traced  partially  to  the 
constant  rubbing  due  to  the  wind.  The  difficulty  of  reforestration  of  coast 
stretches  should  not  be  explained  by  the  salt  content  of  the  sea  winds,  as  is 
often  done-,  but  simply  by  their  mechanical  action. 

The  stunted  forms  of  trees  on  coasts  and  upper  limits  of  the  tree  line 
is,  in  most  cases,  due  to  the  wind.  The  tips  are  partly  dried  and  broken  off 
by  the  wind.  The  weight  of  snow  on  the  branches  may  have  the  same 
result.  In  the  next  period  of  growth  the  tree  attempts  to  develop  a  new  top 
shoot  from  one  of  its  lateral  eyes,  which  succeeds  in  conifers  only  when 
there  is  local  protection,  and  only  rarely  in  stormy  regions.  As  a  result  of 
the  broken  top,  the  lateral  branches  grow  with  increased  rapidity  and  often, 


1  Klein,  Tj.,  Die  botanischen  Naturdenkmiiler  des  Gro.ssherzog-tums  Baden  usw. 
Karlsruhe  1904,  Fig.  26. 

-  Anderlind,  Leo,  Bericht  liber  die  Wirkung  des  Salzgehaltes  der  Luft  auf  die 
Seestrandskiefer  (Pinus  Pinaster).     Forstl.-naturwiss..  Zeitsch.  1897,  Part  6. 


475 

well  covered  with  needles,  lie  on  the  ground.  Preda^  describes  a  good 
example  from  the  Livornian  coasts.  Besides  the  slanting  trunks,  varieties 
of  pine  and  holly  Juniperus  phoenicea  and  Tamarix  gallica  are  found  bent 
like  snakes  and  the  interwoven  branches  of  Phillyrea  and  other  bushes 
creep  over  the  ground.  Hansen-  gives  a  very  similar  description  from  the 
Island  of  St.  Honorat  near  Cannes. 

Bernhardt"  characterizes  certain  regions  in  Germany  as  centres  espe- 
cially frequently  visited  by  storms.  As  examples  should  be  named  Schwedt 
a.  O.,  the  Silesian  mountains,  the  Bavarian  and  upper  Palatinate  forests,  the 
forests  of  Franconia  and,  in  a  limited  way,  also  the  North  German  coast 
(Mechlenburg,  Holstein).  In  these  coast  lands,  northeast  storms  in  general 
prevail  as  frequently  as  west  and  northwest  storms,  while  in  Southern  Ger- 
many, west  and  southwest  winds  have  a  decided  preponderance ;  in  North- 
ern Germany,  as  a  whole,  west  and  northwest  winds. 

It  is  certain  that  the  distribution  of  plants  will  adjust  itself  to  the  wind 
conditions,  since  the  varieties  which  withstand  wind  better  have  survived. 
Schroter  and  Kirchner*  quote,  for  example,  Miiller's  explanation  of  the  dis- 
tribution of  the  tree-like  mountain  pine  {Pinus  niontana)  in  the  Alps.  For- 
merly this  was  found  over  a  larger  area,  but  because  of  its  slow  growth, 
need  of  light  and  lesser  demand  had  become  limited  to  places  where  a  differ- 
ent forest  vegetation  cannot  develop,  viz.,  to  wind-swept  places  with  scanty 
atmospheric  humidity  above  the  forest  line.  This  wind  resistance  capacity 
of  the  pine  is  probably  connected  with  the  anatomical  structure  of  the 
needles.  Zang  and  Scheit  consider  the  so-called  transfusion  tissue  of  the 
vascular  bundles  a  precautionary  structure  which,  because  of  its  constant 
water  content,  makes  possible  the  life  of  the  needles  in  continuous  dry  air\ 
Nevertheless,  naturally,  a  definite  limit  may  not  be  exceeded  and  Zang*^  cites 
as  an  injury  due  to  wind,  the  yellowing  and  drying  of  the  tips  of  the  needles. 

Certainly  in  conifer  needles,  the  heavy  waxy  coating  of  the  epidermis 
and  the  schlerenchymatic  sub-epidermal  cell  row,  just  as  in  the  cacti,  succu- 
lent Euphorbiacae  and  Crassulaceae,  increase  the  resistance  to  wind. 
Gerhard"  emphasizes,  for  the  Cape  flora,  as  a  further  protective  arrange- 
ment, the  reduction  of  the  intercellular  spaces  and  the  depression  of  the 
stomata.  He  emphasizes  the  development  of  sclerotic  hypoderm  fibres  and 
the  strengthening  of  the  edges  of  the  leaf  by  coUenchyma  or  bast  bundles  as 
a  mechanical  effect  due  to  the  wind,  which  manifests  itself  in  spite  of  the 
moisture  of  the  soil. 


1  Preda,  L.,  Effeti  del  libeccio,  etc.  Bollet.  Soc.  Bot.  ital.  1901;  cit.  Zeitschr. 
f.  Pflanzenkrankh.  1902,  p.  160. 

2  Hansen,  A.     Flora  oder  Allgem.  Bot.  Zeitung-  ]904,  Vol.  93,  Part  I,  p.  44. 

3  Die  Waldbeschadigixngen  durch  Sturm  und  Schneebruch  usw.;  cit.  Forsch. 
auf  dem  Geb.  d.  Agrilvulturpliysik  1880,  p.  527. 

■1  Kirschner,  Loew  und  Scliroeter,  Lebensgeschichte  der  Bliitenpflanzen  Mittel- 
europas.     Vol.1,  Part  III,  p.  207. 

5  See  Scheit  Die  Tracheidensaume  im  Blattbiindel  der  Conifren.  Jenaische 
Zeitschr.  f.  Naturwiss.  XVI.  1883. 

c  Zang,  W.,  Die  Anatomie  der  Kiefernadel  usw.     Dissertation.     Giessen  1904. 

'  Gebhard,  G.,  Beitrage  zur  Blattanatomie  usw.  Dissertation,  Basel;  cit.  Bot. 
Jahresber.  1902,  II,  p.  293. 


476 

The  very  interesting  results  of  experiments  made  by  G.  Kraus^  to 
explain  sabre  growths  and  other  tree  forms,  induced  by  the  wind,  are  of 
great  importance.  If  a  fresh  growing  shoot  of  an  herbaceous  or  woody 
plant  be  bent  so  that  its  tip  overhangs,  the  concentration  of  the  cell  sap  on 
the  convex  side  has  become  more  concentrated.  The  increased  sap  concen- 
tration of  the  convex  side  is  due  to  an  essentially  higher  sugar  content. 
This  sugar  is  newly  formed  when  the  shock  takes  place.  This  noteworthy 
peculiarity  is  exhibited  not  only  by  the  trunk  and  branches,  but  also  by  the 
half  grown  and  fully  grown  petioles.  The  sugar  formation,  however,  is 
not  connected  with  the  deformation  but  depends  on  the  motion  as  such,  and 
frequently  when  the  sugar  is  formed,  the  free  acid  disappears.  Ferruza- 
observed  in  palms  and  succulents  that  such  interference  increased  the  trans- 
piration;  after  VViesner"  and  I'.berdt*  had  shown  that  the  wind  hastened  the 
transpiration.  It  was  found  by  Kohl''  and  Baranetzky**  that  even  very 
slight  interference  would  increase  the  amount  of  evaporation.  Reference 
should  be  made  to  Burgerstein  in  regard  to  further  literature". 

The  local  distribution  of  the  sugar  warrants  the  conclusion  that  it  is  a 
preliminary  step,  if  not  a  direct  one,  in  the  formation  of  cellulose  in  the 
plant's  metabolism,  and  it  should  be  stated  that,  with  the  increased  sugar 
formation  in  the  parts  of  the  plant  moved  by  the  wind,  the  formation  of 
cellulose  and  the  development  of  the  cell  wall  will  be  hastened.  It  is  a 
comparatively  rare  occurrence  that  plant  tissues  remain  in  the  stage  of  their 
development  in  which  sugar  is  formed.  More  frequent  is  the  process, 
especially  in  growing  shoots,  that  the  sugar  disappears  to  the  same  extent 
as  the  cells  become  thicker  walled.  We  will,  therefore,  scarcely  go  astray 
in  stating  that  deformations,  resulting  from  the  action  of  the  wind,  are  more 
stable,  since  the  convex  side  of  the  bend  forms  sugar  and  cellulose  more 
easily;  hence  its  growth  is  completed  sooner.  If  we  consider  that  the  place 
bent  is  more  favorable  for  the  action  of  light  and  warmth,  then  the  early 
termination  of  the  period  of  cell  elongation  is  really  a  matter  of  course. 
The  branch  hardens  sooner  and  does  not  grow  so  long;  hence,  therefore, 
the  compact  structure  of  the  windward  side  and  the  slender,  almost  whip- 
like branch  formation  on  the  side  protected  from  the  wind. 

No  more  thorough  discussion  is  necessary  to  understand  the  fact  that , 
seed  beds  and  young  plantations  in  light  soils  may  at  times  be  blown  to 
pieces,  that  surface  soil  may  often  be  blown  away  and  become  sterile  because 
of  the  sudden  imprudent  removal  of  protective  strips  of  forest  and  that 

1  Kraus,  G.,  tlber  die  Wasserverteilung  in  der  Pflanze,  II.  Der  Zellsaft  und 
.seine  Inhalte.  Sep.-Abdr.  aus  d.  Abhandl.  d.  Naturf.-Ges.  zu  Halle,  Vol.  XV;  cit. 
Bot.  Zeit.  1881,  p.  389. 

2  Ferruzza,  G.,  Sulla  traspirazione  di  alcune  palmi,  etc.;  cit.  Bot.  Jahresber. 
1899,  II,  p.  124. 

3  Wiesner,  Jul.,  Grundversuche  iiber  den  Einfluss  der  Luftbewegungen  auf 
die  Transpiration  der  Pflanzen.     K.  K.  Akad.  d.  Wissensch.,  Wien,  1887,  Vol.  96. 

4  Eberdt,  O.,  Transpiration  der  Pflanzen  und  ihre  Abhangigkeit  von  ausseren 
Bedingungen.     Marburg  1889,  p.  82. 

s  Kohl,  F.  G.,  Die  Transpiration  der  Pflanzen.     Braunschweig  1886. 
6  Baranetzky,  tlber  den  Einfluss  einiger  Bedingungen  auf  die  Transpiration  der 
Pflanzen.     Bot.  Zeit.  1872. 

~   Burgerstein,  Transpiration  der  Pflanzen.     1904. 


477 

precaution  can  be  best  taken  against  the  various  injuries  due  to  wind  by 
means  of  a  protective  plantation,  suited  to  the  conditions. 

W'e  now  come  to  wind-caused  injuries  to  the  leaf.  The  fact  that  leaves 
become  slit  or  remain  hanging,  dried  and  sear,  on  the  branches  in  places 
where  wind  frequently  increases  to  a  storm,  is  so  frequent  an  observation, 
especially  in  coast  regions,  that  it  need  not  be  taken  up  thoroughly  here. 
Just  as  little  need  the  injuries  be  touched  upon  here  which  are  produced  in 
unfolding  leaves,  by  the  rubbing  of  the  leaf  edges'^.  Places  thus  rubbed 
through  are  found  with  great  frequency  in  horse-chestnut  and  beech  leaves, 
which,  still  folded,  break  from  the  bud.  Young  branches  are  also  injured 
by  rubbing,  as  may  be  observed  in  the  young  shoots  of  pears  and  weeping 
willows  (Salix  babylonica)  after  stormy  days  in  summer.  Here  belongs, 
further,  the  whipping  of  hop  vines,  whereby  the  catkins  at  times  become 
prematurely  ripe  and  red-.  The  dried  edges  of  the  leaf  are  more  important, 
and  as  yet  but  little  observed.  Since  many  causes  may  lead  to  blighted 
edges,  one  must  distinguish  whether  the  dried  and  discolored  edge  forms  a 
connected  outline  or  one  interrupted  in  places,  or  whether  dry.  discolored 
places  push  further  into  the  leaf  surface  from  the  dead  part  of  the  edge 
(frequently  wedge-shaped  between  the  main  ribs). 

Only  the  dr\%  browning  or  blackening  outline  may  be  considered  as  a 
simple  wind  injury,  as  Hansen  determined  experimentally".  This  investi- 
gator constructed*  an  original  apparatus  for  producing  wind  in  order  to 
eliminate  secondary  factors  (light,  excessive  heat,  drought)  which  co-operate 
in  the  injuries  due  to  wind,  occurring  out  of  doors. 

From  these  experiments,  he  found,  first  of  all,  that /'a^'jr/'ni/  currents  in 
the  air  dry  the  tissues  most.  A  simple  striking  of  the  wind  against  a  plant 
growing  against  a  firm  wall  is  frequently  less  injurious  and,  under  certain 
circumstances,  actually  without  effect  because  the  wall  throws  back  the 
wind  current. 

In  the  experiments  carried  out  with  this  apparatus,  a  wind  continuing 
day  and  night,  lying  between  i  and  2  of  the  Beaufort  scale,  was  used.  All 
the  individual  leaves  of  tobacco  plants,  standing  in  pots,  after  24  hours  had 
slight  brownings  of  the  edges,  while  the  remaining  part  of  the  leaf  blade  was 
perfectly  healthy  and  showed  no  trace  of  wilting.  On  an  average,  the 
mature  leaves  suffered  sooner  than  the  immature  ones.  The  drying  of  the 
tissue  always  began  near  the  thinnest  peripheral  veins.  The  mesophyll  col- 
lapsed, did  not  contain  air  but  rather  appeared  translucent,  "as  if  injected." 
The  cell  content  was  deformed,  the  chlorophyll  grains  could  not  be  clearly 
recognized.  In  many  cells,  the  protoplasm  contained  slightly  brownish 
granules;  the  \ascular  bundles  had  turned  brown;  the  boundary  between 


1  Caspary,  Bot.  Zeit.  1869,  Sp.  201.  —  Magnus,  Verh.  cl.  Bot.  Ver.  f.  d.  Prov. 
Brandenburg.     XVIII,  p.  9. 

-  Beobachtung-en  iiber  die  Kultur  des  Hopfens.  1880.  Herausgeg.  v.  Deutsch. 
Hopfenbauverein. 

3  Hansen,  A.,  Experimentelle  Untersuchungen  iiber  die  Beschadigung  der 
Blatter  durch  Wind.     Flora  oder  Allgem.  Bot.  Zeit.  1904,  Vol.  9.3,  Part  I. 

4  Ber.  d.  Deutsch.  Bot,  Ges.  1904,  Vol.  XXII,  Part  VII,  p.  371. 


478 


dry  and  healthy  tissue  was  sharp  and,  in  tlie  latter,  the  vascular  bundles  not 
discolored.  Hansen's  explanation  is  that  "the  current  of  air  fast  robs  the 
vascular  bundles  of  their  water,  and  so  changes  them  that  they  can  no  longer 
act  as  conductors.  Thus  the  mesophyll  dries  at  this  place."  This  might 
also  be  the  secondary  process  and  the  drying  of  the  conducting  cords  the 
primai7  one,  while  as  yet  the  drying  of  the  parenchyma  of  the  edge  is 
usually  looked  upon  as  the  direct  eflfect.  In  op])osition  to  this,  Hansen 
says:  "If  one  wishes  to  assume  that  the  wind  directly  attacks  the  mesophyll, 
then  it  would  not  be  possible  to  understand  why  the  process  of  drying  should 
not  begin  also  in  the  middle  of  the  lamina." 

llruck^  takes  up  the  matter  in  the  same  way.  He  observed  that  in  gen- 
eral onl}'  those  leaves  with  the  secondary  veins  extending  to  the  edge,  suf- 
fered peripheral  injury,  the  so-called  caspedodromous  or  cheilodromous 
(extending  to  the  edges)  venation.  (Fig.  96.)  Tree  leaves  from  the  same 
region,  which  did  not  exhilnt  the  injury,  had  "more  or  less  camptodromous, 

or  rather  brochidodromous,  vena- 
tion ;  their  course  is  curved  or  looped 
without  ending  at  the  edge  of  the 
leaf."  In  the  latter  form  of  vena- 
lion.  Bruck  percei\ed  a  decided  pro- 
tection of  the  leaves  against  drv'ing 
from  wind.  Browning  of  the  vascu- 
lar bundles  is  very  similar  to  that 
produced  by  frost. 

According  to  my  studies  on  the 
production  of  dry  edges  of  leaves  as 
the  result  of  the  action  of  gases,  the 
process  of  dying  was  different  here. 
In  the  action  of  the  gases  in  smoke, 
the  tissue  did  not  liecome  translucent  previously  and  the  walls  of  the  bast 
elements  color  yellow  to  brown ;  the  cell  content  dried  together  as  a  whole  to 
an  approximately  uniform  substance.  The  vascular  bundles  of  the  peri- 
pheral zone  also  were  altered,  but  I  explained  the  earlier  death  of  the 
peripheral  leaf  mesophyll  by  the  fact  that  even  if  the  fine  ends  of  the  vascu- 
lar bundles  Still  supplied  water  normally,  this  was  not  sufficient  to  cover  the 
increased  loss  due  to  the  action  of  the  acid.  It  might  be  just  the  same  in 
the  dried  edges  due  to  the  wind.  The  evaporation  in  the  mesophyll,  increased 
by  the  wind,  may  very  well  be  the  primary  process.  The  loss  of  water  in 
the  leaf  is  relatively  greater  at  the  edge,  since  the  upper  surface  is  too  large 
in  proportion  to  the  tissue  mass  and  the  water  conducting  system  consists  of 
too  few  elements,  i.  e.,  is  insufficient.  At  the  places  where  the  leaf  is  thicker 
and  the  venation  more  developed,  the  tissues  receive  more  water  and  retain 
more,  since  here  the  same  evaporating  surface,  as  at  the  leaf  edge,  has  a 


Fif?.   96. 
Crasprdodiomous     Ciimptodromous 
venation.  venation. 

(After  Bruck.) 


1  Bruck,  W.   F.,   Zur  P'rage   der  Windbeschadlgungen   an   Blattern. 
Bot.  Centralbl.  Vol.  XX,  Section  2,  Sep. 


Beihett 


479 

much  more  .juicy  parenchyma  back  of  it.  On  this  account,  close  to  the 
larger  veins,  we  find  strips  of  tissue  which  discolor  and  dry  last. 

In  this  section  many  striking  diseases,  held  to  be  due  to  wind,  have  not 
as  yet  been  sufficiently  studied.  An  example  may  be  found  in  the  so-called 
Mombacher  diseases  of  apricots,  which  Liistner^  considers  is  due  to  wind. 
[n  Mombach,  near  Mainz,  apricot  leaves  dry  back  from  the  tip  and  edge,  and 
fall.  Sometimes  only  the  dried  edge  falls,  while  the  rest  of  the  leaf  is  left 
on  the  tree.  Liistner  considers  this  a  wind  disease,  while  Bruck's  opinion- 
is  that  it  is  a  result  of  sunburn. 

It  is  more  necessary  to  protect  garden  plants  against  the  raw  spring 
winds  than  against  frost.  For  example,  it  was  observed  in  April,  1905,  that 
young  rhubarb  leaves,  which  withstand  frost  if  they  thaw  slowly  and  wdthout 
being  touched,  were  much  injured  when  the  frozen  leaves  had  been  struck 
by  the  wind.  In  the  same  way  young  rose  shoots  were  injured  only  where 
blown  by  the  wind.  While  in  protected  places,  young  vegetable  and  flower- 
ing plants  stood  in  perfect  condition ;  they  were  destroyed  where  the  wind 
had  free  access''.  Besides  the  increase  in  the  amount  of  evaporation,  the 
mechanical  rubbing  of  the  still  tender  organ  is  very  destructive. 

In  blowing  the  snow  away,  the  wind  does  great  harm.  The  seeds  of 
various  species  live  in  furrows  on  the  side  away  from  the  wind  even  with  a 
minimal  snow  covering,  while  they  die  on  the  wnndy  side. 

Only  a  properly  constructed  protective  plantation  can  decrease  the 
injuries  due  to  wind.  By  proper  construction  we  mean,  in  the  first  place, 
the  imitation  of  the  system  which  nature  adopts  in  coast  regions,  and,  in  the 
second  place,  the  proper  choice  of  trees. 

The  natural  system  consists  in  the  planting  of  the  lowest  growing  bushes 
on  the  windy  side;  they  are  stunted  or  branches  die  back  where  beaten  by 
the  wind,  but  these  dried  branches  break  the  force  of  the  wind,  letting  the 
opposite  side  develop.  If  higher  bushes  are  planted  behind,  they  remain 
protected  as  far  up  as  the  height  of  the  first  plantation.  If  they  exceed  this 
their  growth  becomes  stunted  and  one-sided,  yet,  nevertheless,  they  grow 
somewhat  higher  and  in  turn  give  protection  to  a  tree  planted  behind  them, 
until  finally  all  the  trees  can  grow  well. 

Where  there  is  chance  that  shifting  sand  may  cause  tron1)lp  H.  Neuer' 
recommends  especially  Populus  alba  and  varieties  of  Salix.  As  intermediate 
plants  Ailanthus  glandulosa  and  Rhus  Cotinus  thrive  well.  Among  bushes, 
Liqustrum  vulgar e,  Cotoneaster  buxifolia,  Spiraea  opulifolia,  Tamarix  and 
Rihea  sanguineum  are  especially  valuable.  Of  decorative  plants,  Pelargon- 
iums, Chrysanthemums  and  stocks  should  be  used  first  of  all. 


1  L/iistner.    Beobachtungen    liber    die    sogen.     Mombacher    Aprikosenkrankheit. 
Ber.  d.  Kgl.  Lehranstalt  zu  Geisenheim  am  Rhein.     Berlin  1904,  p.  222.     Paul  Parey. 
-  Bruck,  loc.  cit.,  p.  74. 

3  Bottner,  Joh.,  Rauhe  Winde.     Prakt.  Ratgeber  im  Obst-   und  Gartenbau  1905, 
No.  8. 

4  Neuer,  H.,  Neue  Erfahrung-en  liber  Anlagen  und  Pflanzungen  an  der  Nordsee- 
kuste.     Die  Gartenwelt  1904,  No.  49. 


CHAPTER  X. 


ELECTRICAL  DISCHARGES. 


Flashes  of  Lightning. 

In  spite  of  numerous  descriptions  of  destruction  in  the  i)lant  world,  due 
to  lightning,  we  have  not  yet  acquired  an  exact  knowledge  as  to  the  way  the 
lightning  acts.  Just  as  in  frost  injuries,  often  similar  to  those  produced  l)y 
lightning,  we  must  distinguish  mechanical  and  chemical  action;  in  lightning 
the  mechanical  action  may  be  the  more  important  one.  Cohn^  compiled  41 
cases  where  lightning  had  struck  and  an  abundant  bibliography.  He  states 
that  when  lightning  strikes,  the  main  current  of  the  electricity,  after  breaking 
through  the  bark,  passes  down  the  tree  through  the  cambial  layer,  which  is 
a  good  conductor.  "The  heat  developed  by  the  action  at  once  vaporizes  the 
liquid  contents  in  the  cambial  cells  entirely  or  in  part.  The  vapor,  under 
pressure,  either  bursts  the  bark,  with  the  l)ast  clinging  to  it  in  strips  or 
larger  pieces.  These  broken  ])ieces  are  fre(|uent]y  thrown  off  to  great  dis- 
tances. Besides  this  main  current,  a  secondary  current  in  the  poorly  con- 
ducting wood  will  cause  it  to  split  where  it  is  least  firm,  as  a  result  of  the 
sudden  dr}'ing  due  to  the  evaporation  of  the  sap.  Therefore,  according  to 
Cohn's  theory,  neither  the  split  wood  nor  the  torn  off  strips  of  bark  should 
be  considered  as  signs  of  the  course  of  the  lightning  but  only  as  indicating 
the  region  of  the  least  resistance.  A\^ith  Caspary,  I  would  rather  think  that 
the  torn  strips  are  the  actual  traces  of  the  lightning. 

Cohn  based  his  assumption  that  a  sudden  vigorous  formation  of  vapor 
due  to  evaporation  in  the  tissue,  struck  by  lightning,  caused  the  explosive 
scattering  of  the  bark  and  wood  splinters  u]ion  the  following  evidence. 
First  of  all.  dried  splinters  were  actually  ff)und.  It  is  possible,  however,  to 
observe  this  only  rarely  since,  as  a  rule,  the  storm  is  accompanied  by  a 
downpour  of  rain  which  immediately  wets  the  dried  chips.  The  fact  that 
trees  may  be  set  on  fire  by  lightning,  also  favors  the  drying  action.  It  should 
be  stated  here,  however,  that  as  yet  it  has  not  been  proved  absolutely  that 


1  Cohn.  Ein  interessanter  Blitzschlag-.  Vorh.  d.  Kais.  Leop.  Carol.  Akad.  d. 
Naturf.  Vol.  XXVI,  P.  I.  —  tlher  die  Einwirkung  des  Blitzes  auf  Baume.  Denk- 
schrift  d.  Schles.  Ges.  f.  vat.  Kultur  1853,  p.  267. 


48 1 

perfectly  healthy  trees  have  been  set  on  fire^ ;  rather  most  investigations  show 
that  only  trunks  rotten  at  the  core  were  set  on  fire. 

The  individual  condition  of  trees,  as  well  as  the  intensity  of  the  light- 
ning, governs  the  extent  of  the  injury.  It  is  found  that  different  varieties 
of  trees  frequently  show  similar  injuries  and  that  certain  kinds  are  especially 
apt  to  be  struck  by  lightning,  while  others  rarely. 

It  should  be  stated,  first  of  all,  in  regard  to  the  nature  of  the  injuries 
that  in  most  cases  the  torn  bark  exposes  the  wood,  but  that  with  varieties 
which  are  good  conductors,  and  in  young  trees,  lightning  may  strike,  leaving 
no  visible  injury.  As  a  rule,  lightning  does  not  strike  the  tip  of  the  pyra- 
midal poplar,  but  further  down  on  the  trunk,  so  that  most  of  the  top  remains 
uninjured;  the  lightning  then  passes  down  the  trunk  in  a  splintered  line 
which  is  straight  or  only  very  slightly  spiral.  Wood  and  bark  splinters  are 
thrown  off;  on  the  edges  of  this  strip  the  bark  is  raised  from  the  wood,  the 
edges  themselves  are  not  discolored.  In  the  oak,  however,  the  tip  is  often 
struck  and  frequently  large  branches  at  the  top  are  killed  and  broken  off. 
The  splintered  strip  usually  exhibits  a  strong  spiral  twisting-  on  the  trunk, 
its  wood  a  more  channel-like,  hollowed  lightning  path,  while,  in  the  poplar, 
sharply  angled  splinters  indicate  the  course  of  the  flash.  Especially  in  oaks, 
besides  radial  splits,  the  lightning  also  produces  many  tangential  ones  in  the 
direction  of  the  annual  ring.  At  any  rate,  the  direction  and  form  of  the  line 
of  splitting  depend  on  the  structure  of  the  wood.  The  lightning  follows  the 
path  of  best  conduction ;  hence  the  more  the  wood  fibres  are  twisted,  the 
more  the  splinters  are  twisted.  In  Fig.  97  F.  Buchenau  and  Nobbe"  repro- 
duced their  observations  on  oak  and  show  the  spiral  course  of  the  line  of 
splitting  especially  well.  Caspary's  experiments  on  the  effect  of  the  sparks 
from  the  discharge  of  a  Leyden  jar,  loaded  with  50  volts,  confirmed  the  fact 
discovered  by  Villari  that  the  electrical  spark  can  travel  a  much  longer 
distance  longitudinally  in  the  wood  than  transversely.  Besides  this,  wood 
offers  a  greater  resistance  to  the  spark  in  a  tangential  direction  than  in  a 
radial  one.  The  relations  of  the  extent  and  the  place  struck  in  longitudinal, 
radial  and  tangential  directions  are,  according  to  Caspary,  in  fresh  linden 
wood  as  19:  2:  I,  in  dry  spruce  wood,  as  7 :  2 :  i.  The  tissue  was  always 
torn  in  the  course  of  the  spark  and  an  extensive  destruction  of  the  cell 
contents  was  perceived  as  a  result  of  the  heat. 

This  result  from  the  lightning  could  be  demonstrated  everv^where  and 
in  the  cases  where  no  injur}'  is  outwardly  recognizable,  a  narrowly  limited, 
easily  overlooked  point  of  entrance  may  never  be  lacking.  Colladon*  also 
observed,  for  example,  in  a  poplar  and  a  spruce,  especially  characteristic 


1  Caspary,  Mitteilungen  liber  vom  Blitz  g-etroffene  Baume  und  Telegraphen- 
stang-en.  Schriften  d.  phys.  okonom.  Ges.  zu  Konigsberg  1871;  cit.  Bot.  Z.  1873, 
p.  410.     Beyer,  Blitzschlag.  Verb.  d.  bot.  V.  d.  Prov.  Brandenb.,  28  .Tan.,  1876. 

-  Buchenau,  Abhandl.  d.  naturwiss.  Ver.  zu  Bremen,  Vol.  VI.  —  Schriften  d. 
Leopold.  Akad.  d.  Naturf.,  Vol.  XXXIII,  1867. 

3  Dobner-Nobbe,  Botanik  f.  Forstmanner.  4.  ed.  Berlin,  P.  Parey,  1882,  p.  34. 

4  Colladon,  Die  Wirkung  de.s  Blitzes  auf  Baume;  cit.  Biedermanns  Centbl. 
1873,  p.  153.     Bot.  Z.  1873,  p.  686. 


482 

circular  places  on  the  surface  from  which  the  bark  had  been  removed. 
These  places  seem  to  be  produced  as  a  result  of  the  very  great  local  drying 
of  young  wood  and  were  colored  by  concentric,  dark  yellow  and  brown 


^L^:^^^^ 


Fig:.  97.     An  oak  23  m.  high,  which  lias  been  struck  by  lightning.      (After  Nobbe.) 

clri.Ml'T,Te\'''''^!i'f,,'',''''''''^  •"■:""'''  'M"l.Joi"txl  the  trunk,  b.  <■,  rf  bra,>cl,es  i„juml  at  tl,eir  h.-,sc  winch  have 

UntH  I.itei..   hranch  reniaimi.sr  uninjured,// ami  /// hanginR  pieces  of  wood,   r  and   i    s,„all  br.-.nches 

injured  in  the  sapwootl. 

rings.     A  number  of  other  causes  have  also  become  known,  in  which  small. 
circular  spots  indicate  the  entrance  or  exit  of  the  flash  of  lightning. 

R.  Hartig,  in  his  text  book^  gives  especially  clear  illustrations  of  the 

different  kinds  of  injury  due  to  lightning.     He  traces  the  difference  in  the 

1  Hartig,  R.,  Lehrbuch  d.  Pflunzenkrankheiten.  3d  Edition,  1900.  Berlin,  J.  Springer. 


483 

lightning  paths  to  the  unequal  conductivity  of  the  tissues  and  to  the  degree 
of  moisture  present  in  them.  If  rain  has  fallen,  weak  flashes  of  lightning 
cannot  penetrate  into  the  interior  of  the  trees,  but  only  tear  off  pieces  of 
bark,  lichens  and  dry  branches.  Trees  which  have  a  very  delicate  cork 
layer,  as,  for  example,  the  pitch  pine,  display  sometimes  very  noteworthy 
traces  of  lightning  only  in  the  outer  bark  tissue.  Often  only  small,  round, 
isolated  places  in  the  bark  or  others  connected  by  zigzag  lines  are  killed, 
which  later  loosen  from  the  living  bark  of  the  tree,  often  after  a  preceding 
formation  of  cork.  In  trees  with  a  heavy  periderm,  the  lightning  must  first 
strike  through  this  poor  conductor  in  order  to  reach  the  inner  bark,  which 
is  a  good  conductor  Hartig  considers  the  outer  layers  of  the  inner  bark 
"which  are  poor  in  fat"  as  especially  good  conductors,  while  the  tissue  rich 
in  protoplasm  and.  as  a  rule,  containing  much  fat  in  the  newest  layers  of  the 
inner  bark,  is  a  very  poor  conductor  on  account  of  its  fatty  contents  and 
often  entirely  escapes  the  lightning.  The  best  conductive  tissue  is  the  young 
wood,  having  only  scanty  cytoplasmic  wall  coatings.  This  is  also  found  to 
be  very  susceptible  to  frost  injuries.  If  (in  powerful  discharges)  the 
cambial  layer  is  also  injured,  there  results  an  "internal  healing." 

The  theory  of  the  influence  of  the  fatty  contents  on  the  conductivity  of 
the  tissue  is  based  on  the  works  of  Jonescu\  He  found  that  the  electric 
spark  struck  through  fresh  wood  the  more  poorly,  the  richer  this  was  in 
fatty  oil.  In  the  same  plantation  the  beech  is  rarely  struck  by  lightning, 
while  the  oak  is  most  frequently  injured.  A  microscopic  investigation 
showed  the  reason :  the  wood  cells  of  the  beech  contained  oil ;  those  of  the 
oak  were  almost  free  from  it.  Other  "fatty  trees"  (in  which  in  winter  and 
spring  all  the  starch  is  turned  to  oil),  as  for  example,  Juglans  regina,  Tilia 
parvifolia,  Betula,  Pinus,  were  also  found  to  be  bad  conductors  when  com- 
pared with  starchy  trees  (Acer,  Corylus,  Fraxinus,  Ulmus,  Crataegus,  etc.). 
If  the  oil  was  removed  from  the  fatty  trees  by  ether,  sparks  penetrated  the 
fresh  pieces  of  wood  just  as  easily  as  that  of  typical  starchy  trees.  It  should 
not  be  forgotten,  however,  in  judging  from  these  conditions,  that  the  oil 
content  in  the  different  tree  varieties  changes  in  different  seasons  of  the  year; 
from  this  it  is  evident  that  their  electrical  conductivity  varies.  Jonescu  found 
with  equally  large  pieces  from  the  trunk  of  Tilia  parvifolia  that  in  February, 
when  wood  and  bark  are  rich  in  oil,  a  much  higher  electrical  tension  was 
necessary  than  at  the  end  of  March,  when  the  young  wood  was  filled  with 
starch  and  glucose.  The  converse  is  true  in  the  beech,  which  from  January 
to  April,  is  rich  in  starch,  but  in  May  is  rich  in  oil,  as  also  the  pine,  spruce, 
hornbean  and  common  oak.  The  pine  is  pretty  often  struck  during  our 
summer  storms.  At  this  time  it  contains  glucose  in  its  wood,  bark  and  pith 
and  starch  in  its  medullary  rays.  But  in  winter,  the  tree  contains  very  finely 
distributed  oil  and  it  is  seen  that  in  countries  with  winter  storms  (Ireland, 


1  Jonescu,  Dlmitrie,  tJber  die  Ursachen  der  Blitzeschlag-e  in  Baumen.  Jahresb. 
d.  Ver.  f.  vaterl.  Naturkunde  in  Wiirtemberg-.  1892.  Schweizerbartsche  Verl.  — 
Weitere  Untersuchungen  liber  die  Blitzschlage  in  Baumen.  Ber.  d.  Deutsches  Bot. 
G.  1894,  p.  129. 


484 

Norway)  lightning  almost  never  strikes  pine  trees.  Tiiese  ditferences  in 
the  composition  of  the  cell  contents,  however,  become  of  less  importance  if 
the  place  of  growth  causes  a  high  electrical  tension,  as,  for  example,  if  the 
tree  stands  on  impervious  layers  of  soil  where  water  has  collected,  or  on  the 
banks  of  rivers,  ponds,  etc. 


Pig.  98.     Ci-oss-section  throuf^h  a  spruce  with  niimeroiis  ovcrsiown  wounds  due  to 
lightning-.      (After  Hartig.) 

The  water  content  of  the  wood  plays  a  \ery  small  part  in  this  question 
of  the  attraction  of  lightning  by  trees. 

The  electrical  spark  under  high  tension  seeks  the  shortest  path  and  then 
strikes  through  even  poorer  conductors. 

Often  in  the  course  of  years  a  tree  will  be  repeatedly  struck  by  light- 
ning and  cases  will  thus  occur  when  a  trunk  shows  small  roundish  or  longish 
traces  of  lightning  on  its  whole  outer  surface  which  might  lead  to  the  sus- 
picion of  hail  injuries,     Hartig  (loc.  cit.,  p.  241)  thinks,  however,  that  the 


485 

characteristic  form  of  the  lightning-  tissue  in  young  wood  would  remove  all 
doubts.  Such  a  picture  of  repeated  and  healed  injuries,  due  to  lightning,  is 
shown  in  Fig.  98.  A  similar  constitution  of  the  trunk  could  also  indicate 
frost  wounds,  only  here  the  protruding  frost  cracks  are  lacking.  Otherwise, 
however,  the  anatomical  changes  in  the  tissue  which  set  in  in  the  sap  wood 
during  the  healing  of  the  wounds  due  to  lightning  also  exhibit  a  very  great 
similarity  to  that  formation  of  parenchyma  wood  which  usually  follows 
a  frost  injury.  Since  we  will  later  consider  the  latter  more  closely,  we  will 
give  here,  only  for  the  sake  of  later  comparison,  R.  Hartig's  picture  which 
V.  Tubeuf  has  recently  reproduced^     We  see  in  the  lowest,  thick-walled 


Fig.  99.     Cross-section  through  an  annual  ring  of  a  spruce  in  the  year  it  was  struck 

|jy  lightning.     The  crumbled  cell  layer  shows  the  effect  of  the  lightning. 

(After  V.  Tubeuf.) 

tracheid  layer  (Fig.  99)  the  end  of  the  previous  annual  ring.  The  new 
annual  ring  has  begun  with  the  formation  of  thin-walled  elements  and  was 
struck  by  lightning  when  the  loth  to  12th  summer  tracheids  had  been 
formed.  The  action  of  the  lightning  consists  in  the  fact  that  the  latest  wood 
elements  have  been  displaced,  slantingly  pressed  together,  as  if  by  a  tan- 
gential pulling,  and  in  part  killed,  while  the  cell  layers,  remaining  capable  of 
life,  have  developed  into  parenchyma  wood  and  then  gradually  passed  over 
again  into  small  celled  normal  wood. 

Healed  wounds  due  to  frost  exhibit  the  same  processes ;  only,  as  a  rule, 
the  abnormal  layer  of  parenchyma  wood  is  found  nearer  the  old  annual  ring. 


1  V.  Tubeuf,  tTl)er  sogenannte  Blitzlocher  im  Walde.     Naturw.  Zeitschr.  f.  Land- 
u.  Fortswirtsch.     1906,  p.  349. 


4^6 

This  difference  may  be  due  to  the  fact  that  the  disturbance  from  late  frosts 
occurs  usually  when  the  trees  ha\e  formed  but  little  new  wood,  while  the 
injuries  due  to  lightning  are  produced  by  summer  storms  later  in  the  season, 

R.  Hartig  did  not  consider  that  the  production  of  the  collapsed  strip  of 
tissue  was  the  direct  result  of  the  action  of  lightning,  for  he  says^  "if  the 
lightning  takes  its  course,  entirely  or  in  part,  in  the  young  wood,  it  is  seen 
in  this,  that  the  cells  remain  unlignified  and  are  pressed  together  by  the 
tissue  structures  produced  later."  He  then  gives  statements,  as  does  also 
Beling-,  on  the  death  of  whole  groups  of  trees  in  which  he  found''  that  the 
bast  was  apparently  killed  in  the  pines  struck  by  lightning  and  in  numerous 
adjacent  trunks.  The  same  observer  also  mentions  a  case  in  a  mixed  spruce 
and  oak  forest,  in  which  the  spruces  predominated,  wherein  only  the  repressed 
(12)  oaks  showed  traces  of  lightning,  while  the  spruces  were  entirely  unin- 
jured. The  fact  that,  in  mixed  tracts,  the  oaks  suffer  with  especial  fre- 
quency from  lightning  has  often  been  mentioned;  just  as  also  that  other 
trees,  not  distinguished  possibly  by  their  height  and  structure,  in  certain 
localities  fall  victims  especially  to  the  lightning  flashes*. 

In  connection  with  the  death  of  trees  in  whole  groves,  R.  Hartig  lays 
emphasis  on  his  observations  that  this  advances  radially  in  tracts  of  pine 
trees,  v.  Tubeuf"'  has  recently  studied  this  condition.  He  describes  a  case 
in  which  only  one  larch  apparently  had  been  struck  by  lightning  and  yet  a 
considerable  number  of  the  surrounding  pines  and  spruces  began  to  die. 
The  larch  showed  an  interrupted  line  of  splitting  extending  down  the  trunk, 
the  top  remaining  green.  The  trees  surrounding  it  showed  no  local  injuries, 
but  died  in  a  semi-circle  of  25  m.  Such  cases  have  often  been  found.  In 
an  earlier  publication  v.  Tubeuf*'  states  the  hypothesis  that  such  dying 
back  of  large  groups  of  trees  is  caused  by  "Hghtning  spray,"  i.  e.,  by  the 
scattering  of  the  lightning  into  a  number  of  rays  pencils ;  while  Ebermayer^ 
traces  the  phenomenon  to  an  internal  lightning  stroke,  due  to  the  sudden 
union  of  electricities  which  had  been  separated.  Through  the  influence  of 
the  thunder  cloud  the  opposed  electricities  divide  in  the  tree ;  the  unlike, 
negative,  draws  up  to  the  upper  part,  while  the  other,  positive,  presses  down 
into  the  lower  part.  "Now  as  soon  as  the  lightning  strikes,  the  cause  of  the 
separation  of  the  two  electricities  inside  a  nearby  body  is  removed  and  these 
suddenly  reunite  in  the  same  moment."  v.  Tubeuf  cannot  adopt  this  point 
of  view  on  the  ground  of  the  results  of  his  artificial  lightning  experiments. 
In  the  investigation  of  trees  taken  from  lightning  depressions,  he  found, 
"coarse  injuries  due  to  lightning"  in  one  or  another  trunk,  and  since  other 


1  Hartig,  R.,  I^ehrbuch  der  Prtanzenkrankheiten.     3d  ed.     1900,  p.  242. 

2  Zeitschr,  f.  Forst-   u.  Jagdwe.sen,  Nov.  1873. 

3  Bot.  Jahresbericht  v.  Just,  1875,  p.  956.  —  Lehrbuch  d.  Baumkrankh.  1882, 
p.  191. 

*  Landwirt  1875,  p.  400  u.  513.  —  Gard.  Chronicle  1878,  II,  p.  667. 

■'■'  V.  Tubeuf,  tJber  sogenannte  Blitzlocher  im  Walde.  Naturwis.s.  Z.  f.  Land- 
u.  Forstwirtsch.     1905,  p.  493.     (Bibliography  here.) 

c  Absterben  ganzer  Baumgruppen  durch  den  Blitz.  Naturwiss.  Z.  f.  Land- 
u.  Fortswirtsch.     1905,  p.  493.     Bibliography  here. 

■    Ebermayer,    Wald   und   Blitzgefahr.     Naturwiss.   Rundschau.     1899. 


4^7 


causes  of  death  (animal  and  fungi  enemies)  werei  proved  to  have  been 
excluded,  he  came  to  hold  the  opinion  that  spray  lightning  must  exist.  A 
division  of  lightning  into  two  branches  was  observed  by  the  head  forester, 
Petzold,  in  the  forestry  district  of  Sachsenreid^. 

Blight  of  Conifer  Tops. 

In  1903  V.  Tubeuf-,  using  numerous  illustrations,  described  a  case  of 
very  extensive  blighting  of  conifer  tops  in  upper  Bavaria.  These  observa- 
tions led  to  the  conclusion  that  only  one  cause,  acting  once,  in  the  winter  of 
1901-1902,  could  have  existed  and  that  it  must  be  sought  for  in  an  equalizing 
of  the  electrical  potential  in  zvinter  storms.  The  characteristic  symptom  is 
the  manner  of  dying.  In  the  up- 
per part  of  the  tip  of  the  tree,  the 
bark,  bast  and  cambium  are  dead, 
further  down  only  parts  of  the 
bark  outside  the  cambium,  so  that 
the  last  can  form  bast  and  young 
wood  during  summer.  "The 
white,  tender  bast  then  can  be 
easily  loosened  from  the  sappy 
wood  as  in  healthy  trees.  The 
dead  bark  zone  joined  the  newly 
formed  bast  and,  outside  this,  the 
green  bark  was  still  living.  Many 
strips  of  dead  tissue,  enclosed  by 
cork,  extended  through  this  green 
bark.  Still  further  down,  the  dead 
bast  and  bark  parts  were  no 
longer  bands,  surrounding  the 
trunk,  but  were  divided  into 
strips ;  finally  only  dead  spots  are 
found  and  some  meters  below  the 

tip  of  the  tree,  ever)'  sign  of  disease  disappeared.  The  trunk  and  the  roots 
were  perfectly  healthy."  (Fig.  100.)  In  the  adjoining  illustrated  cross- 
section  from  a  spruce,  blighted  at  the  tip,  the  bark  is  finally  killed  only  on  a 
few  places  in  connected  strips  extending  from  the  outside  inward.  Other- 
wise, in  the  bark  layer,  only  scattered  smaller  centres  of  browned  tissue  may 
be  found.  Since  these  lie  within  the  living  bark,  they  are  enclosed  by  a 
layer  of  white  cork.  The  bast  ring  seems  browned,  but  broken  in  different 
places  by  healthy  tissue. 

The  correspondence  of  these  charactristics  with  the  changes,  described 
by  R.  Hartig  as  "lightning  traces,"  led  v.  Tubeuf  to  the  opinion  that  this 


/' ' 

■.' 

y'' 

f 

V:, 

"""■----, 

__. 

->^'* 

i 

Fig-.   100.     Cross-section  through  a  bUghted 

spruce   tip;    from   the   Forestry   Division   of 

Starnberg.     (After  v.  Tubeuf.) 


1  Beobachtungen    liber    elektrische    Erscheinungen    im    Walde.     Naturwiss.     Z. 
f.  Land-  u.  Forstwirtsch.     1905,  p.  308. 

2  V.   Tubeuf,   Die   Gipfeldlirre    der  Fichten.     Naturwiss.    Z.    f.    Land-    u.   Forst- 
wirtschaft.     1903,  No.  1.     Continuation  ibid.  No.  7,  8. 


488 

widely  distributed  tip  blight,  appearing  suddenly  in  many  individuals,  must 
be  the  result  of  electricity.  The  most  important  point  to  which  the  author 
himself  calls  attention  is  that  lightning  usually  strikes  below  the  top,  injuring 
the  trunk,  but  leaving  the  crown  uninjured;  in  other  observed  cases  whole 
trees  have  died,  but  never  the  crown  alone.  In  discussing  the  objections  of 
other  pathologists  who  consider  that  this  blight  is  due  to  beetles  or  leaf 
rolling  caterpillars  {Grapholitha  pactolana)^,  v.  Tubeuf  emphasizes  the  fact 
that  the  the  trees  show  the  characteristic  symptoms  of  disease  when  the 
bark  beetles  are  absent,  and  that  these,  attracted  by  the  smell  of  turpentine, 
appear  only  secondarily.  Some  pines  and  larches  behaved  like  the  spruces. 
In  spruces  injured  by  lightning,  the  dead  wood  is  found  in  the  form  of  brown 
strips  of  bark,  surrounded  by  cork,  lying  within  the  otherwise  green  and 
fresh  bark,  and  below  the  dead  tops.  v.  Tubeuf  could  not  find  this  either 
in  trees  which  had  been  broken  ofif,  bent  or  eaten  off,  nor  in  others  which 
had  been  frozen  or  killed  by  insects. 

Further  investigations'-  proved  that  the  anatomical  characteristics  of  top 
blighted  spruces,  are  identical  with  those  found  in  trees  where  lightning  had 
produced  extensive  injuries.  The  main  support  of  the  theory,  however,  lies 
in  the  fact  that  v.  Tubeuf  and  Zehnler"',  by  means  of  experimentally  pro- 
duced sparks,  were  in  a  position  to  produce,  on  the  living  trunk,  external 
appearances  of  top-blight  as  well  as  all  the  similar  anatomical  pathological 
phenomena,  viz.,  the  dead  "bark-eyes"  which  are  surrounded  by  a  layer  of 
white  cork.  So  long,  therefore,  as  it  cannot  be  proved  that  other  causes 
produce  the  same  symptoms,  we  must  hold  to  the  fact  that  the  kind  of  top 
blight  described  is  a  result  of  electrical  discharges.  These,  in  themselves, 
may  be  weak,  but  v.  Tubeuf  states  that  in  his  experiments  with  deciduous 
trees,  and  in  his  observations  in  the  field,  electrical  injuries  do  not  radiate 
far  into  the  healthy  tissue.  In  artificial  electrical  injur)-,  the  leaves  died 
only  to  a  certain  point. 

In  order  to  facilitate  the  conception  of  electrical  discharge,  v.  Tubeuf 
calls  attention  to  the  St.  Elmo's  fire'*  and  has  produced  this  experimentally. 
He  refers  in  this  to  earlier  experiments  by  Molisch"'.  Inspired  by  the  ob- 
servations which  Linnaeus'  daughter  and  son  had  made  on  the  effect  of 
lightning  on  flowers,  he  produced  a  light  cluster,  i.  e.,  a  shiny  but  quiet 
electrical  equalization. 

In  V.  Tubeuf 's  experiments,  potted  plants  were  insulated  by  being 
placed  on  a  ball  of  wax.  The  soil  was  connected  by  a  copper  wire  with  one 
conductor  of  an  induction  machine  and  a  wire  was  likewise  fastened  to  the 
ball  of  the  other  conductor.     As  soon  as  the  machine  was  set  in  motion  the 


1   See  MoUer  in  Zeitschr.  f.  Forst-  u.  Jagdwesen.     1904,  Part  8. 

-  V.  Tubeuf,  t)ber  den  anatomisch-pntholog-ischen  Befund  bei  gipfeldiirren 
Nadelholzern.     Naturwiss.  Z.  f.  Land-  u.  Forstwirtsch.  1903,  No.  9,  10,  11. 

3  V.  Tubeuf  u.  Zehnder,  tJber  die  pathologrische  Wirkung-  kiin.stlich  erzeugter 
elektriseher  Funkenstrome  auf  Leben  u.  Gesundheit  der  Nadelholzer.  Sonder- 
abdruck. 

•1  V.  Tubeuf,  Elmsfeuer-Versuche.  Naturwi.ss.  Z.  f.  I^and-  u.  Forstwirtsch. 
1905,  Part  5. 

5  Molisch,  Leuchtonde  Pflanzen.     Jena  1904,  G.  Fischer. 


489 

flower  pot,  together  with  the  plant,  was  charged.  "If  the  other  wire  is 
brought  near  the  plant,  a  current  of  the  positive  and  negative  electricity  is 
seen  which  had  been  separated  in  the  two  conductors  and  then  in  the  two 
wires.  The  positive  electricity  flows  out  in  the  form  of  a  light  cluster,  the 
negative  appears  like  Httle  beads  of  light  on  the  tips."  Experiments  with 
spruces  and  pines  proved  that  a  considerable  number  of  needle  tips  on  a 
plant,  negatively  charged,  gave  out  the  electricity  in  the  form  of  beads  of 
light  when  approached  by  the  positively  charged  wire.  If,  however,  the 
plant  is  charged  positively,  the  electricity  flows  from  the  tips  of  the  needles 
without  light^. 

It  was  observed  in  tender  plants  that  if  the  positively  charged  wire  is 
held  so  high  above  the  plant  that  there  were  no  beads  of  light  to  be  seen  on 
the  edge  of  the  blossoms  and  that  no  sparks  jumped  over,  no  injurie/s  fol- 
lowed. If  this  precaution  was  not  observed,  after  a  few  minutes  the  petioles 
and  parts  of  the  sprouts  below  them  began  to  wilt.  These  appeared  darkly 
glassy  as  after  frost  or  injury.  It  should  be  deduced  from  these  experi- 
ments, that  quiet  electrical  discharges  can  not  call  forth  a  direct  injury,  but 
that  such  an  injury  is  felt  at  once  if  a  spark  discharge  takes  place. 

Differences  Between  Lightning  and  Frost  Wounds  in  Conifers. 

As  yet,  in  v.  Tubeuf's  published  results  of  his  experiments,  there  is 
still  lacking  an  illustration  of  the  anatomic  condition  of  the  lightning 
traces  which  manifest  themselves  as  eye-like  spots  in  the  bark.  (See  Fig. 
100.)  Although  in  the  works  of  Colladon  and  R.  Hartig,  mentioned  at  the 
beginning  of  this  section,  we  also  find  statements  as  to  isolated,  ring-like 
traces  of  lightning,  it  still  seems  to  me  that  further  experiments  must  be 
made  to  demonstrate  whether  such  injuries  could  not  be  produced  by  frost. 
My  question  has  received  added  force  since  in  deciduous  trees  I  have  ob- 
served similar  phenomena  round  about  bast  groups  which,  lying  near  the 
eyes,  had  been  injured  by  frost. 

In  order  to  get  reliable  comparative  material,  I  begged  from  v.  Tubeuf 
specimens  of  his  spruce,  artificially  struck  by  lightning,  and  produced  frost 
wounds  by  exposing  a  healthy  five  year  old  pine  (v.  Tubeuf  had  also  found 
characteristic  lightning  wounds  in  pines  and  larches)  in  May  for  a  night  to 
a  temperature  of  y°C.  below  zero  in  a  freezing  cylinder.  The  tree,  appar- 
ently uninjured  when  taken  from  the  freezing  apparatus,  was  observed  at 
the  end  of  the  year.  This  delay  was  necessary  in  order  to  give  it  time  to 
heal  over  possible  inner  injuries  as  must  also  have  taken  place  with  the 
lightning  wounds. 

The  pine  showed  inner  injuries  only  in  the  bark  on  one  side  of  the  base 
of  the  trunk ;  indeed,  partly  in  the  form  of  isolated  dead  cells  with  brown 
swollen  contents  in  the  middle  of  healthy  parenchyma;  partly  in  the  form 


1  t)ber  die  Unterschiede  in  der  Wirkung  der  positiven  und  negativen  Elek- 
trizitat.  Compare  Plowman,  Electrotropism  of  roots.  Americ.  Journ.  Sc.  1904.  cit. 
Bot.  Centralbl.  1905,  No.  40,  p.  342. 


490 


of  larger  dead  cell  groups  which  were  enclosed  by  a  living  parenchyma  wall, 
circular  in  form;  thereby  they  formed  a  figure  resembling  an  eye  (Fig.  loi). 
In  the  centre  of  this  eye-like  figure  frequently  a  depression  was  formed  (h), 
which  was  lined  by  slightly  browned,  at  times  almost  colorless,  cells  («)• 
In  comparing  the  pictures,  which  vary  in  each  section,  one  became  convinced 
that  these  cells,  enclosing  the  cavity,  corresponded  to  a  resin  canal  lining 
and  at  times  had  been  pushed  out  like  vesicles  into  this  cavity.  This  was 
bounded  on  the  outside  by  a  dead  bark  parenchyma  (/>),  with  only  rarely 
collapsed  cells  and  usually  of  natural  size,  of  which  the  contents  and  walls 

i7? 


J^— 


~  Isolated  dead  bark 
n  slightlv  colored  or 
exhibits  clearly  the  > 
region  of  the  resin  c; 


iwn  homogeneous  contiiits,  //  cavity  in  the  dea<l  heart  of  the  tissue. 
-ss  lining  of  the  central  cavils  which,  in  structure  and  conii>osition, 
le  liuinR  of  a  resin  canal,  /i  brow  ii  liark  parenchyma  cells  from  the 
■ly  impregnated  with  resin,  ,.'  parenchyma  elongated  like  plates  an<,l 
ing  starch,  >  fi  normal  bark  p.arenchyma. 


were  impregnated  with  resin.  By  clearing  the  sections,  dififerent  groups 
of  oxalates  could  be  recognized  in  the  dead  parenchyma  as  well  as  cells  with 
grains,  which  should  be  considered  as  starch  impregnated  v^'ith  resin.  This 
dead  tissue  was  bounded  on  the  outside  by  the  above  mentioned  circular  zone 
of  plate-like  cells,  which  in  their  arrangement  resembled  a  cork  overgrowth 
when  treated  with  chloriodid  of  zinc,  but  gave  a  cellulose  reaction  in  their 
walls  and  were  often  filled  abundantly  with  starch  and  small  drops  of  resin 
(r).  This  overgrowth  of  the  dead  tissue  centre,  which  gave  the  eye-like 
appearance  to  the  frost  wound,  often  passed  over  into  the  normal  bark  par- 
enchyma (rp)  which  here  and  there  left  recognizable  traces  of  starch. 


491 

Fig.  102  shows  a  cross-section  through  the  bark  of  a  small  spruce  trunk 
injured  by  artificial  lightning.  The  trace  of  lightning  (b)  shows,  first  of  all, 
a  central  brown  strip-like  kernel  of  swollen  parenchyma.  '  This  kernel  is 
surrounded  by  a  broad,  clear  zone  (k)  which  consists  of  radially  arranged 
rows  of  ver}'  thin-walled,  nearly  empty  cells,  often  containing  air. 

Toward  the  outside,  this  zone  adjoins  a  tissue  ring  (kk)  of  plate-like 
cells,  rich  in  cyptoplasm,  the  walls  of  Avhich  give  a  cellulose  reaction.  These 
cells  gradually  pass  over  into  the  normal  bark  parenchyma  (r/>)  with  its 
large  lumina.  The  resin  ducts  (g)  lying  outside  the  trace  of  lightning  but 
pretty  near  to  it,  are,  as  a  rule,  uninjured  ;  the  living  cells  at  times  projecting 
into  the  resin  ducts  are  light-walled.  This  vesicular  outpushing  of  the  Hn- 
ing  cells  is  a  normal  phenomenon;  for  in  branches  of  healthy  spruce  in 
winter,  resin  canals  are  often  found  completely  filled  by  tylose-like  enlarge- 
ments of  the  lining  cells.  Resin  ducts  also  occur  isolated  in  the  immediate 
proximity  of  a  trace  of  lightning  in  which  the  cells  filling  them  are  changed 
to  brown,  swollen,  resinous  masses. 

The  dead  tissue  kernel  in  the  centre  of  the  lightning  trace  consists  fre- 
quently only  of  dead  bark  parenchyma.  Often,  however,  it  can  be  noticed 
that  some  bast  groups  (k')  have  participated  in  this.  The  fact  should  be 
emphasized,  that  the  dead  parenchyma  cells  are  often  entirely  collapsed  and 
dried.  In  my  opinion,  the  production  of  the  light  colored  circular  zones, 
composed  of  thin-walled  cells  with  broad  lumina  which  are  found  to  be  actual 
cork  cells  and  constitute  the  difference  from  the  frost  wound,  is  due  to  the 
drying  up  of  the  cells. 

I  conceive  of  the  production  of  this  difference  in  the  two  forms  of 
wounds  as  follows :  The  electric  spark  causes  a  rapid  drying  out  of  the 
dead  tissue.  Since  this,  like  frost,  does  not  cause  any  slowly  spreading, 
subsequent  death  of  the  adjoining  tissue,  vigorous  cells,  capable  of  reacting, 
directly  bound  the  dead  tissue  centres.  A  reaction  to  the  wound  stimulus 
sets  in  at  once  if  the  vegetative  activity  makes  itself  felt  in  the  bark.  The 
parenchyma  around  the  dead  tissue  responds  to  the  wound  stimulus  by  cell 
elongation  and  increase.  The  cell  groups  dried  by  lightning,  allow  the  sur- 
rounding cells  to  elongate  greatly.  The  more  rapidly  the  process  takes  place, 
the  more  material  is  used  up.  If  this  is  not  present  in  sufficient  amounts 
only  a  formation  of  cork  will  take  place  and  thus  the  fact  is  explained  that 
after  the  electrical  discharge  the  bark  parenchyma  surrounding  the  dried 
tissue  must  elongate  and  divide  to  fill  out  the  large  spaces ;  then  there  is  a 
formation  of  cork. 

When  frost  kills  an  area  of  tissue,  lying  in  the  bark  parenchyma,  at  first 
no  drying  of  the  tissue  takes  place.  The  dead,  swollen  cells  retain  their 
size,  and  are  still  turgid.  Also  the  pressure  of  the  dying  frost-injured  tissue 
on  the  healthy  surrounding  tissue  is  not  essentially  increased.  The  sur- 
rounding cells  have  no  incentive  whatever  to  the  great  elongation  and 
division  which  were  necessary  in  the  drying  out  of  the  lightning  traces. 
Therefore,  there  will  appear  around  the  dead  centre  of  the  frost  wound  the 


?l^-~- 


9^    ^^        sc?i 


d 


Fig.  102.  Spiuce,  showing-  traces  of  artificial  lightning.  (Orig.) 
b  central  portion  of  tlie  trace  of  lightning  in  tlie  hark  pareiichynui.  h  group  of  nonnal  h;ird  bast.  A 
of  bast  enclosed  by  the  lightening  tiace,  k  cork  ring,  kk  the  cell  layer  resembling  the  cork  canil 
resin  canal  in  the  healtliy  bark,  from  the  normal  lining  of  which  some  cells  haye  ciirved  outvva 
vesicles,  gs  resin  canal,  filled  with  resin,  o  oxalate  crystals,  st  bark  cells  filled  with  starch,  rp  hcaltl 
parenchyma,  v  swollen  ti.ssue  gronps  in  this  bark  parenchyma,  sell  bark  scales. 


'  groni) 
)iuni.  jf 
1(1  like 
ly  bark 


493 

new  structure,  produced  as  a  result  of  the  wound  stimulus  and  in  the  form 
of  a  circular  zone  of  scantier  and  smaller  cells.  The  plastic  food  material, 
flowing  toward  these  spots,  cannot  be  longer  used  for  cell  increase,  since  the 
need  has  been  met.  It  will  therefore  be  laid  down  in  the  form  of  reserve 
substances.  Hence  the  noticeable  accumulation  of  starch  directly  about 
the  frost  wound. 

As  a  positive  result  of  the  investigation,  it  should  be  cited  that  in  coni- 
fers a  definite  difference  exists  between  artifically  produced,  eye-like  wounds 
due  to  lightning  and  to  frost.  In  wounds  due  to  lightning  the  dead  bark 
tissue  dries  rapidly  and  is  then  surrounded  by  a  porous  layer  of  cork  which 
forms  a  light  colored  outer  ring.  In  frost  wounds,  the  dead  cells  in  the 
interior  of  the  bark  parenchyma  at  first  retain  their  former  size.  They  are 
enclosed  by  a  circular  zone  of  newly  formed  cells;  these  do  not  develop  a 
porous  layer  of  cork,  but  rather  form  a  slender  parenchyma  zone,  with  nar- 
row lumina,  which  usually  is  richer  in  reserve  substances  than  the  normal 
bark  parenchyma.  This  zone,  in  a  wound  due  to  lightning,  is  formed  next 
to  the  cork  zone. 

These  statements  are  corroborated  by  von  Tubeuf 's  observation  on  the 
differences  between  wounds  due  to  lightning  and  to  frost.  In  injuries 
caused  by  lightning  the  ring  of  dead  bark  radiates  into  the  healthy  tissue  in 
constantly  widening  bands,  while  similar  phenomena  in  the  injuries  due  to 
frost  have  not  been  observed  in  conifers  up  to  the  present. 

In  regard  to  the  theor\'  of  the  action  of  lightning,  the  present  obsena- 
tions  on  the  structure  determine  that  the  electric  spark  primarily  produces 
a  dr>'ing  of  the  tissue. 

Injuries  to  Trees  in  Cities  and  Towns. 
With  the  increased  use  of  electricity  in  cities,  there  is  a  serious  menace 
which  must  be  mentioned.  Stone's  investigations^  show  that  the  alter- 
nating and  the  direct  currents  cause  injuries  by  local  burning.  In  dry 
weather,  this  is  less  to  be  feared,  but  becomes  essentially  greater  when  the 
bark  is  damp.  The  direct  currents  used  by  street  car  lines  come  under 
especial  consideration  here.  Besides  killing  this  tissue,  the  weaker  currents 
also  stimulate  action.  Both  conditions  should  be  closely  examined.  Dis- 
charges into  the  earth  during  thunder  storms  are  more  frequent,  according 
to  Stone's  observations,  than  is  usually  supposed  and  they  explain  many 
injuries  in  the  trees,  which  often  are  also  mistreated  by  the  inconsiderate 
cutting  out  of  the  branches  in  order  to  isolate  the  wires. 

Effect  of  Spray  Lightning  on  Grapevines. 
Among  Calladon's"  numerous  observations  on  the  action  of  lightning, 
the  statement  is  found  that  in  a  vineyard,  the  upper  surface  of  the  soil  which 
had  been  struck  by  lightning  presented  a  regular,  sharply  defined  circle,  the 


1  stone,  G.  E.,  Injuries  to   Shade   Trees  from  Electricity.     Hatch  EXper.    Stat. 
Massachusetts  Agric.  Coll.  Bull.   91.     Amherst,   1903.  , 

2  Colladon,  Daniel,  Effects  de  la  foudre  sur  les  arbres  et  les  plantes  ligneuses. 
Mem.  de  la  soc.  de  phys.  et  d'histoire  nat.,  de  Geneve  1872,  p.  548-53. 


494 

centre  showing  the  strongest  action.  The  vine  leaves  showed  a  number  of 
spots,  which  at  first  appeared  dark  green  and  after  several  days  turned 
brick  red.  In  the  younger  sappy  stems,  especially  the  cambium  had  turned 
brown,  while  the  wood  was  uninjured.  In  the  injured  tissues,  the  cell  walls 
remain  unchanged,  but  the  protoplasm  was  contracted  and  killed.  Rathay^ 
has  described  the  same  obser\'ation  of  the  distribution  of  the  eflfect  of  light- 
ning on  numerous  individuals  and,  after  mentioning  earlier  cases,  also  refers 
to  the  fact  that  the  same  phenomenon  of  the  spreading  out  of  the  lightning 
is  observed  in  sheep  herds,  where  likewise  several  individuals  were  always 
hit.- 

Like  Colladon.  Rathay  also  ol)ser\ed  that  the  leaves  became  red  in 
varieties  whicli  sliowcd  a  red  autumnal  coloring.  All  the  ends  of  the 
branches  died  back.  The  process  of  the  red  coloration  in  leaves  has  already 
been  determined  by  Wiesner  and  by  me  as  a  result  of  ringing  and  bending 
experiments.  Rathay  supplemented  this  by  observing  that  the  reddened 
leaves  transpired  much  less  than  normally  green  ones.  Leaves  reddened 
after  having  been  struck  by  the  lightning,  resembled,  in  all  particulars  as  yet 
tested,  those  which  turned  red  from  ringing  the  branches  and  actually  the 
injury  from  lightning  resembled  in  many  points  mechanical  girdling,  since 
here  the  bark  lying  outside  the  cambium  was  killed.  "The  cambium  of  the 
I)arts  struck  by  lightning  remains  alive  and  develops  inside  the  dead  tissue, 
toward  the  outside,  a  callus  surrounded  by  wound  cork  and.  toward  the 
inside,  a  woodring  which  is  separated  from  the  older  wood  by  a  fhin  brown 
layer."     The  grapes  on  the  vine  struck  by  lightning  dried  up  absolutely. 

We  find  in  a  work  by  Ravaz  and  Bonnet-  different  points  of  importance, 
showing  parallelism  between  the  efifect  of  lightning  on  grapevines  and  on 
conifers.  After  calling  attention  to  the  fact  that  a  place  struck  by  lightning 
which  was  planted  with  50  to  100  vines,  showed  that  the  strongest  plants 
were  much  injured,  it  should  be  emphasized  that,  after  being  struck  by 
lightning  on  the  20th  of  May,  the  tips  of  the  shoots  turned  down  toward  the 
ground  and  dried  up.  The  nodes  remained  green  for  some  time,  while  the 
internodes  looked  almost  scalded.  The  phenomenon  of  disease  gradually 
decreased  toward  the  bottom.  Below  the  dried  tips,  the  pith  was  torn  in 
the  injured  young  shoots  and  pressed  against  the  woodring.  The  roots 
remained  uninjured.  Some  weeks  after  having  been  struck,  the  injured 
internodes  appeared  a  reddish  brown,  shrivelled  and  cracked  longitudinally. 
The  tears  showed  a  scar  tissue.  The  intermediary  nodes  were  strikingly 
swollen.  Where  the  tips  had  not  been  struck,  the  branches  grew  further, 
but  had  very  short  internodes.  The  young  wood  tissue  appeared  brown 
and  its  cells  empty  and  with  unthickened  walls.  The  injured  parts  of  the 
bark  were  enclosed  by  cork  so  as  to  form  island-like  structures   (compare 


1  Rathay,  Emerich.  iJber  eine  mprkwiirdige  durch  den  Blitz  an  Vitis  vinifera 
hervorgerufene  Erscheinung.  Denkschr.  d.  math.-naturwiss.  Klasse  d.  kais.  Akad. 
d.  Wissensch.     Wicn  1891.     Extensive  biblioiarraphy  here. 

2  Ravaz,  I^.  ct  Bonnet,  Effects  de  la  foudre  sur  la  vigne.  Extr.  des  annates  de 
I'ecole  natjonale  d'agricult.  de  Montpellier;  cit.  Bot.  Jahresb.  1900,  II,  p.  417, 


495 

Fig.  102).  The  cambium  formed  first  an  irregular  tissue,  which  gradually 
passed  over  into  normal  wood  (compare  Fig.  99). 

From  these  statements  we  arrive  at  the  conclusion  that  lightning  (like 
frost)  also  causes  considerable  injury  by  m'echanical  action  and,  in  fact,  as 
a  result  of  sudden  excessive  differences  in  tension.  The  trunk  reacts  in  a 
different  degree  according  to  its  age  when  injured  by  lightning.  Where  the 
bark  is  not  injured  to  its  whole  extent,  the  dead  places  are  surrounded  by  a 
cork  layer.  If  the  young  wood  is  not  entirely  killed  but  only  compressed 
or  torn,  a  parenchyma  wood  develops  later,  which  slowly  passes  over  into 
normal  wood,  so  that  false  annual  rings  can  be  produced.  All  phenomena 
spread  out  gradually  from  the  base  of  the  trunk ;  that  is,  they  finally 
disappear. 

It  is  a  matter  of  course  that  micro-organisms  infest  all  wounds  due  to 
lightning  and  it  is  easily  comprehensible  that  these  cases  have  been  described 
as  parasitic  diseases.  An  example  is  offered  by  "Gelivure"  of  the  grape 
which  has  been  described  as  bacteriosis,  but,  according  to  Ravaz  and  Bonnet, 
is  nothing  less  than  a  wound  caused  by  lightning  and'  infested  by  bacteria-. 

Spray  Lightning  on  Fields  and  Meadows. 

Steglich-  observed  one  July  a  potato  field  which  had  been  struck  by 
lightning.  The  lightning  hit  in  two  places  and  the  plants  became  yellow 
and  died ;  the  stems  seemed  cracked  open  and  perforated  so  that  the  walls 
of  the  wound  appesared  torn. 

V.  Seelhorst^  describes  injuries  to  hects  from  lightning.  In  one  case 
the  place  struck  formed  a  circle  about  15  m.  in  diameter.  In  the  middle  of 
the  circle  the  heets  were  all  killed.  The  leaves  on  the  plants  near  the  peri- 
phery were  wilted  and  discolored.  Often  individual  specimens  slightly  in- 
jured, stood  between  plants  greatly  injured.  At  times  small  cavities  were 
noticeable  in  the  beet,  especialh'  in  the  head.  In  other  cases,  practical 
workers  speak  of  discoloration  and  weakening  of  the  heads  of  the  beets  and 
similar  phenomena ;  nevertheless,  secondary  parasitic  influence  may  have 
made  itself  felt  here.  Colladon*  also  makes  a  report  of  a  beet  field  struck 
by  lightning.  The  leaves  of  injured  plants  were  colored  red,  shrivelled  or 
torn  in  places  and  the  edges  partially  dried.  In  one  potato  field  the  ma- 
jority of  the  plants  in  the  upthrown  soil  were  found  to  be  healthy;  only  in 
one  place  did  the  base  of  the  potato  stem  seem  torn  and  burned.  In  the 
place  struck  by  lightning  on  a  meadow,  with  a  diameter  of  6  m.,  the  highest 
thistle  tips  were  killed,  while  the  lower  parts  and  the  grass  remained  healthy, 
although  here  and  there  the  earth  was  found  to  have  been  torn  up. 

To  explain  the  circumstance  that  the  condition  of  individuals  hit  on 
similarly  planted  bits  of  land  always  varies,  Rathay  cites  photographs  of 


1  Ravaz,  L.  et  Bonnet,  A.,  Les  effets  de  la  foudre  et  la  gelivure.     Compt.  rend. 
1901,  I,  p.  805. 

2  Jahrb.  d.  D.  Landw.-Ges.  1892. 

"  V.  Seelhorst,  Riibenbeschadigung  durch  Blitz.     D.  Landw.  Presse  1904,  p.  515. 
4  Loc.  cit.,  p.  555. 


496 

lightning  showing  that  it  usuall}'  is  not  a  sini[)Ic  discharge  between  two 
points,  but  is  scattered  and  ends  in  niany  points.  In  addition  to  this,  it 
should  be  emphasized  that  when  grapevines  arc  trained  on  wires,  these 
spread  the  injurious  effect  over  a  greater  area. 

V.  Bezold's^  statements  that,  according  to  the  statistics  of  the  Fire  In- 
surance Company  in  Bavaria,  the  danger  from  lightning  had  increased  three- 
fold between  1833  and  1882,  are  especially  significant.  The  extensive 
removal  of  forests  and  marsh  drainage  and  the  rapid  increase  of  rails  and 
electric  wire  conductors  are  supposed  to  play  a  part  in  this. 

DiSAi)\ANTA(;i:s  IX   IClixtro-Culturf.. 

The  attempts  to  use  electricity  dircctl}'  in  plant  culti\ati()n  have  fol- 
lowed three  lines.  In  tb-e  first  place,  it  was  desired  to  increase  the  assimi- 
latory  activity  by  illuminating  with  electric  light ;  in  the  second  place  it  has 
been  attempted  to  let  an  electric  current  pass  through  the  earth  by  sinking 
two  metal  discs  in  the  soil  connected  with  some  source  of  current ;  in  the 
third  place,  an  attempt  was  made  to  cause  the  current  to  pass  directly 
through  the  plant  (or  tree). 

As  yet  the  results  have  been  very  contradictory,  so  that  no  decision 
has  been  reached.  Great  hope  is  set  often  on  the  influence  of  a  silent  elec- 
tric discharge.  This  takes  place  when,  for  example,  a  net  of  wires  is  laid 
over  a  field  without  touching  the  soil  and  one  pole  of  an  electrifying  machine 
is  connected  with  the  wire  and  the  other  with  the  soil.  In  such  cases  the 
plants  act  as  conductors  and  through  them,  by  means  of  the  silent  electric 
discharge,  the  electricity  will  stream  out  from  the  tip  of  the  cultivated 
plants.  Such  a  current  must  actually  take  place  constantly  in  nature,  since 
the  soil  exhibits  an  electric  charge  differing  from  that  in  the  layers  of  air 
lying  above  it.  The  best  known  experiments  are  those  of  Lemstrom-  and 
Pringsheim^'.  Older  works  on  experiments,  in  which  the  electrical  current 
is  conducted  through  the  soil,  had  been  collected  and  enlarged  by  Wollny'*. 

The  results  of  Pringsheim's  experiments,  in  which  the  electricity  waf 
produced  by  a  static  electric  machine,  sound  extremely  favorable,  since  in 
potatoes,  sugar  beets,  beans  and  strawberries  a  quantitatively  and  quali- 
tatively better  yield  is  obtained.  Since,  however,  many  unfavorable  experi- 
ences exist,  this  field,  for  the  present,  should  not  be  considered  any  further, 
as  it  is  not  sufficiently  cleared  up.  However,  Lowenherz'^  work  must  be 
mentioned  because  it  has  been  carried  through  with  scientific  exactness  and 
opens  up  new  points  of  view. 


1  V.    ]?czold.    W.,    tthcr    ziindende    Blitze    im    Konigreich    Bayern    wahrend    des 
Zeitraums  1833  bis  1882.     Abh.  d.  KrI.  Bayer.  Akad.  d.  Wiss.     IT.  CI..  Vol.  XV. 

2  I.,emstrrim,    Elektrokultur.     Translated    by    O.    Prinssheim.     Berlin    1902.     W. 
Junk. 

3  Prinssheim,    Otto,    Neue    Elektrokulturvcrsuche.     Osterr.     landw.    Wochenbl 

1904,  No.  24;  cit.  Centralbl.  f.  Agrikulturch.  190.5.  Part  6. 

4  Forschungen  auf  dem  Gebiete  der  Agrikulturphysik.     Vol.  II.  1888,  p.  88. 

5  T^owonherz,    Richard,    Versuche    liber    Elektrokultur.     Z.    f.    Pflanzenkrankh. 

1905,  p.  137. 


497 

The  experiments  were  made  with  Chevalier  barley ;  a  direct  current  of 
electricity  was  used  which  was  conducted  through  the  soil.  The  grains 
were  very  carefully  sown,  so  that  in  half  the  experimental  pots  the  seeds  lay 
with  their  long  axes  parallel  to  the  direction  of  the  current,  thus  being 
traversed  longitudinally  by  the  current,  while  in  the  other  pots,  the  grains 
were  laid  at  right  angles  to  the  direction  of  the  current.  It  was  thus  found 
that  the  different  position  of  the  grain  in  relation  to  the  direction  of  the 
current  resulted  in  a  very  unexpectedly  great  difference  in  the  effect  of  the 
electricity. 

With  the  strength  of  current  used  (0.015  ^o  0.030  amperes)  an  injury 
in  the  process  of  germination  was  universally  noticeable,  but  it  could  always 
be  recognized  that  the  grains,  which  were  traversed  longitudinally,  germin- 
ated less  well  than  those  through  which  the  stream  passed  crosswise ;  yet  in 
the  first  named  series,  a  difference  was  perceptible  in  the  grains  lying 
parallel  with  the  direction  of  the  current,  inasmuch  as  those  developed  the 
most  poorly  in  which  the  positive  stream  entered  at  the  tip  of  the  grain  and 
left  at  the  end  where  the  embryo  lies.  If  the  direction  of  the  current  was 
reversed  two  or  three  times  within  the  24  hours,  no  difference  in  the  results 
could  be  produced,  but,  if  the  current  was  changed  two  times  per  minute, 
such  a  difference  became  clearly  evident.  The  grains  laid  perpendicular  to 
the  direction  of  the  current  sprouted  just  as  well  as  seed  not  electrically 
treated.  In  those  traversed  longitudinally  by  electricity,  the  disadvantage 
manifested  itself  noticeably  only  in  the  fact  that  the  grains  germinated 
12  to  24  hours  later.  This  experiment,  w-hich  deserves  consideration,  shows 
clearly  that  varied  conditions  must  be  taken  into  consideration  in  cultivation 
with  electricity 

Supplementarily,  the  endeavor  to  treat  electrically  the  roots  and  older 
wood  of  grapevines  by  currents  of  high  voltage  should  be  considered  here^. 
At  the  request  of  the  Imperial  Agricultural  Association  at  Moscow,  experi- 
ments were  introduced,  incited  by  reports  of  combatting  Phylloxera  by  elec- 
tric currents,  in  which  experimental  cases,  containing  roots  and  cuttings, 
were  exposed  for  10  minutes  to  an  electrical  discharge.  Some  roots  were 
then  treated  with  a  spark  discharge.  It  was  found  that  currents  of  high 
voltage  caused  an  earlier  and  more  favorable  development  of  the  vines. 
Roots,  however,  which  had  been  treated  directly  by  being  connected  with 
the  machine  exhibited  injuries,  for  the  upper  parts  did  not  sprout.  Sprouts 
appeared  only  on  the  subsoil  nodes. 


1  From   a   review   of  the   "Weinlaube"    1904,    No.    34;    cit.    Centralbl,    fiir   Agri- 
kulturchemie  1005,  p.  394, 


CHAPTER  XL. 


LACK  OF  HEAT. 


A  General  Survey. 


Life  Phenomena  at  Low  Temperatures. 

The  plant  is  much  more  dependent  on  the  temperature  of  the  air  than 
on  the  temperature  of  the  soil.  Before  the  soil  can  follow  the  fluctuations 
in  the  warmth  of  the  air,  this  has  already  awakened  plant  life  and  at  times 
brought  it  to  considerable  development.  The  individual  parts  of  the  plant 
naturally  do  not  respond  to  the  fluctuations  in  the  temperature  equally 
quickly.  While  the  warmth  of  leaves  and  thin  stems,  in  the  shortest  possible 
time,  increases  or  decreases,  parallel  with  the  temperature  of  the  air,  thick 
trunks  will  need  considerably  longer  time,  more  particularly  since  all  plant 
tissues  are  poor  conductors  of  heat.  From  this  last  circumstance  it  is 
evident  that  thick  trunks  are  sometimes  warmer  than  the  surrounding-  air, 
sometimes  cooler,  and,  in  fact,  are  on  an  average  cooler  than  the  air  in  the 
daytime  and  warmer  at  night.  Rut  those  parts  of  the  plants  which  extend 
into  the  air  are  also  cooler  in  the  daytime.  The  cooling  down  of  the  leaves 
comes  from  their  radiation  of  heat.  This  will  be  greater  the  greater  the 
surface  of  the  part  in  proportion  to  its  bulk.  Evaporation  should  also  be 
taken  into  consideration  as  a  further  cause ;  it  proceeds  at  the  expense  of 
the  warmth  of  the  plant  part.  These  two  causes  explain  the  phenomenon 
that,  on  bright  nights,  the  thermometer  shows  a  temperature  several  degrees 
lower  if  it  stands  directly  between  densely  growing  plants  with  thin  leaves, 
such  as  meadow  grass,  than  is  found  in  the  air  layer  above  them.  If  the 
temperature  of  the  air  itself  approaches  the  freezing  point  of  water,  the 
parts  of  the  plants  may  be  cooled  below  zero  degrees  C.  by  their  heat  radi- 
ation and,  as  a  result,  die,  or,  at  least,  at  times  some  of  their  functions  are 
arrested.  According  to  Sach's^  observations  the  chloroplasts  of  the  firebean 
(Phascohis  miiltiflorus)  and  maise  (Zea  Mays)  cannot  turn  green  if  the 
temperature  does  not  rise  to  at  least  6  degrees  C.     Rape  acts  in  the  same 


1  Lehrbuch  III,  p.  636. 


499 

way.  The  stone  pine  (Pinus  Pima)  requires  at  least  7  degrees  C.  In 
Potamogeton,  the  breaking  down  of  carbon  dioxid  is  found  first  between 
10  to  15  degrees  C. ;  on  the  other  hand,  in  ValHsneria  even  above  6  degrees  C, 
and  in  the  leaves  of  the  larch  at  0.5  to  2.5  degrees  C,  and  in  meadow  grass 
at  1.5  to  3.5  degrees  C.  The  movement  of  the  leaves  of  the  sensitive  plant 
{Mimosa  pudica)  first  occurs  when  the  temperature  of  the  surrounding  air 
exceeds  15  degrees. 

The  difference  in  the  amount  of  heat  required  by  different  plants  is 
Fhown  best  by  the  observations  made  on  the  germination  of  seeds  in  ice. 
Uloth^  found,  for  example,  that  seeds  of  wheat  and  maple  {Acer  platanoides) 
germinated  in  ice  and  bored  their  way  deep  into  the  ice,  which  they  melted 
by  the  heat  developed  during  germination.  The  fine  lateral  roots  of  the 
wheat  had  traversed  ice  pieces  one-eighth  of  a  meter  in  thickness.  Later 
experiments-  showed  the  same  observer  that  several  of  the  Cruci ferae 
{Lapidium  ruderale  and  L.  sativum,  Sinapis  alba  and  Brassica  Napus),  oats, 
barley  and  r\'e,  as  well  as  other  grasses,  had  germinated  in  large  percentages. 
In  barley  and  oats  the  percentage  of  germination,  however,  was  noticeably 
less  than  in  wheat  and  rye.  Of  the  Papilionaceae,  80  per  cent,  of  the  peas 
had  germinated  in  the  ice-cellar  and  12  per  cent,  of  the  lentils;  60  per  cent, 
of  sown  parsley  seeds  showed  germination.  Incited  by  these  observations, 
Haberlandt^  later  undertook  further  experiments  with  sowing  the  common 
agricultural  seeds  in  cases  which  were  kept  constantly  at  a  temperature  of 
zero  degrees  to  i  degree  C.  by  means  of  ice.  After  a  month  and  a  half,  rye, 
hemp  {Cantelina  sativa),  red  clover,  alfalfa,  vetches,  peas,  and  bastard 
clover  showed  the  beginnings  of  germination.  After  four  months,  how- 
ever, a  further  development  of  the  little  roots  could  be  proved  only  for 
mustard,  camelina  (or  gold  of  pleasure),  bastard  clover,  red  clover  and 
alfalfa,  while  wheat,  barley,  oats,  ray  grass,  buckwheat,  beets,  rape,  poppy, 
white  clover,  beans,  etc.,  did  not  reach  germination.  Of  all  the  plants, 
alfalfa  had  strikingly  proved  most  favorable. 

These  results,  in  regard  to  grain  varieties,  stand  in  very  marked  con- 
tradiction to  Uloth's  conclusions  and  also  to  the  results  of  experiments 
which  Hellriegel*  has  published.  Of  all  the  plants  tested,  winter  rye  was 
proved  decidedly  to  require  the  least  heat.  With  an  almost  constant  tem- 
perature of  o  degrees  C.  (within  the  six  weeks  period  of  the  experiments 
the  temperature  only  a  few  times  slightly  exceeded  this,  reaching  i  degree 
C),  this  plant  developed  its  leaf  and  root  apparatus  perfectly  normally. 
Winter  wheat  was  proved  to  need  somewhat  more  heat  because  of  the  small 
size  of  its  germinating  plants,  and,  agreeing  with  Uloth's  results,  to  a  still 
greater  degree,  barley  and  oats,  which  at  o  degrees  C,  only  slightly  devel- 
oped their  rootlets,  while  unable  to  force  the  leaf  cone  out  of  the  grain.     At 


1  Fuhlins's  Neue  landwirtsch.  Z.  1S71,  p.  875. 

2  Flora  1875,  p.  266. 

3  Wissenschaftl.   praktische   Unter.suchung-en   auf   d.    Gebiete   d.   Pflanzenbaues. 
Wien  1875,  I,  p.  109ff.,  117. 

4  Beitrage    zu    den   naturwissenschaftl.     Grundlagen    des    Ackerbaues.     Braun- 
schweig, Vieweg  1883,  p.  284-304, 


500 

2  degrees  C,  however,  the  elongation  was  (juite  perfect.  IMaizc  had  not 
changed  at  5  degrees  C.  and  even  at  8.7  degrees  C.  germinated  ver)'  slowly 
and  imperfectly.  Vetches  and  rape  seed  had  germinated  at  o  degrees  and 
exhibited  a  development  of  the  seed  leaves  v^-orth  mentioning,  while  peas  in 
greater  numbers,  and  lupins  and  beans  in  smaller  amounts,  had  elongated 
the  root  body,  to  be  sure,  but  had  not  developed  the  aerial  axillar)^  part.  Of 
seeds  which  had  germinated  at  2  degrees  C,  flax  was  more  sensitive  than 
rape  seed,  which  germinated  at  approximately  o  degrees,  but  did  not  advance 
developmentally  or  show  growth  worth  mentioning  until  given  a  noticeably 
higher  temperature  (8.7  degrees  C).  Peas  and  clover  were  found  to  stand 
next  to  vetches.  They  put  forth  a  root  and  leaf  at  an  average  temperature 
of  2  degrees  C,  while  beans  and  lupins  needed  at  least  3  degrees  C.  for  this. 
Asparagus  developed  slowly  at  2  degrees  C.  For  the  carrot,  approxi- 
mately 3  degrees  seemed  to  be  necessar)-^  for  germination,  and  for  the  beet 
root  about  5  degrees  C.  was  needed. 

It  is  not  necessary  to  state  here  in  detail  that  naturally  the  length  of 
time  of  germination  increases  in  proportion  to  the  amount  of  temperature 
variation  from  the  optimum  of  germination,  but  attention  might  be  called 
to  the  fact  that  such  germination  experiments  with  the  lowest  possible  tem- 
perature could  lead  to  the  growing  of  varieties  hardy  to  frost.  In  all  the 
seeding  experiments  uneven  germination  is  found.  It  may  be  possible  that 
those  seeds  which  have  first  germinated  at  such  low  temperatures  give  plants 
which  have  a  lesser  need  of  heat  for  all  their  life  processes  than  do  other 
individuals  of  the  same  groups. 

Kirchner's  experiments^  show  that  not  only  the  initial  stages  of  ger- 
mination can  take  place  normally  at  such  low  temperatures  but  also  that  a 
further  growth  in  length  is  made  possible.  Kirchner  found  mustard,  rye, 
wheat,  peas  and  hemp  growing,  as  seedlings,  for  some  time  at  temperatures 
which  lay  but  little  above  o  degrees  C.  To  be  sure,  plants  with  a  greater 
need  of  heat  still  show  some  growth  in  length  when  carried  over  into  a  low- 
temperature  ;  but  this  growth  can  be  explained  only  as  the  gradual  dying 
out  of  the  oscillations  of  the  energy  of  growth  obtained  under  earlier,  more 
favorable  conditions. 

Kerner-  has  observed  with  Alj)inc  jilants  that  they  can  even  blossom  at 
o  degrees.  The  melting  water  trickling  into  the  soil  from  the  snow  fields 
is  able  so  to  stimulate  the  life  activity  of  such  plants  that  the  heat  produced 
by  their  respiration  is  able  to  melt  the  ice  crust  when  it  is  even  2  to  5  cm. 
thick,  so  that  the  green  organs  reach  the  open  air  (Soldanello). 

Autumn  Coloration. 

The  coloring  of  the  leaves  in  the  autumn  is  not  always  the  same  for  the 
same  variety.  It  seems  that  the  difference  is  caused  by  the  habitat  of  the 
individual.     In  general  two  types  can  be  distinguished;  either  a  perfectly 


1  4.  Ver.s.  deutsrher  Naturfor.scher  u.  Arzte  zu  Salzburg,  p.  75  d.  Berichtes. 

2  Berichte   d.    naturwissenschaftl.-mediz.   Vereins   zu   Innsbruck,    Sitzung   vom 
15.  Mai  1873,  cit.  Bot.  Z.  1873,  p.  438. 


501 

normal  process  of  yellowing  is  found,  beginning  at  the  edge  of  the  leaf,  and 
followed  by  the  drying  of  the  tissue,  toward  the  centre  of  the  leaf,  or  the 
yellowing  and  drying  do  not  follow  parallel,  but  rather  opposite  paths,  i.  e., 
the  process  of  turning  yellow  begins  at  the  petioles  and  the  larger  veins  and 
advances  toward  the  periphery,  so  that  the  edge  is  colored  last  of  all,  while, 
nevertheless,  the  first  to  dry  subsequently.  I  observed  the  last  course  espe- 
cially well  in  Acer  platanoides,  less  constantly  in  Acer  Pseudoplatanus.  The 
middle  surface  showed  an  uniform  brilliant  quince  yellowy  while  the  peri- 
pheral zone  was  still  green.  With  advanced  lowering  of  the  temperature, 
many  leaves  showed  a  turning  brown  and  dying  of  the  outermost  edge  of  the 
still  green  part  of  the  leaf  peripher}^  while  the  yellow,  middle  field  did  not 
yet  show  any  dead  places  in  the  tissue. 

This  case  can  also  occur  with  Tilia,  and  in  fact  usually  on  one  side, 
since  only  half  of  the  leaf  shows  the  process.  Nevertheless  in  the  linden, 
the  coloration,  advancing,  from  the  edge  toward  the  centre,  is  more  frequent. 
The  investigations  of  numerous  cases  show  that  the  irregularities  of  color- 
ation are  connected  with  the  irregular  dying  of  the  vascular  bundles. 

The  normal  autolysis  in  the  autumn  sets  in  when  the  whole  vascular 
bundle  system  of  the  roots  has  still  retained  its  functioning  and  the  dying 
back  only  begins  at  the  finest  ends  of  the  ner\'es  at  the  edge  of  the  leaf. 
Then  the  leaf  discolors  and  dries  firr.t  along  the  edge ;  the  discoloration  ad- 
vances gradually  in  the  portions  of  the  leaf  between  the  smaller  veins  and 
finally  also  between  the  larger  ones  toward  the  midrib  and  the  petiole.  If, 
on  the  other  hand,  the  functioning  of  the  ducts  is  prematurely  destroyed  in 
the  branch  or  in  the  petioles,  which  can  be  perceived  from  the  browning  of 
the  vascular  bundles,  then  the  discoloration  begins  at  the  petiole,  or  the 
larger  veins,  and  extends  irregularly  toward  the  periphery. 

The  course  of  the  dying  back,  due  to  continued  summer  drought,  re- 
sembles the  normal  autumnal  autolysis,  inasmuch  as  the  parts  of  the  leaf 
receiving  the  least  amount  of  water  are  the  first  to  discolor.  Besides  the 
dr}4ng  of  the  leaf  edges,  however,  that  of  the  middle  region  of  the  larger 
intercostal  fields  becomes  more  noticeable  here,  because  these  lie  fartherest 
from  the  strongly  developed  conducting  strands ;  thus  especially  great  de- 
mands are  made  upon  them  because  of  excess  of  light  and  heat. 

The  autumn  coloring  begins  with  a  change  of  the  chlorophyll  often 
accompanied  by  the  appearance  of  a  red  coloring  matter.  At  first  a  change 
in  the  position  of  the  chloroplasts  is  noticed,  and  a  tendency  to  unite.  I 
found  in  the  spruce  that  the  individual  chloroplasts  form  radiating  processes 
which  unite  with  those  of  the  adjacent  ones.  The  red  coloration  is  condi- 
tioned by  the  presence  of  ferments  and  related  bodies.  Many  evergreen 
plants  turn  a  dirty  brownish  green.  According  to  Kraus^  this  coloring  is 
produced  as  follows :  fine  grained  protoplasmic  masses,  colored  a  bright 
reddish  green  to  copper  red,  occur  in  the  palisade  parenchyma  in  place  of 

1  Kraus,   tjber  die  winterliche  Farbung  immergTiiner   Gewachse.     Sitzungsber. 
d.  phys.-med.  Soc.  Erlangen;   cit.  in  Oekonomische  Forstchritte  1872,  Nos.  1  u.  2. 


502 

the  disappearing  chloroplasts.  The  further  the  cells  of  the  leaf  flesh  are 
separated  from  the  brown  upper  surface,  the  more  transitions  are  noticed 
from  these  reddened  cytoplasmic  masses  to  the  normal  chloroplasts. 

All  these  changed  tissues  may,  in  many  cases,  be  brought  back  to  the 
normal  color,  if  cut  branches  are  brought  into  a  warm  place.  In  this,  how- 
ever, the  intensity  of  the  light  is  not  increased,  and  this  may  explain  why 
only  a  lowering  of  the  temperature  should,  in  general,  be  considered  as  the 
cause  of  the  autumn  coloring.  A  further  proof  lies  in  the  fact  that  in  the 
autumn  natural  ripening  only  the  ripened  places,  i.  e.,  the  places  most  cooled 
down  by  heat  radiation,  change  their  color,  while  the  parts  inside  the  top  of 
the  tree  and  co\^ered  by  the  outer  leaves,  show  no  change. 

In  regard  to  the  change  in  the  coloring  matter  of  the  chlorophyll,  it  has 
been  proved  by  Frank^  and  Wiesner-  that  the  chlorophyll  passes  over  into  a 
substance  which  Pringsheim  called  "Hypochlorin"'-\  This  is  an  oily  body, 
usually  dark  colored,  which  is  produced  from  chloroplasts  by  the  action  of 
anorganic  and  organic  acids  and  finally  crystallizes  into  needles  or  whip-like 
brown  crystals.  Tschirch^  has  proved  that  this  hypochlorin  is  identical  with 
the  "Chlorophyllan"  of  Hoppe-Seyler  and  that  it  should  be  considered  as  the 
first  product  of  the  oxidation  of  the  chlorophyll  (and  in  fact  of  only  one 
part  of  the  raw  chlorophyll,  viz.,  the  cyanophyli  of  G.  Kraus).  This  product 
is  formed  of  itself  if  a  chlorophyll  solution  is  left  standing  for  some  time'. 

Tschirch  found  that  the  formation  of  chlorophyllan  or  hypochlorin, 
increasing  according  to  the  amount  of  acid,  could  be  proved  (tytrimetri- 
cally,  by  means  of  normal  alkali)  in  the  parts  of  the  plants.  Besides  water 
plants,  there  may  be  only  a  few  plants,  the  cell  sap  of  which  does  not  have 
a  marked  acid  reaction.  In  genera  which  contain  little  acid,  the  formation 
of  the  chlorophyllan  will  be  small  and  the  extract  made  from  this  will  have 
to  stand  some  time,  while  in  strongly  acid  plants  (Aesculus,  Rumex)  the 
oxidation  proceeds  so  fast  of  itself  that  no  purely  green  extract  can  be  made, 
since  it  at  once  exhibits  the  peculiarities  of  the  modified  chlorophyll  and, 
even  when  chilled,  deposits  chlorophyllan. 

It  is  worth  mentioning,  .for  our  consideration,  that  according  to  Tschirch 
even  carbon  dioxid  is  able  to  change  the  chlorophyll  into  chlorophyllan. 
Also  the  tannic  substances  with  which  the  red  coloring  matter  is  certainly 
related,  will  have  to  be  reckoned  among  those  bodies  with  an  acid  reaction 
which  attack  the  chloroplasts.  It  is  thus  a  question  whence  it  comes  that 
this  discoloring  influence  of  the  acid  cell  sap  makes  itself  felt  in  the  chloro- 
plasts only  in  the  autumn.  This  can  be  explained  either  because  in  the  course 
of  the  summer  so  little  free  acid  is  available  in  proportion  to  the  rest  of  the 


1   Silzungsber.  d.  Bot.  Ver.  d.  Prov.  IJrandenburg  XXIII,  v.  24.  Feb.  1882. 

a   Bemerk.  iiber  d.  Natur  d.  Hypochlorins.    Bot.  Centralbl.  1882,  Vol.  X,  p.  260. 

3  Untersuchungen  iiber  Lichtwirkung.    Pringsheims  Jahrbiicher  1880,  Vol.  XII. 

4  Sitzungsber.  d.  Bot.  Ver.  d.  Prov.  Brandenburg  XXIII,  v.  28.  April  1882. 

5  Concentrated  hydrochloric  acid  breaks  down  the  chlorophyllan  into  a  body 
dissolving  in  hydrochloric  acid  with  a  blue  color,  the  "Phyllocyanin"  of  the  authors, 
and  a  brown  body  insoluble  in  hydrochloric  acid,  but  soluble  in  ether,  the  "Xanthin" 
of  C.  Kraus.  (Tschirch,  Untersuchungen  iiber  das  Chlorophyll  III.  Ber.  d.  deutschen 
Bot.  Ges.  Vol.  I,  Parts  3  and  4;  cit.  Centralbl.  1883,  Vol.  XIV,  No.  25,  p.  356. 


503 

substances  in  the  leaf  cell  that  the  chlorophyll  used  in  the  formation  of  the 
chlorophyllan  is  constantly  and  quickly  replaced  by  the  preponderant  process 
of  assimilation,  in  which  case  usually  no  yellow  coloration  of  the  chlorophyll 
body  is  noticeable,  or  the  chlorophyll  body  may  be  protected  by  a  substance 
which  does  not  let  the  acid  through,  gradually  losing  this  protection  in  the 
autumn.  However,  both  processes  might  take  pace  and,  according  to  the 
above  experiments,  this  is  most  probable. 

Frank  and  Wiesner  refer  to  the  actual  presence  of  an  arrangement  in 
the  chloroplasts  which  protects  them  against  the  attacks  of  the  acid  cell  sap. 
They  emphasize  that  the  green  grains  lie  imbedded  in  protoplasm  which  is 
impervious  to  acids.  Tschirch  has  also  mentioned  that  each  chlorophyll 
grain  is  surrounded  by  a  colorless  cytoplasmic  membrane  (hyaloplasma- 
layer)  which  is  especially  easily  proved  in  water  plants,  and  in  this  way 
possesses  a  special  protection  against  the  acid  cell  sap. 

As  the  leaf  cell  approaches  the  end  of  its  life  in  the  autumn  the  proto- 
plasm is  no  longer  ver}^  abundantly  present.  But  even  where  it  is  still  more 
abundant,  it  undergoes,  in  the  cold  of  the  autumn,  a  change  (which  may  be 
overcome  by  heat),  making  it  permeable  to  acids.  Frank  found  that  the 
yellow  coloration,  produced  by  the  action  of  acid  on  the  chloroplasts,  had 
already  occurred  when  they,  together  with  the  nucleus,  lay  closely  imbedded 
in  the  cytoplasmic  wall  layer.  Such  a  change  in  the  diosmotic  character- 
istics of  the  protoplasm  of  evergreen  trees  also  makes  possible  the  action  of 
acids.  The  organic  acids  increase,  however,  in  the  autumnal  leaf  in  this 
way,  making  easier  leaf  coloration. 

In  regard  to  the  red  coloration,  C.  Kraus^  has  proved  that  the  Brenz- 
catechin  (orthodihydroxbenzine)  first  found  by  Gorup-Besanez-  in  wood- 
bine occurs  in  all  leaves  which  change  color  in  the  autumn  even  (so  far  as 
the  partial  investigation  extended)  in  all  leaves  still  growing  vigorously. 
This  substance  turns  green  with  ferric  chlorid  and  a  beautiful  red  with  vege- 
table acids.  The  extracts  of  the  leaves  give  the  reactions  of  oxyphen  acid, 
on  which  account  the  conclusion  is  pertinent  that  the  red  coloring  matter  in 
the  young  leaves  and  in  those  which  have  changed  color  in  the  autumn 
comes  from  the  increased  effect  of  the  Brenz  catechin,  due  to  the  increased 
action  of  the  acid. 

Summarizing  all  that  has  been  said  previously  we  can  consider  the 
process  of  the  autumnal  change  of  color  as  a  process  of  oxidation,  increased 
in  proportion  to  the  process  of  assimilation  and  due  to  the  effect  of  light. 

This  acts  very  differently  on  the  substances  present  in  the  cells  of  the 
various  plants,  so  that  the  chlorophyllan  is  produced  from  the  chlorophyll 
coloring  matter  and  the  leaf  becomes  yellow\''  If  the  Brenz  catechin, 
which  may  be  produced  artificially  from  carbo-hydrates  and  probably   is 


1  t)ber  die  Herbstfarbung  der  Blatter  und  die  Bildung-  der  Pflanzensauren. 
Biedermanns  Centralbl.  1874,  I,  p.  126. 

2  Annalen  der  Chemie  und  Pharmacie  1872,  Vol.  CLXI,  Parts  2  and  3. 

3  The  chlorophyllan  extraction  of  leaves  dead  in  the  autumn  shows  the  same 
"bandes  accidentelles  permanentes"  as  Chantard  emphasized  earlier  (Centralbl.  f. 
Agrikulturchemic  1874,  p.  40). 


504 

present  in  opalescing  drops,  is  changed  into  a  red  coloring  matter  by  means 
of  an  autumnal  abundant  formation  of  acid,  a  reddening  and  yellowing  of 
the  leaves  follow.  The  leaf  turns  brown,  however,  if  on  the  other  hand, 
there  predominates  the  formation  of  brownish  yellow  masses  observed  by  G. 
Kraus^  and  Haberlandf-  with  the  destruction  of  the  form  of  chloroplasts, 
which  masses  C.  Kraus  considered  as  the  products  of  oxidation  and  humi- 
faction  of  the  carbo-hydrates  and  which,  as  I  believe,  can  directly  arise  from 
the  decomposition  of  the  chloroplasts. 

The  most  frequent,  but  certainly  not  the  only  cause  of  the  red  color- 
ation, is  the  lowering  of  the  temperature,  whereby  the  action  of  the  light 
becomes  relatively  excessive.  It  is  not  the  absolute  values  of  light  and  heat 
which  are  determinative  here,  but  the  relative  ones,  i.  e.,  those  coming  under 
consideration  in  relation  to  one  another.  A  lowering  of  the  temperature 
reduces  the  process  of  chlorophyll  formation,  while  it  sustains  in  full  activ- 
ity that  of  oxidation,  which,  forming  Brenz  catechin,  requires  more  light^, 
and  initiates  the  red  coloration.  If  the  activity  of  the  chlorophyll  apparatus 
is  increased,  i.  e.,  more  carbo-hydrates  are  formed,  the  accessible  oxygen  is 
no  longer  sufficient  for  so  high  a  degree  of  oxidation  and  the  process  of  red 
coloration  is  suppressed.  If,  however,  the  work  of  the  chloropyll  is  arti- 
ficially retarded  by  a  lack  of  nutriment  and  moisture,  then  the  oxygen  acces- 
sible in  the  cell  can  suffice  to  reoxydize  to  a  high  degree  the  material  which 
has  become  more  scanty;  in  this  case  the  autumn  color  occurs  even  in 
summer. 

As  has  been  mentioned  already,  1  observed  in  August,  with  girdling 
experiments  on  Crataegus,  that  the  autumn  coloring  occurred  even  during 
the  intense  heat  of  summer  and  that  at  times  it  was  possible  with  somewhat 
more  solid  leaves  to  bring  the  tip  of  the  leaf  which  had  been  left  on  the  tree 
to  a  bright  red  autumn  change  of  color  by  breaking  the  midrib  while  the  leaf 
base,  lying  below  the  sharp  point  of  breaking,  retained  its  normal  deep  green 
color.  Besides  this,  in  the  course  of  the  summer,  we  find,  in  many  plants, 
vhat  the  first  formed  leaves  of  the  annual  growth,  which  have  quickly  lived 
out  their  life,  assume  their  autumnal  coloration  in  the  heat  of  summer 
(Ampelopsis).  Places  on  young  red  leaves,  which  have  been  covered, 
remain  greener.  We  will  take  up  these  conditions  again  under  "Defoliation 
due  to  frost."  The  winter  preparation  of  evergreen  plants  will  be  taken  up 
thoroughly  in  the  section  on  "Theories  as  to  the  Nature  of  Frost  Action." 

Frosting  and  Freezing  to  Death. 

In  the  literature  on  this  subject,  we  find  different  conceptions  of  the 
term  "freezing  to  death."  Death  which  gradually  sets  in  in  a  plant  because 
it  has  not  obtained  the  warmth  necessary  for  carrying  through  its  normal 
functions  has  been  explained  in  part  as  freezing.     On  the  other  hand,  only 


1  Okonom.  Fortschritte  1872.  Nos.  1  and  2. 
:;  Biedermanns  Centralbl.  1876,  II,  p.  48. 

3  Batalin.   tlber    die   Einwirkung   des   Lichtes   auf  die   Bildung   des   rnten   Pig- 
mentes.     Acta  Hort.  Fctrop.  VI. 


S05 

the  death  which  occurs  suddenly  as  a  result  of  a  lowering  of  temperature 
below  the  minimum  boundary  of  heat  requirement  and  which  is  connected, 
as  a  rule,  with  the  formation  of  ice,  may  be  considered  as  "freezing  to 
death." 

We  can  best  overcome  this  difiference  in  the  use  of  the  terms  if  we 
consider  the  first  injury^  due  to  a  lack  of  heat,  as  a  "chronic  injury"  and 
sudden  death  as  an  "acute  injury." 

Tender  plants  from  the  tropics,  which  in  our  greenhouses  do  not  con- 
tinuously find  the  heat  necessary  for  all  their  developmental  phases,  often 
furnish  examples  of  chronic  injury.  Failures  in  the  culture  of  Indian 
varieties  of  Anoe^tochilus  and  other  tender-leafed  orchids.  Begonias,  Ges- 
neraceae,  Marantaceae,  etc.,  are  well  known.  I  found  their  leaves  becom- 
ing brown-specked,  curling  and  dying  if  exposed  for  some  time  to  a  tem- 
perature of  3  degrees  above  zero  to  5  degrees  below  zero\  In  wet,  cold 
years,  open  ground  culture  of  melons,  cucumbers,  tobacco  and  beans  became 
diseased  when  the  lack  of  heat  was  prolonged. 

In  acute  injury,  one  is  inclined  involuntarily  to  ascribe  it  to  the  forma- 
tion of  ice.  That  this  in  itself  does  not  cause  death  is  shown  in  many  cases 
,  by  our  hardy  plants,  which  often  are  frozen  stifif  and  as  brittle  as  glass  and 
yet  continue  their  growth  after  the  frost  has  disappeared. 

Let  us  picture  to  ourselves  the  effect  of  the  formation  of  ice  in  the 
tissue.  If  the  temperature  of  the  part  of  the  plant  has  fallen  to  the  freezing 
point  or  somewhat  below  it,  small  ice  crystals  are  formed  on  the  outside  of 
the  cell  w^all.  These  crystals,  produced  at  first  from  the  absorption  water 
and  later  from  the  imbibition  water  of  the  cell  wall,  become  constantly 
larger,  since,  at  their  base,  more  and  more  water  from  the  mycellar  inter- 
stices of  the  cell  wall  is  changed  to  ice.  Finally,  all  the  fine  ice  prisms  are 
united  into  an  ice  crust.  The  cell  wall  has  attempted  to  make  up  for  the 
loss  of  water  which  it  has  undergone  by  taking  up  new  amounts  from  the 
cell  contents. 

Thus  the  protoplasmic  body  of  the  cell  becomes  poor  in  water,  and 
material  changes  begin,  which  finally  reach  such  an  intensity  that  the 
equilibrium  of  the  different  mycellae  of  the  cell  wall  and  of  the  proto- 
plasm is  permanently  disturbed.  They  change  in  such  a  way  that  no  more 
life  activity  is  possible.  The  cell,  killed  by  frost,  thus  shows  that  its  walls 
offered  no  resistance  to  the  pressure  of  the  cell  sap,  gradually  letting  it  flow 
away.  In  direct  contact  with  the  air,  this  passes  over  into  decomposition 
and  the  cell  itself  collapses.  The  frozen  part  of  the  plant  appears  wilted 
and  dried,  or  rapidly  decays.  The  cell  sap,  passing  out  of  it, — this  initiates 
the  decay, — presses  through  the  mycellar  interstices  and  not  through  any 
breaks  in  the  cell  wall  which  might  have  been  produced  by  frost.  Indeed  in 
a  frozen  part  of  the  plant  the  tissue  can  be  blasted  by  the  ice  in  different 


1  Compare  also  Molisch,  Hans,  Das  Erfrieren  der  Pflanzen  bei  Temperaturen 
viber  dem  Eispunkte.  Sep.  Sitzungsber.  d.  K.  Akad.  d.  Wiss.  Wien.  Mat.-naturw. 
Klasse,  Vol.  CV,  sec.  1;   cit.  Z.  f.  Pflanzenkrankh.  1897,  p.  23. 


5o6 

groups  and,  as  frequently  observed,  the  cells  of  the  epidermis  can  be  raised 
from  the  underlying  parenchyma,  while  a  rupturing  of  the  individual  cells, 
due  to  the  freezing  of  the  water,  has  as  yet  been  rarely  observed.  There- 
fore, the  theory  formerly  generally  expressed  and  now  frequently  held  by 
practical  growers,  that  the  frost  kills  the  plants  by  rupturing  the  cells,  has 
been  given  up  as  untenable. 

In  the  same  plant  the  same  degree  of  cold  can  be  uninjurious  at  one 
time  and  fatal  at  another,  according  to  whether  thawing  takes  place  gradu- 
ally or  suddenly.  This  latter  case  may  be  observed  if  frozen  leaves  or 
herbaceous  stems  of  soft-leaved  plants  are  held  in  the  warm  hand.  The 
places  of  contact  frequently  become  black  after  thawing  and  die.  We  will 
return  to  these  phenomena  in  the  following. 

Rapid  and  violent  changes  in  temperature  within  a  scale  above  zero 
degrees  C.  also  did  not  remain  ineffective.  Sachs^  has  proved  that  each 
rapidly  appearing  rise  or  fall  of  temperature  is  followed  by  an  increase  or 
decrease  of  the  rate  of  growth.  While  de  Vries  could  observe  no  disad- 
vantageous results  from  such  fluctuations,  I  found  a  dropping  of  the  leaves 
in  the  most  extreme  cases,  especially  if  the  fluctuations  took  place  in  a  scale 
which  began  several  degrees  under  zero  and  rose  considerably  above  zero. 
The  same  plants  in  fact  die  if  a  change  of  temperature  is  repeated  several 
times  within  a  short  period,  as  shown  by  Goppert's  experiments"-.  Milk- 
weed (Euphorbia  Lathyris)  was  taken  from  a  temperature  of  4  degrees  C. 
below  zero  into  a  room  at  18  degrees  C.  The  leaves,  bent  backward  and 
against  the  stem,  because  of  frost,  were  raised  at  once  and  assumed  their 
normal  horizontal  position.  The  same  process  was  found  in  a  repetition  of 
the  experiments,  which  took  place  five  times  within  two  days.  On  the  third 
day  the  raising  of  the  leaves  began  to  be  less  and  after  eight  days  the  plants 
were  dead.  Here,  therefore,  the  cause  of  death  was  the  re,peated  action  of 
slighter  degrees  of  frost,  while  out  of  doors,  and  uncovered,  they  could 
qndure  10  to  12  degrees  below  zero  for  some  time  without  bad  effects.  The 
same  experiments  gave  similar  results  with  many  other  plants.  This  ex- 
plains the  observation  in  general  practice  that  slighter  degrees  of  cold  in 
many  places  kill  plants  which,  at  the  same  time,  in  a  place  with  more  con- 
stant temperature,  can  endure  much  greater  cold. 

Goppert  also  calls  attention  to  another  fact  which  may  serve  to  explain 
the  frequent  contradictions  in  regard  to  the  fatal  action  of  slighter  degrees 
of  frost  in  those  plants  which  usually  defy  greater  cold.  It  depends  espe- 
cially upon  the  conditions  under  which  the  plant  may  find  itself  at  the  time, 
as  shown  by  the  experiment  with  the  common  groundsel  {Senecio  vulgaris) 
and  meadow  grass  {Poa  annua).  Pots  of  these  plants,  which  had  already 
withstood  a  temperature  of  9  degrees  below  zero,  v^ere  placed  for  15  days  in 
a  greenhouse  at  12  to  18  degrees  C.  above  zero.  After  this  time  they  froze  at 
a  temperature  of  7  degrees  below  zero,  while  other  examples  of  the  same 


Lehrbuch  d.  Bot.,  3d  ed.,  p.  638. 

tJber  die  Warmeentwicklung  in  den  Pflanzen  usw.  1830,  p.  62. 


507 

varieties,  which  had  remained  out  of  doors  during  this  time,  wqre  found 
absolutely  uninjured  by  rapid  thawing.  The  killed  plants  had  been  made 
more  tender  by  the  retention  in  the  greenhouse.  Kornicke^  also  comes  to 
the  same  conclusion  in  his  observations  that  French  varieties  of  grain,  on 
an  average,  more  often  fall  victim  to  frost  than  the  varieties  which  originate 
from  the  provinces  of  Prussia  and  Silesia.  The  longer  cultivation  in  a 
country  with  a  mild  winter  has  made  the  varieties  less  resistant. 

Under  otherwise  equal  conditions,  Haberlandt-  found  that  the  seed- 
lings of  field  beans,  field  vetches,  carrots,  barley,  peas,  rape,  poppy,  red 
clover,  alfalfa  and  flax,  grown  in  a  greenhouse  at  20  to  24  degrees  C,  were 
frozen  to  death  even  at  6  degrees  C.  below  zero;  rye  and  wheat  at  10  to  12 
degrees  below  zero,  while  plants  of  the  same  variety,  grown  at  the  same  time 
in  a  cold  frame,  died  only  at  9  to  12  degrees  below  zero,  and  rye  and  wheat 
only  at  20  to  24  degrees  C.  below  zero. 

The  plants  and  parts  of  plants  whose  growth  has  entered  upon  a  dor- 
mant period,  on  an  average,  suffer  less  and  it  is  well  known  that  dried  seeds 
survive  uninjured  many  degrees  below  freezing,  while  they  go  to  pieces  in 
a  germinating  stage  with  much  slighter  frost. 

During  the  vegetative  development  the  susceptibility  to  frost  changes 
with  the  different  phases  of  the  cell  life. 

In  unfolding  apple  blossom  buds,  which  had  suffered  from  a  spring 
frost,  I  found  the  youngest  cells,  richest  in  protoplasm,  were  not  injured, 
but  those  somewhat  older,  in  an  energetic  stage  of  elongation,  had  turned 
brown,  while  the  still  older  parenchyma  cells  in  turn  seemed  healthy. 

The  cases,  cited  up  to  the  present,  show  clearly  the  difficulty  in  giving 
definite  thermometer  degrees  as  fixed  minimum  and  maximum  boundaries 
for  the  developmental  capacity  of  any  species.  Each  plant  is  certainly  con- 
nected with  a  definite  scale  of  heat,  but  the  boundary  and  optimum  values 
may  change,  to  a  certain  extent,  according  to  the  combination  of  the  remain- 
ing vegetative  factors,  momentarily  present,  which  earlier  contributed  to 
the  construction  of  the  individual. 

On  the  other  hand,  it  must  be  maintained  that  in  spite  of  all  the  vege^ 
tative  conditions,  which  increase  susceptibility  to  frost,  many  plants  (espe- 
cially numerous  algae,  mosses  and  Alpine  plants)  never  show  any  damage 
from  frost.  We  will  have  to  explain  this  phenomenon  by  the  fact  that  the 
need  of  heat  of  such  plants  is  so  small  that  the  greatest  reduction  in  tem- 
perature is  generally  insufficient  to  produce  those  molecular  changes  in 
the  tissues  which  would  prevent  a  reassumption  of  the  normal  life  functions. 

Theories  as  to  the  Nature  of  Frost  Action. 
After  discussing  the  circumstances  which  modify  the  freezing  of  plant 
parts,  we  will  consider  the  theories  which  have  been  formed  as  to  the  nature 
of  frost  action. 


1  Annalen  d.  Landw.;  cit.  in  Neue  landw.  Zeitung  v.  Fiihling  1871,  Part  8, 
p.  586  ff. 

-  Haberlandt,  tJber  die  Widerstandsfahigkeit  verschiedener  Saaten.  Wissensch. 
praktisch.    Untersucliungen,  Vol.  I. 


5o8 

In  this,  the  phenomena  of  crippling,  due  to  chronic  action  of  cold,  no 
longer  come  under  consideration  ;  for  these  phenomena  are  primarily  normal 
functions  which  are  only  retarded  gradually  by  a  lack  of  heat  until  life 
becomes  extinct\  The  matter  is  quite  dififerent  in  the  acute  cases  where 
death  follows  immediately  upon  the  cold. 

In  the  acute  frost  phenomena,  the  formation  of  ice  becomes  a  consider- 
able factor.  This  does  not  occur,  however,  at  the  point  where  pure  water 
freezes  but  only  below  o  degrees  C,  because  the  cell  sap  represents  a  salt 
solution.  Besides  this,  observations,  of  which  those  of  Miiller-Thurgau'- 
especially  should  be  cited,  show  that  ice  is  produced  only  after  the  freezing 
point  has  been  exceeded  to  a  certain  degree,  either  to  an  excessive  chilling  or 
supercooling.  As  an  example  of  how  often  the  supercooling  point  lies 
considerably  below  the  freezing  point,  a  few  statements  of  the  above  named 
investigators  may  serve  as  examples. 

In  grapes,  the  freezing  point  (G)  was  found  to  be  at  3.1  degrees  C. 
below  zero,  the  supercooling  point  (U)  at  6.7  to  /.S  degrees  C.  below  zero; 
in  apples  and  pears,  1.4  to  1.9  degrees  C.  below  zero  (G)  and  2.1  to  5.1 
degrees  C.  below  zero  (U)  ;  in  potatoes  i.o  to  1.6  degrees  C.  below  zero  (G) 
and  2.8  to  5.6  degrees  C.  below  zero  (U),  etc. 

The  formation  of  ice  occurs  suddenly;  therefore,  in  cases  where  some 
supercooling  has  taken  place,  there  follows  a  sudden  change  in  temperature. 
Our  hardy  plants,  which  can  still  grow  unimpaired  after  they  have  become 
brittle  with  ice,  show  that  the  formation  of  ice  is  fatal  only  for  certain 
varieties.  In  other  cases,  however,  it  has  been  observed  that  parts  of  plants, 
under  certain  conditions,  can  be  cooled  down  to  a  still  lower  temperature 
and  remain  alive,  while,  with  lesser  cold,  but  dififerent  conditions,  they  are 
frozen  as  soon  as  the  formation  of  ice  has  taken  place. 

This  formation  of  ice,  the  process  of  which  we  have  already  described 
thoroughly,  is  now  ascribed  by  Miiller-Thurgau^  and  Molisch*  to  such  a 
withdrawal  of  water  from  the  cell,  that  the  cell  dies  on  this  account.  Ac- 
cording to  this,  death  from  frost  would  be  a  simple  process  of  drying  up. 
The  investigators  support  their  theoi-y  by  the  physical  process,  that,  in 
freezing  swollen  colloidal  substances,  pure  water  will  be  cr}'stallized  out, 
and  the  colloidal  substance,  thus  gradually  dr}dng,  becomes  stifif. 

In  contrast  to  the  above  theory,  is  the  one  we  hold,  that  death  from  frost 
is  no  specific  process  of  drying  but  should  be  sought  in  a  molecular  irre- 
parable destruction  of  the  protoplasmic  structure.  This  destruction  is 
expressed  mechanically  as  well  as  chemically.  The  destructive  tempera- 
ture is  specific  for  each  variety,  each  individual,  each  part  of  the  plant  and 
each  method  of  growth  of  any  plant  part,  but  is  not  directly  connected  with 


1  Compare  Kunisch,  H.,  Vsher  die  ttitliche  Wirkung  niederer  Temperaturen  auf 
die  Pflanzen.  Inauguraldissertation.  Breslau  1880.  —  Sachs,  Landw.  Versuchs- 
stationen  1860,  p.  196. 

2  Landwirtschaftl.  Jahrbucher  1886,  p.  490. 

3  L.OC.  cit.,  .  534. 

4  Molische,  tJber  das  Erfrieren  der  Pflanzen.     Jena  1897. 


509 

the  formation  of  ice,  as  was  evident  in  the  number  of  plants  which,  without 
injury,  endure  the  formation  of  ice  in  their  tissues.  These  plants  are  called 
"resistent  to  ice"  and  they  freeze  only  if  the  parts,  which  have  been  frozen 
stifif,  are  cooled  down  below  this  specific  minimum. 

This  specific  minimum  is  not  fixed  but  rises  with  the  amount  of  cell  sap, 
i.  e.,  death  from  cold  occurs  at  a  higher  temperature  and,  conversely,  a  loss 
of  water  will  cause  an  increase  in  resistance  to  all  factors^  and  therefore, 
with  frost,  will  cause  death  only  at  a  lower  temperature. 

Mez-  adds  to  these  the  following  observations :  Any  aqueous  solution 
of  a  substance  must  be  cooled  down  below  the  freezing  point  of  water 
before  ice  can  be  crystallized  out.  In  dilute  solutions,  as  they  exist  under 
normal  circumstances  in  cell  sap,  the  lowering  of  the  freezing  point  is  pro- 
portionate to  the  molecular  concentration  (Raoult's  law^).  Dalton's  law  in 
regard  to  the  solution  of  osmotic  substances  which  contain  several  sub- 
stances in  solution,  holds  good  here.  According  to  it,  the  amount  that  the 
freezing  point  is  lowered  equals  the  sum  of  those  amounts  which  each  sub- 
stance would  produce  of  itself. 

Since  now  each  cell  in  the  same  plant  may  have  a  content  gradually 
dififering  from  that  of  the  other  cells,  the  point  of  minimum  cooling  of  the 
cell  sap  will  be  a  constantly  changing  one.  Since  the  composition  of  the  cell 
sap  within  the  latitude  of  the  specific  limits  of  all  varieties  of  plants  fluctu- 
ates according  to  the  nutrition,  it  is  easy  to  understand  that  the  various 
individuals  possess  a  different  resistance.  This  also  explains  the  different 
behavior  of  dry  and  juicy  parts  of  plants.  The  fact  that  in  seeds,  which 
may  be  dried,  death  can  result  also  from  a  removal  of  water  is  explained  by 
Miiller  and  Molisch  by  the  assumption  that  it  takes  place  because  of  the 
sudden  formation  of  ice  in  the  supercooled  plant,  whereby  the  water  is  veryr 
rapidly  removed.  Pfeffer*  opposes  this  hypothesis  and  his  book  contains 
a  thorough  treatment  of  the  pertinent  literature.  Mez's  studies,  already 
mentioned,  support  Pfeffer,  for  his  investigations  led  to  the  following 
results.  The  fall  in  temperature,  indicating  the  end  of  crystallization,  did 
not  lie,  in  any  of  the  objects  tested,  below  6  degrees  C.  below  zero.  (The 
experiments  were  made  with  petioles  of  Helleborus,  Saxifraga  and  Strelitzia, 
with  leaves  of  Sempervivum  and  sprouts  of  Opuntia,  Asparagus,  Begonia, 
Peperomia,  etc.). 

"But  the  cell  sap,  capable  of  coagulation  and  not  absorbed,  stiffens  be- 
tween o  and  6  degrees  C.  below  zero.  Accordingly,  at  30  degrees  C.  below 
zero,  no  greater  dr}dng  of  the  protoplasm,  resulting  from  the  removal  of 
water  in  the  formation  of  ice,  takes  place  than  at  6  degrees  C.  below  zero. 
A  plant  which  always  survives  the  formation  of  ice  in  its  tissues,  does  not 


1  Pfeffer,  Pflanzenphysiologie,  2d  ed.,  p.  315,  note. 

2  Mez,  Carl,  Neue  Untersuchung-en  iiber  das  Erfrieren  eisbestandiger  Pflanzen. 
Sond.  Flora  oder  Allgem.  Bot.  Z.  1905,  Vol.  94,  Part  I. 

3  Raoult's  law:  cit.  Nerst,  Theoretische  Chemie,  4th  ed.  1903,  p.  152. 

■i   See  the  chapter  on  "Die  Ursachen  des  Erfrierens"'    in  "Pflanzenphysiologie," 
II.  Vol.,  1904,  p.  314. 


510 

die,  therefore,  as  a  result  of  tlic  dying  of  the  protoplasts,  but  of  a  cooling 
down  below  the  specific  minimum." 

We  find  in  this  a  confirmation  of  our  earlier  standpoint,  viz.,  no  simple 
process  of  crystallizing  out  the  water  is  caused  by  the  action  of  the  cold  but 
a  material  disassociation.  This  action  of  the  cold  makes  the  life  functions 
impossible.  Besides  these  essentially  mechanical  processes,  however,  chem- 
ical decomposition  often  plays  a  part.  This  will  be  initiated  sometimes  by 
too  great  cooling,  sometimes  without  it.  Not  every  plant  needs  to  be  first 
cooled  down  in  order  to  freeze,  but  it  probably  freezes  more  rapidly,  i.  e., 
is  cooled  down  to  a  sub-minimum  temperature,  if  the  freezing  occurs  in 
association  with  supercooling.  At  least  this  is  shown  by  Mez's  experi- 
ments with  pieces  from  the  stem  of  Impaticns  parviflora.  We  learn  from 
these  experiments  how  very  much  the  supercooling  depends  upon  the  con- 
stitution of  the  cell  sap.  Gases,  dissolved  air,  hinder  or  decrease  super- 
cooling just  as  do  emulsified  oil,  gum  or  plant  mucilage.  It  is  also  found 
that  pruned  plant  parts,  cooled  down  in  water,  always  freeze  without  any 
further  reduction  of  temperature  or,  at  least,  without  an  essential  one.  It 
happens  that  plant  stems,  standing  partially  in  water,  are  found  to  be  frozen 
as  far  back  as  they  extend  into  the  air.  Molisch  tested  the  question  experi- 
mentally by  letting  branches  of  Tradcscantia  zehrina  lie  half  in  water. 
During  the  night  a  temperature  of  5  degrees  C.  below  zero  acted  upon  them. 
After  a  slow  thawing  in  a  cool  room,  the  half  of  the  sprouts  which  had  been 
left  in  the  air  were  found  to  be  frozen,  while  the  lower  half,  sticking  in  the 
ice,  remained  uninjured.  The  upper  half,  surrounded  by  air,  will  have 
been  cooled  down  rapidly  by  supercooling  and  is  thereby  frozen.  On  the 
other  hand,  as  far  as  the  plants  stood  in  water,  the  cooling  down  takes  place 
slowly  on  account  of  the  high  specific  warmth  of  the  water,  and  the  super- 
cooling will  be  hindered  by  the  freezing  water  about  the  stem  as  well  as  by 
the  ice  in  the  tissues  above  the  water,  which  have  been  frozen. 

An  observation  made  by  Miiller-Thurgau,  that  in  a  heap  of  beets,  the 
outer  frozen  roots  protect  the  inner  ones  from  freezing,  calls  attention  to 
the  specially  favorable  influence  of  the  formation  of  ice.  This  point  is 
emphasized  by  Mez,  since  he  says  in  general  that  the  transformation  of  the 
cell  sap  into  a  solid  aggregate  condition  forthwith  protects  from  too  rapid 
radiation  the  energ}^  still  retained  in  the  plant.  The  conducting  of  heat  is 
very^  much  lower  in  ice  than  in  water  in  which  the  warmth  is  distributed  by 
currents. 

The  danger  of  freezing,  i.  e.,  the  lowering  of  the  temperature  to  the 
specific  death-dealing  minimum,  can  in  part  be  promoted  by  secondary  cir- 
cumstances and  in  part  hindered  by  them.  The  decrease  lies  in  the  use  of 
the  specific  heat  of  water;  this  will  be  mentioned  again  in  methods  of  pro- 
tection against  frost  and  further  in  the  formation  of  ice  itself,  which  occurs 
at  zero,  or  a  very  little  below  it,  while  death  sets  in  only  at  lower  tempera- 
tures or  finally  in  a  change  of  the  cell  sap,  since  a  greater  quantity  of  oil, 
gum  and  mucilage  acts  retardingly. 


511 

The  increase  of  the  danger  of  freezing  to  death  exists  in  all  conditions 
which  hasten  the  appearance  of  a  fatal  supercooling. 

Thus,  for  example,  the  anatomical  structure  of  the  individual,  depend- 
ing upon  the  vigor  of  nutrition,  can  influence  this.  In  very  luxuriant 
growth,  the  lumina  of  the  cells  and  ducts  are  wider  and  the  intercellular 
spaces  larger.  However,  the  wider  the  duct,  the  more  the  lowering  of  the 
freezing  point  is  suppressed  by  capillarity.  We  find  this  fact  emphasized 
by  Bruijning^  He  found  that  the  extract  of  Taxus  leaves,  in  narrow 
capillary  tubes,  has  a  freezing  point  of  8.8  degrees  C.  below  zero,  while  the 
same  extract  in  open  reagent  glasses  freezes  at  1.3  degrees  below  zero. 

Besides  the  greater  amount  of  water  in  the  tissues,  the  constitution  of 
the  air  (amount  of  humidity  contained)  and  its  movement  come  under  con- 
sideration. In  the  later  connection,  attention  should  be  called  to  the  wide- 
spread discovery  that,  in  protected  positions  (in  narrow  valleys,  fields  sur- 
rounded by  woods,  etc.)  plants  freeze  which  would  remain  uninjured  in 
regions  accessible  to  the  wind. 

In  order  to  explain  this  circumstance,  we  will  have  to  recall  the  fact 
that  air  in  motion  increases  evaporation  and  thus  concentrates  the  cell  sap. 
With  stronger  evaporation  the  formation  of  ice  will  occur  more  quickly, 
whereby  supercooling  will  be  avoided,  and,  at  the  same  time,  protection 
of  the  remaining  heat  in  the  tissue  will  be  brought  about. 

In  its  prevention  of  supercooling  by  the  superimposed  ice,  may  be 
found  the  advantage  of  the  "open  furrow"  for  winter  grain ;  it  retains 
snow  much  longer. 

Fog  will  also  act  as  a  protection.  We  find  a  recent  example  of  this  in 
the  observations  made  by  Thomas"-,  who,  in  Thuringia,  found  that  the  foli- 
age of  young  beeches,  on  the  heights  covered  with  fogs  was  uninjured, 
while  in  the  valleys  it  was  brown  and  wilted  as  a  result  of  frost.  In  this 
case,  an  evident  boundary  line  could  be  found.  In  mountain  forests,  the 
covering  of  clouds  is  a  protection  against  frost  which  one  should  not 
underestimate. 

We  will  now  turn  once  again  to  the  fact  that  in  many  cases  a  rapid 
thawing  of  frozen  plant  parts  can  bring  about  death,  while  a  slow  warming 
does  not  kill.  The  correctness  of  this  assertion  is  often  contested.  If  it  is 
given  as  an  universal  rule,  it  seems  inconclusive;  but  if  it  is  limited  to  cer- 
tain cases,  it  certainly  is  of  value.  An  older  and  very  instructive  example 
is  given  by  Karsten^.  A  large  shipment  of  tree  ferns  (Balantium)  had  to 
withstand  20  degrees  below  zero  enroute.  Some  of  the  plants,  when  they 
arrived,  were  put,  in  a  still  frozen  condition,  into  a  warm  place  and  were 
killed,  while  almost  all  of  those  first  thawed  in  cold  water  and  then  taken 


1  Bruijning,  F.  F.,  Zur  Kenntnis  der  Ursache  des  Frostschaden.  Sond. 
Wollny's  Forschungen  auf  dem  Gebiete  d.  Agrikulturphys.  1896;  cit.  Centralbl.  f. 
Agrikulturchemie  1898,  p.  173. 

-  Thomas,  Fr.,  Scharfe  Horizontalgrenze  der  Frostwirkung  an  Buchen.  Thiir- 
inger  Monatsblatter  1904,  12.  Jahrg.,  No.  1. 

3  tJber  die  Wirkung  plotzlicher  bedeutender  Temperaturanderung-  usw.  Bot. 
Z.  1861,  No.  40. 


into  a  cold  place,  rcmaiiicd  alive.  TVom  this,  it  is  c\  idenl  that  the  rapid 
thawing  and  not  the  frost  is  the  cause  of  death. 

Miiller-Thurgau  has  stated  of  ripe  fruit  and  Molisch  of  the  leaf  of 
Agava  americana,  that  these  objects  can  be  kept  alive  after  moderate  freez- 
ing, if  thawed  very  slowly,  but  that  they  die  when  thawed  rapidly. 

I  pressed  the  surfaces  of  the  frozen  leaves  of  herbaceous  Cinerarias 
between  my  finger  tips.  The  plants,  left  in  their  places  of  growth,  showed, 
^fter  thawing,  that  only  the  places  pressed  with  the  fingers  were  killed. 
According  to  the  discoveries  of  gardeners,  it  is  only  the  tender-leaved,  juicy 
spring  blossoming  plants,  grown  in  greenhouses  (Cinerarias,  herbaceous 
Calceolarias,  etc.),  which,  after  a  night  of  freezing,  can  be  rescued  by  the 
longest  possible  retardation  of  the  thawing. 

In  plants  perfectly  resistant  to  ice,  however,  the  rate  of  freezing  and 
thawing  seems  to  have  but  little  influence  on  life. 

In  explanation  of  the  matter,  two  points  should  be  taken  into  consid- 
eration. First,  in  rapid  thawing,  the  same  processes  will  be  enacted  which 
occur,  for  example,  in  the  evaporation  of  fluid  carbon  dioxid  whereby  the 
formation  of  solid  carbon  dioxid  takes  place,  as  is  well  known.  In  rapid 
thawing,  the  warmth  necessary  for  melting  will  be  removed,  not  only  from 
the  surrounding  air,  but  also  from  the  deeper  layers  of  this  part  of  the  plant, 
which  are  thereby  cooled  down  still  more.  In  such  plants  in  which  the 
critical  point,  i.  c,  the  specific  minimum,  lies  close  below  the  freezing  point, 
this  removal  of  heat,  increased  by  rapid  thawing,  can  cause  death. 

The  second  point  to  be  taken  into  consideration  is  that  the  cell  wall, 
from  which  ice  has  been  crystallized,  cannot  possibly  soak  up  the  great 
amounts  of  water  which  are  produced  suddenly  by  rapid  thawing.  The 
water  remains  in  the  intercellular  spaces  and  evaporates  there  while  the  cell 
of  the  leaf  is  not  able  to  regain  the  necessary  turgid  condition.  From  this 
comes  the  gardening  method  of  protecting  from  the  rising  sun  all  i)lants 
which  have  sufifered  from  late  frosts. 

Let  us  consider  finally  the  natural  processes  of  the  autumnal  changes 
of  material  from  the  standpoint  of  Mez's  theor)'  as  here  discussed.  When 
the  plants  prepare  for  winter,  they  collect  the  greatest  possible  amounts  of 
reser\'e  substances  and  reach  the  maximum  at  different  times,  according  to 
their  individuality.  In  Plniis  ansfriaca,  for  example,  Leclerc  du  Sablon^ 
found  this  maximum  in  May,  but  in  the  spindle  tree  (Evonymous  Euro- 
peus),  which  sends  out  its  shoots  earlier,  he  found  it  in  March;  in  decidu- 
ous trees  the  maximum  is  reached  in  the  fall.  In  evergreen  plants,  the 
reserve  carbo-hydrates  remain  abundant  in  the  leaves-.  Their  activity 
seems  reduced  to  a  minimum,  since  their  stomata  are  closed  permanently. 


1  Leclerc  du  Sablon,  t)bor  die  Reservekohlehydrate  der  Baume  mit  au.sdauern- 
den  Bliittern.  Compt.  rend.  1905.  p.  1608;  cit.  Centralbl.  f.  Affrlculturchemle  1906, 
p.  322.  —  Fabricius,  K,  Untersuchungen  iiber  Starke-  und  Fettgehalt  der  Fichte 
usw.     Naturwiss.  Z.  f.  Land-  u.  Forstwirtschaft  1905,  p.  137. 

2  Simon,  Der  Bau  des  Holzkorpers  sommer-  und  wintergriiner  Gewachse  usw. 
Her  d.  D.  Bot.  Ges.  1902,  p.  229. 


EDGAR  TULLIS 

PART  VII. 


MANUAL 


OF 


PLANT  DISEASES 

BY 

PROF.  DR.  PAUL  SORAUER 


Third  Edition --Prof.  Dr.  Sorauer 

In  Collaboration  with 

Prof.  Dr.  G.  Lindau       And       Dr.  L.  Reh 

Private  Decent  at  the  Univeraity  Asaistant  in  the  Museum  of  Natural  Hiitory 

o{  Berlin  in  Hamburg 


TRANSLATED  BY  FRANCES  DORRANGE 


Volume  I 
NON-PARASITIC  DISEASES 

BY 

PROF.  DR.  PAUL  SORAUER 

BERLIN 


WITH  208  ILLUSTRATIONS  IN  THE  TEXT 


PART  VII. 


MANUAL 


OF 


PLANT  DISEASES 


BY 


PROF.  DR.  PAUL  SORAUER 


Third  Edition-Prof.  Dr.  Sorauer 

In  Collaboration  with 

Prof.  Dr.  G.  Lindau        And       Dr.  L.  Reh 

Private  Decent  at  the  University  Assistant  in  the  Museum  of  Natural  History 

of  Berlin  in  Hamburg 


TRANSLATED  BY  FRANCES  DORRANGE 


Volume  I 
NON-PARASITIC  DISEASES 

BY 

PROF.  DR.  PAUL  SORAUER 

BERLIN 


WITH  208  ILLUSTRATIONS  IN  THE  TEXT 


Copyrighted,    1917 

By 

FRANCES    DORRANCE 


THE    RECORD   PRESS 
Wilkes -Bane,    Pa. 


513 

Thes-e  reserve  substances  are  protected  so  far  as  is  possible  against  frost. 
Part  of  the  starch  wanders  into  the  protected  central  portion  of  the  trunk 
and  branches  (pith,  medullary  rays  and  parenchyma  wood),  and  part  is 
transverted  into  sugar  or  occurs  instead  as  a  fatty  oil.  In  the  needles  of 
Alpine  spruces,  the  substance  of  the  chloroplasts  is  found  to  flow  away  and 
the  cell  content  in  winter  forms  a  homogeneous  cytoplasmic  mass  with 
abundant  oil  drops.  Lidforss'  has  proved  this  transformation  for  all  the 
green  cells  of  evergreen  plants ;  in  the  spring  the  starch  is  reformed. 

This  removal  of  solid  bodies  from  the  cell  with  the  appearance  oi 
winter  takes  place,  according  to  Mez,  as  an  advantageous  arrangement  in 
plants  resistant  to  freezing.  He  calls  the  fluid  substances  "thermally  active," 
for,  in  cr^'stallization,  they  set  free  heat.  The  solid  elements,  on  the  other 
hand,  follow  retardingly  the  temperature  of  the  fluids ;  they  are  "thermally 
passive"  and  absorb  heat,  since,  with  the  formation  of  ice,  the  change  of 
temperature  from  the  point  of  supercooling  towards  zero,  they  must  again 
give  up  this  heat  relatively  rapidly.  This  circumstance  acts  in  such  a  way 
that,  with  the  accumulation  of  solid  bodies  in  the  cell,  the  melting  point 
of  the  cell  sap  cannot  be  reached  after  supercooling  has  taken  place.  A 
great  number  of  thermally  passive  elements  consequently  form  a  menace 
for  the  plant,  while  the  fluid,  thermally  active  bodies  are  proved  advan- 
tageous as  producers  of  heat.  Profiting  by  the  experiments  of  A.  Fischer-, 
we  will  distinguish  between  oil  trees  and  starch  trees,  according  to  whether 
they  change  their  starch  into  oil  or  let  it  pass  into  the  interior  of  their  trunks 
and  branches  and  convert  it  into  sugar  in  the  bark.  The  fatty  oil  of  oil 
trees  (conifers,  birches),  which  we  have  learned  to  recognize  from  Jonescu 
as  a  protection  against  lightning,  besides  this  peculiarity  of  preventing 
supercooling,  like  sugar,  is  thermally  active,  i.  e.,  stores  up  heat  to  be  given 
out  in  crystallization.  The  trees  which  transform  all  their  starch  into  oil, 
conifers,  may  be  fitted  to  survive  a  higher  degree  of  cold  than  those  in  which 
a  part  of  the  starch  is  left  free  and  becomes  sugar  only  in  the  bark  (the  ma- 
jority of  deciduous  trees).  This  circumstance  surely  explains  the  phe- 
nomenon that  conifers  and  birches  extend  farther  up  into  cold  regions. 

Disturbance  due  to  Chilling. 

Cases  occur  in  potted  plants  in  greenhouses,  in  which  the  plants  suffer 
when  carried  from  one  house  to  another,  in  case  they  are  thus  exposed  to  a 
temperature  below  zero  degrees  at  times  for  only  a  few  minutes.  Practical 
gardeners  maintain  that  the  plants  have  "taken  cold." 

Moebius^  has  studied  this  statement  very  recently,  and  has  been  able  to 
confirm  the  above  assertion.  For  example,  he  took  a  Begonia  mctallica 
from  a  warm  house,  kept  it  one  or  two  minutes  out  of  doors  in  a  tempera- 
ture of  5  degrees  C  below  zero  and  then  put  it  again  in  its  former  place. 


1  Lidforss,  Zur  Physiologie  und  Biologie  der  wintergriinen  Flora.  Bot. 
CentralbL  1896,  p.  33. 

-'   Jjihrb.  f.  wiss.  Bot.  1891,  p.  155,  cit.  by  Pfeffer  loc.  cit..  p.  137. 

3  Mobius,  M.,  Die  Erkaltung  der  Pflanzen.  Ber.  d.  D.  Bot.  Ges.  1907,  Vol.  XXV 
pt.  2,  p.  67. 


5T4 

Even  the  same  day,  he  noticed  newly  produced  brown  spots  on  some  of  the 
older  leaves.  Later  these  leaves  got  a  "glassy,  dark  appearance,  hung 
down  and  dried  up."  The  young  leaves  did  not  suffer.  The  same  kind 
of  discoloration  and  wilting  phenomena  were  observed  in  other  similar 
experiments  and  are  in  all  essentials  the  characteristics  which  have  been 
given  by  practical  growers  as  a  result  of  taking  cold.  Moebius  emphasized 
that  no  formation  of  ice  in  the  tissues  can  be  concerned  here.  1  can  bring 
proof  of  this  in  an  experiment  which  I  made  with  Begonia  ariiyrost'ujma. 
A  pot  of  this  plant  was  taken  from  a  warm  house  and  put  out  of  doors 
after  the  temperature  had  risen  to  0.5  degrees  C.  Within  a  short  time,  I 
saw  glassy  spots  appear  on  some  leaves. 

According  to  the  experimental  results  given  in  different  places  in  the 
present  chapter,  I  perceive  in  the  wilting  and  glassiness  of  different  leaves, 
with  sharp  falls  in  temperature  the  results  of  sudden  differences  in  tension 
in  the  tissue.  The  contraction  of  tiie  cells  as  a  result  of  the  excessi\e  cool- 
ing will  cause,  in  places,  an  outpressing  of  water  into  the  intercellular  spaces. 
Besides  this,  the  dift'erence  in  the  diff'erent  tissue  forms  united  in  the  leaf 
organ  makes  itself  felt.  We  will  refer  in  this  connection  to  the  subsequent 
section  on  frost  blisters  where  various  elevations  of  the  epidermis  and  loos- 
enings  of  the  tissue  are  described. 

The  practical  grower  at  any  rate  should  kecj)  in  mind  llie  fact  that,  in 
transporting  plants  from  warm  houses,  there  is  a  possibility  of  taking  cold, 
even  if  plants  are  exposed  only  a  few  minutes  to  a  freezing  temperature. 
Since  a  sharp  change  of  temperature  should  be  avoided,  the  wrapping  of  the 
pots  with  cloth  or  paper  must  be  recommended  for  all  cases. 

B.     SPECIAL  LMSTANCES  OF  FROST  ACTION. 

TuRNiNc  Sweet  of  Potatoes. 

In  the  well-knf)wn  phenomenon,  that  potatoes  turn  sweet  when  suii- 
jected  to  slight  degrees  of  frost,  Goppert^  and  Einhof-  had  noticed  that  in- 
dividual dift'erences  make  themselves  felt.  Under  the  same  conditions  only 
part  of  the  tubers  turned  sweet  and  remained  soft,  while  the  others  became 
hard.  If  the  potatoes  were  brought  quickly  into  considerable  cold  (about 
10  degrees)  they  were  frozen,  as  a  whole,  without  showing  any  formation  of 
sugar.  The  turning  sweet  could  not  be  observed  except  at  temperatures 
which  lay  only  a  little  below  the  freezing  point.  Miiller-Thurgau  found 
that  this  change  set  in  only  in  potatoes  which  had  been  taken  from  the  soil 
at  least  a  month  earlier.  It  could  not  be  produced  in  freshly  harvested 
tubers.  Probably  similar  phenomena  led  Payen"  to  the  conclusion  that  even 
before  the  action  of  the  frost,  the  tubers,  which  showed  the  formation  of 
sugar,  might  have  started  to  grow  again. 


1  "Warmeentwickluiifr,  p.   38. 

-   Neues  allgem.  Journ.  f.  Chemie.       Berlin  1805,  p.  473. 

3    Cf,  Czapek,  Fr„  Biochemie  der  Pflanzeen.    Fischer,  Jena,  Part  1,  p,  371.     Here 
also  notes  on  older  literature, 


515 

The  fact,  established  by  Einliolf  and  Goppert,  that  potatoes  freeze  with 
greater  degrees  of  cold  without  becoming  sweet  and  that  those  which  have 
become  sweet  remain  soft,  is  explained  simply  by  Miiller-Thurgau's^  experi- 
ments. He  found  that  the  potato  tuber  freezes  only  at  3  degrees  C.  below 
zero.  To  be  sure,  its  real  freezing  point  lies  possibly  about  i  degree  below 
zero,  but  the  cell  juices  must  first  be  cooled  down  to  2  to  3  degrees  below 
freezing,  i.  e.,  be  "supercooled,"  before  the  first  ice  crystals  can  be  formed 
between  the  cells.  Naturally,  a  lowering  of  the  temperature  from  zero  to  2 
degrees  below  zero  retards  many  life  processes.  Among  these  are  two  which 
come  especially  under  consideration  here;  viz.,  the  transversion  of  the  starch 
into  sugar  and  the  utilization  of  the  sugar.  It  may  be  assumed  that  the 
sugar  from  the  protoplasm  of  the  cell  is  partly  used  in  respiration,  partly 
during  the  period  of  growth  in  the  regeneration  of  the  cytoplasm  and  the 
starch  reversion.  Miiller-Thurgau^  found,  in  fact,  that  potatoes  which  had 
become  sweet  after  having  been  kept  at  a  temperature  of  20  to  30  degree  C. 
had  increased  their  starch  content  at  the  expense  of  the  sugar.  This  had 
disappeared ;  with  a  lowering  of  the  temperature  to  o  degrees  and  2  degrees 
below  zero,  the  process  of  respiration  (and  most  probably  also  that  of  the 
regeneration  of  the  protoplasm)  decreases,  while  the  transversion  of  the 
starch  into  sugar  does  not  fall  off  so  quickly.  Consequently,  the  sugar 
accumulates  in  the  tuber  and  becomes  noticeable  in  the  flavor.  It  amounts 
to  about  2.5  per  cent,  of  the  fresh  substance,  yet  comparatively  wide  fluctu- 
ations are  found  in  different  individuals  of  the  same  variety.  A  higher 
water  content  in  the  tubers  favors  the  turning  sweet.  This  increase  of  sugar 
corresponds  to  the  loss  of  starch  yet,  according  to  Czubata's''  analyses,  no 
corresponding  proportion  can  be  proved  in  the  two  processes.  According  to 
Czubata,  a  part  of  the  protein  passes  over  from  the  insoluble  into  the  soluble 
condition  during  freezing.  Miiller  assumes  that  the  ferment  here  concerned 
increases  with  the  lower  temperature. 

If  potatoes  which  have  become  sweet  are  left  for  some  days  in  a  room 
with  a  temperature  of  more  than  10  degrees,  respiration  increases  and  the 
sugar  is  oxidized,  i.  e.,  the  potatoes  lose  their  sweetness  and  in  this  way 
again  become  usable  for  cooking.  Other  proposed  means,  as.  for  example, 
the  leaching  of  the  tubers  with  water,  did  not  lead  to  any  results.  Besides 
this,  however,  it  should  be  emphasized  that  one  need  not  hesitate  to  use 
potatoes  for  seed  which  have  become  sweet.  Such  potatoes  freeze  only 
with  a  greater  degree  of  cold  than  non-sweet  tubers^. 

I  should  like  to  add  here  supplementarily  a  statement  made  to  me 
verbally  that  in  Reinerz  a  cellar  is  said  to  exist  in  a  cave  in  which  potatoes 
become   sweet   even    without   the    action    of    frost.      This   phenomenon    is 


1  Miiller-Thurgau,  Ein  Beitrag  zur  Kenntnis  ties  Stoffwechsels  in  stiirkehal- 
tigen  Pflanzenorganen.     Botanisches  Centralbl.  1882,  No.  6. 

2  Landwirtsch.  Jahrb.  1883,  p.  807. 

"  Czubata,  Die  chemischen  Veranderungen  der  Kartoffee  beim  Frieren  und 
Faulen.  Oster.-Ungar.  Brennerei-Zeitung  1879;  cit.  in  Biedermanns  Centralbl. 
1880,  I,  p.  472. 

■1  Muller-Thurgau,     Landwirtsch.  Jahrb.  1883,  p.  826. 


5i6 

ascribed  to  a  strong  exhalation  of  carbon  dioxid.  I  have  not  been  able  to 
prove  experimentally  an  increase  of  sugar  in  the  tubers,  by  a  two  days' 
retention  in  a  carbon  dioxid  atmosphere.  \e\  erthelcss,  it  might  be  possible 
that  some  effect  would  be  noticeable  after  a  longer  time.  The  statement 
gains  probability  from  a  work  by  Bachet'  and  Savelle,  according  to  which, 
by  the  use  of  carbon  dioxid  with  a  somewhat  higher  temperature  and  greater 
pressure,  starch  flour  was  rapidly  turned  into  dextrine  and  grape  sugar,  espe- 
cially if  the  process  of  saccharification  was  facilitated  l)y  the  addition  of 
gluten.  It  can  be  assumed  that,  because  of  an  abundant  supply  of  carbon 
dioxid  in  the  above  mentioned  case  from  Reiner/.,  natural  respiration  is 
repressed  just  as  by  a  lower  tem[)erature  and  the  process  of  sugar  formation 
which,  according  to  Miillcr.  can  be  proved  uj)  to  a  temperature  of  lo 
degrees  has  caused  its  slow  accumulation.  The  production  of  saccharose 
during  germination  after  an  increase  of  temperature  is  proved  by  Mar- 
cacci's-  exi)eriments  with  slices  of  potato  which  had  been  dried  in  the  sun 
and  in  an  oven.  In  the  sprouting  tubers,  saccharose  is  found  in  the  young 
shoots  and  later  in  the  leaves  (probably  due  to  the  hydration  of  starch). 

It  is  e\ident  from  the  above  that  the  methods  of  using  these  potatoes, 
wliich  in  outward  appearance  are  rarely  distinguishable  from  healthy,  non- 
sweet  tubers,  can  in  no  way  be  api)licable  for  frozen  ones,  i.  e.,  those  turned 
U)  ice.  A  tuber  which  has  been  frozen  hard  is  dead  and,  in  thawing,  at 
once  falls  \ictini  to  a  high  degree  of  decomposition.  It  becomes  soft  and 
gi\es  off  water,  while  the  cut  surface  turns  brown  at  once,  if  not  immedi- 
ately coated  with  acid.  'J'hc  skin  separates  (|uickl\-  from  the  tk'sli.  like  a 
bladder,  with  a  development  of  gas.  The  bark  cells  beneath  the  cork  layer 
break  apart  because  of  the  dissolution  of  the  intercellular  substance.  The 
cytoplasm  is  brown  and  granular  and  drawn  back  from  the  cell  wall;  the 
protein  crystalls  are  dark  brown;  the  cell  sap  is  strongly  acid. 

The  Ruxmxc;  to  Si-:i:d  of  1]i:i:ts. 

!]}■  this  name  are  characterized  those  specimens  of  sugar  beets  and  fod- 
der beets  which  set  seed  even  in  the  first  summer.  In  some  years  the  phenom- 
enon occurs  very  frequently  and  disturbs  the  harvesting  and  use  of  the  beet 
since  the  root  is  woodier  than  in  the  two-year-old  beets.  Opinions  differ 
as  to  the  cause  of  the  phenomenon.  Tliev  take  two  different  i)oints  of  \iew  ; 
some  make  the  constitution  of  the  seed  responsible  for  this,  others,  the 
atmospheric  conditions  and  especially  spring  frosts.  In  consideration  of 
the  fact  that  actually  in  years  when  late  frosts  have  attacked  the  young  beet 
plants,  unusually  many  may  be  found  which  have  run  to  seed  and,  sup- 
ported by  Aderhold's  experiments  with  kohlrabi,  to  be  mentioned  later,  we 
will  give  here  the  present  cultural  retrogression. 

From  the  abundant  literature  on  sugar  beets  we  will  cite  only  one  work, 
since  it  reports  recent  scientific  investigations  and  makes  brief  references 

1   After  Compt.  lond  1S78;    cit.  in  Biedermanns  Centralbl.  1879,  p.  544. 
-   Marcacci,  A.,  Sui  prodotti  delta  transformazione  dell'  amido,  cit.  But.  Jalireslj. 
isyi,  I,  p.  47. 


517 

to  the  older  experiences.  Andrlik  and  Mvsik\  on  the  ground  of  numerous 
analyses,  have  come  to  the  conclusion  that  the  weight  of  the  seed-bearing 
tuber  may  sometimes  be  less  than  that  of  the  normal  tuber,  at  other  times 
greater.  The  root  of  the  seed-bearing  tuber  is  poorer  in  potassium,  phos- 
phoric acid  and  sulfuric  acid  as  well  as  ammonium  nitrate  and  amido- 
nitrogen.  The  sap  is  purer.  Of  the  organic  substances  formed  by  the 
seed-bearing  beet,  the  sugar  content  amounted  to  only  45  to  50  per  cent. ; 
in  the  normal  beet  54  to  69  per  cent.  "The  greater  part  of  the  organic  sub- 
stance, free  from  sugar,  is  in  the  pith.  i.  e.,  in  the  elements  forming  the  solid 
skeleton  of  the  plant.  *  *  *  _"  "The  pith  formation  probably  takes 
place  at  the  expense  of  the  sugar." 

We  perceive  that  the  beet  plant  has  changed  its  inbred  method  of 
growth.  Instead  of  storing,  in  the  first  year,  only  reserve  substances  in 
the  root  and  making  use  of  them  in  the  following  year  for  the  formation  of 
seed,  it  at  once  makes  furthti  use  of  the  organic  substances  gained  by  the 
leaf  apparatus. 

This  circumstance  points  to  the  fact  that  the  normal  process  in  the  cul- 
tivated beet,  the  uninterrupted  formation  of  new  leaves,  has  undergone 
some  disturbance.  The  growth  has  ceased  for  some  time,  rather  the  beet 
has  passed  through  a  dormant  period  which  would  correspond  to  the  winter 
rest  of  a  normally  ripened  tuber.  The  newly  mobilized  reserve  material 
is  used  here  for  the  production  of  the  inflorescence,  just  as  in  the  normal 
case,  after  the  arrestment  of  growth.  It  is  conceivable  that  the  late  frosts 
may  call  forth  such  an  arrestment.  They  will  incite  a  greater  formation  of 
seed  stems,  the  later  in  the  year  they  occur  and  the  more  the  subsequent 
weather  favors  inflorescence  formation.  If,  howe\er,  the  weather,  follow- 
ing the  frosty  night,  is  especially  favorable  for  the  development  of  foliage, 
the  elongation  of  the  axis,  already  begun,  can  stop  and  the  development  of 
the  root  advance.  In  large  sugar  beet  fields,  as  a  rule,  such  seed-bearing 
beets  and  similar  transitional  forms  are  found.  This  inclination  to  the  set- 
ting of  seed  can  certainly  be  hereditary  in  the  seed,  possibly  can  be  prepared 
in  the  seed  of  normal  beets,  if  not  sufficiently  matured,  i.  e.,  for  example,  if 
harvested  before  it  is  ripe. 

Aderhold-  has  furnished  experimental  proof  of  the  formation  of  seed- 
bearing  roots  in  Kohlrabi,  as  a  result  of  frost  action.  He  brought  seedlings 
in  pots  into  a  freezing  chamber  for  8  to  10  hours  and  then  placed  them  out 
with  others  which  had  been  exposed  to  frost.  In  one  experiment,  he  ob- 
tained, for  example,  two  seed-bearing  roots  from  18  untreated  plants,  while 
from  the  same  number  of  specimens  which,  for  10  hours  in  May,  had  been 
exposed  to  a  temperature  of  2  to  6.5  degrees  C.  below  zero,  he  had  7  seed- 
bearing  plants.  In  both  cases  some  Kohlrabi  plants  later  overcame  the 
impetus  of  frost  action  and  formed  a  root  body. 


1  Schossriibe   unrl    normale   Riibe.     Blatter   f.   d.   Zuckerriibenbau    1905,    No.    24, 
p.  374. 

2  Aderhold,  R.  itber  das  Schiesson  des  KohlrabLs.  Mitt.  d.  K.  Biolog.  Anst,  190(), 
No.  2,  p.  16. 


It  is  well  known  that,  in  sDnic  years,  such  premature  (le\  el(i|iment  of 
inflorescences  occurs  often  in  other  plants,  which  form  fleshy,  storage 
organs  (celery,  carrots,  radishes).  Jt  is  very  i)rohable  that  not  only  frost 
action  hut  also  other  processes  (jf  arrestment  are  effective  here. 

I'^kosTV  Taste  in  GRArES. 

The  processes  which  occur  in  the  turning  sweet  of  potatoes  take  place 
also  in  woody  plants.  In  this  connection,  Pfefifer'  mentions  Fischer's  inves- 
tigations'- on  the  Huctualions  hetween  the  starch  and  sugar  in  the  so-called 
starch  trees,  such  as  the  linden  and  birch'.  W  hen  branches  are  taken  in 
winter  from  out  of  doors  into  a  warm  room,  starch  is  formed  in  the  bark 
parenchyma,  within  a  few  hours,  and,  in  the  cold,  can  again  pass  over  into 
sugar.  A  similar  formation  of  sugar,  connected  with  tlie  decrease  of 
organic  acids,  is  found  to  occur  in  grapes  after  the  action  of  frost, 

I'^en  when  the  main  stem  of  immature  clusters  had  been  attacked  by 
frost  but  was  still  green  and  the  berries  clear,  a  considerable  decrease  of  acid 
and  increase  of  the  sugar  content  was  founds  An  investigation  on  Riesling 
grapes  of  the  decrease  of  acids  in  a  ])lant  which  had  been  exposed  from 
October  19  to  November  9  to  a  temperature  as  low  as  5  degrees  C.  proved 
an  acid  reduction  of  4  per  cent.  Half  ripe  clusters,  greatly  injured  by  frost 
when  cut  off,  showed  from  October  1  to  11,  an  acid  loss  of  4.5  per  cent. 

The  frosty  taste,  however,  does  not  seem  to  be  due  alone  to  the  increase 
of  sugar  and  decrease  of  acid,  but  material  compounds  may  perhaps  diffuse 
from  the  stems  of  the  grapes  which  the  protoplasm  of  cells  would  not  have 
let  pass  through,  if  there  had  been  no  frost  action.  Through  these  changes, 
the  susceptibility  of  the  grapes  to  the  fungus  of  white  rot  may  be  increased, 
since  Viala  and  I'acottet"'  have  shown  that  this  fungus  is  able  to  infest  only 
the  berries  which  ha\e  a  high  sugar  and  a  smaller  acid  content.  The  be- 
havior of  black  rot  is  exactly  the  reverse. 

Chances  in  the  Blossom  Organs. 

In  the  action  of  frost,  the  permanent  processes  are  sometimes  chemical, 
sometimes  mechanical.  In  the  former  it  is  difficult  to  decide  in  how  far  they 
are  initiated  by  the  freezing,  or  if  they  begin  only  with  thawing.  Thus  for 
example,  (i()i)pert'''  has  obserxed  in  the  blossoms  of  Phajus  and  Calanthe 
that  they  turned  blue  when  frozen.  Tliis  change  in  color  is  explained  by 
the  fact  that,  through  the  action  of  the  frost,  the  indicans,  which  is  abun- 
dant in  the  normally  colorless  cells,  especially  around  the  vascular  bundles, 


1   I'hysiologie,  2d  edition,  I,  p.  514. 

-•  .Jahib.  f.  d.  wiss.  Hot.  1891,  v.  XXII. 

■'•  t)ber  die  Periodizitiit  der  Starkezii-  und  aJm.ihme  in  den  Biinmen.  Compare 
Mer,  E.  in  Bot.  Jahresb.  1891,  I,  p.  46. 

*   Hiedeimanns  Centralbl.  1879,  I,  p.  23.S. 

•"'  Viala,  P.  et  Pacottet,  Sur  la  culture  du  black-rot .  Compt.  rend.  1904, 
CXXXVIII,   p.  306. 

•i  tUier  Einwirkung  des  Frostes  auf  die  Gewachse.,  Sitzungsber.  d.  Schles. 
Ges.  f.  vaterl.  Kultur  1S74,  cit.  Bot.  Zeit.  IST.'i,  p.  609. 


519 

is  oxydized  to  indigo.  Prillieux^  states  that  this  change  appears  first  with 
thawing.  Other  statements  on  the  behavior  of  the  coloring  matter  in  blos- 
soms vary  as  greatly  and  it  can  only  be  said  in  general  that  the  red  coloring 
matter  is  one  of  the  most  resistant ;  in  fact,  according  to  Goppert'-,  who  has 
collected  many  observations  on  the  color  phenomena  produced  by  frost,  it 
can  be  increased  in  the  leaves  and  blossoms  with  slight  frost  action. 

Most  frequent,  and  therefore  most  important,  are  the  disturbances  in 
the  blossoms  of  our  fruit  trees  due  to  frost.  For  all  practical  purposes,  the 
way  the  process  of  discoloration  takes  its  course  is  immaterial.  Scien- 
tifically, however,  it  may  be  of  interest  to  become  more  exactly  acquainted 
with  the  frost  action.  But  since  it  is  impossible  to  determine  in  natural 
spring  frosts  what  are  the  first  effects  and  what  the  subsequent  changes,  I 
have  subjected  apple  blossoms  to  artificial  frost. 

After  a  blossoming  apple  branch  had  been  exposed  for  2  hours  to  a 
temperature  of  4  degree  C.  below  zero,  the  investigation,  carried  on  imme- 
diately after  the  removal  of  the  freezing  cylinder,  showed  that  all  the  petals, 
and  also  some  places  in  the  leaves,  had  taken  on  a  glassy  consistency. 

Even  after  a  few  minutes  (the  air  temperature  was  11  degrees  C.) 
a  flabbiness  and  a  turning  brown  began  in  the  parts  which  had  become 
glassy.  The  brown  discoloration  of  the  leaves,  therefore,  is  not  the  direct 
effect  of  the  cold  but  a  phenomenon  making  itself  felt  first  with  thawing. 
The  petals,  with  the  natural  reddish  tinges  on  the  under  side,  had  brown 
veins  and  were  spotted.  The  edges  began  at  once  to  collapse  and  dry  up.  A 
cross-section  showed  that  the  discoloration  was  due  less  to  the  turning  brown 
of  the  cell  walls  than  to  that  of  the  cell  content,  since  these  excreted  reddish 
yellow  to  brownish  yellow  solid  masses  deposited  usually  in  the  longitudinal 
axis  of  the  cells  and  resembling  carotin.  The  different  cell  layers  of  the 
petals  behaved  differently.  The  excreted  yellow  masses  could  be  proved  to 
be  especially  abundant  beneath  the  colorless  epidermis  which  had  remained 
at  its  natural  height.  Besides  this,  the  parenchyma  cells  which  accompany 
the  vascular  bundles  of  the  fine  veins  showed  these  excretions  especially 
distinctly.  This  latter  circumstance  caused  the  venation  of  the  fine  petals 
to  appear  strikingly  brown  to  the  naked  eye.  With  the  rapidly  advancing 
process  of  drying,  the  cells  of  the  mesophyll  collapsed,  wdiile  the  cells  of  the 
epidermis  retained  their  natural  size. 

Fig.  103  shows  a  part  of  a  petal  soon  after  it  had  been  removed  from 
the  freezing  cylinder.  It  shows  the  leaf  still  in  its  natural  dimensions,  with 
the  large  intercellular  spaces  (/)  between  the  very  thin  walled  cells  of  the 
flesh  and  with  the  unchanged  epidermis  (c).  The  discoloration,  due  to  the' 
yellowish  brown  contracted  mass  of  the  cell  content  (b),  is  most  intense 
near  the  vascular  bundles  (g)  and  in  fact  especially  so  on  the  under  side  of 
the  leaf.    In  the  vascular  bundle  the  narro\N-  spiral  ducts  have  turned  brown. 


1  Bot.  Zeit.  1871,  No.  24.— Bull,  de  la  Soc.  bot  de  France  1872,  p.  152. 

2  Kunisch,    H.    tJber    die    todliche    Wirkung-    niederer    Temperaturen    auf    die 
Pflanzen.     Inauguraldissertation,  p.  29.     Breslau   1880. 


The  hrowninf:^  process  took  a  diflerent  course  in  tlie  stamens.  After 
they  liad  heen  taken  out  of  the  freezing  cyHnder  they  remained  apparently 
unchanged,  while  the  petals  had  already  begun  to  wiU.  ( )nly  later  did  the 
stamens  become  yellowish  brown  and  the  anthers  a  jjale  \ellow.  A  cross- 
section  through  the  stamens  showed  that  the  brown  coloration  was  essen- 
tially conditioned  by  the  epidermis  which  is  rich  in  contents.  To  be  sure, 
in  all  the  tissues,  the  cell  contents  seemed  contracted  into  drops  or  lumps 
and  were  brown,  but  the  amount  of  substances  in  the  inner  cells  was  so 
scanty  that  the  coloring  of  the  whole  tissue  remained  pale.  The  spiral  ducts 
of  the  stamens,  like  those  in  the  petals,  had  light  brown  walls.  In  the 
anthers,  the  discoloration  depended  likew  ise  on  the  amount  of  cell  contents. 
These  were  most  al)undant  in  the  connective  tissue  and  this  consequently 
seemed  most  deeply  brown,  while  the  epidermis  in  the  antliers  themselves 
and  the  underlying  fibre  cells,  arranged  like  palisades,  had  only  \ery  scanty, 
solid  masses  of  contents  and,  tlierefore.  seemed  almost  colorless.     The  rem- 


Fis".  lO.S.     Cros.s- sect  ion  of  a   petal  of  the  apple  injured  hy  artificial   frost. 

nants  of  the  ground  tissue  near  the  connectixe  tissue  were  somewhat 
darker. 

The  pistils  showed  the  greatest  injuries.  They  were  a  deey)  brown  and 
l)ent  when  taken  (uit  of  the  freezing  cylinder.  At  first  no  collapse  of  the 
tissue  could  be  seen  anywhere.  The  papillae  of  the  stigma  seemed  stiff  and 
filled  with  brown  cytoi)lasmic  contents.  As  in  a  fresh  condition,  they  still 
held  fast  the  somewhat  swollen  and,  therefore,  differently  formed  pollen 
grain.s.  tilled  with  cloudy,  uniform  contents.  In  the  pistil,  as  in  the  stamens, 
the  peripheral  layers  were  richest  in  content  and,  therefore,  their  contents 
and  walls  most  deeply  colored  brown. 

Among  the  mechanical  disturbances,  tangential  holes  were  observed 
here  and  there  in  the  tissue  of  the  pistil  as  in  that  of  the  stamens.  They 
were  partly  produced  by  the  loosening  of  the  cells  from  one  another,  but 
also  by  the  tearing  of  the  cells  themselves.  The  number  and  ."^ize  of  the 
holes  in  the  tissue  increased  towards  the  bottom  of  the  pubescent  pistil,  the 
hairs  of  which.  i)oor  in  contents,  showed  a  browning  of  the  walls.  Here 
the  tissue  at  the  base  of  the  pistil  widened  into  five  diverging,  bluntly  conical 


521 


parenchyma  groups,  arranged  with  tlieir  tips  toward  the  centre,  as  the  point 
of  transition  into  tlie  fi\e  carpels.  Each  of  these  displayed  an  epidermal 
covering  and  a  parenchymatous  inner  tiesh.  In  the  cross-section  shown 
in  Fig.  104.  through  the  receptacle  of  the  apple  we  see  that  the  future  flesh 
is  already  traversed  by  numerous,  regularly  arranged  vascular  bundles  (g). 
The  receptacle,  covered  with  a  firm  epidermis  (c),  extends,  toward  the  inner 
side,  into  five  anchor-like  branches  (a).  These  are  the  five  ovaries  into 
which  the  pistil  has  widened.  On  their  reflexed  edges,  which  in  the  cross- 
section  look  like  the  flukes  of  an  anchor  (r).  the  seed-primordia  are  formed 


9^- 


Fig'.  104.     Cross-section  throagh  a  young  receptacle  of  the  apple  injured  by  frost, 


in  the  under  part  of  the  receptacle  and  get  their  nutrition  through  the  vascu- 
lar bundles  (//r).  The  seed  cavities  {sf)  and  the  cavity  left  free  in  the 
centre  {h)  because  the  edges  of  the  o^ aries  have  not  united,  are  lined  with 
regular  epidermis  {c).  The  cells  of  the  epidermis  of  the  axillary  side  {hr), 
as  also  within  the  fruit  cup,  are  found  to  be  richest  in  contents  and,  there- 
fore, most  deeply  browned,  while  the  central,  at  first  meristematic  part  of 
each  ovary  is  only  slightly  discolored. 

A  splitting  of  the  tissue  manifesting  itself  in  the  appearance  of  tan- 
gential holes   (/),  due  to  the  separation  of  the  collenchymatous  layers   {c) 


from  the  inner  Hesh  of  the  fruit  (  'H  )  may  be  seen  in  the  transitional  zone 
from  pistil  to  ovaries,  even  with  a  low  magnification.  It  should  he  empha- 
sized that  in  this,  as  in  the  stamens,  a  tearing  of  the  cells  (cj  actually  takes 
place,  while  in  the  coarser  tissues  only  the  usual  separation  of  the  different 
cell  layers  is  formed.  These  mechanical  disturbances  which,  as  we  shall 
see  later,  are  so  im])ortant  in  the  vegetative  organs,  have  a  lesser  influence 

in  the  blossoming  organs.  The 
inflorescences  die  l>ecause  of 
the  chemical  change  in  the 
cell  contents  and  drop  more 
(|uickly  if  the  tissue  splits  at 
the  same  time.  The  experi- 
mental results  correspond  to 
the  phenomena  after  natural 
spring  frosts. 

The  dependence  of  the 
susceptibility  upon  the  consti- 
tution of  the  cell  sap  may  be 
]K'rccived  from  the  adjoining 
illustration  of  a  young  apple 
blossom  severely  frosted  (Fig. 
105 ).  The  shading,  carried  out 
only  on  one  side  in  this  and 
other  drawings,  holds  good 
naturally  for  both  halves.  All 
the  shaded  parts  indicate  tis- 
sues with  intercellular  spaces, 
which  clearly  contain  air.  At 
;-  sugar  may  be  proved  by  the 
glycerin  reaction.  The  crosses 
indicate  the  regions  where 
metal)olism  has  already  ad- 
vanced so  far  that  abundant 
calcium  oxalate  is  deposited. 
The  rings  (/)  are  intended  to 
indicate  the  different  places 
turned  brown  by  frost ;  all  the 
younger,  inner  parts,  rich  in 
cytoplasm,  have  remained 
healthy ;   the   dark   line   is   a   vascular  bundle. 

Here  we  should  mention  only  supplementarily  the  fact  that,  besides  the 
acute  affects  of  cold  already  described,  chronic  disturbances  in  the  life  of 
the  blossoms  also  occur  which  concern  only  the  retarding  of  the  normal  life 
processes.  The  best  known  example  might  well  be  the  suppression  of  the 
opening  of  the  blossoms  in  Crocus  renius  and  TiiJipa  Gesneriana.     Because 


Fis.   lor.. 


I'rimordia    of    an    apple    flower    butl 
injurerl   by   frost. 


523 

of  the  low  temperature,  no  sufficiently  strong  growth  of  the  inner  side  of 
the  perianth  leaves  takes  place,  so  that  the  bending  out  of  these  leaves  and, 
therefore,  blossoming  is  suppressed.  The  blossoms  of  Ornithogalum 
umhellatum,  Colchicum  anfmnnalc,  Adonis  T'cryiaUs  and  others,  react  simi- 
larly but  more  weakly.  The  processes  in  Mimosa  pudica,  Oxalis  acetosella, 
etc.,  prove  that  even  green  leaves  act  thermostatically  because  of  the  influ- 
ence of  lower  temperatures.  Material  on  this  subject  may  also  be  found  in 
the  later  sections  which  treat  of  the  mechanical  effects  of  frost. 

The  Rust  Rings  in  Fruit. 

The  so-called  rust  rings  appear  as  the  result  of  slight  injuries  from 
frost  in  young  fruits.  By  this  are  understood  various  formations  of  cork  in 
the  skin  of  the  fruit,  spreading,  especially  in  the  pomaceous  fruits,  in  ring- 
like zones.  In  many  varieties  the  appearance  of  cork-color  etchings  is  a 
very  normal  process.  Our  Reinettes,  for  example,  often  possess  star-like, 
small  rusty  spots.  The  so-called  "netted  Reinettes"  have  linear  cork  trac- 
ings on  the  outer  skin  of  the  fruit  and  often  such  cork  formations  obtain 
a  surface-like  extent,  as,  for  example,  in  the  French  Reinettes,  Parker's 
gray  pippin,  in  the  gray  autumn  butter  pear,  the  medlar,  etc.  This  condi- 
tion is  morbid  only  when  the  phenomenon  is  very  extensive  in  some  years 
(for  example,  1900)  on  many  fruit  varieties  which  otherwise  remain  smooth 
and  when  the  formation  of  the  cork  covers  the  greater  part  of  the  fruit. 
The  initial  stages  are  found  in  early  youth.  It  is  evident  after  the  appear- 
ance of  very  late  May  frosts  that  the  contents  of  some  groups  of  epidermal 
cells  turn  brown  and  the  cells  begin  to  die.  Beneath  such  places  plate  cork 
is  formed,  and  the  dying  epidermis  becomes  somewhat  convex.  During 
the  swelling  of  the  young,  green  fruit,  the  formation  of  cork  advances 
further  into  the  fruit  flesh,  producing  considerable  groups  of  parallel  rows 
of  cells  arranged  perpendicular  to  the  upper  surface.  In  a  special  case 
observed  in  "Amanli's  butter  pear"  these  cells,  arranged  in  rows,  appeared 
to  the  same  extent  as  those  in  the  epidermal  cells ;  they  were  found  actually 
suberized,  however,  only  in  the  peripheral  layers  while  the  light-colored, 
thick  walls  of  the  more  deeply  lying  cells  gave  a  cellulose  reaction.  The 
greater  the  new  formation,  the  more  the  overlying,  dying  cell  layers  are 
separated  and  the  outer  surface  of  the  fruit  becomes  rough  and  scaly. 

In  flask-shaped  pears  the  pouchy  part  of  the  fruit,  bearing  the  blossom 
end,  often  appears  to  have  rusty  grayish  scales,  while  the  half  toward  the 
stem  is  smooth  and  green.  In  other  cases,  a  broad,  cork-colored  band  is 
seen  near  the  blossom  end,  etc.  At  times  with  this  splitting  of  the  waxy 
covering  and  dying  of  the  epidermal  cells  is  connected  the  development  of 
the  newly  produced  underlying  tissue  into  stone  cells.  These  appear  later  in 
circular  aggregations  on  the  outer  surface  of  the  fruit,  so  that  the  conditions 
are  produced  which  we  have  described  as  "Lithiasis"  (p.  170).  ("Diel's 
butter  pear,"  "Good  Louise  of  Avranches").    Since  such  changes  are  usually 


524 

found  on  one  side  the  i,M-()\\th  of  tliis  cork-color  side,  containing:;  tlie  stone 
cells,  is  often  retarded,  thus  producing  deformed  fruit. 

After  1  had  succeeded  in  causinjj  a  splitting  of  the  cuticle  in  tough 
leaves  by  the  action  of  artificial  frost,  I  did  not  hesitate  to  trace  the  injuries 
in  the  wax  coat  of  young  fruit  to  frost  action,  more  particularly  the  forma- 
tion of  such  "rust  rings"  as  had  been  observed  only  in  years  with  late  frosts. 
The  pears,  which  are  susceptible  to  frost,  suffer  most  abundantly  and 
greatly,  in  fact  usually  on  one  side  and  at  a  certain  height  on  the  tree. 

Thk  r>i:H a\i()r  of  Oi.di  k  I'oi.iac.i'.  With  .A.ctjtk  Frost  Action. 

During  frost,  changes  in  the  chlorophyll  grains  are  noticeable  inasmuch 
as  they  usually  round  up  into  lumps  in  the  cells  which  have  become  poor  in 
sap.  A  chemical  change  of  the  chlorophyll  coloring  matter,  due  to  the  frost 
alone,  is  not  assumed  by  the  majority  of  investigators,  so  far  as  found  in 
statements  concerning  frozen  chloropliyll  solutions.  \\  iesner  found'  no 
difference  in  a  chlorophyll  solution  in  oli\e  oil  exposed  to  a  temperature  of 
30  degrees  C.  below  zero.  On  the  other  liand  Kunisch-  states  that  the 
alcoholic  extract  of  chlorophyll  from  hyacinth  leaves,  frozen  at  7  degrees 
below  zero,  was  found  to  diff'er  from  that  of  leaves  which  had^  not  been 
frozen.  Often  dull  whitish  spots  are  found  in  frozen  leaves  which  can 
arise  from  ice  accumulations  crystallized  out  into  the  intercellular  spaces, 
Hoffmann  found  in  Ceratonia,  Laurus  and  Camphora,  a  vesicular  raising 
of  the  epidermis  and  called  it  a  "frost  blister-''.  In  heavy  frost,  the  leaves 
which  have  been  frozen  through  become  as  brittle  as  glass  and  transparent. 
When  such  leaves  are  thawed,  the  change  in  color  depends  upon  whether 
the  protoplasm  of  the  cells  has  been  killed  or  not.  If  it  is  dead,  it  becomes 
permeable  to  acids  in  the  cell ;  these  penetrate  to  the  chlorophyll  grains,  and 
cause  their  decomposition  (the  formation  of  chlorophyllan)  :  the  cytoplasm 
turns  l)rown  ;  the  cell  sap  exudes  rapidly;  the  leaf  dries  into  a  brittle,  brown 
mass.  Ciopperf*,  who  describes  the  various  colorations  of  foliage  leaves, 
also  mentions  an  extremely  strong  weedy  smell  in  frozen  plants.  In  ferns 
the  odor  peculiar  to  the  whole  family  is  retained  in  frozen  and  dried  speci- 
mens in  an  unusual  intensity.  In  artificially  frozen  branches  of  the  sweet 
cherry  I  noticed  a  decided  odor  of  bitter  almond.  These  phenomena  are  the 
result  of  the  chemical  changes  which  make  themselves  felt  immediately 
and  strongly  during  thawing,  h'luckiger'  has  observed  a  dift"erent  effect  in 
the  frozen  leaves  of  the  cherry  laurel.  During  distillation,  these  gave  off 
an  oil  differing  from  that  of  the  fresh  leaves  and  no  prussic  acid,  while 
leaves  covered  with  ice,  but  not  frozen,  gave  both  substances  under  normal 
conditions. 


1  Wiesner,  Die  natiiilichen  Erscheinungen  zum  Schutze  des  Chlorophylls,  etc. 
Festschrift  d.  k.  k.  zoologr.-bot.  Ges.  zu  Wicn  1876,  p.  23. 

-  Kunisch,  H.,  tJber  die  ti'.dliche  Wirkung  niederer  Temperaturen  aiif  die 
Pflanzen.     Inauguraldisscrtation.     Breslau  1880. 

:'   Kunisch,  loc.  cit.  p.  22. 

•*  Gi'ippert,  t)l)er  Kinwirkung  des  Frostes  auf  die  Gewiichse.  Sitzungsb.  d. 
Schles.  Ge.s.  f.  vaterl.     Kultur  1874;   cit.  Bot.  Z.  1875,  p.  609. 

5   The  effect  of  intense  cold  on  cherry-laurel;   cit.  Bot.  Centrall)l.  1880,  p.  887. 


525 

It  is  important  to  refer  here  to  the  behavior  of  the  mineral  substances 
in  leaves  killed  by  frost,  because  we  thus  obtain  an  insight  into  the  loss  in 
substance  caused  by  the  destruction  of  the  foliage  in  spring  frosts. 

Schroeder's^  analyses  of  red  beech  foliage  which  a  May  frost  had  killed 
and  which,  four  weeks  later,  was  examined  in  the  dried  condition,  gave  the 
following:  In  the  frozen  foliage,  the  whole  nitrogen  content  (3.56  per 
cent.)  of  the  fresh  May  leaves  is  found,  while  in  the  autumnal  leaves,  only 
about  1.33  per  cent,  remains,  so  that,  therefore,  almost  three  times  as  much 
nitrogen  is  lost  for  the  plant  from  the  loss  of  the  May  foliage  as  in  that  of 
the  autumnal  falling  of  the  leaves.  The  dry  substance  gives  3.01  per  cent, 
ash.  Of  this  ash,  22  per  cent,  was  phosphoric  acid,  i.  e.,  as  much  as  fresh 
May  leaves,  while  the  July  leaves  possess  only  5  per  cent.  In  May  leaves 
about  30  per  cent,  of  potassium  was  present  normally ;  in  frozen  ones,  how- 
ever, only  5  per  cent.  Naturally  very  little  calcium  was  present  in  the 
young  foliage  (6.78  per  cent,  in  healthy  foliage,  4.70  per  cent,  in  frozen 
foliage)  ;  while  the  vegetating  July  leaves  possessed  three  times  as  much 
(20.34  per  cent.)  the  dead  November  leaves  actually  exhibited  37.O0  per 
cent. 

In  opposition  to  the  opinion  that  foliage  killed  by  spring  frosts  remains 
hanging  on  the  trees,  wdiich  thus  gives  its  valuable  mineral  elements  time 
to  wander  back  into  the  trunk,  reference  should  be  made  to  Ramann's  inves- 
tigations-. He  proved  that  the  foliage  of  the  oak,  spruce  and  fir,  killed  by 
cold,  at  first  possessed  the  same  composition  as  fresh  foliage,  when  analyzed 
before  a  rain,  but,  during  the  rain,  it  underwent  a  very  considerable  change. 
Ramann  found  that,  within  yi  hours,  water  withdrew  not  less  than  19.219 
per  cent,  of  the  whole  ash  of  red  beech  leaves  and  actually  26.46  per  cent,  of 
the  oak.  This  easy  diffusibility  of  the  ash  elements  should  not  be  considered 
to  be  the  result  of  later  decomposition,  as  is  proved  by  the  fact  that  the 
greater  amount  had  been  leached  out  in  the  first  24  hours  ;  viz.,  in  the  beech 
15.42  per  cent.;  in  the  oak,  19.66  per  cent.  These  latter  amounts  gave  in 
pure  ash  11. 15  per  cent,  and  of  extraction  for  the  trunk,  14.18  per  cent, 
for  the  oak. 

The  amount  to  which  loss  of  the  foliage  injures  the  main  body  is  shown 
in  another  difi:'erent  work  by  Schroeder^  on  "The  migration  of  nitrogen  and 
mineral  elements  during  the  first  development  of  the  spring  growth."  The 
exhaustion  of  phosphoric  acid  in  the  trunk  during  the  production  of  the 
young  growth  is  the  greatest,  namely,  46  per  cent. ;  then  follows  potassium, 
X2  per  cent,  of  which  is  used  up ;  nitrogen  and  magnesium  are  removed  from 
the  trunk  up  to  possibly  26  per  cent.  Before  the  end  of  this  period,  12  per 
cent,  calcium  and  84  per  cent,  of  the  initial  amount  of  silicic  acid  are  added 
and  replace  the  loss.     Of  the  whole  amount  of  nitrogen,   potassium  and 

1  Schroeder.  Unter.suchung'  erfrorenen  Buchenlaubes.  Forstchemische  u.  pflan- 
zenphysiologische  Untersuchungen.  Part  1,   1878,  Dresden,  iJ.  87. 

^  Ramann,  Aschenanalysen  erfrorener  Blatter  und  Triebe.  Bot.  Centralbl. 
1880,  p.  1274. 

^  loc.  cit.  p.  83. 


526 

phosphoric  acid  wandering  into  the  young  growth,  possibly  one-fifth  comes 
from  the  trunk,  and  four-fiftlis  from  the  root  and  soil.  These  figures  favor 
the  theory  that  the  root-body,  to  a  still  higher  degree  than  the  trunk  organs, 
gives  up  its  rcser\  c  [)ro\  ision  of  nitrogen,  phosphoric  acid  and  [)otassium. 

Deficient  Gkeemng  of  Younger  Leaves. 

A  special  form  of  the  eft'ect  of  lower  temperatures  on  the  coloring  of 
plant  bodies  is  the  remaining  yellow  of  grozving  organs  due  to  the  lack  of 
temperatures  necessary  for  turning  green.  Klving'  found  that  ctiolin  was 
formed  at  temperatures  which  were  still  too  low  for  the  formation  of 
chlorophyll  in  spindling  seedlings,  which,  cxi)osc(l  for  a  short  time  to  the 
light,  became  yellower  than  those  left  in  the  dark.  When  plants  are  uncov- 
ered in  the  early  spring,  numerous  examples  are  found  in  which  the  etiolated 
shoots  which  had  been  produced  under  the  cover,  in  s])ite  of  the  at  times 
abundant  illumination,  generally  do  not  lose  their  yellow  color  or  lose  it 
only  slowly  and  irregularly  in  spots.  The  most  abundant  examples  were 
furnished  by  garden  hyacinths.  If  these  are  uncovered  too  early  in  the 
spring  and  frost  surprises  the  young  leaf  cones  which  are  not  yet  green  the 
leaves  develop  later  a  normal  color  but  their  young  tips  remain  white  or 
yellow. 

In  the  parts  which  appear  yellow,  we  usually  find  the  chloro])lasts 
formed  and  arranged  normally,  i.  e.,  along  the  free  lying  parts  of  the  cell 
walls  or  those  bordering  intercellular  passages  (epistrophe),  but  the  color 
ing  matter  is  only  a  more  or  less  intensive  yellow.  In  this  stage,  all  possible 
transitions,  up  to  the  complete  absence  of  the  grains  in  the  wholly  bleached 
tip  of  the  leaf,  are  found  ;  these  are  not,  however,  conditions  due  to  disso- 
lution but  are  arrestment  formations.  In  the  whitest  parts  of  the  meso- 
phyll,  the  cells  are  filled  with  a  watery  cell  sap  which  is  traversed  by 
cytoplasmic  cords,  without  the  deposition  of  any  chlorophyll  bodies  in  the 
cytoplasmic  wall  layer.  In  other  cells  of  the  yellowish  parts,  the  differenti- 
ation of  the  contents  extends  to  the  primordia  of  the  chloroplasts,  but  these 
appear  more  whitish,  more  tender,  we  might  say,  and  at  times,  cloudier, 
less  dense  and  less  sharply  defined.  Normally  formed,  intensively  green 
chloroplasts  are  finally  found  in  the  parts  of  the  leaves  which  have  grown 
out  of  the  soil  after  frost  action.  At  times  the  lack  of  green  is  connected 
with  the  presence  of  red  coloring  matter.  Charguerard"  furnishes  an 
example  ;  he  obser\ed  in  Plialaris  ariindinocea  picta,  that  the  young  leaf  tii)s, 
with  their  well-known  white  stripes,  appeared  reddened  by  frost.  The  rose 
red  coloring  disappeared  with  warm  weather.  .Schell''  confirms  the  appear- 
ance of  the  red  coloration  with  cold.  In  the  spring  he  placed  plants  with 
red-colored,  young  leaves  under  three  different  tem])eratures  and  observed 
that  the  specimens  kept  in  a  room  at  15  degrees  C.  became  green  within 


1   Arbeiten  d.  Bot.  Instituts  zu  Wiirzbuig,    Vol.   II,    I 'art    3;    cit.   Bot.   Centralbl. 
1880,  p.  835. 

•.;  Revue  horticole,  Paris  1874,  p.  249. 

3  Botanischer  .Jahrcsbericht  1876,  p.  717. 


527 

i8  hours,  while  those  kept  at  8.5  degrees  C.  turned  green  only  after  5  days. 
The  plants  left  out  of  doors,  with  a  maximum  temperature  of  about  4 
degrees  C.  became  green  only  after  20  days  when  the  temperature  of  the  air 
had  risen.  These  observations  favor  my  theory,  that  the  red  coloring  is 
conditioned  by  the  preponderance  of  a  process  of  oxidation,  connected  with 
the  action  of  light,  over  the  process  of  assimilation.  A\'ith  equal  amounts 
of  light,  a  rise  in  temperature  so  increases  assimilation  that  the  process  of 
turning  green  preponderates. 

To  avoid  a  fixation  of  the  morbid  yellowish  ai)pearance  of  leaf  tips, 
l)leache(l  by  frost,  it  is  advisable  to  remove  the  winter  coxering  gradually, 
or,,  for  the  first  few  days,  to  spread  a  light  layer  of  brush  over  the  plants. 

Defoliation  Due  to  Frost. 

The  sudden  falling  of  the  foliage  during  and  after  the  appearance  of 
the  first  autumnal  frost  is  only  one  form  of  the  autumnal  defoliation  which 
should  be  designated  death  from  senility  (in  contrast  to  the  cases  already 
described  of  abnormal  defoliation  after  excessive  heat,  drought,  lack  of 
light,  excess  of  moisture  and  other  causes,  producing  a  sudden  loss  of  func- 
tion of  the  organ).  The  leaf  has  simply  lived  out  its  life.  A  normal  death  of 
this  kind  has  the  least  disadvantageous  results  for  the  trunk  which  remains 
alive.  From  the  senile  leaf  apparatus  man\-  plastic  as  well  as  important 
mineral  substances  gradually  wander  back  into  the  trunk  and  are  used  again 
in  the  following  period  of  growth.  The  retention  of  abundant  amounts  of 
organic  structural  substances  and  the  leaching  of  easily  soluble  nutritive 
substances  by  rain  are  ven'  disadvantageous  in  leaves  which  die  in  a  juven- 
ile stage,  since  these  are  thus  lost  to  the  trunk.  But  both  processes  have 
but  little  significance  when  the  leaves  die  of  old  age.  In  this  case,  as  has 
recently  been  emphasized  repeatedly  by  B.  Schultze\  the  assimilation  of 
carbon  dioxid  may  well  be  proved,  up  to  the  last  moment,  even  if  naturally 
with  weakened  power.  Through  the  preponderance  of  the  processes  of 
decay  over  those  of  construction  the  leaf's  supply  of  easily  soluble  proteins 
is  especially  impoverished.  A\'ith  the  increasing  thickening  and  calcification 
of  the  membranes,  the  conducting  of  new  nutritive  substances  becomes 
constantly  more  difficult,  so  that  the  demonstrable  reduction-  of  nitrogen, 
phosphoric  acid  and  potassium  thus  becomes  explicable,  even  if  no  consid- 
erable process  of  retrogression  is  accepted. 

After  all  that  has  been  said  in  earlier  sections  on  the  influence  of 
position,  soil  constitution  and  weather,  it  is  not  necessary  to  emphasize  here 
the  fact  that  the  life  period  of  the  leaves  can  be  proved  to  be  very  difl^erent 
for  the  same  species  and  that  in  this  frost  also  acts  on  leaves  which  \ary 


1  Schultze,  B.,  Stvidien  iiber  die  Stoffwandlungen  der  Blatter  von  Acer  Negundo 
L.,  76  Versammlung  d.  Ges.  Deutsch.  Naturf.;  cit.  Centralbl.  f.  Agrikulturchemie 
1906,  p.  35. 

-  Fruwirth,  C.  and  Zielstoff,  W.,  Die  herbstliche  Riiclvwanderung  von  Stoffen 
bei  der  Hopfenpflan^e.  Landw.  Versuch.sstat.  1901;  cit.  Bot.  Jahresb.  1901.  Part 
2,  p.  161. 


528 

greatly  in  age.  Accordingly  the  [)r(jce.ss  of  leaf  fall  is  not  always  the  same. 
The  most  usual  case  consists  in  the  formation  of  a  tissue  zone  at  the  base  of 
the  leaf  which  is  a  characteristic  abscission  layer.  W'e  repeat  here  the 
illustration  of  the  autumnal  abscission  layer  in  the  leaf  of  .Icsciihts  Hippu- 
castanum  (cf.  Fig.  io6).  The  illustration  gi\es  a  section  made  longitudin- 
ally through  the  joint  at  the  base  of  the  petiole,  a  is  the  bark  parenchyma  of 
the  branch;  b,  the  layer  of  plate-corR  cells  which  remains  when  the  petiole 
has  fallen  and  thus  forms  a  protection  for  the  bark  tissue;  c  indicates  the 
cells  at  the  base  of  the  petiole  which  at  e  pass  over  into  the  firmer  paren- 
chyma of  the  broadened  bases  of  the  i)etioles,  provided  with  abundant  accu- 
mulations of  calcium  oxalate,  netween  c  and  e  takes  place  the  process  of 
separation,  since  at  </  the  cells  round  off  and  l)egin  to  separate  from  one 
another.  If  now  the  leverage  of  the  leaf,  mo\ed  b}-  the  wind,  makes  itself 
felt,  the  i)etioles  break  off  at  the  loosened  cell  layer. 


Fig.    lOtj.     Autumnal  abscission  layer  of  a  horse  chestnut  leal'. 
(After   Dobncr-Nobhe.) 

The  riper  the  leaf  is  at  the  time  of  the  final  autumnal  frost,  the  more 
easily  it  falls;  on  this  account,  the  old  leaves  of  the  branch  arc  found  to  be 
the  first  ones  broken  off  by  the  wind  in  the  autumn.  The  greater  the  life 
energy  and  the  quantity  of  plastic  inaterial,  the  more  resistent  the  youthful 
leaf  seems  to  frosts  which  are  not  killing  frosts. 

If  killing  degrees  of  frost  occur  in  the  autumn  at  a  time  when  the  leaf 
has  not  yet  sufficiently  matured  its  abscission  hner,  i.  e.,  the  tree  is  still  far 
distant  from  its  dormant  period,  then  the  dead  foliage  remains  on  the 
branches  o\  er  winter  (beech  and  oak).  The  beeches  in  which  the  foliage 
remains  hanging  often  leaf  out  later  in  the  spring  than  do  normally  matured 
specimens'. 

At  the  time  of  the  first  night  frost,  it  is  found  in  the  early  morning,  if 

the  frost  still  lies  on  the  ground  and  even  in  windless  weather,  that,  as  soon 

as  the  sun  comes  up,  the  simple  leaves  of  the  trees  break  off  and  the  leaflets 

of  composite  leaves  fall  from  the  common  spindle,     v.  Mohl-  found  in  such 

1   dc  Candollc,  A.,  in  Contralbl.  t.  Agrikulturchemie  1879,  I,  p.  159. 
-  Bot.  Zeitung-  1860,  p.  16. 


529 

cases  that  the  leaf  scars  of  the  fallen  leaves,  or  those  just  about  to  be 
loosened,  were  covered,  in  a  number  of  plants,  by  a  thin  layer  of  ice.  Paul- 
ovvnia,  for  example,  exhibited  an  especially  thick  ice  crust.  Often  the 
leaves  were  still  connected  with  their  scar  only  by  the  ice  crystals.  These 
ice  crystals  had  l)ecn  formed  in  the  abscission  layer  of  the  leaves.  The 
columnal  structure  of  the  crystals,  their  cloudiness,  produced  above  the 
vascular  bundles  b}-  little  air  bubbles,  and  their  arrangement,  ending  sharply 
with  the  boundary  of  the  leaf  scar,  favor  the  view  that  no  considerable 
masses  of  cell  sap,  which  had  possibly  Howed  out,  ha\e  been  frozen  but  that 
small  particles  of  water  pass  through  the  cell  walls-  exactly  at  the  place 
where  they  are  observed  and  are  there  stiffened  to  ice. 

Thf  formation  of  ice  may  often  occur  very  early  and  thereby  cause, 
when  thawing,  the  fall  of  lea\es  which  otherwise  would  ha\  e  remained  for 
some  time  on  the  tree  and  may  e\en  still  be  green.  Besides  this  action  of 
the  ice  lamellae,  a  premature  autumnal  defoliation  may  set  in  because  the 
leaf  is  partially  or  entirely  frozen;  it,  therefore,  suddenly  becomes  function- 
less  and  is  then  pushed  oif . 

In  autumnal  defoliation  the  loosening  of  the  leaf  always  takes  ])lace  in 
the  abscission  layer  which,  according  to  W'iesner's  observations',  docs  not 
always  arise  from  a  secondary  meristem  but  is  often  found  also  as  a  rem- 
nant of  the  primary  meristem.  In  other  cases  of  leaf-fall  the  process  of 
disarticulation  can  take  place  in  different  tissues. 

If  the  process  of  disarticulation  within  the  layer  of  separation  be  con- 
sidered in  general,  the  following  modifications  will  be  found,  according  to 
\\  iesner-.  So  strong  an  osmotic  pressure  can  be  produced  in  the  cells  of 
the  abscission  layer  that  the  tissues  separate  from  one  another,  leaving 
smooth  surfaces.  This  we  find  in  defoliation  which  is  the  result  of  excess 
of  water  even  where  this  excess  arises  from  abundant  watering  after  a  long 
period  of  dryness.  The  phenomena  of  the  dropping  of  the  leaves  of 
Azaleas,  Ericas  and  New  Holland  plants,  so  well  known  to  gardeners,  after 
the  drying  of  the  root  ball,  belong  here,  as  does  also  summer  defoliation 
with  the  occurrence  of  rains  after  a  long  drought. 

According  to  AViesner,  in  autumnal  defoliation  the  macerating  action 
of  organic  acids  comes  especially  under  consideration.  He  assumes  that 
the  surfaces  of  separation,  in  death  from  frost,  as  a  result,  have  an  acid 
reaction,  and  explains  this  by  the  fact  that  the  frost  kills  the  cytoplasm, 
thereby  making  it  permeable  to  the  acids  which  occur  in  the  cell  content  and 
then  act  on  the  membranes.  Oxalic  acid  may  play  a  great  part  in  this. 
The  above-named  investigator  laid  the  stems  of  various  plants  in  a  2.5 
per  cent,  solution  of  oxalic  acid  and  found  that  the  leaves  had  loosened 
within  a  few  days.  The  stems  of  plants  which  form  abscission  layers  at 
the  internodes  also  disarticulated  within  a  short  time. 


1  Wiesner,   Julius,    tjber   Frostlaul>fall    nebst    Bemerkung-en    iiber   die   Mechanilv 
der  Blattub]osun.a-.     Ber.  d.  D.  Bot.  Ges.  1905,  Part  1,  p.  49. 
-   loc.  cit.  p.  54. 


530 

It  the  leaf  surface  is  injured  In'  frost,  lait  tlie  part  of  the  leaf  lying 
helow  the  abscission  la>er.  i.  e..  the  leaf  stump,  remains  alive,  the  frozen 
part  of  the  leaf  will  dry  ui),  but  the  leaf  base  will  be  found  intact  and  turgid. 
Between  the  leaf  base  and  the  dried  ])art  differences  in  tension  must  arise 
which  lead  to  the  loosening  of  the  leaf  body. 

Experiments  made  by  l*runet'  show  how  c}uickly  the  parts  injured  by 
frost  have  dried  up.  A  frozen  \ine  branch  with  four  leaves  placed  in  water, 
evaporated  475  mgr.  of  water  within  two  hours.  In  this,  its  loss  in  weight 
amounted  to  14.46  per  cent.  Under  the  same  conditions  a  similar  branch, 
not  injured  by  the  cold,  evaporated  only  132  mgr.  of  water  and,  because  of 
the  absorption  of  water  which  had  taken  place  simultaneously,  increased  its 
weight  by  0.26  per  cent. 

Wiesner  has  also  shown  experimental])-  how.  in  jjlants  which  retain 
their  frozen  foliage  for  some  time,  often  for  the  winter,  this  may  occasion- 
ally be  based  on  a  rapid  drying.  He  took  branches  of  Ligustnim  ovalifoliiiin 
with  frozen  leaves  and  placed  them  in  a  warm  room  in  such  a  way  that  the 
sprouts  could  constantly  soak  up  water.  After  6  to  12  days,  these  dro])ped 
ihcir  leaves  while  the  leaves  of  shoots  not  provided  with  water  remained 
firmly  attached.  In  cases  occurring  out  of  doors,  where  the  dead  foliage 
remains  in  place  on  the  branches,  the  separation  takes  place  only  after  the 
destruction  of  the  tissue.  The  moldering  of  the  membranes  within  the 
abscission  layer  will  gradually  advance  so  that  the  wind  or  some  other 
mechanical  cause  finally  brings  about  the  breaking  off  of  the  leaf.  In  these 
moldering  processes  micro-organisms  will  doubtless  cooperate. 

From  what  has  been  said,  it  is  clear  that  the  mechanics  of  separation 
in  the  autumnal  senile  defoliation,  as  well  as  in  that  due  to  frost,  can  often 
(liff'er  e\en  in  the  same  individual,  according  to  the  age  of  the  leaves  and 
the  existing  accessory  circumstances.  In  many  plants  (grapes),  besides 
the  loosening  of  the  whole  leaf  from  the  axis,  the  loosening  of  the  leaf 
blade  from  the  petiole  also  occurs.  In  other  disturbances  also,  this  region 
is  especially  susceptible  and  at  times  manifests  its  similarity  to  the  base  of 
the  petiole  through  a  similar  discoloration.  For  example,  in  poplars,  it  can 
be  observed  that  in  tlic  autumn  the  base  and  tip  of  the  [)etiole  become  red 
while  the  remainder  is  yellow. 

The  diiTerence  in  the  time  when  these  i)rocesses  set  in  in  dift"crent  indi- 
viduals, and  in  the  same  individual  at  different  heights  of  the  various 
Itranches.  is  connected  with  the  physiological  age  of  each  leaf.  The  yonnijer 
this  is.  the  later  it  falls  from  the  branch,  under  otherwise  equal  conditions, 
as  Dingier'-  has  determined,  by  pruning  experiments.  He  observed  a 
greater  power  of  resistance  in  the  young  leaves,  especially  to  autumn  frosts. 
The  young  leaves  of  Carpinus  Betuhis  did  not  freeze  during  frost  periods. 


1  Prunet,  A.,  Sur  los  modifications  de  I'absorption  et  de  la  transpiration,  qui 
surviennent  dans  les  plantes  atteintes  par  la  g-elee.  Compt.  Rend.  d.  I'Acad.  des 
Sciences  1892,  II,  p.  964. 

-  Dingier,  Hermann,  Versuche  und  Gedanken  zum  herbstlichen  Ijaubfall.  Ber. 
d.  D.  Bot.  Ges.  1905.     Part  9,  p.  463. 


lasting  all  day,  but  older  ones  were  affected  and  finally  died.  I  found 
similar  conditions  in  plane  trees  in  which  the  age  of  the  tree  made  itself  felt 
in  the  same  way.  In  street  trees,  young  specimens  had  been  planted  be- 
tween the  older  trees.  Although  they  did  not  stand  under  the  protection  of 
the  older  trees,  they  still  retained  their  considerably  stronger  foliage  when 
most  of  that  of  the  older  trees  lay  on  the  ground. 

Behavior  of  Bef.t  and  Cabbage  Plants  in  Frost. 

In  storing  sugar  beets  the  loss  of  sugar,  which  occurs  in  the  heaps 
because  of  the  respiration  of  the  beet  body,  can  be  decreased  only  by  the 
lowest  possible  temperature\  In  sugar  beets  which  have  been  frozen,  a 
raising  of  the  sugar  content  was  actually  found  when  the  water  was  frozen 
out.    This  has  been  reckoned  by  Ninger  to  be  0.39  per  cent'-. 

The  new  formation  of  saccharose  which  takes  place  during  the  process 
of  freezing  is  no  greater  than  the  amount  destroyed.  Also  the  amount  of 
nitrogenous  substances  and  the  proportion  of  proteins  to  non-proteins  re- 
mains unchanged.  So  soon,  however,  as  thawing  begins,  the  latter  appear 
to  be  increased  at  the  expense  of  the  former.  The  elements  of  the  raw^ 
fibers  (cellulose  and  related  substances)  become  more  soluble  in  acids  and 
alkalis  and  in  part  also  more  soluble  in  water  because  of  the  freezing^.  In 
this  an  increase  of  non-sugar  substances  is  produced  in  the  sap.  I  observed 
in  frozen  beets  partial  swellings  of  the  membranes  which  might  be  ex- 
plained as  a  visible  expression  of  the  chemical  changes  in  the  cellulose. 
Strohmer  and  Stift  found  a  striking  increase  in  the  acid  content. 

The  large  sugar  content,  produced  by  the  loss  of  water,  and  the  conse- 
quently more  concentrated  cell  sap  will,  however,  retard  the  actual  freezing 
of  the  beet  body.  Besides  this,  in  the  storage  piles,  the  outer,  frozen  tubers 
will  protect  the  inner  ones  from  freezing.  Miiller-Thurgau  has  referred  to 
this  especially  and  Mez*  has  explained  it  by  the  fact  that  the  conversion 
of  the  cell  sap  into  a  solid  aggregate  condition  preserves  the  energy  still 
present  in  the  cell  from  too  rapid  dispersal.  The  conduction  of  warmth 
takes  place  much  more  slowly  in  ice  than  in  water,  where  the  warmth  is 
distributed  by  radiation. 

The  statements  of  market  gardeners  that  brown  cabbage  (Brassica 
oleracea  acephala)  obtains  its  desired  sweetness  only  after  frost,  may  find 
adequate  explanation  in  the  accumulation  of  sugar  due  to  the  low  tempera- 
ture. According  to  the  analyses  made  by  Marker  and  Pagel^,  an  amount 
of  sap  equal  to  68.66  per  cent,  of  the  remnants  of  the  plant  may  be  pressed 


1  Heintz,  Atmung'  der  Riibenwiirzeln.  Zeitschrift  d.  Ver.  f.  d.  Riibenzuckei'in- 
dustrie  d.  deutsch.  Reiches  1873.  v.  XXIII;   cit.  Bot.  Jahresb.,  I,  p.  358. 

2  Bot.  Jahresber.  1880,  p.  665. 

3  Strohmer,  F.  und  Stift,  A.,  tjber  den  Einfluss  des  Gefrierens  auf  die  Zusam- 
men-setzung-  der  ZuckerriJbenwurzel.  Osterr-Ung.  Z.  f.  Zuckerindustrie  und  Land- 
wirtsch.  1904.    Part  6. 

4  Mez,  Carl,  Neue  I^'ntersuchungen  iiber  das  Erfrieren  eisbestandiger  Pflanzen. 
Send.  Flora  od.  Allgem.  Bot.  Zeit.    1905,  p.  109. 

5  Marker  und  Pagel,  tJber  den  Einfluss  des  Frostes  auf  Kohlpflanzen.  Bieder- 
mann's  Centralbl.  1877,  v.  XI,  p.  263-66. 


532 

out  from- frozen  cahbajre  plaiit^^  wliilc  llic  same  [)ressure  ga\e  only  7.1  per 
cent,  sap  in  examples  which  had  not  l)een  frozen.  100  com.  of  sap  con- 
tained in 

frozen  plants     not  frozen  [)lants 

Dry    substance    7.96  'fH;  4.04  g 

]\a\\    Ash    ' 1.63  "  0.97  " 

( irape  Sugar   4-1/   "  1.41   " 

1  )extrin    (  ?)    0.80  "  0.58  " 

Nitrogenous  substances   0.80  "  0.51   " 

l'^xtracti\e  substances  free  from  nitrogen  0.50  "  0.54  " 

This  shows  that  the  soluble  elements  in  the  sap  have  undergone  a  con- 
siderable increase  and  that,  in  this,  grape  sugar  is  especially  concerned. 
Here,  therefore,  just  as  great  a  formation  of  sugar  has  been  found  as  in 
the  potato;  .Schmidt'  states  this  to  be  21.85  per  cent. 

Frost  I'li.stf.ks. 

Frost  bHsters  are  of  less  significance  agriculturally  but  certainly  worthy 
of  consideration  scientifically  because  of  the  ])roduction  of  mechanical  dis- 
turbances in  the  tissues  inside  the  organs  which  remain  ali\e.  These  mani- 
fest themseKes  in  the  ai)i)earancc  of  usually  small,  blister-like  places  in  the 
epidermis  and  at  times  also  in  the  suli-epidermal  layers  which  are  raised 
from  the  thin-walled  i)arenchyma  of  the  leaf  flesh  or  the  tougher  [)aren- 
chyma  ot  the  leaf  \eins.  Instead  of  an  extensi\e  descvij)tion.  we  will 
reproduce  in  I'ig.  107  a  cross-section-  of  the  frost  blister  on  an  api>le  leaf. 
O  indicates  the  upper  side,  U,  the  under  side.  M  is  the  mid-rib.  .v  a  larger 
lateral  veiri. 

In  the  r!ii(l-rib.  the  crescent-like  wood  bod_\',  with  its  numerous  ducts 
((/),  forms  the  chief  part.  On  the  upper  side  adjoins  a  thin  walled  layer 
of  parenchyma  (in)  free  from  chlorophyll.  corres[)onding  to  the  pith  body 
of  the  axis.  This  parenchyma  layer  is  co\ered  by  thick-walled  collen- 
chymatous  cells  (c)  ;  these  dexelo])  more  abundantly,  the  larger  the  \ein  is. 
The  collenchyma  extends  as  firm  wedges  somewhat  abo\e  the  part  of  the 
leaf  surface  which  consists  only  of  leaf  flesh.  The  leaf  flesh  shows  the 
usual  di\ision  into  palisade  parenchyma  (p)  and  spongy  parenchyma  (sp). 
Of  these  layers,  containing  chloroplnll,  the  palisade  parenchyma  does  not 
extend  over  the  \ascular  bundles  on  the  upper  side  but  spreads  out  on  both 
sides  like  a  keel  so  that  it  terminates  in  a  short  cell  layer  (br).  This  be- 
comes one  layered,  between  the  collenchyma  and  the  parenchyma  of  the 
body  of  the  ^ein.  The  spongy  parenchyma,  on  the  other  hand,  extends  on 
the  under  side  over  the  body  of  the  vascular  bundle  and  forms  the  bark  part 
of  the  vein  in  which,  as  in  the  l)ark  of  the  branch,  may  be  found  oxalate 
crystals  (0)  arranged  in  crescent-like  rows.  The  e])idermis  (c)  covers 
the  whole  leaf  uniforml}. 

1    After  Ritthau.sen;    cf.  "Dor   l^aiulwirt"   1875,   j).   .501. 

-   Sorauer,  P.     I-'rostblasen  an  Blattein.     Z.  f.  I'Hanzeiikrankh.  1U02,  p.   44. 


533 

The  mechanical  action  of  frost  is  shown  here  in  the  form  typical  for 
the  majority  of  our  plants  since,  on  the  upper  side  of  the  leaf,  the  collen- 
chyma  tissue  aboxe  the  vascular  bundle  of  the  large  vein  is  raised  up  from 
the  parenchyma,  thereb}-  forming  an  opening  (/').  On  the  under  side  of 
the  leaf,  the  spongy  parenchyma  has  been  freed  from  the  bark  part  of  the 
vein  on  the  scarps  of  the  very  prominent  body  of  the  vein  so  that  cavities 
(h),  containing  air,  are  produced  on  both  sides  of  the  rib.  The  formation 
of  the  caxities  is  explamed  by  the  fact  that  the  youthful,  still  hyponastic 
leaf,  the  edges  of  which  are  up-curled,  from  the  action  of  frost,  C(jntracts 
at  both  sides  of  the  mid-rib  from  above  downward,  as  well  as  tangentially. 
If  the  up-curled,  trough- like  leaf  contracts,  the  curling  must  become  greater, 
i.  e.,  the  distension  of  the  under  side  becomes  stronger.  This  manifests 
itself  in  a  pulling  toward  the  raised  edges  (see  the  direction  of  the  arrow  in 


Fig-.   107.     Cro.cis- sect  ion   through    a    t'lost   boil   m  an  apple   leaf. 


the  illustration).     The  tension  is  the  greatest  at  the  scarp  of  the  vein  and 
can,  at  times,  lead  to  a  splitting  of  the  epidermis  (e'). 

If  thawing  now  takes  place,  the  result  of  the  action  of  the  frost  is  the 
overlengthening  of  the  tissue  ^^-hich  has  been  strained,  for  the  tissues  are 
indeed  distensible  but  not  completely  elastic.  They  do  not  regain  their 
former  size  and  arrangement.  The  lower  epidermis,  which  has  been  most 
strained,  elongates  and  no  longer  exercises  on  the  spongy  parenchyma, 
lying  beneath  it,  the  previous  amount  of  pressure.  The  pressure  in  the 
epidermis  is  broken  and  the  spongy  parenchyma  responds  at  once,  elongat- 
ing into  pouches.  If,  at  the  time  of  the  greatest  tension,  the  epidermis  is 
torn  apart,  the  over-elongated  edges  of  the  tear  {e')  form  a  crater-like 
opening  toward  which  grow  out  the  rows  (/)  of  the  spongy  parenchyma 
which  develop)  into  threads. 


534 

We  find  further  investigations  of  frost  blisters  in  a  work  by  Xoack'.  who 
comes  to  the  conclusion  that  they  are  produced  "because  water  from  the 
cells  is  pressed  into  the  intercellular  spaces  and  there  turns  to  ice  so  soon 
as  the  temperature  falls  to  a  certain  degree  below  the  freezing  point,  differ- 
ing for  the  different  varieties  of  plants."  The  formation  of  ice  crystals 
was  found  by  Noack  to  be  strongest  at  the  place  where  later  the  separation 
of  the  epidermis  becomes  visible.  We  owe  a  recent  study  to  Solereder-'. 
He  observed  in  the  leaves  of  Buxus  the  same  hairy  outgrowth  of  the  meso- 
phyll  cell  rows  that  I  had  found  in  apples,  cherries,  apricots  and  have  illus- 
trated in  Pig.  107.  Solereder  has  proved  experimentally  that  this  elongation 
of  the  cells  of  the  leaf  flesh  is  a  secondary  phenomenon  occurring  with  an 
abundant  supply  of  water.  He  removed  the  under  side  of  the  leaf  and  set 
the  plants  in  a  moist  place.  Cuticular  warts  were  then  produced  on  the  cell 
membranes,  similar  to  those  which  we  have  illustrated  by  the  woolly  stripes 
in  ai)i)le  cores  (p.  324)  and  lia\e  ()bser\cd  also  in  the  frost  blisters  of  cherry 
leaves.  The  beginning  of  this  hair-like  elongation  of  the  cells  is  found  in 
the  sheath  of  the  vascular  bundles,  i.  e.,  in  places  where  the  cork  disease  of 
the  cactus  (p.  429,  Fig.  71)  may  be  recognized  as  the  initial  point  of  the 
diseased  processes  of  elongation.  We  find  in  this  an  experimental  proof  of 
our  theory  that  the  disturbances  named  may  be  traced  back  to  excess  of 
moisture. 

We  will  discuss  later,  in  connection  with  other  mechanical  disturbances 
due  to  frost,  the  (|uestion  whether  the  frost  blisters  were  produced  by  the 
crystallized  ice,  or  formed  previously  by  a  difference  in  tension  due  to  the 
cold,  thus  oft'cring  for  the  formation  of  ice  the  most  convenient  places  of 
deposit.  We  will  for  the  present  only  emphasize  the  fact  that  the  holes  in 
the  tissue  pictured  in  the  apple  leaf  (on  the  upper  side  of  the  veins  and 
below  on  their  scarps)  are  a  typical  frost  peculiarity  found  frequently  in 
very  difl'erent  leaves  which  also  remain  green  during-  the  winter. 

COMR-I.TKE    Sl'I.lTTIN(;    OF   THK    LkAVES. 

In  some  years  with  late  frosts  the  phenomenon,  in  which  the  otherwise 
continuous  surfaces  of  tree  leaves  often  appear  slit  and  thereby  approach 
those  forms  which  are  characterized  as  "folia  laciiiiafa"  may  be  found  not 
infrequently.  While,  however,  in  commercial  \arieties,  the  slit  leaf  form 
is  a  condition  fixed  in  the  developmental  course  of  the  individual  and  may 
be  transmitted  by  grafting,  the  slitting  due  to  frost  forms  a  transitory  stage 
which,  even  in  the  same  summer,  may  return  to  the  normal  leaf  form. 

I  had  opportunity  in  the  spring  of  1903  to  observe  the  very  frequent 
occurrence  of  the  phenomenon  in  Aescuhis  Hippocastanum^.  The  structure 
shown  in  Fig.  loS  was  restricted  to  the  lowermost  leaves  of  the  shoot,  i.  e.. 


1  Noack,    Fr.,    t)ber   Frostblasen   iind    ihre   Ent.stehung.      Z.    f.    Pflanzenkrankh. 
1905.  p.  29. 

2  Solereder,  H.,    tJber  Frostblasen  und  Fiostflecken  an  Bliittern.     Centralbl.  f. 
Bakteriol.     2d  Section,  v.  XII,  1904,  No.  6-8. 

3  Sorauer,  P.,  Kammartige  Kastanienbliittei-,  Z.  f.  Pflanzenkrankh.     1903,  p.  214. 


535 

those  appearing  first  from  the  bud.  On  the  same  leaflet  could  be  found  all 
transitions  from  deep  incisions  extending  as  far  as  the  mid-rib  (Fig.  io8f ) 
to  the  normal  undivided  leaf  surface  (Fig.  io8/).  It  was  observed  on  those 
transitional  places  that  exactly  in  the  middle  line  of  each  intercostal  field 
and  spread  between  two  parallel,  lateral  veins,  occurred  a  lighter,  colored, 
transparent  stripe  along  which  the  tissue  was  broken  in  places.  (Fig.  108/7.) 
The  edge  of  such  a  ruptured  place,  like  the  edge  of  the  individual  feathery 


Fi.a:. 


108.     Horse  chestnut  leaf,  injured  in  the  bud  liy  frost,  and  torn,  like  the  teetii 
of   a    comb,   during   unfolding. 


tips  of  the  slits,  often  shows  a  somewhat  yellowish,  harder  line,  sometimes 
appearing  a  little  callused.  This  callused  edge  consisted  of  plate  cork  cells, 
to  which,  on  the  outside,  were  not  infrequently  attached  rags  of  dead  meso- 
phyll  cells.  It  is  evident  from  this  that  the  comb-like  incisions  had  not  been 
formed  in  the  bud,  but  were  produced  later. 

In  the  above  mentioned,  transparent  lines,  of  which  the  first  are  broken 
only  in  places,  the  mesophyll  is  found  to  be  dead  on  the  uninjured  part. 
The  cell  content  was  still  abundantly  present  but  brown  and  collected   in 


halls.  The  vascular  hundk-s  showed  the  well-known  frost  hrowninj;-.  The 
fact  that  exactly  the  midline  of  the  intercostal  helds  is  always  the  part 
injured  by  frost  is  explained  hy  the  peculiar  folding  of  the  leaf  surfaces 
in  the  bud  primordia. 

1  found  the  same  phenoniena  also  in  .leer  PsciiJoplatinius  and  some 
other  thick-leaved  varieties  of  maple;  in  these,  however,  only  in  the  form 
of  irregular  i)erforations.  l.aubert'  observed  a  feathery  slitting  of  the 
leaves  of  the  birch  and  the  white  beech.  Thomas-  explains  the  slit  condi- 
tion of  the  leaves  chiefly  as  a  result  of  the  action  of  the  wind.  It  has  been 
known,  e\er  since  A.  Braun  and  Caspary,  that  chestnut  leaves  can  be  per- 
forated and  in  places  slit  by  the  mutual  rubbing  of  the  leaf  surfaces,  but 
the  ])henonienon  here  described  has  nothing  to  do  with  the  action  of  the 
wind.  1  lia\e  found  the  beginnings  of  the  sjjlit  leaf  condition  in  little  trees 
which  had  been  brought  into  the  house  soon  after  the  action  of  the  frost'''. 

Thf.  Hi:.\viNr,  of  Seeds. 

Aside  from  the  injuries  which  hardy  herbaceous  plants  can  suffer  from 
lying  too  long  under  a  snow  cover,  because  they  are  often  suiYocated,  we 
have  to  take  into  consideration  another  phenomenon  which  becomes  espe- 
cially disadvantageous  for  grains,  i.  e..  the  heaving  of  young  plants. 

It  is  onlv  the  soils  which  contain  a  great  deal  of  water  which  exhibit 
the  heaving  of  seed  by  frost.  After  unsettled  winter  weather,  when  sharp 
frosts  suddenly  follow  wet  days  in  the  early  spring,  a  number  of  young 
plants  with  exposed  roots  are  not  infrecfuently  found  on  the  upper  surface 
of  the  field.  A  part  of  the  roots,  to  be  sure,  still  touch  the  earth  with  their 
tips,  and  eke  out  for  the  seedlings  a  pitiful  existence,  while  other  rootlets, 
jjerfectly  free,  with  torn  tips,  are  exposed  to  drying  wind  and  sun.  The 
explanation  of  this  occurrence  is  \ery  pertinent  here.  The  heavy  soil 
retains  large  tjuantities  of  water;  this  freezes  into  long,  needle-like  crystals 
and  thereby  raises  the  ui)per  layers  of  the  soil,  together  with  the  young  seed, 
if  a  part  of  the  hue  roots  ha\e  alread\-  reached  a  considerable  depth  they 
are  torn  loose.  In  the  subsequent  thawing  the  soil  can  settle  back  in  place, 
but  not  so  the  young  plants.  A  repetition  of  the  process  finally  brings  the 
above  result  and  may  cause  consideral)le  loss  if  help  is  not  brought  quickly. 
The  help  consists  mainly  in  the  use  of  a  heavy  roller  at  a  time  when  the 
soil  has  already  dried  to  some  extent.  P)y  pressing  the  sprouted  seed,  the 
lower  nodes  of  the  stem  obtain  protection  and  dampness  enough  to  put  out 
new  adventitious  roots  and  in  this  way  gradually  overcome  the  injury  to 
the  organs  which  hold  them  fast  and  nourish  them,  h'.specially  in  grain 
plants  rolling  acts  beneficially  and  in  damp  si)ring  weather  strong  blades 
will  grow  from  plants  which  ha\  e  thus  been  drawn  out  of  the  soil. 


1  Laubert,  R.  Resel\viclri.i;o  Ka.stenienlilatlPi-.  fJartenflora,  '>2.  .lahrg-.,  1903, 
Ol<toher. 

■-  Thomas,  Fr.  Die  meteorologischen  Ursachen  der  Schlitzt)liitteriskc'it  von 
Aesculus    Hippocastanum,     Mitt.  d.  Thuring.  Bot.  Vor.   I!t04,   fait  liJ,  p.  10. 

•:   ri.  Z.  f.   I'llanzinkrankh.  1905,  p.  234,  Note. 


537 

Drainage  will  naturally  act  as  a  precautionary  method.  A  loosening 
of  moor  soil  by  raking  it  over  with  sand  may  also  be  proved  favorable. 
Kuhn\  in  this  connection,  found  that  drill  cultivation  was  also  effective 
since  all  seeds  were  thus  hoed  in  again.  Between  these  seeds  are  produced 
thereby  "small  grooxes  into  which  the  moisture  chiefly  passes  and  thus, 
under  the  conditions  cited,  an  upraising  (jf  the  soil  is  observed  in  the  s])aces 
between  the  plant  rows,  while  the  jjlant  rows  themselves  remain  untouched." 
Hedwig-  recommends  early  sowing  in  order  to  obtain  as  abundant  deep 
growing  roots  as  possil)le  and  therel>y  to  secure  the  plants  more  firmly  in 
the  soil. 

Ekkert'  recommends  a  surface  sowing,  but  chiefly  the  growing  of 
strong  plants.  In  favoring  this  surface  sowing,  Ekkert  seems  to  have  been 
influenced  by  the  statements  of  Count  Pinto-Mettkau,  who  says  that  only 
seeds  which  lie  deep  are  heaved  out  of  the  soil  and,  in  this  are  torn  at  the 
base  of  the  primary  internode,  i.  e.,  at  the  i)art  of  the  stem  which  is  strongly 
elongated  onl)-  in  deep  sowing  and  wliich  raises  the  node  of  the  i)lant  toward 
the  upper  surface  of  the  soil.  This  theory  is  shared  also  by  Breymann'. 
Ekkert's  investigations  on  the  firmness  and  elasticity  of  this  lowest  part  of 
the  stem  and  of  the  roots  fa\or  the  view  that,  in  this  heaving  from  the  soil, 
the  roots  are  torn  sooner  than  the  internodes.  With  surface  sowing,  it  is 
possible  that  only  the  roots  will  be  torn  and  the  superficially  lying  grain, 
therefore,  also  carried  up  so  that  it  will  still  remain  as  a  possible  retainer  of 
reserve  substances  for  the  injured  plant.  The  injury  would  consequently 
be  less  and  more  easily  overcome  with  the  additional  help  of  a  rapidly 
eft'ective  spring  fertilizing. 

Johannes  rye  has  been  recommended  as  a  resistant  variety.  In  wheat. 
a  Russian  variety,  (■rtoha  ivlicaf.  is  f(jund  to  be  especially  resistant.  How- 
ever, neither  variety  nor  depth  of  sowing  will  determine  this  in  the  end,  but 
chiefly  the  constitution  of  the  soil  and  its  power  to  retain  water  become  of 
especial  importance. 

In  young  tree  plantations,  the  heaving  of  the  seed  occurs  also  with 
black  frost.  The  seedlings  of  pines  and  oaks,  provided  with  strong,  long 
tap  roots,  did  not  suffer,  but  those  of  the  superficially  rooting  spruce  and 
hemlock  arid,  among  many  deciduous  trees,  the  black  alder  in  boggy  soils, 
do  so. 

Internal  Injuries  in  Young  Grain. 

As  yet,  no  attention  has  been  paid  to  the  fact  that  grain  plants  suffer 
internal  injuries  from  black  frosts,  even  if  they  are  not  heaved  from  the 
soil.  These  injuries,  with  continued  wet  weather,  form  convenient  centres 
for  the  attack  of  parasitic  fungi.     Besides  the  common  black  fungi,  we  will 


I    Krankheiten  der  Kultiiipflanzen  1S59,  p.  11, 

-   cit.  in  Giippeit,  Warmeentwicklung-,  etc.,   p.  236. 

'■'■  Ekkert,  tJber  Keimung,  Bestoekung  und  Bewurzelung  der  Getreidearten,  etc. 
Inauguraldissertation,  Leipzig-,  1874;    cit.  in  Biedermann's  Centralbl.  1875,   p.  204. 

■i  tJber  das  Auswintorn  des  Weizens,  des  Rapses  und  des  Rotklees.  Bieder- 
mann's Centralbl.  1.  Agrikulturchemie  1881,  p.  829. 


538 

also  find  the  snow  mold,  the  breaker  of  the  rye  blade,  the  killer  of  the  wheat 
blade,  etc.,  all  of  which  cause  the  further  destruction  of  the  plant.  Besides 
the  browning  of  the  vascular  bundles  in  the  plant  nodes,  the  frost  injuries, 
predisposing  the  plant  to  fungous  diseases,  consist  especially  of  a  blister-like 
raising  of  the  outer  membrane  in  definite  places  of  the  grain  leaf.  Such 
blisters  are  found  even  in  very  young  leaves  in  the  bud  as  is  shown  in  the 
adjoining  Fig.  109.  We  find  that  the  outermost  edge  (B)  of  the  young  leaf 
is  so  injured  by  frost  that  the  cell  contents  have  become  brown  and  rounded, 
the  cells  have  collapsed  and,  therefore,  die  in  a  short  time   (gs).     On  the 


Fiff.  ]09.     Young-  rye  leaf,  injured  by  fro.st.  with  eruplion.s  nn   the  epidermis. 


other  hand,  the  part  of  the  leaf  spirally  rolled  up   (//)   apjicars  perfectly 
fresh  and  capable  of  further  development. 

The  leaf,  of  which  the  outer  side,  while  in  the  bud,  is  curved  outward 
like  a  bow,  possesses  a  main  vascular  bundle  (g)  above  which  are  deposited 
hard  bast  cords  (b)  on  the  outside,  and  also  weaker  bundles  (g'),  ramifying 
in  the  middle,  broader  region  of  the  leaf,  which  nourish  the  increased  meso- 
phyll.  Among  the  changes  in  tissue  produced  by  frost,  the  one  should  be 
emphasized  in  which  the  enlarged  cells  (r)  become  noticeable  after  the 
thawing.  These  are  radially  elongated  and  in  part  irregularly  pulled  out  of 
shape   (r),  with  greatly  bowed  walls.     This  condition  proves  the  presence 


539 

of  abnormal  tension  conditions.  To  these  should  be  ascribed  also  the  ver\- 
conspicuous  phenomenon  of  the  production  of  holes  (/)  regularly  arranged. 
The  holes  are  produced  by  the  blister-hke  upraising  of  the  epidermis  from 
the  real  leaf  flesh,  usually  on  the  upper  side,  between  the  rows  of  stomata 
(sp).  The  under,  or  outer  side,  of  the  leaf  shows  only  scattered  holes  of 
small  extent.  The  tangential  elongation  of  some  of  the  epidermal  cells, 
noticeable  at  times  ( cp  and  es)  offers  an  important  proof  of  the  production 
of  these  holes.  The  epidermal  arch  has  become  larger  than  it  was  before 
the  action  of  the  frost ;  this  elongation  is  the  result  of  the  stretching  of  single 
cells.  Besides  this  upraising  of  the  leaf,  a  radial  splitting  in  the  vascular 
bundle  indicated  at  /'  is  very  characteristic  of  frost  injury;  this  becomes  of 
especial  importance  in  the  axillary  body. 

To  distinguish  the  formation  of  holes,  due  to  the  action  of  frost,  from 
the  tearing  of  the  tissue,  due  to  senility,  we  give  in  Fig.  no  the  cross-section 
of  the  first  sheath-like  leaf  of  a  rye  plant,  the  inner  tissue  of  which,  in  the 


Natural   cavities  in  the  sheath-lilve   rye  leaf,   formed  during-  growth. 


course  of  normal  development,  splits  at  death.     The  holes   (h),  produced 
thereby,  are  ahvays  tangential. 


Internal  Injuries  in  the  Grain  Stalk. 

More  important,  however,  than  the  leaf  injuries  is  the  eft'ect  of  frost  in 
the  stalk  itself.  A\'e  usually  have  no  suspicion  of  this,  since,  to  the  naked 
eye,  no  change  is  noticeable  in  the  plant.  Fig.  1 1 1  illustrates  a  lower  node 
of  rye  injured  by  frost. 

The  tissue  of  the  stalk  (//)  is  firmly  enclosed  by  the  sheath  (Sch),  the 
outer  epidermis  of  which  is  indicated  by  e,  the  inner  by  e'  while  e"  indicates 
the  upper  epidermal  cells  of  the  stalk.  The  browning  of  the  ducts  in  the 
different  bundles,  which  occurs  in  all  frost  injuries,  is  indicated  at  u  and  ?/' 
wdiere  the  narrower  spiral  ducts  between  the  wide  annular  ducts  seem  the 
most  injured.  At  br  are  found  aggregations  of  brown  parenchyma  cells 
in  the  sheath;  at  br'  the  same  in  the  stalk  itself.  At  v  and  v'  are  shown 
brown  groups  of  cells  in  the  sheath  and  in  the  stalk,  the  walls  of  which  are 
very  strongly  szvoUcn  up  so  that  the  whole  cell  seems  converted  into  a  uni- 


540 


rd 


^  rd 


Fig-.   111.      (Upper  figure)      Leaf  node  fi-om  a   rye  plant,   injured   l)y  Irost. 

Fig.  112  and   113.      (Lower  figures)     Swelling  of  the  membranes  on  the  leaf  .sheaths 

of  a  rye  bla(3e  injured  by  frost. 


541 

form  yellow,  gum-like  mass.  At  other  places  (r)  the  parenchyma  in  the 
inner  part  of  the  sheath  is  torn  or  is  filled  -with  peripheral  holes,  due  to  the 
raising  of  the  epidermis.  Elongated  cells  occur  near  such  holes  or  often 
instead  of  them,  and  point  to  the  fact  that,  in  freezing,  the  stalk  is  most 
often  contracted  tangentially,  thus  pulling  the  epidermis  out  of  shape. 
Because  the  epidermis  is  not  so.  elastic  as  the  rest  of  the  bark  tissue,  it 
remains  permanently  elongated  as  the  result  of  this  tension.  When  the 
frost  ceases,  it  is  raised  in  places  (/  and  /'),  or  perforated,  and  its  pressure 
on  the  underlying  parenchyma  decreases,  causing  the  parenchyma  cells  to 
elongate  into  pouches  ird).  The  elongated  cells,  usually  under  the  outer 
epidermis  (c),  but  more  rarely  on  the  inner  side  (c').  often  possess  strongly 
curved,  or  stretched  walls. 

These  conditions  are  magnified  and  illustrated  in  Figs.  112  and  11.3. 
Here  the  processes  of  wall  swelling  appear  to  be  so  great  that  one  is  able  to 
distinguish  only  indistinctly  the  limits  of  the  individual  cells;  some  cell 
lumina  disappear  almost  entirely  (7').  The  loosening  of  the  epidermal 
pressure,  connected  in  the  above  case  with  the  phenomena  of  swelling,  has 
caused  the  over-elongation  of  the  underlying  tissue  and  the  formation  of 
considerable  groups  of  bent,  abnormally  enlarged  cells  in  some  places  {rd) 
and  isolated  ones  {z)  in  others. 

Finally,  the  phenomenon  of  splitting  within  and  around  the  vascular 
bundles  is  most  worthy  of  consideration.  In  the  vascular  bundles  the  si)lit- 
ting  takes  place  usually  in  a  radial  direction  (Fig.  iii^)  ;  in  fact  in  such  a 
way  that  the  more  tender  tissue  between  the  two  wide  ducts  is  torn.  The 
part  surrounding  the  vascular  bundles  can  be  so  greatly  torn  (r)  that  the 
bundle  projects  into  the  cavity.  This  phenomenon  gives  the  impression 
that  the  parenchyma  had  contracted  so  strongly,  as  a  result  of  the  frost 
action,  that  it  is  torn  off  from  the  resisting,  firm  bundles.  In  case  such 
differences  of  tension  make  themsehes  felt  less  extremely,  the  parenchyma 
near  the  bundles  is  only  greatly  strained,  causing  a  subsequent  production 
of  enlarged  cells  with  curved  walls  (^'). 

Injuries  to  the  vascular  bundles,  for  which  the  vascular  elements  must 
certainly  compensate  by  their  conductive  activity,  are  of  great  importance 
to  the  life  of  the  plant.  This  explains  the  developmental  retarding  of  plants 
injured  by  frost.  Such  plants,  even  without  the  cooperation  of  the  para- 
sitic organisms,  which  especially  seek  out  weak  seed,  furnish  less  straw  and 
especially  badly  nourished  grain.  As  a  rule,  however,  there  is  an  addi- 
tional parasitic  injury  due  to  rust,  black  fungi  and  other  leaf  and  beard 
inhabitants.  The  development  of  the  stalk  is  irregular  since  all  plants  in 
the  field  never  suffer  ecjually  strongly ;  besides  the  individual  differences  in 
power  of  resistance,  the  inequality  of  the  soil  sometimes  favors  the  frosts 
and  sometimes  gives  protection  from  them.  The  more  injured  specimens 
stand  under  the  shade  and  pressure  of  vigorously  growing  ones.  A  defi- 
ciency of  light  and  air  and  the  increase  of  moisture  among  the  oppressed 
plants  favor  the  infection  and  extensive  distribution  of  the  fungi. 


54:? 
T.oih;ini;  of  thk  Stalk. 

The  frost  injuries  ahoxe  described  in  stalks  show  different  secondary 
phenomena,  according  to  the  phice  where  the  frost  acted  most  intensively. 
The  most  common  case  is  where,  with  late  frost,  the  base  of  the  stalk  is 
attacked.  Usually  these  injuries  occur  in  deiinite  centres  in  the  fields  be- 
cause the  cold  air  accumulates  in  low-lyinj:;  hollows.  Here  also  most  of  the 
moisture  from  atmospheric  precipitations  collects  so  that  parasitic  infection 
is  added  to  the  frost  disturltances.  The  base  of  the  stalk  begins  to  molder 
and  the  stalk  itself  falls  o\er.  Many  of  the  cases  of  lodging  of  the  stalks, 
ascribed  to  Leptospliaeria  and  ( )plii()b()Ius,  are  found  to  be  combination 
l)henomena  of  which  frost  is  the  primary  cause. 

There  are,  however,  other  cases,  in  which  the  stalks  do  not  bri'ak  at  the 
l)ase  but  at  different  heights.  The  i)henomcnon  does  not  always  occur  in 
definite  centres  in  the  field  but  may  also  be  found  in  bands  and  manifesting 
itself  in  such  a  way  that  healthy  and  diseased  stalks  stand  side  by  side. 
.Such  cases  not  infrequently  cause  disputes  since  they  bear  a  great  resem- 
blance to  injuries  due  io  hail.  Rei)aration  is  refused  by  the  Hail  Insurance 
Companies  since  it  is  not  possible  to  prove  where  the  hailstones  have  hit. 

In  the  basal  lodging  of  the  stalk,  its  ground  tissue  is  found  to  l)e  brown 
and  the  shoot  almost  entirely  dead.  It  is  often,  indeed,  soft  and  always 
infested  by  fungi  ;  also  bacteria,  mites  and  anguilla  in  continued  dampness. 
When  the  break  occurs  higher  in  the  stalk,  the  ground  tissue  seems  firm 
and  green  and  the  shoots  die  only  in  places,  often  without  infection  by  fungi. 
Most  frecjuently  the  broken  place  in  the  stalk  is  found  at  the  second  or  third 
internode  above  the  surface  of  the  soil  and  is  characterized  sometimes  as  a 
one-sided,  sometimes  as  a  circular  brown  zone,  the  coloration  of  which  in- 
creases in  intensity  towards  the  next  higher  node.  Accordingly  the  i)art  of 
a  stalk,  lying  close  below  a  node  seems  to  be  the  most  susceptible  place. 
Nevertheless,  the  node  adjoining  the  upper  side  of  the  deep  brown  tissue 
can  fre(|uently  lead  to  a  secondary  upbending  of  the  fallen  stalk  so  that  it 
finally  stands  upright  again  beyond  the  bent  place.  T^ut  the  heads  of  such 
plants  are  weak  and  imperfect;  the  roots  ap[)ear  healthy,  the  brown  part 
almost  alwa}s  without  any  fungous  growth. 

Tni".  Condition  ok  .Sti:kii.k   IIi:ai)s. 

A  disease  which  apparently  has  the  least  connection  with  frost  injuries 
is  the  condition  of  sterile  heads,  as  met  with  in  Fig.  114,  A  and  B.  As  yet 
I  have  found  the  phenomenon  only  in  rye  and  will  describe  only  a  special 
case  which  I  had  opportunity  to  observe  in  June.  1900'.  Here  the  stalks 
were  mostly  of  a  normal  size  and  vigorous  growth,  but  the  uppermost  mem- 
ber, or  the  one  next  below  it,  had  pale  yellow  spots.  Later  these  became 
straw-colored   to  a  brownish-yellow,   often   with    darker   edges,   which   en- 


1    Soiauer,  I».     tJbei-  Frostbe.schadungen  nm  Gctreidc   uiul  lUimit  in  Veibinduiiy 
stehende  Filzkrankheiten.    Landw.    Jahrbiicher  1903,  p.  1. 


543 


larged  to  a  band  girdling 
the  stalk.  In  other  cases 
the  stalk  was  perfectly 
healthy  up  to  its  upper- 
most internodes. 

The  uppermost  leaf 
sheaths  and  leaves,  how- 
ever, had  ."^traw-colored 
siK'cks  (Fig.  114  H  /) 
or  jjjts.  The  upper  part, 
together  with  the  base 
rif  the  si)indlc  of  the 
head,  was  a  reddish 
straw  color.  The  spinrll'- 
itself  was  brownish,  dot- 
ted with  salmon  spots, 
entirely  bare  at  the  base 
(k)  but.  further  up, 
co\'ered  with  paper}' 
glumes,  at  first  thread- 
like but  later  becoming 
somewhat  broader  (sp). 
The  tip  of  the  head 
could  develop  fully,  as 
shown  in  Fig.  114,  /y, 
and  the  nearer  this  green 
tip  the  thread-like,  white 
glumes  stand,  the  coarser 
and  larger  they  become 
and  the  more  their  con- 
stitution approaches  the 
normal  condition.  At 
times  groups  are  found 
with  green  fleshy  glumes 
on  the  part  of  the 
spindle  which  remains 
bare  CFig.  j  14,  B  a). 

Fig.  \\4  A  repro- 
duces a  case  in  which 
the  lower  glumes  are 
normal  and  green.  The 
upper  ones  are  normal 
m  size  and  form  but 
have  a  reddish,  straw- 
colored  appearance;  the 


Viii.   114.     DifRiont  fuirnK  ol  .sterility. 


544 

spilidlc  is  naked  ln'twcfii  the  tip  and  the  ha^e.  In  more  extreme  cases 
of  injury,  in  place  ot'  the  head.  onl\-  a  i'are,  hrowii  niemhraned  spindle 
with  salmon-colored  spots  remains.  The  salmon-colored  points  are  the 
places  of  attachment  of  the  i^rains  and  colored  hy  luxuriantly  de\elopcd 
tufts  of   fungi. 

In  almost  all  cases  of  sterile-head  condition,  the  axis  is  bent  in  the 
form  of  a  crook  (F'ig.  1 14  I'>  i' )  hy  the  drying  of  the  bare  part  of  the  spindle. 
In  the  examples  pictured,  it  is  clearly  seen  that  the  sterile  head  condition 
owes  its  production  to  locally  effective  causes.  When  these  phenomena 
were  studied  on  a  field  where  especially  many  i)lHnts  had  suffered  from 
sterile-head  condition,  it  was  noticed  that  the  zone  of  injury  could  be  found 
at  approximately  equal  distances  from  the  soil.  Therefore,  the  injurious 
cause  must  be  found  in  a  layer  of  air  which  is  present  exclusively  at  a 
certain  distance  abo\  e  the  sf)il.     The  rye  plants,  aff'ected  in  different  stages 


Fig.   115. 


Cioss-.sectiun  IhrouKh   the  intc-inodo  ol    the   head  of  a  rye 
Irom  .sterility. 


ide  sulLeriiig 


of  indi\i(lual  dexelopmcnt.  are  injured  differentl}',  according  to  the  extent 
to  which  they  ha\  c  penetrated  into  this  injurious  air  layer. 

It  is  thus  e\  ident  that  sometimes  the  lower  part  of  the  head  w  ill  Itecome 
bare,  sometimes  the  ui)per  part.  In  the  best  developed,  tallest  plants,  in 
which  the  heads,  standing  on  the  longest  stalks,  are  already  abo\e  the 
injurious  air  layer,  the  heads  remain  perfectly  uninjured;  onl)-  the  upper- 
most section  of  the  stalk  has  a  pale  band. 

In  discussing  the  cause  of  this  sterile-head  condition,  the  sui)position 
would  seem  most  i)ertinent,  that  the  disease  is  caused  by  the  fungus,  recog- 
nizable on  the  l)and  and  especially  on  the  spindle  of  the  head  and  appearing 
in  salmon-colored  ridges  at  the  places  of  attachment  of  the  blossoms. 

This  hypothesis,  however,  is  erroneous  since  even  greater  injuries  to 
the  spindle  hax'c  been  obser\ed  when  the  presence  of  the  fungus  could  not 
be  proved.     On  this  account,  this  fungus,  which  belongs  to  the  genus  Acre- 


545 

monium,  is  to  be  considered  as  a  secondary  infection,  just  like  the  almost 
omnipresent  Cladosporium. 

If  now  the  injured  spindle  is  examined  in  those  places  which  Acre- 
monium  has  not  infested,  the  pictures  reproduced  in  Figs.  115  and  116  are 
obtained.  Fig.  115  represents  a  cross-section  through  an  internode;  Fig. 
116,  one  through  a  node  of  the  head  spindle;  c  indicates  the  epidermis;  h, 
its  hairs ;  g,  a  healthy  vascular  bundle ;  </',  a  bundle  with  shrivelled  brown 
walls;  gs,  vascular  bundle  sheath;  h,  bast  parenchyma;  kg,  wood  part  of 
the  bundle ;  u,  deep  brown  tissue  between  the  two  large  ducts,  which  is  very 
sensitive  and  is  proved  to  be  injured  first  by  various  causes;  pr,  healthy 
prosenchyma  cells;  pr' ,  the  same  with  healthy  walls  but  brown,  filled  lumina; 


.^'< 


pr 


Fig.   116.     Cross-section  through   the   node    of  the   sterile  stalk. 

pr",  prosenchyma  possessing  colorless  cell  cavities  but  deeply  browned  walls  ; 
v,  parenchyma  cells  in  the  epidermis  and  bark  tissue  with  yellow,  thickly 
swollen  walls  and  barely  distinguishable  lumina ;  .::,  elongated  cells  near  the 
gum-like,  swollen  tissue  centres;  bl,  basal  part  of  a  head  which  separates 
here  from  the  node. 

Thus,  in  the  bare  parts  of  the  head  spindle,  all  those  forms  of  injury 
are  found,  which  are  noticeable  in  the  lower  nodes  of  all  frost-injured 
grains,  only,  instead  of  clefts  in  the  tissue,  swellings  of  the  membrane  pre- 
dominate. These  are  especially  extensive  at  the  places  of  attachment -of 
the  heads  because  much  more  abundant  parenchyma  tissue,  i.  e.,  tissue  more 
susceptible  to  frost,  is  present  there.  And  such  gum-like,  szvollen  tissue 
centres  lie  deep  in  the  interstices  of  the  spindle.     By  means  of  this  ana- 


546 

tomical  condition,  the  sterile  heads,  due  to  frost,  are  (hl'ferentiated  from  the 
similar,  well-known  injuries  to  the  heads  due  to  thrips,  the  suction-points  of 
which  remain  superficial.  At  any  rate,  thrips  are  found  not  infrequently  on 
heads  injured  by  frost  since  these  animals  seek  out  weakened  organs;  but 
their  usual  small  number  and  the  change  in  the  tissue  of  the  spindle  leaves 
no  doubt  that  the  infection  is  secondary. 

The  fact  that  T  have  succeeded  in  producing,  hy  artificial  frost,  all  the 
injuries  to  leaf,  stalk  and  head  described  here  is  decisive.  All  the  different 
forms  of  shrivelling  of  the  grain  could  also  be  produced  experimentally. 

The  condition  of  sterile  heads  tlue  to  frost  occurs  only  in  dilYerent 
years  and  not  extensively  except  in  definite  localities. 

The  thought  that  only  certain  parts  of  the  stalk  are  injured  by  frost,  as 
must  be  presupposed  in  the  condition  of  sterile  heads,  at  first  seems  strange, 
but  one  at  once  becomes  more  familiar  with  it  if  the  alTected  regions  are 
examined,  luther  the  basal  part  of  the  head,  which  ai)peared  last  from  the 
sheath,  together  with  the  adjoining  upi)er  pari  of  stalk,  is  afTected,  or  the 
part  of  the  internode  lying  directl}'  under  the  node,  showing  the  frost  band. 
Hie  parts  named,  however,  are  the  most  tender  and  susceptible  of  the 
whole  stalk  and  we  find  analogous  phenomena  also  in  dicotyledonous  plants 
where  the  stems  of  the  blossoms  and  fruit  are  injured  and  blackened  only 
directly  at  the  base  of  the  blossom,  while  the  older  part  remains  healthy. 

It  could  not  be  determined  by  observation  what  atmospheric  conditions 
must  exist  in  order  to  produce  interrupted  heads  or  bands  on  the  stalks, 
because  attention  was  not  called  to  the  phenomenon  until  some  time  after 
the  action  of  the  frost.  Some  of  the  meteorologists  consulted  incline  to  the 
ojjinion  that  dew  plays  a  ])art  in  this. 

Frosty  nights  in  May  arc  usually  windless  and  the  injury  to  the  i)lants 
results  from  the  cooling  down  of  the  organs  by  their  radiation  of  heat.  The 
ujiper  surface  of  the  soil  itself  cannot  be  cooled  down  very  greatly  in  a 
close  standing  r}e  field  since  it  retains  its  dail}-  warmth  for  some  lime 
through  the  mantle  formed  by  the  air,  found  between  the  stalks,  which  can 
be  moved  with  difficulty.  The  greatest  amount  of  cooling  through  radiation 
can  take  place  only  in  the  upper  part  of  the  stalks.  These,  however,  are 
covered  by  the  evening  dew.  The  morning  wind  rises  suddenly  with  the 
sunrise  and  starts  a  rapid  evaporation  of  the  dew.  The  cold,  due  to  this 
evaporation,  can  fall  even  below  the  freezing  point.  The  places  \\ith  a 
lesser  amount  of  dew,  the  i)arts  which  are  protected  by  other  stalks  lying 
in  front  of  them,  thus  remain  protected  from  this  cooling  down  to  the  freez- 
ing point.  The  (listril)ution  of  the  dew  on  the  same  part  of  the  plant. 
howe\er,  will  differ  since  the  ])laces  which,  through  bending,  are  inclined 
more  horizontally  than  others,  will  retain  e\en  larger  amounts  of  dew. 
Among  the  organs  exposed  to  the  freezing  temperature,  however,  only 
especially  tender  ones  will  suflfer.  This  explains  the  fact  that  on  a  head 
isolated  places  alone  can  be  injured.  In  addition  to  the  fact  that  the  base 
of  the  head  is  proved  to  be  the  most  injured,  the  circumstance  that  the 


547 

frost  does  not  injure  the  organs  richest  in  cytoplasm  first  but,  under  similar 
conditions,  those  poorest  in  it  is  a  further  explanation. 

The  grains  at  the  base  of  the  head  are,  ho\ve\'er,  the  most  poorly  nour- 
ished and  poorest  in  cytoplasm,  as  may  be  recognized  in  any  healthy  head 
of  grain. 

As  a  result  of  a  conversation  with  the  director  of  the  German  Naval 
Observatory,  Admiral  Herz,  the  latter  sent  me  later,  most  kindly,  the  fol- 
lowing explanation :  "In  a  stand  of  plants,  whether  high  or  low,  the  soil 
is,  on  the  one  hand,  protected  against  the  nocturnal  radiation,  while,  on 
the  other  hand,  this  radiation  takes  place  strongly  from  the  surface  of  the 
plantation  and,  because  of  poor  warmth  conductivity,  is  very  effective. 
However,  the  air.  cooled  near  the  leaves,  sifts  down  through  the  plantation 
just  as  on  decli\ities  it  sinks  into  depressions  in  the  soil.  It  is,  therefore, 
very  conceivable  that  the  lowest  air  temperatures  begin  somewhat  below 
the  upper  surface  of  such  a  plantation,  especially  if  its  denseness  increases 
towards  the  ground,  or  if  the  tips  are  protected  from  too  extensive  cooling 
by  a  light  wind." 

The  way  in  which  the  processes  actually  take  place  out  of  doors  which 
bring  about  the  injurious  cooling  of  different  horizontal  air  layers  at  con- 
siderable distances  from  the  upper  surface  of  the  soil  is  left  for  further 
observation.  The  experiment,  in  which  a  w^ooden  cylinder,  with  a  mantel 
containing  a  cold  mixture  was  set  over  the  upper  part  of  the  blossoming 
rye  stalk,  pro\cs  that  the  condition  of  sterile  heads  is  produced  by  such 
action  of  the  frost.  Because  of  the  impossibility  of  rapidly  mixing  the 
individual  horizontal  air  layers  in  the  freezing  cylinder  it  was  proved  that 
only  a  definite  zone  was  so  cooled  down  that  it  brought  about  the  described 
injury  to  the  heads. 

We  conclude,  for  example,  from  Nordlinger's  observation'^  that  the 
injuries  take  place  in  forest  trees  and  indicate  the  existence  of  a  layer  of 
air.  which  causes  death  from  frost  above  the  warm  surface  of  the  soil. 
Nordlinger  found  "in  June.  1862.  in  the  Hohenheimer  Oberen  forest  young 
shoots  of  willow,  oak  and  aspen  frozen  at  the  base  of  the  petioles,  and  in 
August,  1883,  several  kinds  of  willow,  especially  Salix  fraijilis,  when  there 
had  been  no  night  frost. 

Phenomena  of  Movement  Due  to  Frost. 

In  many  plants  surviving  frost  peculiar  phenomena  of  movement  result 
from  freezing,  which  disappear  again  with  thawing.  Goppert-  mentions 
Linneus'  observation  that  the  leaves  of  the  milkweed  {Euphorbia  Lathyris) 
bend  their  tips  backward  until  the  leaf  lies  against  the  petiole.  The  leaves 
of  the  wall-flower  (Cheranthus  Cheiri)  look  wilted  in  the  frozen  condition 
and  often  bent,  but  after  thawing  they  regain  their  former  consistency  and 
position. 


Nordling-er,  H.,  Lehrbuch  des  Foistschutzes.     Berlin,  P.  Parey  1884,  p.  347. 
Warmeentwicklung  in  den  Pflanzen,  p.  12. 


548 

Wittrock^  percc*i\e(l  in  tlie  phenomt-na  of  mo\c'mcnt  a  protection 
against  the  cold  of  winter.  For  example,  the  evergreen  root-leaves  of 
numerous  plants  hend  backward  and  downward  so  that  at  last  the  outermost 
part  of  the  under  leaf  surface  seems  i)ressed  against  the  soil ;  in  summer 
they  have  a  slanting  position.  This  is  especially  clearly  noticeable  in  Hypo- 
choeris  maciilaia  L..  Gcum  urbanum  L.,  Ccrcfolium  satii'ion  L.,  and  others. 
Also  a  few  early  spring  plants  like  Ranunculus  Ficaria  L.  l)eha\e  similarly. 
Hartig  recognized  in  these  phenomena  rather  a  zciltiiuj  of  the  f^arts  of  the 
plant,  resulting  from  the  limpness  of  the  cells,  from  which  the  water  has 
been  frozen  out  into  tlic  intercellular  spaces.  Since  the  freezing  of  tlie 
water  in  the  \arious  {jarts  of  the  organ  will  dilTer  according  to  the  age  and 
maturity  of  the  tissue,  the  difference  in  the  movement,  due  to  frost,  might 
be  explained  in  this  way. 

."^^uch  phenomena  of  movement,  ho\\e\er,  seem  in  no  way  connected 
with  the  formation  of  ice  and  are  onl}-  extreme  cases  of  thermonastic  reac- 
tion which,  as  Pfeffer-  states,  are  exi)ressed  in  the  nocturnal  droo|)ing  of 
the  blossoms,  leaves  and  shoots.  X'ochting'  obser\ed  in  M'nuuhis  'filinfiii 
Rgl.  that  shoots  of  a  certain  age  grow  upward  in  tlie  spring  with  a  high 
temperature  or  maintain  a  horizontal  direction  with  a  low  one,  while  in 
case  they  ha\  e  developed  an  upright  position,  they  reassume  the  horizontal 
one.  Light  and  humidity  have  no  influence.  He  believes  that  with  con- 
tinued low  temperatures  the  jilant  might  develop  only  creeping  shoots  on 
which  blossoms  are  never  [)roduced.  This  sensitiveness  ceases  in  the  blos- 
soms which  arc  termed  psycho-clinic.  Lidforss'  concludes  from  nunK•rou^ 
observations  on  Holosteum,  Lamium,  \''eronica,  etc.,  with  which  klinostatic 
experiments  were  also  made,  that  in  such  moxements  not  only  changes  in 
turgor  are  concerned  but  actually  the  effects  of  stimulation.  With  a  higher 
temperature  the  petioles  are  negatively  geotropic,  but  in  temperatures  below 
6  degrees,  they  are  dia-geotropic  and  epinastic.  Here,  howe\er.  the  light 
acts  as  a  modifier  since,  with  its  exclusion,  the  petioles,  in  spite  of  the  lower 
temperature,  are  no  longer  dia-geotro])ic  but  negatixely  geotropic. 

The  moxements  of  the  peduncles  of  .Incmonc  ncniorosa  are,  on  tlie 
other  hand,  of  a  purely  thermonastic  nature.  The}-  curl  downward  with  a 
lower  temperature  but  stand  upright  with  a  higher  one. 

In  petioles  and  leaf  surfaces,  the  resumption  of  a  horizontal  position  is 
often  noticed,  or  a  bending  backward  below  the  horizontal  plane  on  taller, 
upright  axes.  In  this,  however,  we  wish  to  emphasize  the  fact  that  the 
movements  take  place  usually  in  the  points  and  are  not  alwa}s  of  the  same 
nature  in  the  same  plant.  It  can  hai)i)en  that,  in  compound  leaves,  some  of 
the  leaflets  turn  upward  while  the  majority  bend  downward;  that,  therefore. 


1  Bot.    Ges.    zu    Stockholm.    Sitz.    v.    24.    Oktob.    1883;    cit.    Bot.    Centralis.    18; 
No.  BO.  p.  350. 

2  Pfeffer.    PfianzcnphysioloRie,  2d  edition,  v.  II  (1904),  p.  495. 
•T    Bot.  .Tahresb.  1898,  I,  p.  582. 

4   I^idforss,  Bengt.  tJber  den  Geotropi.smu.s  einig-er  Fruhjahrsi)ttanzen.     .Jahrlj. 
wiss.  Bot.,  V.  38,  1902,  p.  343.     (Z.  f.  Pflanzenkrankh.,  1903,  p.  277.) 


549 

sometimes  the  morphologic  upper  side,  sometimes  the  under  side  of  the  joint 
cushion  is  shortened.  Among  the  changes  appearing  especially  clearly  with 
ice  formation,  the  curling  of  the  leaf  surfaces  should  be  emphasized.  An 
example  very  easily  observed  is  furnished  by  our  Rhododendron.  Harsh- 
berger^  describes  a  case  of  Rhododendron  maximum  in  which  the  petioles 
sank  to  70  degrees  while  the  edges  of  the  leaf  curled  backward  so  much 
that  the  upper  surface  appeared  convex.  If  the  plants  were  brought  into  a 
warm  room,  their  leaves  resumed  their  normal  position  after  5  minutes. 
Hartig  ascribes  this  process  to  a  peculiar  irritability  of  the  cytoplasm  while 
I  assume  diiferences  of  tension  between  the  differently  constructed  layers 
of  tissue. 

In  many  woody  plants  a  movement  of  the  branches  and  twigs  propor- 
tionate to  the  degree  of  cold  is  found.  According  to  Caspary-  Acer 
negundo  and  Pterocarya  caucasica  direct  their  branches  upward,  while 
Larix,  Pinus  S'trobus  and  Tilia  parvifolia  lower  their  branches.  Aesculus 
Hippocastanum  and  Aesculus  Hippocastanum  rubra,  as  well  as  Car  pinus 
Behdus  lower  their  branches  with  a  slight  degree  of  frost  and  raise  them 
again  when  the  cold  becomes  greater.  Simultaneous  with  this  raising  and 
lowering  is  a  lateral  motion,  in  some  varieties  toward  the  right,  in  others 
toward  the  left.  In  Cornus  sanguinea  Frank''  found  that  the  one  to  three 
year  old  branchlets  became  wavy  and  twisted  above  each  other.  Most  of  the 
twistings  were  found  to  be  clearly  directed  toward  one  and  the  same  point 
of  the  compass  so  that  Frank  concluded  it  was  the  effect  of  a  current  of 
cold  air  coming  from  a  certain  direction. 

As  stated  above,  we  might  seek  the  causes  for  the  movements  in  leaves 
and  petioles,  as  well  as  in  branches,  in  dift'erences  of  tension  which  takes 
place,  partly  because  of  changes  in  turgidity,  partly  from  unecjual  contrac- 
tion of  different  tissue  forms  within  the  same  organs  due  to  the  appearance 
of  cold. 

An  experiment  which  I  carried  out  with  Aesculus  Hippocastanum 
proves  that  an  increase  of  turgidity  of  the  parenchymatous  tissues  in  "leaf 
zvilting  due  to  frost"  can.  inider  certain  circumstances,  again  cause  the  stif- 
fening of  those  leaves. 

A  three  year  old  potted  specimen  was  put  into  a  warm  place  in  Febru- 
ary. It  developed  very  vigorously  until  the  middle  of  March  so  that  the 
terminal  shoot,  14  cm.  long,  had  developed  six  leaves.  The  largest  leaflet 
of  the  two  youngest  leaves  was  2.5  cm.  long  and  in  the  lower,  older  leaves 
the  length  of  the  petiole  was  from  5  to  9  cm. 

The  plant  was  put  out  of  doors  on  March  14th.  The  following  night 
the  temperature  fell  to  2.5  degrees  C.  below  zero,  and  the  next  morning  a 
sharp  bending  or  breaking  of  the  petioles  was  noticed  on  four  of  the  older 


1  Harshberger,  .John,  Thermotrophic  movements  of  the  leaves  of  Rhododen- 
dron maximum;  eit.  Bot.  Jahresb.  1899,  II,  p.  141. 

-  Report  of  the  International  Horticultural  KxhiV)ition,  etc.,  I^ondon  1S66;  cit. 
in  Niirdlinger,  Forstbotanik,  I,  p.  201. 

3  Frank,    A.  B.,  Krankheiten  d.  Pflanzen.  Breslau  \^^:^,  v.  1,  p.  187. 


550 

leaves,  approximately  in  the  centre  or  somewhat  below  it.  The  places  of 
breaking  were  flatly  compressed  and  began  at  once  to  become  flabby.  The 
tips  of  the  leaflets,  which  otherwise  did  not  appear  wilted,  were  flabby  on 
the  broken  leaves  and  began  to  turn  brown. 

Since  such  a  breaking  of  the  ])etioles  had  not  been  observed  previously, 
this  i)lant  was  again  placed  out  of  doors  on  the  niglit  of  the  2i-22d  of 
March.  The  temperature  fell  to  7  degrees  C.  below  zero  and  the  next 
morning  the  leaflets  of  all  the  leaves  hung  downward  at  a  sharp  angle.  The 
youngest  leaves  showed  this  ])henomenon  the  least  of  all.  Even  in  a  still 
frozen  condition,  no  part  of  the  young  growth  seemed  brittle,  or  of  a  glassy 
consistency,  so  that  any  conclusion  as  to  a  formation  of  ice  crusts  in  the 
tissue  was  scarcely  possible.  Tlie  leaflets  were  soft  and  flal)by,  of  a  grayish 
green  color,  and  the  petioles,  as  long  as  the  ])lant  stood  out  of  doors,  cur\ed 
downward  sharply  but  were  not  broken.  The  breaking  took  place  only 
after  some  hours  indoors  and,  indeed,  as  in  the  first  observed  injur)',  near 
the  middle  of  the  petiole.  This  place  shrivelled  at  once  and  turned  brown. 
At  the  same  time  all  the  leaflets,  with  the  exception  of  the  youngest,  began 
to  turn  black,  starting  at  their  ])lacc  of  insertion,  and  the  tii)s  curled  ui)ward 
and  became  dry. 

The  processes  of  breaking  must  be  traced  back  to  a  lever  action  con- 
nected with  decreased  turgidity,  for,  as  soon  as  some  of  the  leaves,  broken 
by  weak  frost  action,  were  removed  and  placed  in  water,  they  lost  the  ap- 
pearance of  wilting  in  spite  of  the  liroken  place,  and  a  great  stifi^ness  of  the 
tissues  set  in.  To  be  sure,  the  leaflets  retained  their  downward  inclination, 
peculiar  to  the  youthful  stage,  but  their  intercostal  fields  curved  outward 
strongly  between  the  veins  and  their  side  edges  began  to  turn  under. 

The  wilting  and  breaking  is  explained  by  the  inner  phenomenon  of 
cleavage  in  the  pith  body  of  the  petioles.  In  the  chestnut  the  petiole  has  a 
structure  similar  to  the  trunk,  inasmuch  as  it  possesses  a  closed  circle  of 
vascular  bundles  which  completely  and  uniformly  surrounds  the  broad, 
colorless  pith  disc  and  passes  over  into  it  in  a  gradation  similar  to  the  pith 
crown.  Even  after  the  weakest  frost  action  it  was  noticed  that  the  pith 
body  of  the  petioles  which  had  not  yet  broken,  contained  holes,  usually  of  a 
radial  arrangement,  and  seemed  ready  to  break,  because  of  the  limpness  of 
the  corresponding  place.  This  occurred  near  the  base  of  the  petiole.  Be- 
cause the  vascular  body,  running  through  the  centre  of  the  pith  disc  and 
consisting  of  two  or  three  bundles,  remained  intact  and  the  tears  in  the  pith 
parenchyma  ran  radially  to  all  sides,  a  peculiar  star-like  figure  of  cleavage 
was  sometimes  found.  In  the  leaves,  which  had  been  broken  only  after  a 
second,  stronger  frost  action,  the  splitting  of  the  pith  disc  at  times  was  so 
strong  that  the  central  vascular  bundle  cord  was  connected  with  the  peri- 
pheral vascular  bundles  only  by  a  slender  parenchyma  strip  and  all  the  rest 
of  the  pith  disc  had  been  dissolved.  The  holes  were  continued,  not  infre- 
quently, in  or  between  the  peripheral  vascular  bundles  and  formed  splits 
which  extended  to  the  edge.     Within  these  occurred  also  tangential  out- 


EDGAR  TULLIS 


/ 


pushings  of  two  to  four  outer  collenchyma  layers,  witli  a  tender,  inner  tissue. 
The  latter  tissue  was  seen  to  be  rich  in  chlorophyll  and  at  times,  in  fact, 
showed  still  definite  chlorophyll  grains.  Similar  disturbances  could  be 
proved  also  in  the  midribs  of  leaves  more  greatly  injured. 

Here  the  phenomena  of  browning  were  first  perceived  in  the  walls  of 
the  ducts  and  then  in  the  various  peripheral  groups  of  the  bark. 

In  wilting  out  of  doors,  due  to  frost,  naturally  such  an  increased  supply 
of  water,  as  obtained  here  in  the  experiment  by  placing  the  cut  leaves  in 
water,  cannot  take  place  and,  on  this  account,  the  wilted  organs  retained 
for  some  time,  or  permanently,  the  wilted  condition,  especially  if  a  splitting 
of  the  tissue  and  changes  in  the  ducts  reduced  the  conductivity.  This  can 
take  place  differently  not  only  in 
the  different  varieties  and  individu- 
als, but  even  in  the  different 
branches  of  the  same  specimen. 
An  example  of  this  was  furnished 
by  an  elm  which  stood  in  a  pot 
and  in  winter  was  brought  into  the 
hothouse  for  forcing.  The  little 
tree,  which  had  been  exposed  to 
a  frosty  night  at  only  i  degree  C. 
below  zero,  had  developed  t\\  o 
forked  apical  branches  which  ap- 
proximately corresponded  to  one 
another  in  length,  leaf  number  and 
size.  In  this  frosty  night,  however, 
only  scattered  leaves  of  one  shoot 
had  begun  to  wilt  but  did  not 
change  color.  The  relaxed  organs 
did  not  recover  after  several  days 
retention  in  the  warm,  room  but 
showed  no  advance  of  the  wilting. 

It  is  clear  from  this  that  zvilting  due  to  frost  is  a  very  local  phenomenon 
not  directly  connected  with  the  upward  forcing  of  water  by  the  root. 

In  the  phenomenon  of  the  movement  of  twigs  the  different  kinds  of 
movement  may  be  easily  explained  if  the  structure  of  the  individual  branches 
is  more  closely  observed  and  it  is  seen  how,  in  the  maturing  of  the  annual 
rings,  the  thin-walled  spring  wood  (Fig.  ii8)  constantly  changes  to  a  thick- 
walled  autumn  wood  with  small  lumina.  In  this  connection  the  studies  of 
R.  Hartig^  should  be  compared  showing  the  change  from  thick-walled,  red 
wood  to  the  light,  porous  strain  wood  within  the  same  cross-section  of  a 
spruce  branch.  In  the  adjoining  Fig.  117  the  red  wood  is  found  especially 
strongly  developed  in  the  first  annual  periods  on  the  upper  side  of  the 
branch.     In  later  years  these  showed   a  sudden  change,   since  rather   the 


Fig-.  117.  Cross-section  through  a  spruce 
branch.  In  the  inner  part  of  the  wood 
disc  the  solid  red  wood  is  shown  on  the 
upper  side  of  the  branch  but  in  the  outer 
annual  rings  it  is  seen  on  the  under 
side.     (After  R.  Hratig.) 


Hartig,  R.,  Holzunteisuchungen.  Bei'lin,  Springer,  1901,  p.  .50. 


552 


^^^s^ 


FipT.  118.     Red  wood  from  the  under  side  of  a  spruce  branch   (Cross-section).     The 

uppermost  cell  row  is  spring  wood;   the  lower  four  rows  are  red  wood  with 

large  intercellular  spaces    (at  the  left).     (After  R.  Hartig.) 


Fig.   119.     Cross-section  through   strain    wood   on  the   upper  surface   of 
a   spruce   branch.      (Alter  R.    llai-tig.) 


553 

under  side  of  the  branch  a])pears  dark  l)ecause  of  the  dense  formation  of 
red  wood.  We  perceive  in  the  anatomical  pictures  in  Figs.  ii8  and  119 
the  different  structure  of  the  elements  of  the  ''red  wood"  and  "strain  wood." 

We  obtain  from  R.  Hartig  reports,  well  worth  considering,  as  to  the 
production  of  such  differences.  He  states  that,  for  example,  in  trunks  with 
an  eccentric  growth,  the  formation  of  the  annual  rings  is  especially  strongly 
developed  on  the  branched  side.  The  formation  of  red  wood  is  proved  to 
be  often  dependent  upon  the  prevalent  direction  of  the  wind,  since  the  side 
away  from  the  wind  favors  red  wood  formation.  If  the  west  wind,  for 
example,  strikes  a  spruce  constantly,  the  west  side  will  be  strained.  The 
east  side,  toward  which  the  tree  is  bent,  is  more  strongly  pressed  and  incited 
to  a  stronger  formation  of  red  wood  while  the  windy  side,  stretched  by  the 
bending  of  the  trunk,  produces  strain  wood.  Every  branch  will  show  just 
such  differences,  for  the  weight  of  the  needles  will  bend  it  downward.  Its 
morphologically  upper  side,  therefore,  is  under  a  constant  strain  which 
exercises  a  stimulus  on  the  cambium.  This  consequently  forms  thinner- 
walled,,  less  woody  but  longer  tracheids  and  these  represent  the  "strain 
wood." 

Besides  the  action  of  the  wind,  the  formation  of  the  wood  on  every 
branch  is  influenced  by  its  surroundings.  Shade  from  other  trees,  or  prox- 
imity to  cliff's  or  walls,  the  one-sided  eft'ect  of  greater  moisture,  partial 
defoliation  due  to  the  grazing  of  animals,  or  other  one-sided  changes  in  the 
nutrition  of  the  branch  will  call  forth  a  lack  of  uniformity  in  the  quantity 
and  quality  of  the  annual  ring.  From  this  it  is  clear  that,  in  the  action  of 
cold,  the  contraction  of  the  tissue  must  vary  greatly  and  the  depression  of 
the  branches  must  be  very  manifold,  according  to  the  distribution  of  strain 
and  red  wood.  Therefore,  the  observations  made  by  diff'erent  investigators 
can  have  no  general  significance  but  should  only  be  registered  for  the 
present  as  individual  cases. 

We  will  discuss  thoroughly  the  differences  due  to  strain  in  the  section 
on  "Internal  Cleavage." 

Freezing  Back  of  Older  Branch  Tips. 

A  freezing  back  of  the  branch  tips  is  found  in  some  of  our  woody 
plants,  almost  as  regularly  as  defoliation.  Mulberry  trees,  acacias  and 
raspberries  furnish  the  commonest  exam])les  of  this.  We  owe  more  exact 
studies  on  this  point  to  v.  MohP,  who  refers  to  the  different  stages  in  which 
our  woody  plants  are  found  at  the  beginning  of  the  winter. 

In  many 'plants  the  grov/th  of  the  branches  continues  undisturbed  so 
long  as  the  conditions  are  at  all  favorable  for  further  development.  This 
growth  only  stands  still  during  the  period  of  cold  and,  as  soon  as  the  tem- 
perature allows,  begins  again  immediately  at  the  point  where  it  stopped  in 
the  autumn.     This  is  the  case  in  the  ivy   (Hedera  Helix)   and  the  Savin 


1    Bot.  Zeitung-  1848,  p.  6. 


554 

(Juniperus  Scibino).  In  many  trees  the  developmental  ])eriod  of  a  l)ranch 
ends  of  itself  towards  the  close  of  summer.  In  this  a  terminal  bud  is 
formed  which,  the  following  spring,  takes  over  the  direct  continuation  of 
the  branch,  as  in  fruit  trees,  oaks,  ashes,  spruces  and  hrs.  In  our  culti- 
vated plants  the  case  often  occurs  when  a  second  shoot  (Joliaiincstrieh)  is 
developed  in  the  same  year.  This  not  infref|ucntly  produces  unripe  wood 
which  freezes  easily  in  winter,  while  the  wood  of  the  spring  shoot  is  always 
completely  matured.  A  third  large  group  drops  the  tip  of  the  branch  all 
at  once  in  the  course  of  the  summer  while  unfolding,  where  the  develop- 
ment is  otherwise  perfectly  normal.  The  continuation  of  the  branch  is 
then  taken  over  in  the  following  year  by  the  uppermost,  lateral  bud  as 
shown  in  Gymnodadus  canadeyisis  and  Ailanthus  glandulosa.  I^^urther 
examples  are  ofifered  by  the  linden,  the  elm,  the  plane  and  the  hazelnut. 
V.  Mohl  proved  that  the  trees,  the  tips  of  whose  twigs  almost  regularly 
freeze,  belong  to  this  last  group.  .S^tecimens,  for  example,  in  Rome  have 
regularly  thrown  off  the  tips  of  their  branches  in  October  and  thus  have 
actually  closed  their  period  of  gro\\th.  This  hapi)ens  in  the  case  oi  the 
linden.  In  trees  of  this  group,  which  are  favorites  in  planting,  such  a 
normal  ending  of  growth  does  not  take  place  in  the  majority  of  cases.  This 
indicates  that  our  summer  is  too  short  and  too  cold  for  them  to  reach  full 
development. 

Frost,  therefore,  always  attacks  immature  growth.  Here  belong 
Rohlna  Pseudacacia,  (ileditschia,  Sophora  japon'ica,  Broussonetia  papy- 
rifera.  Morns  alba,  Salix  babylonica  and  Vitis  v'lnifera.  If  the  twigs  are 
to  be  retained,  their  premature  defoliation  would  be  advisable.  Thus,  for 
example,  according  to  the  observations  of  Lawrence'  in  the  winter  of  1708- 
1709,  of  all  fruit  trees,  only  the  mulberry  survived  because  its  leaves  had 
been  picked  for  feeding  the  silk  worms  some  time  before  the  occurrence 
of  the  cold. 

In  our  fruit  trees,  the  dying  of  the  branch  tips,  as  a  result  of  the 
occurrence  of  winter  cold,  is  usually  termed  tip  blight.  Not  infrequently, 
however,  a  resulting  ])henomenon  is  associated  with  it,  which  first  makes 
itself  felt  in  summer.  If  it  happens  in  many  branches  that  only  the  espe- 
cially delicate  basal  rings  are  injured,  these  branches,  as  a  rule,  develop 
further  and  the  blossom  buds  already  formed  develop  fully.  About  June, 
however,  a  yellowing  pf  the  foliage  appears,  a  dropping  of  the  fruit  already 
set  and  a  drying  of  the  twigs.  As  a  result  of  the  injury  to  the  branch  ring, 
the  conducting  of  the  nutritive  substances  is  disturbed  and  the  branches 
themselves  remain  alive  only  as  long  as  reserve  substances  are  present. 
After  these  are  used  up  the  branch  dies. 

In  grapevines  the  case  in  which  the  ^-ines  freeze  back  to  the  old  wood 
deserves  especial  mention.  There  then  dexelop  from  the  base  of  the  trunk 
uncommonly   luxuriant   shoots  which,   it   was    formerly  thought,   would   be 


Gijppert,  Wiirmeeiitwirkhing',  p. 


555 

sterile  in  the  next  year  and  only  bear  fruiting  wood  the  year  after.  Op- 
posed to  this  theory,  the  investigations  of  Miiller-Thurgau^  have  shown 
that  such  wood,  even  in  August  of  the  year  of  its  production,  can  form 
fruit  buds  and  that  the  treatment  of  the  vine  is  to  be  planned  accordingly. 

The  Dying  of  the  Cherry  Trees  Along  the  Rhine. 

As  a  special  example  of  the  phenomenon  previously  described,  we  will 
consider  the  disease  of  the  sweet  cherry  in  the  provinces  of  St.  Goar,  St. 
Goarshausen  and  Unterlahn  which  has  been  much  discussed  since  the  be- 
ginning of  this  century. 

According  to  the  material-  which  1  obtained  from  that  region,  and 
cases  which  I  obser\ed  elsewhere,  the  phenomenon  appears  as  follows : 
a  turning  yellow  of  the  foliage  of  some  branches,  or  of  the  whole  crown 
sets  in  rather  suddenly  and  usually  with  the  appearance  of  considerable 
gum  exudation;  the  branches,  or  even  the  whole  trunk,  die.  Often  the 
tips  of  the  branches  develop  further  while  the  rest  remains  bare.  Micro- 
scopic investigations  determine  a  high  degree  of  gummosis ;  gum  holes 
can  be  found  even  in  the  youngest  shoots.  In  the  wood  and  in  the  bark 
body,  the  phenomena  of  browning  are  often  found,  which  we  will  discuss 
later  when  describing  the  action  of  artificial  frost.  Indeed  these  are 
provable  often  in  the  apparently  healthy  shoots,  leaves  and  fruit  stems.  In 
older  trees  definite  forms  of  tissue  clefting  are  frequently  found  which 
correspond  with  those  produced  by  artificial  frosts.  Because  of  this  dis- 
covery, I  am  of  the  opinion  that  not  only  in  the  "Dying  of  the  Rhenish 
cherry  tree,"  but  also  in  similar  cases  which  appear  often  but  usually  to  a 
lesser  extent,  frost  action  at  the  time  of  the  spring  growth  is  to  be  consid- 
ered as  the  actual  cause. 

G6the-\  who  agrees  with  our  theory,  describes  as  follows  the  weather 
conditions  for  the  localities  lying  along  the  Rhine,  in  the  year  when  the 
disease  appeared :  "The  cherries  were  already  in  bloom  when  on  the  22nd 
of  March  they  were  surprised  by  a  drop  in  temperature  to  9.7  degrees  C. 
below  zero.  In  the  course  of  the  spring  abnormally  strong  fluctuations 
took  place  between  great  cold  and  great  warmth.  I  consider  such  weather 
contrasts  to  be  the  cause  of  the  very  numerous  cases  of  subsecjuent  disease 
which,  in  the  stone  fruits,  are  almost  always  connected  with  strong  gum- 
mosis and  are  accompanied  by  infection  with  wound  parasites  or  parasites 
of  weakness.  Also,  for  the  special  case  on  the  Rhine,  such  a  fungus  Valsa 
leucostoma  was  at  first  made  responsible'*.     Soon  after,  however,  Wehmer'' 


1  Muller-Thurgau,  tJber  die  Fruchtbarkeit  der  aus  den  alteren  Teilen  der  Weln- 
stocke  hervorgehenden  Triehe,  sowie  der  sog.  Nebentriebe.  Der  Weinbau  1S82. 
No.  28. 

-  Sorauer,  P.,  Das  Kirschbaum.sterben  am  Rhein.  D.  Landwirtsch.  Presse  1900, 
p.  201. 

3  Gothe,  R.,  Das  Absterben  der  Kirschenbaume  in  den  Kreisen  St.  Goar,  St. 
Goarshausen  u.  Unterlahn.  D.  Landwirtsch.  Presse  1899,  p.,  1111. 

4  Frank,  A.  B.,  in  D.  Landwirtsch.  Presse  1899,  No.  83,  p.  949. 

s  Wehmer,  Zum  Kirschl^aumsterben  am  Rhein.  D.  Landwirtsch.  Presse  1899, 
No.  96. 


55^ 

drew  attention  to  the  fact  that  this  fungus,  which  Frank  at  first  liad  de- 
scribed as  Cytospora  rnhesccns,  was  not  able  to  produce  the  disease  but 
should  be  considered  as  a  secondary  phenomenon,  just  like  the  simultaneous 
occurrence  of  bacteria.  Aderholt'  first  cited  the  experimental  proof  that 
Valsa  is  not  able  to  penetrate  at  once  into  healthy  tissue.  This  investi- 
gator found,  in  his  artificial  freezing  experiments,  that  the  co-operation  of 
late  frosts  w^as  unmistakable  in  the  growth  of  fungus. 

In  regard  to  the  abo\e  named  fungus,  Aderholt  is  of  the  opinion  that 
if  the  fungus  reciuires,  for  its  infection,  the  injury  produced  b\-  frost  or 
some  other  good  cause,  it  still  is  able  to  strengthen  itself  later  so  much  that 
it  can  spread  parasitically.  This  theory  agrees  perfectly  with  that  of 
Vuillemin-  in  regard  to  the  cherry  disease  observed  in  Lorraine  in  1887, 
which  bears  great  similarity  to  the  one  here  discussed;  Coryneum  Beijer- 
inckii  is  named  as  the  cause,  and  the  author  associates  with  it  /Iscospora 
Reijcrinckii  as  the  ascospore  stage.  It  would  thus  seem  to  be  the  theory 
of  the  above  investigator  that  climatic  causes  have  produced  the  condition 
for  the  disease  but  the  fungus  produced  the  disease  itself.  Accordingly, 
in  combatting  this  disease,  all  wood  infested  with  Valsa  or  its  conidial 
form,  the  Cytospora,  must  be  carefully  destroyed. 

However,  we  obtain  an  insight  into  the  real  relation  of  this  fungus  to 
the  disease  only  from  the  very  recent  inoculation  experiments  which 
Liistner"  has  carried  out.  Among  others,  he  took  two  small  cherry  trees 
of  different  varieties  and  broke  back  their  crowns.  The  end  broken  and 
the  piece  of  the  trunk  left  standing  were  inoculated  with  the  conidia  of  the 
fungus  and  also  later  painted  with  water  containing  them.  Since  the  crown 
did  not  die  back  as  a  result  of  the  breaking,  it  was  later  cut  oiY  and  tied  on 
to  the  trunk.  \\\  the  end  of  October  the  fungus,  as  shown  in  Fig.  120  at 
the  places  marked  with  an  X ,  had  spread  over  the  broken  and  dead  end  of 
the  tip,  while  the  remaining  part  of  the  trunk,  although  inoculated  in  the 
same  way,  remained  perfectly  healthy  and  continued  to  grow.  The  wound 
due  to  inoculation  had  healed  normally. 

Liistner  quotes  similar  results  from  I'eijerinck  and  I\ant\  who  could 
not  produce  a  gummy  exudation  on  peaches  and  cherries  with  Cytospora. 
and  report  nothing  as  to  the  death  of  the  inoculated  branches. 

Suj)ported  by  these  experiments  and  my  personal  observations,  I  con- 
sidered not  only  the  disease  under  discussion  but  also  the  others  produced 
by  varieties  of  Valsa,  or  their  pycnidial  forms,  as  occurring  with  the 
co-operation  of  parasites  of  weakness,  in  which  only  the  appearance  of 
disease  was  determined  bv  the   fungus.     Tlie   fungi  are  able  to  infest  the 


1  Adcrhold,  R.,  f)ber  das  Kirschbaumsterben  am  Rhein.  seine  Ursachen  un«l 
seine  Bekampfung.  Arb.  d.  Biolog.  Abt.  f.  l^and-  u.  Forstw.  um  Kais.  Gesundheit- 
samte.     Berlin  1903,  P.  Parey  u.  .1.  Springer,  v.  Ill,  Part  4. 

2  Vuillemin,  Paul,  Titres  et  travaux  scientifiques.  Paris,  Typographie,  A.  Davy 
1890,  4o. 

3  Liistner  G.,  Beobachtungen  iiber  das  rheinische  Kirschbaumsterben.  Bericht 
d.  Kgl.  Lehranstalt,  fiir  Wein-,  Obst-  und  Gartenbau  zu  Geisenheim  a.  Rh.  f.  d. 
Jahr  1905,  von  Prof.  Wortmann.  Berlin,  I'aul  l-'arey  1906,  p.  122. 

4  Centrallilatt  fiir  Bakteriologie  und  I'arasitenkunde,  I'art  II,  v.   lii,  p.   374. 


557 


Fig.  120.  Cherry  sapling  infected  in  two  places  with  the  eonidia  of  Valsa 
leucostoma.  After  infection,  the  top  was  cut  off  Ijelow  the  upper  wound.  At  O 
the  normally  healed  wound.     At  X  pycnids  of  Valsa   leucostoma.     (After  Llistner.) 


55^ 

branch  r)nl}-  when  it  has  liLconic  diseased,  or  at  least  weakened,  as  a  resuU 
of  disturbances  in  nutrition  due  to  atmospheric  or  soil  conditions.  On 
such  a  foundation  no  further  injury  is  needed  for  the  penetration  of  the 
fungi ;  this  can  take  place  also  through  the  lenticels.  The  disturbance  in 
nutrition,  which  must  of  necessity  exist  previous  to  the  infesting  by  such 
parasites  of  weakness,  is  not  always  necessarily  caused  by  frost.  Unsuitable 
habitat  and  excess  of  moisture  or  drought,  etc.,  can  just  as  well  give  tiie 
first  impetus.  Ldstner  considered  the  last  named  factor  as  the  cause  of 
weakening  in  the  cherr}-  trees  on  the  Rhine,  while  I  would  rather  hold  to 
the  theory  that,  in  the  majority  of  cases,  injuries  due  to  frost,  and  in  fact 
those  which  take  place  in  spring,  represent  the  [)rimary  cause. 

Accordingly.  I  see  only  a  very  slight  consolation  in  the  careful  destruc- 
tion of  the  parts  attacked  by  fungus.  One  should  not  forget  esjjecially 
the  ubi(|uity  of  the  Cytosporeae  and  similar  groups  f)f  fungi.  The  main 
point  is  the  cuUiiHitlon  of  varieties  ■z^'hleh  Inrve  adjnsled  fheiiiseiz'es  to  a 
definite  lueallty.  llesides  this  one  should  exi)eriment  to  see  whether  the 
sensitiveness  to  frost  can  be  decreased  by  an  addition  of  calcium  to  soils 
rich  in  humus. 

r.KAN(.H    Ib.lCIir    IN    T-'oKI'-ST   TkEKS. 

1  judge  in  the  same  way,  as  in  the  d\ing  of  the  cherry  tree,  a  disease 
which  l'\ickel  has  observed  in  apricots  and  peaches.  A  characteristic  yel- 
lowing and  wilting  of  the  ff)liagc  with  a  sul)sc(|uent  dying  of  scattered 
branches  began  in  June.  T'\ickel  considers  Cytospura  nibeseens  as  the  cause 
and  J 'also  pntiiasfrl  Vr.  as  the  perfect  stage. 

()f  the  better  known  occurrences  of  diseases  of  this  character.  I  will 
add  here  "the  black  blight  of  red  beech  shoots."  According  to  W'illkomm' 
the  cause  of  the  dying  of  the  shoots,  which  turned  black  at  the  base,  should 
be  sought  in  a  fungus  which  develoi)s  a  conidia  form  like  I'ttslsporiiiiii 
candlciiin  Lk.  and  ma}'  be  associated  with  Llbertella  fcu/lnea  Desm.  'J'he 
perfect  stage  would  accordingly  be  Qitafernarla  Perscoonli  Tul.- 

The  dying  of  the  pyramidal  poplars  which  was  found  in  varying  inten- 
sity through  northern  and  central  Germany  aroused  discussion  at  the  begin- 
ning of  the  8o's  in  the  last  century.  A  similar  occurrence  had  been 
observed  in  luigland  between  i(S2o  and  1840''.  Younger  shoots  had  brown 
places  in  the  bark  under  which  the  wood  body  also  was  usually  attacked. 
The  lea\  es  became  yellowish  and  limp  and  the  branch  died. 

Among  the  different  theories  which  were  brought  forward  to  explain 
the  phenomenon,  the  degeneration  of  the  species  through  continued  sexual 
propagation  jilayed  a  chief  role.  Although  much  reference  was  made,  from 
the  beginning,  to  the   fact  that   a  late   frost   might  be  taken  as  the  cause, 


1    Wlllkomm,   Die  mikro.skoiii.schen    Feindo   dos   \V;ildes,    ISGU,    I'urt   1,    p.    101 

-   Selccta  t'ung'.  carp.  II,  p.  105. 

■■■   Biolog.  Centralbl.  XI,  1891,  p.  129. 


559 

which  in  spring  had  injured  the  but  Uttle  matured  branches\  the  theory 
that  a  discomycetous  fungus  Dothiora  sphaeroides  Fr.  produced  the  dying- 
finally  prevailed.  In  other  places  a  different  fungus,  Didymosphacria 
populina,  was  made  responsible  for  it^.  Vuillemin*  cites  Maminia  fimbriata 
in  the  dying  of  the  twigs  of  the  hornbean  and  Didymosporium  salicinutn 
as  the  destroyer  of  zvUlotv  plantations.  Finally  we  will  call  attention  once 
more  to  the  dying  of  the  red  alders  described  by  Appeh^  as  due  to  Valsa 
oxystoma,  which  ftmgus  can  complete  its  work  of  destruction  only  in  speci- 
mens weakened  by  disturbances  in  nutrition. 

Freezing  of  the  Spring  Growth. 

If  late  frosts  surprise  the  tree  at  a  time  when  the  leaf  buds  have  began 
to  elongate,  or  have  already  developed  into  short  shoots,  repeated  injuries 
and  also  phenomena  of  regeneration  will  then  set  in.  A  case  which  I  have 
found  frequently  in  cherries  shows  the  dying  of  the  youngest  growing 
point  in  the  opening  leaf  bud.  Hie  injury  is  not  noticeable  at  first  since  all 
the  leaf  buds  have  remained  intact.  After  some  time,  however,  a  peculiar 
spreading  appears,  called  forth  by  the  turning  back  of  the  very  turgid 
bracts  and  the  absence  of  growth  excites  investigation.  Later,  sickly, 
lateral  shoots  appear  from  the  uninjured  lateral  buds  and  at  times  also  a 
fasciated  growth  after  such  spring  injuries. 

I  succeeded  not  long  ago  in  producing  the  same  kind  of  disturbance 
by  the  action  of  artificial  frost.  Fig.  121  represents  a  cherry  branch  in 
which  three  buds  have  lost  their  growing  points  from  frost.  The  vegeta- 
tive activity,  very  energetic  in  the  spring,  has  so  made  itself  felt  in  the  two 
upper  buds  that  the  bract-like,  early  leaves  have  become  larger,  a  darker 
green  and  fleshier  and  have  spread  out  from  one  another  almost  hori- 
zontally. At  the  lowest  bud  there  is  a  beginning  of  two  lateral  compen- 
satory shoots. 

In  Fig.  121  B  the  condition  of  the  bud  with  a  frozen  growing  point  is 
more  exactly  reproduced.     The  growing  point  (a)  is  blackened  and  dried 


1  The  explanation  of  this  disease  as  a  result  of  frost  has  been  substantially  sup- 
ported by  the  observations  of  Count  von  Schwerin  (Gartenflora  1905,  Part  5,  p.  400). 
He  proved,  on  an  Italian  trip,  that  south  of  the  Alps  the  pyramidal  poplars  were 
not  diseased,  i.  e.  no  degeneration  of  this  tree  could  be  observed  in  its  present  home. 
Its  death,  occurring  in  bands  throughout  Germany,  is  explained  simply  as  the  result 
of  spring  frosts  repeatedly  occurring  at  the  end  of  the  '70's  after  long,  damp  and 
mild  autumns.  Of  the  earlier  observers  Hausknecht  (Bot.  Ver.  f.  Gesamtlhiiringen; 
cit.  Bot.  Centralbl.  1SS4,  p.  275)  had  already  called  attention  to  the  fact  that  the 
dying  showed  itself  almost  entirely  in  the  river  valleys  and  depressions,  but  spared 
higher  positions.  We  find  another  valuable  note  by  Pertsch  in  St.  Petersburg 
(Deutsche  Gartnerzeitung  1884,  No.  10).  He  found  on  a  trip  through  northern, 
western  and  central  Germany  that  the  length  of  the  dead  tips  became  constantly 
shorter,  the  farther  south  he  went.  The  fact  that  Populus  pyramidalis  is  not  found 
in  St.  Petersburg,  while  P.  alba,  P.  laurifolia,  P.  suaveolens,  P.  Balsamea,  etc.,  thrive 
there  shows  that  it  is  more  susceptible  to  frost  than  most  of  the  poplars. 

-'  Rostrup,  Pyramidepoplens  Undergang.  Tillaeg  til  Nationaltidende  13.  Novem- 
ber 1883. 

■"  Vuillemin,  P.,  Remarques  etiologiques  sur  la  maladie  du  Peuplier  P5'ramidal. 
Revue  mycol.  1892,  p.  22. 

4    Vuillemin,  P..  Titres  et  travaux  scientifiques.  Paris  1890. 

"■'  Appel,  O.,  tJber  bestandweises  Absterben  von  Roterlen.  Naturwiss.  Z.  f. 
Land-  u.  Forstw.  1904. 


^6o 


and  is  cut  off  by  a  cork  layer  w  itliin  the  boundaries  of  the  living  tissue.  In 
the  part  of  the  axial  cylinder  which  has  remained  alive,  however,  frost 
action  is  shown  in  the  form  of  horizontal  splits  in  the  pith  (Fig.  121  B,  I) 
and  a  browning  which  must  necessarily  retard  its  functions  as  a  body 
capable  of  swelling.  These  are  the  reasons  why  the  axis  does  not  elongate 
again  so  (|uickly.     The  spiral  ducts  {(J)  which  pass  out  into  the  leaves  (bl) 


A.  Uiaiu'h  ol  a  sweet  cherry.  The  buds,  injured  by  artificial  frost, 
ed  and  fleshy  scales,  enlarged  and  bent  away  from  one  another. 
Liongitudinal  section  through  an  injured  bud  of  the  branch. 


also  appear  greatly  browned,  but  tlie  parenchyma  {p)  of  the  bark  body  is 
but  little  injured  and  of  unusual  tenseness.  Traces  of  starch  were  found 
here  and  there  at  the  time  of  the  investigation  (June  21).  It  is  clear  that 
the  almost  fleshy  bark  body  contains  an  excess  of  water  and  nutritive  sub- 
stances and,  accordingly,  must  take  over  an  increased  productivity.  The 
greatly  increased  upward  forcing  of  the  water  is  also  to  be  taken  as  a 
cause  of  the  position  of  the  bud  bract  and  the  bract-like  leaves  {bs),  both 


56i 

of  which  have  become  longer  lived  through  the  chlorophyll  content  of  the 
inner  tissue  layers. 

In  occurrences  of  this  kind,  frequent  in  many  years  in  certain  locali- 
ties, it  is  noticed  that,  as  a  rule,  the  tip  bud,  which  has  already  advanced 
farthest  in  development,  can  grow  on  undisturbed.  Then  the  branches 
have  a  whip-like  appearance,  inasmuch  as  their  tips  are  richly  leaved  while 
the  lower  internodes  remain  bare.  Another  phenomenon  with  which  I 
became  acquainted  in  older  pear  shoots  consisted  in  a  blackening  and  dying 
of  the  basal  parts  of  the  young  shoots  which  otherwise  still  appeared  green 
and  did  not  dry  up  until  later. 

Potonie  has  given  special  study  to  the  phenomena  of  the  restitution  of 
spring  shoots  lost  through  frost \  Different  varieties  of  trees  behave  dif- 
ferently. In  many  varieties  lateral  shoots  grow  from  the  still  uninjured 
basal  buds  of  the  frozen  branch  as,  for  example,  in  Castanea  sativa  Mill, 
and  also  in  varieties  of  Celtis  and  Platanus.  If  the  young  shoot  is  entirely 
destroyed,  a  new  foliage  growth  takes  place  in  many  plants  by  the  forma- 
tion of  "accessory  sprouts."  Many  tree  varieties,  especially  with  increas- 
ing twig  nutrition,  form  not  one  alone  but  a  succession  of  buds  in  the  axil 
of  a  leaf  by  the  sprouting  of  the  inner  bud  stem  called  "loxver  buds." 
These  "lower"  or  "accessory  buds"  under  normal  conditions  can  develop 
only  on  strong  shoots  of  some  trees  (Cercis).  In  disturbances,  however, 
as  for  example,  severe  pruning,  grazing  and  frost,  which  destroy  the  shoot 
produced  from  the  main  bud,  they  also  form  the  compensatory  material 
in  other  trees,  as  for  example,  in  Calycanthus  fioridus,  Cercis  Siliquastrum, 
Gymnocladus,  Liriodendron  tulipifera  and  Robinia  Pscudacacia,  and  de- 
velop as  many  as  four  "lower"  buds  hidden  in  the  base  of  the  petiole.  On 
the  other  hand,  compensation  can  also  be  secured  from  their  so-called 
"fringing  buds"  formed  the  year  before.  These  are  the  buds  in  the  axils 
of  the  basal  bud  bracts  which  at  times  succeed  in  developing  regularly  as  is 
perceived  clearly  in  many  varieties  of  willow.  If  the  covering  formed  by 
the  union  of  the  two  bracts  drops  off,  an  axial  bud  is  found,  corresponding 
to  each  half  bract  and  this  can  form  a  compensatory  branch  when  the 
main  branch  is  injured. 

In  other  cases  the  tree  must  depend  on  the  dormant  buds  of  the  shoots 
of  the  previous  year  for  compensation,  as  may  be  observed  especially  with 
Rhus,  Carya  glabra  Mill,  and  Juglans  nipestris  Engelm,  while  Carya  amara 
Mich,  and  Pterocarya  fraxinifolia  Lam.  chiefly  unfold  "lower  buds." 
Conifers  generally  replace  the  frozen  sprouts  by  the  awakening  of  buds 
dormant  up  to  that  time,  and  also  by  a  new  formation  of  bud  primordia  in 
otherwise  budless  leaf  axils,  especially  those  of  the  bracts  at  the  base  of  the 
annual  growth. 

No  special  limitation  in  the  kind  of  compensation  in  frozen  shoots  of 
different  varieties  of  trees  can  be  made,  however,  since  the  strength  of  the 


1    Potonie,    tJber    den    Er.satz    oi-rrorener    Fruhlingstriebe    durch    accessorische 
und  andere  Sprosse.  Sitzungsber.  d.  bot.  Ver.  d.  Prov.  Brandenb.  XXII,  1880,  p.  81. 


562 

frost  injury,  on  the  one  hand,  and  tlic  prcxious  nutrient  eonthtion  of  the 
tree,  on  the  otlicr.  to^ctlicr  witli  a  greater  or  lesser  ease  of  adventitious 
hud  formation,  oharaeteristie  of  each  \ariety.  call  forth  different  compen- 
satory shoots  in  different  cases.  The  more  luxuriantly  a  variety  grows, 
the  more  it  inclines  to  the  formation  of  "lower  buds."  as  can  he  observed 
frec|uently  by  the  breaking  of  eyes  on  the  main  stem. 

In  gra}ie\ines.  regeneration  takes  place  from  the  lateral  buds  if  frost 
has  killed  the  main  ones.  This  depends  greatly  on  the  time  of  the  frost 
action.  If  the  death  of  the  main  bud  takes  place  so  earl\-  in  the  \ear  that 
it  has  used  but  \  ei"y  little  reser\  e  material  in.  its  elongation,  then  fre(|uently 
the  reser\e  material  still  jiresent  in  the  \ine  is  sufiicicnt  to  strengthen  the 
lateral  buds  so  that  blossom  buds  can  still  be  set.  If,  however,  the  main 
bud  dies  from  a  frost  in  May.  strong  shoots  can  dexelop.  to  be  sure,  from 
the  lateral  buds,  but  without  setting  blossoms.  These  shoots  become  fertile 
only  in  the  next  year. 

Fki-:i-:zinc;  of  Koots. 

Not  infreciuently.  especially  in  wet  places  after  open  winters,  the  roots 
of  very  different:  woody  plants  are  found  to  ha\e  been  frozen  while  the 
aerial,  axillary  parts  have  remained  ali\e.  This  phenomenon  i^  exjilained 
by  the  fact  that  the  wood  of  the  roots  is  softer  and  more  porous  than  that 
of  the  trunk.  The  softness  is  due,  on  the  one  hand,  to  the  fact  that,  at  the 
time  when  the  cold  penetrated  deepest  into  the  soil,  the  growth  of  the  root 
had  not  entirely  stop])ed  ;  therefore  the  frost  attacked  still  )<)ung,  unthick- 
ened  elements.  On  the  other  hand,  howe\er,  the  already  matured  elements 
of  the  wood  body  are  not  so  thick-walled  as  the  corresponding  parts  of  the 
aerial,  axillary  body.  This,  is  uni\ersall\-  true  w  ithout  taking  into  consid- 
eration the  nutriment  and  water  content  of  the  soil.  That  the  degree  of 
luxuriant  development  will  also  exert  an  influence  on  the  sensitiveness  to 
frost  cannot  be  denied,  but  this  influence,  according  to  \ .  Mohl's  investiga- 
tions', manifests  itself  differently. 

A  consideration  of  the  annual  range  of  temi)erature  will  gi\e  the 
necessary  explanation  in  regard  to  the  first  point,  the  action  of  the  frost 
wave  on  roots  not  yd  dormant. 

It  should  be  noted  in  advance  that  measurements  of  the  tree's  tem- 
I)erature  prove  the  dependence  of  this  temperature  in  the  tree  toj)  on  the 
fluctuation  in  the  atmospheric  warmth,  while  the  temperature  of  the  trunk, 
especially  at  the  l)ase  and  in  thick  barked  varieties,  is  \ery  considerably 
influenced  b}-  the  warmth  of  the  soil-,  since  the  water,  necessarily  rising  to 


1  V.  Mohl,  I<]iiiise  anatomi.sctip  unci  ))hysiok)g:i.sche  Hemerkunsen  iibcr  das  iio\y. 
der  Baumwurzeln.     Bot.  Zoit.  3  862,  Nos.  29,  33,  34,  ff. 

-  Breitenlohner  and  Boehm  (Sitz.  d.  Kais.  Akad.  d.  Wis.s.  zu  Wcin,  May  17th, 
1877)  found  that  under  usual  eondition.s  the  temperature  of  the  lower  part  of  the 
stem  is  entirely  influenced  by  soil  temperature,  but  if  transpiration  is  arrested,  the 
temperature  of  the  tree  depends  entirely  on  the  air  temperature. 


563 

make  up  for  the  evaporation  of  the  foliage',  has  the  temperature  of  the  soil 
layers.  R.  Hartig-  furnishes  very  clear  proof  of  this.  The  branches  were 
removed  from  one  of  two  similar  trees,  on  which  the  sun  shone,  so  that  in 
the  current  of  evaporation  they  almost  came  to  a  standstill.  The  ther- 
mometer then  proved  a  temperature  of  about  lO  degrees  lower  in  the  tree 
on  which  the  leaves  had  been  left  than  in  that  from  which  the  branches 
had  been  removed.  After  the  removal  of  the  branches  of  the  second 
specimen,  its  temperature  at  once  increased  about  lo  degrees. 

Since,  in  spring,  the  air  body  warms  up  very  quickly,  it  soon  increases 
the  direct  action  of  the  sun's  rays  on  the  branches"  and  keeps  them  at  a 
temperature  at  which  they  can  grow.  The  more  intense  and  lasting  the 
warmth  in  the  air,  the  more  the  cambial  ring  is  stimulated  so  that  its  pro- 
duction of  new  wood  and  bark  elements  extends  from  the  crown  down- 
ward until,  in  April  and  May,  it  reaches  the  roots  and  then  finally  causes 
the  production  of  a  new  wood  ring.  The  time  of  the  awakening,  the 
thickness  of  the  new  wood  ring  and  its  maturation  diifer  in  different  tree 
species.  In  fact,^  an  individual  difference  disappears  inasmuch  as  all  speci- 
mens are  not  able  every  year  to  produce  so  much  plastic  material  in  the 
tree  top  that  it  will  sufhce  for  the  nutrition  of  the  cambial  mantel  of  the 
roots.  It  then  happens  that  the  thickening  ring,  in  such  a  lean  year, 
extends  from  the  top  only  to  the  base  of  the  trunk  where  it  tapers  out  to 
nothing,  so  that  the  roots  in  this  year  do  not  become  any  thicker. 

The  heat  wa\c  and  therefore  the  acti\ity  of  the  cambial  ring  gradually 
disappear  in  autumn  from  abo\e  downward,  just  as  they  had  advanced. 
Since  the  soil  remains  warm  longer  than  the  air,  the  root  has  still  oppor- 
tunity to  continue  its  growth  e\en  if  no  longer  so  intensively.  This 
explains  v.  Mohl's  observation  tliat  roots  in  December,  January  and  Febru- 
ary are  still  active  in  thickening  the  cell  walls  of  the  last  formed  annual 
ring. 

Definite  figures  will  give  the  clearest  idea  of  this.  v.  Mohl  found  in 
the  winter  of  1861-62  that  the  root  formation  in  a  sweet  cherry  tree  had 
not  stopped  by  the  4th  of  April.  In  this  the  branch  buds  had  already 
developed  a  length  of  more  than  2  cm.  and  the  new  wood  ring  in  the  parent 
branch  had  so  far  matured  its  new  ducts  that  their  pitting  was  recognizable. 


1  Ebermaj'er,  Die  phy.sikalischen  Einwirkungen  des  Waldes  auf  Luft  und  Boden. 
I,  Aschaffenburg-  1873,  p.  119-39.  Measurements  show  that  no  essential  difference 
exists  between  the  temperature  of  the  trees  (breast  hig-h)  and  of  forest  soil.  With 
increasing  depth  of  soil  and  height  of  tree,  however,  the  differences  become  marked. 
In  general  it  is  found  that,  from  October  to  March,  forest  trees  are  colder  than 
forest  soil.  "The  roots  in  this  period  are  the  warmest  part  of  the  tree;  the  mean 
tree  temperature  decreases  with  increasing-  height  and  is  lowest  in  the  branches  and 
twigs."  "In  the  summer  half  of  the  year  (April  up  to  and  including  September), 
conversely,  forest  trees  are  warmer  than  the  soil,  i.  e.,  the  temperature  of  the  tree 
decreases  from  above  downward  and.  during  the  day,  is  highest  in  the  twigs  and 
branches,  lowest  in  the  roots."  The  mean  annual  temperature  of  the  tree  fluctuates 
between  3.9  to  6.7  degrees  according  to  the  elevation  in  the  plane  of  growth.  It  is 
less  than  the  mean  air  temperature  and  higher  than  the  mean  soil  temperature  of 
the  forest. 

2  Lehrbuch  der  Baumkrankheiten  1882,  p.  177. 

3  Compare  Krutsch,  Untersuchung  liber  die  Tcmperatur  der  Baume,  etc.  Jahrb. 
d.  Kgl.  Sachsischen  Akad.  zu  Tharand,  v.  X,  1854. 


564 

The  \vof)(l  cells  l\ini,^  between  the  ducts  were  still  thin-walled  and  had  only 
half  their  typical  size.  In  the  roots,  hoxccver,  the  outermost  zcood  cells  of 
the  previous  annual  rimj  had  not  once  been  thickened.  After  the  tree  had 
blossomed,  on  the  iith  of  April,  investigation  still  showed  no  complete 
termination  of  the  previous  annual  ring  in  the  roots  and  not  until  the  26th 
of  April  did  the  roots  become  dormant. 

At  the  time  the  new  annual  ring  in  the  branches  of  the  [)re\ious  year 
was  alread}-  completely  lignitied  and  so  thick  that  six  successive  ducts  coukl 
be  counted  in  a  radial  direction  in  the  lowest  i)art  of  the  trunk,  only  a 
single  row  of  ducts  had  developed  and  only  the  innermost  wood  cells  were 
found  to  be  thickened.  In  the  main  root,  the  annual  ring  of  the  previous 
year  was  complete  and  the  cambium  already  prepared  for  renewed  activity 
since  the  bark  could  be  easily  separated  from  the  wood  body:  nevertheless, 
no  traces  could  be  seen  of  a  new  wood  ring.  The  bark  of  the  lateral  roots, 
which  were  as  thick  as  one's  little  finger,  could  not  be  loosened.  Thus  no 
complete  winter  rest  was  present  here.  They  lingered  in  this  condition 
until  the  30th  of  April,  when  some  of  the  leaves  were  already  fully  grown 
and  a  new  wood  ring  in  the  main  root  had  begun  to  develop  young,  still 
unthickened  ducts. 

We  will  get  an  insight  in  regard  to  the  second  of  the  abo\e  mentioned 
points,  i.  e.,  the  anatomically  different  structure  of  the  roots,  conditioning 
a  lesser  power  of  resistance,  if  we  bear  in  mind  the  time  when  the  annual 
rings  in  the  trunk  wf)uld  be  developed  in  contrast  to  those  of  the  root. 

In  the  trunk  growth,  the  complete  termination  of  the  annual  ring  will 
take  [dace  so  much  the  earlier  in  the  year  the  higher  it  is  in  the  tree  top. 
Consequently  its  development  there  will  consist  chiefly  of  spring  wood, 
lief  ore  the  production  of  the  annual  ring  has  extended  to  the  base  of  the 
trunk,  summer  has  come  and  there  is  not  much  more  time  for  the  develop- 
ment of  spring  wood.  Therefore,  the  diliferentiation  of  the  annual  ring 
must  so  proceed  that  (no  matter  whether  it  is  thick  or  thin)  the  relative 
amount  of  sprinn  ivood  to  autumn  wood  decreases  from  above  doi<'nward, 
i.  e.,  relatixely,  the  autumn  wood  increases  toward  the  base  of  the  trunk. 
This  hypothesis  has  been  actually  confirmed  l)y  direct  measurements  made 
by  v.  Mohl',  as  well  as  by  Hartig-  and  Sanio''.  It  should  be  added  here 
that  the  thicker  the  part  of  the  trunk  is  the  higher  the  maximum  of  warmth 
it  attains*. 

The  firmness  of  the  l;ase  of  the  trunk  depends  ui)on  the  predominant 
formation  of  autumn  wood. 

The  character  of  the  tree  \  ariety  comes  into  consideration  in  the  devel- 
opment of  the  root  wood.  In  conifers,  with  their  early  termination  of  root 
growth,  the  dc\elopment  falls  at  a  time  of  greater  soil  warmth  and  dryness 


1  loc.  cit. 

-  loc.  cit. 

"■  .Tahrbiicher  f.  wissen.sch.     l?ot.  IX,  j).  1.55ff. 

■«  Ihne.  tjiier  Baumtempeiatur  unter  deni  Einllus.s  der  Insolation.  Pot.  Cen- 
tralblatt  1883,  No  34,  p.  234.  Vonhau.sen,  Untersucliungen  iiber  den  Rindenhrand. 
All.er.  Forst-   und  Jagdzcitung,  X873. 


565 

and,  on  tliis  account,  chiefly  autumn  wood  is  formed.  If  much  material  is 
present,  i.  e.,  the  annual  ring  is  broad,  a  strong  autumn  wood  ring  has  been 
developed  (v.  Mohl).  In  deciduous  trees  in  which  the  development  of  the 
root  body  is  continued  until  the  next  year  and,  in  fact,  as  has  been  shown 
above,  often  does  not  end  before  the  blossoming  time  of  the  next  growth, 
all  differentiations  are  weaker  and  the  boundaries  of  the  annual  rmgs  less 
distinct.  .Since  it  becomes  spring  in  the  layers  of  the  soil  only  after  it  has 
Ijecome  summer  above  ground,  spring  wood  is  always  formed  in  the  roots. 
In  the  further  advance  of  the  annual  ring,  its  development  depends  on  the 
degree  and  continuance  of  the  soil  warmth  and  dryness.  If  a  year  has  a 
long  dry  period,  autumn  wood  is  formed.  If  this  is  not  the  case,  develop- 
ment is  limited  to  spring  wood,  with  only  a  weak  beginning  of  autumn  wood 
formation.     Hence  the  porous  structure  of  the  slender  ringed  root. 

By  briefly  repeating  what  has  already  been  stated,  we  can  summarize 
the  dift'erence  between  root  and  trunk  in  deciduous  trees,  since  first  the 
annual  rings  in  the  root  are  much  more  slender  than  the  corresponding  ones 
of  the  trunk  and,  second,  in  the  constant  development  of  porous  spring 
wood,  these  slender  layers  are  predominantly  porous.  In  conifers  the  same 
difference  is  found  between  trunk  and  root,  so  far  as  the  slenderness  of  the 
annual  rings  is  concerned  and,  in  the  same  way,  the  thicker  the  annual 
ring  the  more  the  autumn  wood  decreases  in  proportion  to  spring  wood. 
The  wood  cells  are  everywhere  longer  and  wider  and  their  walls  thinner 
in  the  roots  than  in  corresponding  parts  of  the  trunk. 

Therefore,  greater  attention  should  be  paid  to  the  freezing  of  the  roots 
because  in  this  is  found  the  explanation  of  numerous  cases  of  summer 
death  in  indi\idual  trees  and  groups  among  those  of  the  same  age  and  of 
the  same  species.  Trees  with  frozen  roots,  like  healthy  ones,  usually 
sprout  in  the  spring  and  often  develop  normal  shoots,  even  if  they  bear  as 
a  rule  smaller  leaves.  Not  until  summer,  but  then  advancing  especially 
quickly,  does  a  yellowing  of  the  leaves  begin  and  also  a  drying  of  the  twigs. 
The  water  supply  of  the  trunk  is  then  used  up  by  the  transpiration  of  the 
leaves. 

Even  in  localities  and  varieties  wdien  no  injury  of  the  aerial  axis  is  to 
be  feared  from  winter  frosts,  fruit  trees  in  pots  should  be  brought  into 
protected  places,  because  of  the  sensitiveness  of  the  roots  and,  in  open  land 
cultures,  the  natural  protection  from  foliage  and  snow  should  not  only  be 
left  but,  if  possible,  increased.  In  planting  tree  plantations,  it  will  only  be 
possible  to  carry  out  the  otherwise  advantageous  autumn  planting  without 
danger  if  absolutely  hardy  trees  are  used  or  the  planting  takes  place  so 
early  in  the  autumn  that,  preliminary  thorough  puddling  being  taken  for 
granted,  rooting  and  a  close  packing  in  of  the  roots  in  the  earth  may  be 
assumed.  DuhameT  observed  that  a  formation  of  fibrous  roots  can  take 
place  even   in  winter.     This  was   later  substantiated   by  Lindley.     In   less 


De.s  semis  et  plantations  des  aibres,     p.  155. 


566 

extensive  tree  plantations,  a  deejjcr  jjcnelration  of  tlic  cold  can  he  pre- 
vented by  covering  the  loosened  soil.  It  is  a  frecjuent  but  not  universal 
discovery  that  the  roots  of  recently  transplanted  trees  suffer  more  from 
winter  frosts  than  do  specimens  left  in  their  orig^inal  jtlace  of  ,<^ro\vth. 

Frost  Clefts. 

The  temperature  inside  strong  tree  trunks  can  ff)llo\v  the  temperature 
of  the  outer  air  only  slowly  and  thus  the  inner  part  of  the  trunk  is  colder 
than  the  surrounding  air  from  morning  until  noon  but  is  warmer  in  the 
evening\  Then  a  contraction  of  the  tissues,  due  to  the  appearance  of  cold, 
will  manifest  itself  in  the  outer  layers  of  the  trunk  while  the  core  still 
retains  its  original  distension.  In  this  way,  dit'ferences  in  tension  arise 
which  become  the  greater,  the  shari)er  the  change  in  temperature.  Xow  , 
with  a  fall  in  temperature,  the  wood  body  contracts  more  stronglx-  in  the 
direction  of  the  circumference,  i.  e.,  tangentially,  rather  than  radially,  so 
that  the  peripheral  mantel  of  the  still  warmer  core  of  the  trunk  really 
becomes  too  tight.  It  must  accordingly  be  stretched  tangentially  if  it  shall 
still  entirely  enclose  the  core.  If,  with  increasing  cold,  it  can  not  stretch 
sufficiently,  it  must  split.  In  this  way  tears  are  produced  in  the  bark  of 
the  tree  which  advance  the  deeper  into  the  wood,  the  greater  the  cold  and 
the  difference  between  the  cooled  peripheral  and  the  warmer  central  tissues 
of  the  trunk.  In  great,  sudden  cold,  it  has  been  found  that  some  tree 
trunks  crack  audibly  and  then  show  hjng,  deep  gaping  splits  following  the 
twisting  of  the  wood  fibres.  Some  varieties  of  trees  show  this  phenomenon 
especially  frequently.  The  horse  chestnut  suffers  most  of  all;  besides  this, 
the  oak,  poplar  and  cherry  should  be  especially  emphasized.  The  cleft 
remains  gaping  only  so  long  as  the  heavy  cold  lasts.  With  the  apjjearance 
of  warmer  weather  the  edges  of  the  split  approach  one  another,  even  closing 
the  wound  entirely.  The  wound,  however,  is  almost  ne\er  well  healed  and 
breaks  open  again  the  following  winter.  The  process  of  healing  is  normal, 
since  circumvallation  rolls  are  formed  from  the  cambium,  the  young  wood 
and  the  bark,  and  strive  to  unite.  In  other  injuries  with  free  lying  wound 
surfaces,  these  projecting  overgrowth  edges,  howcxer,  do  not  find  the  space 
necessary  for  their  extension,  but  are  forced  to  grow  directly  against  one 
another  and  to  i)ush  out  over  the  edge  of  the  cleft  wound.  They  therefore, 
from  mutual  pressure,  form  rolls  projecting  outward,  depressed  in  the 
centre  like  lips,  which  are  called  "frost  ridges.' 

In  Fig.  \22  we  see  such  a  frost  ridge  on  a  strong  trunk  of  Acer  cam- 
pcstrc,  which  shows  a  number  of  radial  clefts.  One  of  these  has  split 
through  the  stem,  so  that  an  outwardly  \isil)le  cleft  has  been  [)roduced 
which,  at  the  beginning,  gaped  widely  but,  with  the  ai)pearance  of  warmer 
weather,  has  become  very  narrow.  WHien  in  spring  the  tree  would  have 
closed  the  split  by  growth  of  the  cambial  layer,  the  circum\allation  edges 


1   Squires,  Roy  \V.,  Minnesota  Dot.  Studies.  Bull.  9,  189J 


56/ 

found  no  room  to  grow  into  tlie  clet't  and  therefore  were  forced  outward. 
On  this  account  we  find  the  Hp-Uke  processes  made  recognizable  in  the 
cross-section.  Such  a  process  of  healing  lias  not  yet  been  observed  in  any 
other  trunk  injury,  so  that  its  appearance  may  be  considered  absolutely 
certain  evidence  of  frost  action. 

Caspary'  has  experimentally  examined  this  phenomenon  more  closely. 
He  proved  by  direct  measurement  that  the  coefficient  of  the  distention  of 
the  fresh  wood  consideral)lv  exceeds  that  of  all  solid  bodies,  even  that  of 


Fig-.  122.     Ffost  rid.iie  on  the  trunk  of  Acer  campestre 


iron,  tangentially  as  well  as  radially,  and  is  exceeded   only  by  air.     This 
explains  the  sudden  production  of  deep  clefts. 

The  extent  to  which  a  cleft  opens  varies  in  the  same  tree  species  and 
with  the  size  of  the  trunk,  but  all  cases  show  that  if  the  frost  clefts  have 
once  been  produced  (eyen  after  they  have  closed  in  thawing  weather)  a  very 
light  degree  of  cold  is  sufficient  to  re-open  them.  This  is  explained  by  the 
fact  that  the  amount  of  strength  necessary  for  the  production  of  the  cleft 
may  be  sufficient  to  overcome  the  cohesion  of  the  cell  elements  in  the  whole 


1   Caspary,  Neue  Untersuchungen  liber  Frostspalten,  Bot.  Zeit.  1857,  No.  20-22. 
In  an  earlier  treatment,  Bot.  Zeit.  1855,  p.  449,  he  also  cites  the  earlier  literature. 


568 

extent  of  the  trunk  j^  radius;  with  the  appearan-^e  of  renewed  cold  in  the 
same  year,  no  resistance  has  to  be  overcome  in  re-opening  the  clefts,  and 
the  following  winter  only  enough  to  overcome  the  newly  formed  wound 
cover. 

The  frost  clefts  produced  in  winter,  usuall}-  extend  deep  into  the  inner 
part  of  the  trunk.  The  tree  is  unable  to  form  a  new  cicatrization  mem- 
brane in  the  older  wood  and,  conse(|uently,  each  frost  cleft  rei)resents  a 
persistent,  outwardl)-  covered  o\er  but  inwardly  unhealed  wound  This 
becomes  the  more  significant  the  more  some  lateral  tangential  clefts  are 
added  to  the  radial,  large  frost  cleft.  These  tangential  clefts  usually  extend 
into  the  layers  of  the  spring  wood  and  may  be  connected  with  one  another  b)- 
radial  cross  tears.  There  then  occurs  an  intersected  splitting  which  makes 
the  wood  absolutely  of  no  practical  use  and  hastens  the  death  of  the  tree 
by  facilitating  the  spread  of  wood-destroying  fungi. 

We  thus  obtain  such  structures  as  are  shown  in  I'ig.  123,  wliich  repre- 
sents a  cross-section  tlirough  an  oak  trunk  which,  infectecl  by  rolyponis 
siilfnrcus  from  a  wound  in  the  branch,  has  become  cleft. 

While  the  splitting  of  the  trunk,  due  to  long  clefts,  transversing  the 
greater  part  of  the  tree  shaft'  has  often  been  described,  the  production  of 
shorter,  shallower  clefts,  which  are  more  easily  closed,  has  not  been  suffi- 
ciently investigated.  R.  Hartig-  considered  them  in  the  white  fir  where 
they  are  often  very  shallow,  appear  in  the  upper  parts  of  the  shaft  and 
usually  coalesce  very  soon  without  forming  frost  ridges.  Also,  thev  follow 
the  direction  of  the  wood  fibres,  i.  e.,  usually  somewhat  at  an  angle.  P.e- 
sides  occurring  in  the  fir,  I  find  this  kind  of  short  frost  clefts  often  with  a 
lip-like  v/all  in  the  red  beech,  tlie  cherry  and  the  plane  tree.  Curiously 
enough,  these  varieties  are  distinguished  by  a  bark  which  remains  smooth 
for  a  long  time.  In  this,  the  preference  for  certain  sides  of  the  tree,  in 
the  production  of  frost  clefts,  is  most  easily  perceived.  If  the  trees  are 
not  accidentally  protected  by  adjacent  ones  but  stand  free  it  is  possible  in 
the  majority  of  cases  to  determine  that  the  west  and  southwest  sides  display 
the  most  abundant  injury  from  frost.  Street  plantations  of  plane  til'es. 
for  example,  show  how  differently  the  different  sides  of  the  trees  beha\e. 
At  the  time  when  the  well-known,  normal  dropping  of  the  bark  scales  from 
the  trunk  begins,  it  will  be  found  that  most  of  them  are  thrown  off  first  on 
the  southwest  side  of  the  trunk. 

At  times  "tears  due  to  druiKjht"  are  described  as  frost  tears.  X()rd- 
linger'''  has  called  especial  attention  to  this.  Tears  due  to  drought,  which 
occur  especially  in  strong  trees  growing  on  an  impervious  soil  layer,  or 
undergoing  a  sudden  great  scarcity  of  water,  are  characterized  by  repeated 


1  Giippeit,  tjber  die  Folgen  iiusserer  Verletzungen  der  Biiume,  p.  30,  Breslau, 
1873.     He  found  frost  tears  in  76  different  varieties  of  trees. 

-  Hartig-,,  R.,  Lehr))uch  der  Pflanzentirankheiten,  3d  edition,  p.  214,  Berlin,  1900, 
Julius  Springer. 

y  Nurdlinger,  Trockenrisse  (falsche  Frostrisse)  an  der  Fichte.  Auch  eiu  Oiiind 
der  Rotfaule.     Centralbl.  f.  d.  gesamte  Forstwesen.  Wein  1S78,  Part  6. 


569 

changes  in  their  radial  course  in  the  older  annual  rings,  than  in  the  younger 
ones,  or  by  the  radial  si)]itting  of  one  or  two  annual  rings  in  the  wood  disc. 
Such  inner  clefts  then  have  the  form  of  a  lance  tip.  i.  e.,  are  l)roadened  at 
the  centre.  Since  in  clefts  extending  to  the  hark  the  wound  remains  open, 
the  circumvallation  walls  incline  toward  the  cleft  and,  therefore,  form  no 
projecting  ridges  in  frost  clefts. 


Fig.   123.     Oak   stem   cleft   li\     Polyporiis   sulfureus.     (After   Frank- Schwarz.) 


Frost  Blisters. 

In  connection  with  frost  clefts,  the  so-called  "internal  frost  tears" 
should  Vie  considered,  which  R.  Ilartig'  has  observed  in  oaks  and  firs. 

"If  the  tree  shrinks  with  great  cold"-  he  says,  "tears  can  arise  in  the 
wood  body  on  the  surface  of  the  cleft  which,  however,  extend  only  to  the 
bark  mantel  zvithout  splitting  it.  The  bark,  which  has  no  radial  cleft  sur- 
faces, holds  the  wood  body  together.     However,  the  elastic  bark  of  the  nr 


1  Hartig-,   R.,   Innere  Frostspalten.   Forstl-naturwis; 

2  Lehrbueh  der  Pflanzenkrankheiten,   1900,  p.  214. 


Zeitschr.    1896,   p.    483. 


570 

is  distended  where  tlic  frost  tear  opens  internally  and  thus  loses  a  part  of 
its  elasticity.  1  f  the  tree  later  grows  thicker,  the  bark  exercises  a  lesser 
pressure  on  the  cambium  at  this  place  and  the  additional  growth  is.  there- 
fore, locally  increased.  Outwardly  the  trunk  is  not  round  but  has  ridge- 
like processes." 

I  assume  a  \ery  similar  course  in  the  production  of  the  structures, 
which  I  term  frost  blisters.  'J'hese  are  broadly  conical,  but  usualh  flattened 
processes  at  times  one  centimeter  high  on  the  smooth  bark  of  trunks  or 
branches  two  or  more  years  old. 

These  blisters  should  not  be  confused  with  the  conical  bosses,  occur- 
ring not  infrequently  on  luxuriantly  cultivated  varieties.  In  them  a  hani 
ivood  core  is  recognized  immediately  under  the  bark,  while  the  frost  wood 
blister,  in  some  cases,  consists  permanently  of  a  soft  tissue  mass,  easily 
indented  with  the  finger  nail  which,  in  other  cases,  lasts  only  during  the 
year  of  its  production. 

The  projections,  strongly  lignified  from  the  start,  and  for  which  I 
would  like  to  propose  the  name  of  "duct  boss,"  almost  always  have  a 
definite  position  in  relation  to  the  bud,  while  the  frost  blisters  are  found  on 
any  part  of  the  young  trunk  or  the  branch  internode.  "Duct  bosses"  are 
bark  covered,  wood  swellings  with  one  or  two  points,  which,  like  the  begin- 
nings of  a  gnarl,  i)roject  above  the  perijjhery  of  the  rest  of  the  wood  body. 
They  owe  their  production  to  the  excessi\e  develoi)ment  of  the  two  \ascu- 
lar  bundles  which  normally  pass  into  the  bud  cushions  and  unite  with  the 
central,  strongest  bundle  of  the  vascular  bundle  body  of  the  petiole. 

In  the  tender  frost  blisters  we  find  no  connection  with  the  cords  of  the 
leaf  spur.  They  are  found  at  any  place  and  arise  from  a  blister-like  dis- 
tention of  the  bark  body  away  from  the  wood  cylinder.  The  young  wood, 
lying  on  the  wood  cylinder,  at  once  begins  cell  increase,  since  the  distention 
takes  place  only  in  late  frosts  and,  therefore,  at  the  time  of  growth  activity. 
This  young  wood  fills  the  ca\ity  with  a  thin-walled  parenchyma  wood 
which  gradually  [)asses  over,  at  the  j)eriphery,  into  normal  wood. 

The  wdiole  process  taking  place  here  is  the  same  as  occurs  in  the  new 
formation  of  bark  on  an  artificially  produced  wound  surface.  In  blister 
formation  the  dift'erence  lies  alone  in  the  fact  that  the  bark  does  not  scale 
off,  but  is  only  raised  in  places  by  the  frost  and  that  thereby  the  new  struc- 
tures, lying  above  the  wood  body,  at  first  do  not  become  visible  to  the 
naked  eye.  At  times  they  can  be  very  clearly  recognized  by  their  unusual 
luxuriance  when  the  bark  is  cut  on  large  frost  blisters.  It  is  then  possible 
to  expose  here  and  there  a  wrinkled  outgrowth,  several  centimeters  long 
and  0.5  to  T.o  cm.  high,  which  is  not  connected  at  all  with  the  old  bark  and 
only  rests  on  the  wood  body.  In  one  case  (in  the  pear  Bonne  Louise 
d'  Avranche)  the  outgrowth  had  ruptured  the  bark  mantel  and  had  ex- 
tended far  beyond  the  circumference  of  the  trunk  as  an  irregularly  outlined, 
somev^'hat  conical  mass  with  a  wartv,  crumblv  surface. 


5/1 

I  could  observe  other  stages  of  healed  frost  blisters  in  the  maple  and 
the  apple.  As  yet  the  best  examples  have  been  found  m  the  maple,  and,  in 
fact,  on  two  year  old  shoots,  more  than  1.5  m.  long.  Many  of  these,  in 
their  whole  course,  excepting  the  tip  region,  and  on  all  sides,  showed  small 
flat,  completely  bark  covered  bosses,  possibly  0.5  mm.  high  which  were 
more  noticeable  to  the  touch  than  to  the  eye.  The  outer  bark  appeared 
perfectly  normal  and  the  direct  continuation  of  the  remaining,  not  rough- 
ened part  of  the  branch.  In  cross-section,  the  cause  of  the  out-pushing  of 
the  bark  may  be  recognized  in  the  swelling  of  the  wood  body  which,  at  the 
beginning  of  the  second  annual  ring,  has  formed  an  aggregation  of  paren- 
chyma wood  cells  very  broad  and  rich  in  starch.  As  a  rule,  such  an 
aggregation  of  wood  parenchyma  is  found  lying  exactly  between  two 
medullary  rays  so  that  the  lateral  transition  from  this  diseased  wood  tissue 
to  the  healthy  tissue  is  rather  sudden,  while  the  abnormal  wood  elements 
assume  very  gradually  in  a  radial  direction  the  normal  dimensions  and 
thickness.  Only  in  the  radially  and  laterally  adjacent  wood  with  a  regular 
structure  are  found  greatly  widened  and  shortened  wood  cells  filled  witli 
starch    (investigated  in  May). 

In  the  wood  parenchyma  aggregations,  irregularly  extended,  yellow- 
stripes  are  found;  the  yellow  color  arises  from  swollen  cell  walls  which  are 
universally  present  in  frost  injuries.  Also,  other  characteristics  of  a 
definite  group  of  frost  injuries  are  present  as,  for  example,  the  lateral  dis- 
placement of  the  medullary  ray  cells  at  the  frosted  place  and  the  barrel- 
shaped  widening  of  the  medullary  ray  where  it  enters  the  parenchyma 
aggregation.  This  barrel-shaped  widening  of  the  medullary  ray  is  pro- 
duced less  often  by  the  increase  of  its  cells  than  by  their  broadening  at  the 
expense  of  their  length.  In  this,  not  infrequently,  a  very  striking  thicken- 
ing of  the  secondary  membrane  is  noticed.  Cell  increase  is  found  most 
frequently  in  the  one-celled  medullary  rays  which,  from  the  point  injured 
by  frost,  become  two-celled.  The  further  such  a  medullary  ray  extends 
into  a  parenchyma  aggregation,  the  broader  and  shorter  its  individual  cells 
appear  in  cross-section  and  with  relatively  more  slanting  walls ;  they  dove- 
tail into  one  another,  instead  of  remaining  bluntly  placed  against  one 
another.  At  last  the  shape  of  all  the  cells  in  the  parenchyma  aggregation, 
of  which  the  elements  are  widest  near  its  centre,  become  the  same  so  that 
no  difference  can  be  recognized  in  the  medullary  rays. 

A  brown  bark  zone,  tangentially  elongated,  which  was  formerly  con- 
nected with  the  parenchyma  but  is  now  separated  by  newly  interposed 
wood,  corresponds  in  the  same  radius  to  the  yellow  or  brown  striped 
aggregations  of  parenchyma  wood. 

By  coloring  the  section  with  campeche  wood  extract,  very  interesting 
pictures  are  often  shown,  if  a  concentrated  solution  of  chloriodid  of  zinc 
is  added.  The  difference  in  thickness  in  the  walls  of  the  wood  cells 
becomes  more  apparent.  The  walls  of  some  groups  of  wood  cells  are 
colored  more  intenselv  yellow  and  are  more  swollen. 


572 

These  were  the  avails  of  the  rad'niJly  divided  zvood  eells^  surronndimi 
the  ducts  and  containing  starch  which,  therefore,  niii/ht  he  more  sensitiir 
than  the  other  elements  of  the  vascular  bundles. 

In  frost  Misters  of  the  cherry,  illustrated  in  Figs.  125  and  126.  the 
anatomical  structure  evidently  differs  from  that  of  the  frost  blisters  of  the 
maple  branch,  inasmuch  as  here  the  gummy  exudation  usually  sets  in  as  a 
result  of  the  injury.  V\g.  125  is  a  cross-section  tiirough  the  centre  of  a 
blister.  V\g.  126  a  longitudinal  section  made  at  one  side  of  the  medial  line 
of  the  wound ;  r  is  the  brown  stripe  of  dead  tissue  which  immediately 
bounds  the  inner,  fine  tear  which  caused  the  blister.  This  tear  was  not 
visible  externally  since  the  outermost  bark  layers  (c)  had  remained  unin- 
jured, although  the  wound  was  deep  and  extended  to  the  old  wood  (h). 
It  must  from  the  beginning  have  been  very  narrow,  however,  and  produced 
at  a  time  when  an  immediate  overgrowth  was  possible  since  the  oxergrowth 
tissue  had  sunk  at  once  into  the  wound    (r)   witliout  causing  tlie  death  of 


m^^m^ 


^^t 


.1^ 


1  If,  at  the  time  of  the  awakening  of  vegetation,  cross  sections  of  Acer,  Salix 
viminalis,  and  other  trees  are  treated  with  a  strongly  acid,  concentrated  .«oliiti()n 
of  c'liloriodid  of  zinc,  large  dark  blue,  variously  shaped  starch  structures  may  ]>v 
seen  to  pass  out  fiom  these  radially  divided  wood  cells  (compare  Fig.  124  r).  The 
foi-ms  of  these  are  different.  At  times  they  may  clearly  be  seen  composed  of  sep- 
arate, ii-regular,  swollen  starch  grains  because  the  cores,  remaining  firmer,  appear 
granular  on  the  smooth  upper  wall  surface  of  the  pouch-like  structure;  they  are 
left  after  the  dissolution  of  the  peripherial  layer  of  the  starch  grains.  At  times, 
however,  the  substance  of  the  hollow  body  is  uniformly  memljraneous  and  the  upper 

surface     smooth;      the 

I til)     often     appears 

notched.    In  older  wood 
^  such  starch  structure.s 

appear  most  numei- 
ously  in  the  autumnal 
wood  of  the  last  two 
annual  rings.  Glycerin 
clears  up  the  starch 
pouches  which  occur 
on  the  upper  side  as 
well  as  the  under  side 
of  the  section.  Alcohol 
l)iings  out  their  con- 
touis  more  sharply 
and  makes  them  seem 
darker.  P  o  t  a  s  )i 
bleaches  them  and 
shows  better  the  gran- 
ular elements  of  the 
walls.  Their  formation 
seems  to  res-ult  from 
the  swelling  of  the 
starch  gi-ains  which 
they  rupture  and,  with 
the  reagent,  transform 
their  contents  into  a 
membrane  in  which, 
at  times,  bright  circu- 
lar spots  may  V)e  seen, 
just  as  if  vacuoles  had 
been  deposited  during  the  formation.  The  notched  form  of  the  tip  is  conditioni^a 
by  the  irregular  pushing  forward  of  the  individual,  outermost  starch  grains.  I 
would  like  to  consider  these  structures  Traube's  cells;  strongly  acid  chlorzinc  with 
potassium  alone  showed  a  membraneous  precipitate.  Tin-chlorid  (neutral)  and 
iron  chlorid  (acid)  i)roduce  no  such  structures.  They  are  also  not  destroyed  by 
sulfuric  acid  or  hydrochloric  acid.  A  drying  of  the  branches  which  had  previously 
displayed  many  such  structures,  decreases  their  formation  or  stops  it  entirely. 
This  phenomenon  can  not  always  be  produced.  It  -seems  to  be  connected  with  the 
special  constitution  of  the  starch  shortly  before  its  dissolution  in  the  early  spring. 


•\,i30l/!Jp)^r<?'ooc/ 


'r 


Fig.    124.     Starch    structures   formed   in   the   treatment   of 

sections  of  a  young  willow  branch  with  chloriodid  of  zinc. 

They  pass  out  of  the  bisected  wood  c'clls  and  often  curve 

into  the  duct  lumina. 


573 

considerable  amounts  of  tissue.  This  young  tender  overgrowth  tissue,  as 
well  as  the  cells  bounding  the  diseased  parts  of  the  bark,  at  once  produced 
thick  Itark  layers  (kn)  which  completely  encased  the  dead  tissue  and  iso- 
lated it  from  the  healthy  tissue.  The  hard  bast  bundles  (b)  which,  in  the 
midst  of  the  healthy  bark  tissue,  became  diseased  immediately  about  the 
wound,  had  been  enclosed  by  isolated  cork  circumvallation  (Fig.  125  u)  so 
that  from  them  no  furtlier  decomposition  of  the  surroundmg  bark  paren- 
chyma, containing  chlorophyll,  could  take  place. 

In  the  process  of  healing,  the  new  wood  (w  h)  and  the  new  bark  (//  r) 
endeavor  to  cover  the  wound,  beginning  at  the  sides  and  extending  inward. 


,e 

,ku. 

|j 

U, 

nr 

n/.___J_';'^^-^ 

'€:x^% 

i 

___/!. 

r 

V 

Fig'.  12.5.     Frost  lioil  on  a  Ijranch  of  .'^weet  clierrj'.     Medial  section. 

in  the  centre  of  the  wound,  where  the  gaping  edges  stand  further  apart 
(Fig.  125  n  h)  no  closing  has  yet  been  possible.  On  the  other  hand,  this 
is  the  case  at  the  sides.  The  edges  of  the  two  new  wood  layers  (Fig.  126 
n  h  and  n  h' )  have  become  united  and  the  dead  piece  of  the  bark  (Fig.  126  w) 
is  separated  from  the  dead  piece  of  the  wood.  The  older  and  thicker  the 
new  wood  and  bark  layers  become,  the  more  the  dead  bark  is  pushed  out- 
ward and  finally  pushed  off.  The  dead  wood  (A  p) ,  of  a  parenchymatous 
nature,  and  the  momentarilv  fresh  wound  edges  (Fig..  125  }i  p'),  likewise 
formed  of  parenchyma  wood,  at  first  gradually  pass  over  into  firmer,  normal 
tissue.  The  first  formed  new  wood,  suitable  for  circumvallation,  bears  in 
itself,   in   the   central   wound    region,   the   germ   of   death;   numerous   gum 


574 
■med.  w 


)rt  tiiiK"  will  dissolve 


centres  (Fig.  125  //)  lia\e  Ween  f( 
the  less  resistant  tissue. 

In  older  circumxallatioii  on  a  maple  hranch,  which  was  not  at  all  lux- 
uriant, a  spliitin(j  of  the  annual  rina  was  noticed,  since  the  region  of  the 
autumn  wood  on  one  side  of  the  branch  was  divided  into  two  parts  by  a 
considerably  thicker  zone  of  spring  wood,  rich  in  duels,  and  then  rcuniti-d 
with  the  zones  tirsl  formed  so  that  one  more  annual  ring  could  be  counted 
on  one  side  of  the  twig  than  on  the  other. 

When  such  excrescences  are  remarked  for  the  first  time  in  trunks 
which,  up  to  that  time,  had  been  healthy  (this  is  the  case  in  the  early  summer 
months)  it  will  be  advisable  to  strongly  scarify  the  tree.  The  knife  could 
be  inserted  above  the  excrescence  and  several  long  cuts  be  made  through 
the  l)lister  into  the  healthy  undcrlving  tissue.      Hv  the  wound  stimulus  thus 


[•'ii;.    i:.'<j.      Tile    .same   wound   as    in    Ki 


A    latcial    -section. 


brought  to  bear  on  the  healthy  tissue  near  the  blister,  it  is  incited  to  an 
increased  circunn  allation  acli\it}-.  and  the  pressurt-  of  the  diseased  excres- 
cent tissue  on  the  plastic  untlerlying  niaterial  is  reduced. 

Frost  W'kimklk.s. 

While  the  raising  of  the  whole  bark  bod}'  from  the  wood  cylinder 
found  in  places  in  frost  blisters  could  be  proved  to  have  been  their  cause, 
in  frost  wrinkles  a  loosening  of  the  outer,  coarser  bark  layers  from  the 
tender,  inner  bark  is  concerned.  The  phenomenon  has  been  obser\ed  as 
yet  only  on  the  new  growth  of  cherry  branches  in  June.  The  branches 
were  conspicuous  because  of  the  coarse  wrinkles  on  one  side  of  the  other- 
wise smooth  bark.  The  cambium  was  not  disturbed,  the  i)ith  was  some- 
what browned. 

;\s  has  been  pro\ed.  a  penetrating  frost  produces  great  ditiferences  in 
tension  in  the  trunk.     The  frost,  without  necessarily  forming  frost  crystals 


i 


575 

in  the  intercellular  spaces,  contracts  the  tissue,  and  so  much  the  more  the 
thinner  walled  the  tissue  is.  The  bark  suffers  considerably  more  than  does  the 
wood  which,  reached  later,  cools  down  less  easily  and  contracts  less.  The 
tangential  contraction  is  greater  than  the  radial.  This  difference  acts  likes 
a  one-sided  strain,  taking  place  in  the  direction  of  the  circumference  of  the 
trunk  to  which  the  dift'erent  layers  of  the  bark  will  respond  to  a  different 
degree,  when  the  bark,  as  a  \\hole,  is  Aery  young.  \\'ith  an  equal  amount 
of  contraction  at  all  points  in  the  bark,  the  cells  lying  nearest  the  periphery 
and  most  elongated  in  the  direction  of  the  circumference  of  the  trunk,  will 
be  most  displaced.  If  one  considers  that  the  outer  cells  of  the  primary 
bark,  because  of  the  great  coarseness  of  their  walls,  are  not  as  elastic  as 
the  underlying,  thinner-walled  ones,  it  is  clear  that,  when  the  strain  ceases 
in  them  the  permanent  increase,  caused  by  the  incomplete  elasticity,  will  be 
ihe  greatest. 

After  the  frost  action  has  stopped  (it  continues  only  a  short  time  in 
late  frosts )  the  increased  turgor  will  cause  the  cells  to  retain  their  distended 
form  and,  since  the  outer,  greatly  distended  bark  layers  no  longer  have 
sufficient  space  in  the  previous  tangential  plane,  they  become  raised  in 
wrinkles  or  blisters  above  the  plane  of  the  circumference  of  the  trunk  and 
in  this  way  form  "frost  wrinkles." 

Besides  the  tangential  and  radial  contraction,  there  is  an  additional, 
longitudinal  change  in  the  young,  still  herbaceous  twigs,  which  must  be 
produced  with  the  twisting  of  the  axillary  body,  caused  by  the  frost  action. 
One  can  easily  produce  cross  wrinkles  artificially  on  one  year  old  shoots 
by  bending  them.  Reference  should  be  made  to  a  work  by  Ursprung'  in 
regard  to  the  tensile  conditions  developing  in  bent,  herbaceous  stems. 

Bark  Tatters  and  Cork  Holes. 

The  loosening  processes  which  set  in  after  a  drying  of  the  outermost 
tissue  layers  when  the  branches  have  been  killed  by  frost  occur  more  fre- 
c|uently  than  the  phenomena  of  raised  bark,  appearing  in  the  form  of  frost 
wrinkles  and  blisters  in  living  bark  tissue.  In  Fig.  127  is  shown  a  branch 
with  loosely  rolled  back,  flapping,  dry  bark  tatters  on  the  autumn  (Sylves- 
ter) pear.  Even  in  the  soft  wooded  apples  (Morning  Breath)  the 
l)henomenon  was  found  in  May  and  June,  on  branches  and  young,  still 
smooth  barked,  sapling  trunks.  The  periderm  is  seen  at  first  to  be  dis- 
tended in  blisters  ;  later  the  blisters  split  longitudinally.  Th.e  whole  bark 
l)arenchyma  underneath  the  tear  seems  blackened  and  dries  up  quickly. 
The  death  of  the  bark  tissue  advances  further,  the  more  the  tear  widens, 
since  it  at  first  becomes  yellowish  green  and  tender,  then  grows  dark,  col- 
lapses and  finally  dies. 

In  time  these  dead  spots  become  entirely  bare,  since  the  longitudinal 
tear  in  the  periderm  l)lister  lengthens  and  new  cross  tears  divide  the  whole 


1    Ursprung-,  A.,   Beitrag   ziir  Krklarung   de.s  exzentrisclien   Diekenwachstuin.s  an 
Krautpflunzen.     Ber.  d.  D.  Bot.  G.  1906,  Part  9,   p.  498. 


576 

raised  cf)rk  into  many  tatters.  In  drying,  the  xarious  tatters  curl  backward 
and  thereby  expose  tlie  bark  parenchyma  which  has  been  C(jvered.  It 
should  also  be  observed  that  such  cork  tatters  are  most  trc'iucntly  found 
directly  at  the  base  of  the  young,  still  smooth  barked  trunks,  while  the 
younger  shoots  seem  outwardly  unaffected  and  also  sprout  but,  yet,  after 

some  time,  the  leaves  turn  yellow  and  wilt. 
1"he  life  of  the  tree  depends  (ju  the 
extent  and  frequency  of  such  holes  in  the 
cork  which  are  found  repeatedly  separated 
from  one  another  b\-  healthy  spots.  The 
tree  usually  dies  since  the  cambium  under 
the  Idackened  parts  of  the  bark  is  dead. 
The  region  near  the  buds  or  near  cut 
branches  seems  especially  dis})osed  to  such 
injuries   1  rom   frost. 

TiiK    l*HF..\c)iMi;x.\    OF    Discoloration'    in 

Tr  U  N  K  S    ;\  M )    B  RAN  CH  ES. 

bruit  growers  in  spring  pruning  usu- 
all\'  decide  after  a  consideration  of  the  cut 
surface,  whether  a  \ariely  of  fruit  ha:- 
pro\ed  hardy  ior  a  certain  region,  or  has 
been  injured  by  the  cold.  The  decision  is 
made  according  to  whether  the  cut  surface 
is  uniformly  white  or  browned  in  places. 
Tlie  browning  sometimes  occurs  in  circular 
zones,  sometimes  in  flat  surfaces.  In  the 
first  case  (often  on  one  side  of  the  branch  ) 
the  cam])ial  region,  or  the  periphery  of  the 
pith  disc,  the  so-called  pilh  crcnun  where 
the  innermost  ducts  of  the  wood  ring  pene- 
trate into  the  pith  parenchyma,  is  the  centre 
of  the  discoloration.  In  the  surface  brown- 
ing, a  part  of  the  wood  surface  together 
with  the  pith  body  is  usually  attacked  on 
that  side  of  the  branch  where  the  bud  lies 
which  belongs  to  it.  The  discoloration  is  a 
sign  of  the  humification  which  sets  in 
gradually  in  the  walls  wlicn  the  cell  con- 
tents dry  up.  Not  infreciuentiv  phenomena  of  swelling  are  noticed  in  the 
l)r()wn  cell  walls. 

If  difl'erent  parts  of  the  trunk  are  frozen,  brown  stripes  are  found  at 
times  extending  downward  to  different  depths  in  ihe  wood  body;  in  the 
browned  parts  through  its  whole  diameter.  These  stripes  often  have  a 
symmetrical  arrangement  so  that  a  cross-section  through  the  semi-healthy 


127.  Raggedly 
lac  on  branches 
fi-ost. 


11  red 


577 

part  of  the  trunk  shows  a  regular,  brown  figure.  Most  well-known  is  the 
"Landzvchr  cross"  in  the  maple  and  similar  structures  in  Cytisus  and 
Fraxinus.  Cytisus  and  other  Papilionaceae  show  at  times  a  very  attrac- 
tive bright  coloration  of  the  cross-sections  which  should  be  made  of 
practical  use.  The  bright  coloration  is  caused  by  the  different  degrees  of 
browning  in  the  heart  wood  and  cambial  zones. 

Such  regular,  surface-like  discolorations  are  of  rare  occurrence.  The 
most  frecjuent  phenomenon  consists  of  an  irregular  browning  of  those  parts 
of  the  bark  which  surround  a  bud  and  of  those  outcurvings  of  the  pith 
which  lead  to  this  bud.  The  amount  of  tissue  disease  naturally  depends 
upon  the  time  and  intensity  of  the  action  of  the  cold  as  w^ell  as  the  specific 
sensitiveness  of  the  variety  and,  with  equal  intensity,  on  the  age  of  the  axis. 
As  a  rule,  the  younger  a  branch  is,  the  more  extensive  is  the  tissue  browning. 

The  cross-section,  shown  in  Fig.  128,  of  a  pear  branch  injured  by 
artificial  frost,  gi\es  an  insight  into  the  variety  of  browning  due  to  frost. 
In  this,  m  indicates  the  pith  body,  m  k,  the  pith  crown,  ;;;  h,  the  outcurving 
of  the  pith  disc,  called  pith  bridges,  which  lead  to  the  bud,  lying  close  above 
this  section  but  not  visible  in  it.  At  the  place  where  the  bud  lies,  each 
stem  is  more  or  less  thickened  and  pushes  out  from  a  "bud  cushion."  In 
this  bud  cushion  lie  also  the  vascular  bundles  //'  and  (/",  which  pass  down- 
ward into  the  petiole,  in  the  axil  of  which  is  found  the  bud.  The  cap  of 
tissue,  which,  in  the  drawing  lies  above  the  central  cord  of  the  leaf  spur, 
and  seems  laid  against  the  bark  body  of  the  twig,  represents  the  cicatriza- 
tion tissue  which  had  formed  in  the  previous  year  after  the  falling  of  the 
leaf.  The  different  ducts  in  the  cords  of  the  leaf  spurs  and  in  the  wood 
ring  are  distinguished  by  g,'  g"  and  //.  The  wood  ring  (h)  wdth  the  medul- 
lary rays  (ni  s)  shows  diverse,  predominantly  radial  clefts,  while  the  tissue 
openings  (/)  in  the  bark  tissue  usually  extend  tangentially.  Noteworthy  is 
also  a  gaping,  longitudinal  split  which  breaks  the  pith  bridge  and,  by  the 
amount  of  injury,  makes  apparent  that  it  represents  the  part  of  the  branch 
most  susceptible  to  frost. 

In  many  deciduous  trees  there  is  still  a  second  region  of  great  sus- 
ceptibility to  frost,  viz.,  the  hard  bast  cells  and  their  outer  parenchymatous 
covering.  In  my  experiments  w^ith  artificial  freezing,  cherries,  plum^,  red 
beeches  and  apples  were  proved  especially  susceptible,  while  pears  showed 
a  greater  power  of  resistance.  In  the  adjoining  picture  the  bast  bundles 
(b)  are  found  to  be  unattacked.  just  as  little  is  the  collenchyma  (cl). 
The  cambium  zone  (c)  which,  by  its  brown  color,  indicates  to  tree  breeders 
in  the  spring  pruning  of  fruit  trees  that  the  branches  have  been  injured  by 
frost,  has  not  been  browned  in  the  pear.  In  microscopic  investigations,  it 
is  found  that  usually  the  still  cambial,  thin-walled,  young  wood  and  the 
innermost  young  bark,  of  the  same  age,  have  been  browned,  while  the 
meristem  layer,  rich  in  cytoplasm  and  lying  between  both  regions,  appears 
colorless  and  uninjured. 


5/8 

By  surveying  the  cross-section  as  a  whole,  which  may  serve  as  an  ex- 
ample of  frost  discoloration  for  all  trees,  we  see  that  the  region  of  the  bud 
cushion  is  the  most  susceptible  part  of  the  branch.     In  this  region  the  twig 


Fig.    128.     Browning-    and    splitting    ot    the    tissue    of    a    pear    branch    produced    by 

artificial  frost. 


has  the  slenderest  wood  ring  and  the  largest  accumulation  of  parenchyma. 
The  spots  kept  dark  in  the  drawing  represent  the  browned  parts.  So  far 
as  susceptibility  is  concerned,  the  ])ith  crown  and  the  medullary  rays  follow 


579 

next.  The  pith  body  itself  usually  does  not  suffer  until  later  and  the  older 
the  branch  is  the  less  is  the  injury  to  the  pith  body.  In  the  present  case, 
the  experiment  was  carried  out  toward  the  middle  of  May,  at  which  time 
the  storing  of  starch  had  already  taken  place  in  the  pith  and  bark.  The 
injury  to  the  pith  was  limited  here  to  a  checkered  marking  of  the  pith  disc, 
while  the  contents  of  some  of  the  cells  containing  starch  had  turned  brown. 
Investigation  showed  that  the  cytoplasmatic  substances,  and  not  the  starch 
grains  themselves,  were  discolored. 

The  irregular  distribution  of  cells  browned  by  frost  in  all  tissues  can 
be  explained  only  by  the  different  cell  content.  Probably  cells  rich  in 
sugar  are  the  most  susceptible.  The  cytoplasmatic  content  has  suffered 
even  when  the  cell  membrane  is  still  clear.  In  injuries  to  the  pith  crown 
the  narrow,  spiral  ducts  are  the  first  ones  to  be  browned. 

The  Frost  Line. 

Mention  was  made  in  the  previous  section  that  the  fruit  grower  usually 
considers  the  browned  cambial  region  as  an  indication  of  frost  injury. 
This  zone  is  now  often  termed  "frost  line."  Even  unskilled  forest  workers 
showed  me,  as  frost  hues,  the  circular  zones,  setting  in  after  spring  frosts, 
between  older  annual  rings  with  which  we  will  later  become  better  ac- 
quainted in  the  discussion  of  "false  annual  rings"  and  "moon  rings."  By 
these  terms  are  understood  the  brown  circular,  or  zigzag  stripes  found  by 
testing  microscopically  the  tissues  injured  by  frost.  These  stripes  are  com- 
posed of  collapsed  misshapen  parenchymatous  cells,  and  occur  very  often 
but  as  yet  have  been  but  little  studied.  I  have  investigated  more  exactly 
the  phenomenon  on  branches  of  an  apple  tree  which  had  been  forced  in  a 
greenhouse  and  then,  in  May,  exposed  for  only  22  minutes  to  a  temperature 
of  4  degrees  C.  below  zero. 

By  the  middle  of  June,  in  the  experiments  carried  out  on  a  branch  of 
which  the  tip  was  frozen,  a  sharp  boundary  was  found  between  the  dead 
part  and  that  which  had  remained  alive.  This  observation  is  confirmed 
in  all  frost  injuries.  A  gradual  extension  of  the  injured  zone  does  not 
become  noticeable  subsequently,  if  no  secondary  factors,  such  as  wood- 
destroying  fungi,  enter  into  co-operation.  However,  the  action  of  the  frost 
itself  can  radiate  out  into  the  healthy  tissue  in  the  death  of  certain  parts  as 
was  the  case  in  the  experiment  under  consideration.  If  the  branch  which 
had  died  after  its  tip  was  frozen  was  cut  off  directly  below  the  bud  which, 
adjoining  the  dead  tissue,  had  remained  healthy  and  liad  sprouted,  a 
browned,  sharply  defined  stripe  was  found  to  extend  from  the  dead  places 
out  into  the  healthy  part  of  the  axis  past  three  healthy  buds.  This  stripe 
traversed  the  axis  in  a  diagonal  direction  from  the  outside  inward. 

The  sharp  limitation  of  the  brown  stripe  and  its  diagonal  course  were 
explained  by  a  microscopic  investigation.  This  proved  that  the  main 
vascular  bundle  of  the  lowest  dead  bud  of  the  frozen  tip  is  involved  here. 
This  was,  therefore,  a  case  where  the  death  of  the  bud  gradually  induced 


s8o 


the  dying  hack  of  the  condnctinij  curd  (vascular  bundle)  ^vhich  traversed 
the  healthy  tissue  and  the  tissue  zchich  became  diseased.  This,  therefore, 
could  be  the  only  after-efifect  which  can  take  place  in  frost  injuries  in  case 
there  is  no  subsequent  parasitic  infection. 

In    order    to    discoxer    wliich 

might  1)0  the  \  ery  first  effect  of 
frost  on  the  tissue  of  the  tree 
and,  therefore,  which  injury  sets 
in  with  the  appearance  of  \er\- 
lii^ht  frosts,  a  whole  course  of 
experiments  was  made  on  the 
effect  of  slight  degrees  of  cold, 
but  they  did  not  lead  to  the  de 
sired  results,  lather  no  effect  at 
all  was  shown  or  the  al)o\e-men- 
tioned  initial  stages  api)eared 
simultaneously.  The  pruning  was 
extended  further  and  further 
back  from  the  completely  frozen 
tissues  into  the  healthy,  basal  i)art 
of  the  twig  and  obser\  ations  were 
made  to  see  which  disturbance 
had  extended  farthest  from  the 
frost  centre  into  the  healthy  tissue. 
The  frost  action  which  could 
be  traced  farthest  into  the 
healthy  zvood  was  found  to  be 
the  sivellinii  of  the  intercellular 
substances,  i.  e..  the  middle  la- 
mella {V\g.  I2()  i). 

J  found  this  striped  swelling 
and  browning  of  the  intercellular 
substances  to  be  in  general  more 
frecjuent  tangentially  than  in  the 
direction  of  the  medullar  rays, 
esi)ecially  often  near  the  old 
autumn  wood,  i.  e.,  in  the  first  vas- 
cular layers  of  the  si)ring  wood. 
But  this  condition  of  the  inter- 
cellular substances  is  rarel}"  found  by  itself;  it  is  usually  associated  with  a 
slight  yellowish  colormg  and  swelling  of  the  secondary  membranes  of  the 
adjacent  wood  cells  (Fig.  129  h).  Tn  some  cases  this  change  becomes  so 
extensive  that  the  entire  cell  lumen  is  filled,  excepting  a  narrow  cavity  (hh). 
The  power  of  refraction  becomes  extraordinarily  weak  with  the  swell- 
ing, being  retained  only  by  the  outermost  manbrane  and  the  firmer,  inner 


Fig.   129.      vSwel 


)f  the  ct 
111    frost. 


58i 

lining?.  The  swelling  can  become  so  great  that  even  the  outermost  mem- 
brane tears  (p)  and  this  tearing,  as  a  rule,  extends  to  several  adjacent  cells, 
so  that  the  changed  secondary  membrane  with  the  swollen  intercellular 
substances,  coalesces  into  a  uniform  yellowish  to  brown  stripe  in  which 
are  recognizable  parallelly  deposited   remnants  of  the  primary  membrane 

(St). 

It  has  thereby  been  proved  experimentally  that  processes  of  loosening 
are  initiated  in  the  cell  membranes  by  frost.  These  become  apparent  in 
the  so-called  "frost  lines." 

Internal  Splitting  of  the  Trunk  and  Branches. 

In  the  section  on  frost  blisters,  the  disturbances  were  considered  which 
take  place  in  smooth  barked  branches  and  trunks  without  any  external 
injury  being  noticeable  at  first.  Not  until  the  year  following  the  produc- 
tion of  the  blister  do  the  primary  bark  layers,  which  cover  the  frost  blister, 
rupture  because  this  blister  has  gradually  enlarged.  These  torn  bark 
layers  surround  the  protruding  new  structure  as  dried  edges.  The  cause, 
however,  is  to  be  seen  only  in  the  raising  up  of  the  bark  layers,  without 
any  splitting  of  the  wood. 

If,  however,  the  occurrence  out  of  doors  in  so-called  frost  holes,  i.  e., 
places  where  late  frost  occurs  almost  annually  and  very  extensively,  is 
more  closely  examined,  blister-like  protuberances  will  be  found  on  the 
branches  and  trunks  which  internally  show  repeated  splittings  of  the  annual 
ring. 

I  have  accidentally  succeeded  in  producing  such  blisters  artificially  bv 
exposing  to  sharp  brief  frost  action  branches  in  which  the  wood  ring  of  the 
current  year  had  attained  a  considerable  thickness.  The  subjoined  Fig.  130 
represents  a  healed  inner  wound,  due  to  the  splitting  of  a  cherry  branch. 
The  frost  wound  has  been  produced  by  a  one-sided  raising  of  the  bark  from 
the  young  wood,  a  is  the  old  wood  of  the  previous  year;  b,  the  spring 
wood  of  the  current  year,  formed  before  June;  g  is  the  sapwood  region 
with  the  normal  cambial  zone.  About  this  time  the  branch  vv'as  placed  in 
a  freezing  cylinder.  It  was  found,  in  the  subsequent  investigation,  that  the 
bark  had  been  split  off  from  the  sapwood  in  a  wide  curve  (s  p)  and  that 
the  young  wood  (b)  seemed  split  radially.  The  splitting  extended  along 
the  medullary  rays  which  more  rarely  were  torn  apart  than  loosened  at  one 
side  from  the  prosenchymatous  cells  and  ducts  and  then  partially  dried  up. 
A  radial  enlargement  of  the  holes  represented  at  0  in  the  drawing  takes 
place  in  many  cases  because  of  the  extensive  drying  of  the  prosenchy- 
matous cambial  elements  which  are  still  partly  thin-walled.  In  general  the 
radial  clefts  in  the  wood  remain  slender  and  only  the  walls  of  the  elements 
which  drew  apart  from  one  another  turn  a  deep  brown. 

Near  the  breaking  buds  in  which  a  medullary  bridge  traverses  the 
whole  wood  body  from  the  pith  to  the  bark  in  all  trees,  the  tissue  is  more 
tender,  the  number  of  thick-walled  cells  is  less;  the  elements  lying  next  to 


582 

the  medullary  rays  have  developed  into  wood  cells  with  strongly  refractive 
walls,  while  the  cell  forms,  to  be  found  at  a  further  distance  from  t\Vo 
medullar}'  rays,  are  still  thinner-walled  and  richer  in  content,  also  showing 
no  broad  ducts  between  them.  In  such  sapwood  layers,  near  the  bud,  a 
tangential  clefting  of  the  tissue  on  the  line  between  the  wood  of  the  pre- 
vious year  and  that  of  the  current  year  is  found  at  times  as  the  continu- 
ation of  the  radial  split. 

Radial  holes  (/)  in  the  tissue  of  the  secondary  bark  (>/).  corres])ond 
to  tlie  clefting  of  the  wood  body,  while  the  j)rimary  bark  ( i)i )  with  its  bard 
bast  bundles  (h)  shows  no  ruptures  whatever  but  only  a  partial  browning 


^■y 


FiK.  i; 


Internal  .splitting-  of  a  clion-y  Viranrh   produced  by  artificial  tro.st. 


of  the  contents  and  of  the  walls  of  some  of  the  hard  bast  cells  and  bark 
parenchyma  cells  (r).  Here  also  the  holes  are  produced  often  by  the 
separation  from  one  another  of  the  different  tissue  complexes,  less  often 
by  the  splitting  of  the  membranes  of  the  individual  cells.  The  thin- 
walled  cell  groups  which,  in  the  secondary  bark,  correspond  to  the  bast 
parenchyma  of  the  primary  Itark,  separate  from  the  bark  rays  which  ha\e 
already  advanced  further  developmentally  and  are,  therefore,  thicker 
walled.  At  the  sides  of  these  bark  rays  the  rows  of  cells,  accompanying 
the  hard  bast  cords  and  containing  calcium  oxalate,  are  especially  noticeable. 
The  radial  splits  and  clefts,  however,  are  only  secondary  phenomena 
in  comparison  with  the  great  tangential  clefts  {s  p)  which  separate  the  bark 


583 

from  the  wood.  Tlie  line  of  separation  extends  irregularly,  sometimes  in 
the  cambial  layers  of  the  bark,  sometimes  into  those  of  the  sap-wood.  Since 
it  can  be  assumed  that  in  all  parts  of  the  tissue  of  the  line  of  separation  an 
equally  strong  strain  was  active  in  producing  the  tear,  it  is  evident,  from 
the  irregularity  of  the  line  of  separation,  that  the  tissue  at  the  same  radial 
distance  from  the  centre  of  the  branch  does  not  possess  throughout  the 
same  firmness.  Such  an  irregularity  is  shown  by  the  tissue  fragments  {k) 
which,  remaining  attached  to  the  sapwood,  die  later  and  are  indicated  at 
the  side  of  the  projecting  wood  (/), 

^^'ith  the  exception  of  these  fragments  very  little  collapsed  tissue  is 
found  at  the  torn  place,  even  the  cells  of  the  youngest  bark  (w),  which 
have  turned  a  deep  brown  and  become  poor  in  contents,  have  not  collapsed. 
Instead  they  have  become  stiff  and  their  walls  (/")  much  more  resistant  to 
sulfuric  acid. 

The  healing  of  such  wounds  does  not  as  a  rule  take  place  by  lateral 
circumvallation.  Rather,  in  similar  places,  a  radial  stretching  of  the  older 
cambial  parenchyma  is  observed  at  first.  Later  isolated  meristemic  aggre- 
gations are  produced  in  the  bark  between  the  bark  rays  which  form  new 
wood  elements.  The  new  wood  gradually  presses  the  tissue  layers  (m) 
which,  in  this  case,  have  not  been  changed,  against  the  split  sapwood  in  the 
direction  /,  o,  e,  and  forms  from  the  dead  tissue  remnants  a  brown  stripe 
which  becomes  narrower  with  a  greater  wood  accumulation  abov^e  the  place 
of  rupture,  i.  e.,  greater  pressure.  The  isolated  meristemic  zone  of  the 
wood  bundles,  produced  in  the  raised  pieces  of  the  bark,  later  unite 
laterally  with  one  another  and,  finally,  with  the  cambial  zone  (/),  pro- 
duced on  all  sides  of  the  still  uninjured  branch.  Such  a  blister,  produced 
by  tangential  raising  and  radial  splitting  of  the  wood  ring,  may  remain 
recognizable  externally  for. many  years. 

Open  Frost  Tears. 

An  apparently  very  unessential  phenomenon,  to  be  found  most  easilv 
in  vigorously  growing  nursery  specimens,  is  tlie  occurrence  of  small  tears 
which  have  been  overgrown.  These  extend  also,  more  or  less  like  blisters, 
above  the  smooth  bark  but  are  distinguished  from  those  already  described 
in  that  they  have  a  long  grove  on  their  upper  surface.  From  this  it  is 
evident  that  they  have  been  produced  by  the  coalescence  of  the  two  edges 
of  wounds  which  have  pushed  forward  like  lips.  These  elevations  grow 
less  and  less  conspicuous  with  later  growth  and  finally  have  no  further  sig- 
nificance for  the  life  of  the  trunk. 

These  are.  however,  of  uncommon  theoretic  importance  in  explaining 
the  production  of  the  tissue  excrescences  described  later  as  frost  canker. 
So  far  as  my  investigations  ha\e  gone,  they  support  the  theory  that  the 
swellings  of  frost  canker  have  their  origin  in  such  small  tears  as  are  pro- 
duced in  the  spring  at  the  time  of  the  most  luxuriant  cambial  activity  of 
the  trunk.     .Such  tears  are  found  usually  in  the  immediate  proximity  of  the 


5^4 

hiuls  and  iheir  appearance  can  he  traced  hack  primarily  to  a  local  increase 
in  growth.  It  cannot  he  denied  that  this  is  the  most  pertinent  explanation, 
but  the  condition  of  the  wound  in  many  cases  also  indicates  some  frost 
action. 

It  is  finally  possihle.   in   artificial    frost   experiments,  to  produce  such 
frost  tears  and  thereby  ])ut  an  end  to  such   douhts.     Fig.    131    gives  the 


ig-.    131.      Cross- sect  i 


throush    th(>    Inui    cushii 
aitiflcial  frost. 


larch    bi-anch,    injured    l)y 


anatomical  appearance  of  such  a  v^ound  which  had  l)een  produced  by  the 
action  of  artificial  cold  on  a  larch  branch  a  year  and  a  half  old.  The 
branch  was  cut  through  a  bud  cushion;  the  wood  (h),  which  otherwise 
would  have  formed  an  uniform  ring  about  the  pith  (m),  appears  inter- 
rupted by  the  broad  parenchymatous  medullary  bridges  (m-mtr). 


585 

This  tissue  has  been  killed  b)-  frost  and  torn  by  the  subsequent  drying. 
The  parenchyma,  lying  in  the  direction  z'-i'o,  had  not  been  formed  at  the 
time  of  the  frost  action  (May  i8th),  but  the  splitting  of  the  medullary 
bridge  was  extended  outward  through  the  bark.  The  bark  in  the  cambial 
zone  at  that  time  was  also  split  away  from  the  sapwood  at  both  sides  and 
formed  the  split  (s  p)  but  only  the  cells  lying  directly  on  the  edges  of  the 
wound  had  died  and  partially  dried.  The  two  sides  of  the  bark  above  the 
split  (s  p),  which  originally  had  been  separated,  at  once  formed  the  initial 
stages  of  the  overgrowth  edges  in  the  manner  common  to  all  processes  of 
circumvallation  by  the  outcurxing  of  the  peripheral  healthy  cells  and  their 
division.  These  o\ergrowt]i  edges  are  formed  further  and  further  out 
toward  one  another  until  in  a  short  time  they  coalesce. 

The  place  of  coalescence  of  the  circumvallation  edges  (n  r)  may  be 
recognized  by  the  diseased  depression  {v  a),  but  especially  by  the  position 
of  the  hard  bast  cells  (b).  which  seem  inclined  toward  one  another.  The 
whole  tissue,  which  covers  the  split,  has  been  formed  anew  in  the  course 
of  six  weeks  (the  wound  was  investigated  on  the  4th  of  July).  The  old 
bark,  which  had  been  split  by  the  frost  tear,  is  pressed  back  by  the  lip-like, 
protruding  circumvallation  edges  and  now  surrounds  the  new  structure 
like  a  sharp  edge  (t).  The  circumvallation  edge  at  this  time  had  formed 
wood.  The  whole  thick-walled  zone  (hp)  is  new  wood.  This,  however, 
has  been  produced  with  so  little  bark  pressure  that  it  has  become  parenchy- 
matous and  short  celled.  Only  later  did  the  cambial  zone  (c-c),  produced 
by  the  coalescence  of  the  zones,  which  had  been  isolated  in  two  halves,  form 
normal  wood  elements  and  deposit  firmer  layers  about  the  frost  wound. 

Similar  to  this  injury  to  the  larch  is  a  wound  produced  on  an  apple 
branch  by  the  action  of  cold  at  3  degrees  C.  which  lasted  for  25  minutes 
in  July  (Fig.  132).  In  this,  a  indicates  the  old  wood  of  the  previous  year; 
/;,  new  wood  formed  up  to  July;  c,  the  region  in  which  the  cold  had  killed 
the  tissue.  In  the  very  luxuriant  overgrowth  edges,  extending  above  the 
surface  of  the  wound,  the  spirally  curved  cambial  zone  (/)  has  produced 
a  thick  new  bark  {g )  and  a  new  wood  body  (e),  divided  radially  by  the 
medullary  rays  (d).  But  this  formation  of  wood  from  prosenchymatous 
elements  begins  first  rather  far  back  in  the  circumvallation  edge.  The  lip- 
like part  of  the  edge,  lying  in  front  of  it,  consists  of  parenchyma  wood,  on 
the  edge  of  which  may  be  recognized  gradually  dififering  prosenchymatous 
cell  groups  (h).  In  the  same  radius,  in  which  the  first  thick- walled  wood 
cells  occur,  the  beginnings  of  the  hard  bast  cells  (h  b)  appear  in  the  bark. 

The  circumvallation  edges  extend  over  the  bark  as  a  knob  with  a  lip- 
like  cleft.  This  appearance  is  retained  because  of  the  natural  swellings 
which  are  met  with  at  times  in  the  branches  from  cankered  trunks  of 
apple,  beech,  ash  and  cherry  trees,  and  which  I  consider  to  be  the  initial 
stages  of  the  closed  canker  swelling  (cf.  Fig.  135  in  the  ^following 
section). 


586 
Canker  (Carcinoma). 

As  "canker,"  I  consider  those  wounds  which  develop  their  overgrowth 
edges  into  excessive  wood  swellings.  The  character  of  the  excrescence  lies 
in  the  exclusive,  or  predominant  fonnation  of  parenchyma  wood  instead 
of  the  normal  prosenchymatous  wood  elements.  The  canker  excrescences 
have  a  typical  form  for  each  tree  variety. 


0:   'O'vJm, 


OK 


Fig-.  132.     Overgrowing  frost  split  in  apple  lii-anch,  produced  by  artificial   cold. 


a.     Canker  of  the  Apple  Tree. 

The  canker  of  the  apple  tree  occurs  in  two  forms,  of  which  the  more 
common  one  is  distinguished  by  a  broad,  central  exposed  wood  surface 
formed  from  the  open,  protruding,  blackened  wood  body  and  is  surrounded 
l)y  roll-like,  strong  calluses,  developing  outwardly  each  year  like  terraces. 
At  the  centre  of  the  wound  is  found  frequently  the  remainder  of  a  small 
stump  of  a  branch.  This  is  indicated  in  Fig..  133  by  :;,  while  the  nearest 
overgrowth  edge  is  indicated  by  «'.  ^\'e  see  how  the  wound  surface  gradu- 
ally increases  since  the  first  formed,  still  rather  flat  edge  dies  and  turns 


58/ 

black,  while  that  of  the  next  year  (n")  develops  in  the  form  of  terraces. 
The  process  is  repeated  from  year  to  year  (see  u"'-u"")  until  nearly  the 
whole  extent  of  the  axis  has  been  attacked  by  the  canker  excrescence  and 
dies.  Such  places,  with  open  wounded  surfaces  which  become  wider  and 
wider,  are  called  "open  canker." 

The  increase  in  thickness  of  the  overgrowth  edges  toward  the  outside 
is  explained  by  the  fact  that  plastic  material,  coming  from  above,  from  still 
living,  leaved  twigs,  has  to  be  divided  in  each  successive  year  over  a  smaller 
part  of  the  twig  or  trunk  surface  because  of  the  retrogression  of  the  over- 
grow^th    edges    and   accordingly    provides    relatively    more    al)undant    food 


Fig-.  133.     Open  apple  canker. 


Fig.  134.     Closed  apple  canker. 


substances  for  the  formation  of  new  parts,  in  the  cambial  zone,  which  is 
growing  shorter  and  shorter. 

The  closed  canker  (Fig.  134)  when  completely  developed,  represents 
approximately  a  spherical  wood  excrescence  (u)  at  times  exceeding  the 
diameter  3  or  4  times,  knotted  and  usually  completely  covered  w-ith  bark. 
This  wood  excrescence  is  flattened  at  its  tip  and  deepened  in  the  centre  of 
the  upper  surface  like  a  funnel  (/).  In  contrast  to  open  canker,  this  swell- 
ing covers  a  much  smaller  part  of  the  axis  bearing  it  but  makes  up  for  its 
lesser  extent  in  width  liy  a  considerably  greater  radial  elevation,  i.  e.,  greater 
height. 


588 

I>li<^ht  may  often  lie  proved  also  on  the  liranches  and  twigs  on  which 
occur  canker  excrescences.  In  all  three  varieties  of  injury  a  bright  red  to 
brown,  flat  conical,  or  oval  fruit  body  of  Nectria  dilissima  may  be  found, 
not  infrequently,  in  winter  on  the  dead,  cracked  edges  of  the  wound. 

If  a  cross-section  is  made  througli  the  excrescence  of  a  closed  canker, 
approximately  the  following  i)icture  is  found. 

We  see  (Fig.  135)  the  whole  large  swelling  divided  radialh'  into  two 
groups  by  the  split  (sp)  with  its  roll-like  edges.  This  cleft  forms  the  inner 
continuation  of  the  outwardl}-  recognizable  funnel-like  depression  on  the 
flattened  toj)  oi  the  canker  excrescence  (  b'igs.   134,  135  /).     At  the  bottom 


Fi{?.  ]3i).     Cross-sec-tion  through  ;in  apple  b 


met  of  "closed  ranker." 


of  the  cleft  usually  lies  a  brown,  mealy,  or  putty-like  mass  which  is  found 
to  consist  of  humified  cell  remnants.  The  edges  (r)  of  the  cleft  are  also 
strongly  browned.  They  arc  formed  by  thick-walled,  parenchymatous-like 
porous  cells,  provided  with  a  dead,  brown  content.  The  further  back  one 
goes  from  the  edges  of  the  cleft,  or  the  point  of  dying,  toward  the  healthy 
tissue  of  the  trunk,  the  less  noticeable  is  the  brown  color.  The  tissue  be- 
comes white  and  is  formed  of  parenchymatous  wood  which  contains  an 
unusual  amount  of  starch,  (jroups  of  strongly  refractive  cells  gradually 
appear  in  these  masses  of  parenchyma  wood.  They  are  clearly  elongated, 
thick-walled  wood  cells  which,  isolated  at  times,  or  in  small  groups,  appear 
irregularly  distributed  in  the  parenchymatous  wood.      (Fig.  135  h).     Com- 


5^9 

pare  the  cross-section  given  in  Fig.  132,  due  to  an  artificially  produced  frost 
split  on  the  branch  of  an  apple  tree.  Parallel  with  the  appearance  of  the 
first  wood  cells  is  that  of  the  hard  bast  cells  (Fig.  132  h  h)  in  the  bark. 
These  prosenchymatous  elements  in  the  edge  of  the  wound,  formed  of 
parenchymatous  wood,  are  the  initial  stages  of  the  normal  annual  ring  for- 
mation and  extend  from  the  edge  of  the  wound  backward,  approaching  one 
another  more  and  more  closely,  until  they  have  united  in  a  normal  annual 
ring  on  the  healthy  side.  If  we  start  with  the  normal  annual  ring  zone  on 
the  healthy  side  of  the  trunk,  we  may  thus  conceive  this  formation  as 
follows;  it  is  as  if  the  prosenchymatous  tissue  of  a  healthy  annual  ring 
(Fig.  135  c  h)  had  been  divided  into  several  radiating  branches  (Fig. 
135  ^^)  within  the  canker  excrescence  which  chiefly  consists  of  parenchyma 
wood,  rich  in  starch  and  containing  here  and  there  large  crystals  of  calcium 
oxalate.      (Radial  division  of  the  annual  ring.) 

The  edges  of  the  wound,  themselves,  are  not  found  united;  the  cleft, 
therefore,  in  spite  of  its  narrowness,  has  never  completely  coalesced  since 
the  outermost  cells,  edging  the  cleft,  constantly  die. 

In  proportion  to  the  uncommonly  luxuriant  new  formation,  the  number 
of  dying  cells  in  "closed  canker"  is  very  small.  The  dead  place  here  always 
forms  only  a  narrow  tv^isted  cleft ;  while  in  "open  canker"  the  originally 
dead  tissue  represents  a  broad  surface  and  the  dying  back  of  the  edges  of 
the  wound  extends  so  far  that  not  only  the  wood  surface  which  first  remains 
uncovered,  but  also  each  overgrowth  edge  is  incompletely  covered  by  the 
succeeding  one. 

The  characteristic  radial  division,  or  splitting  of  an  annual  ring  (Fig. 
135  nh,  h)  within  the  woody,  parenchymatous  edges  of  the  excrescence  is 
less  conspicuous  in  open  canker  and  may  completely  disappear  in  case  the 
entire  trunk,  which  has  remained  healthy,  participates,  at  the  height  of  the 
canker-wound,  in  the  exorbitant  thickening,  i.  e.,  excludes  a  one-sided  hy- 
pertrophy of  the  trunk. 

The  determination  of  the  dry  substances  in  normal  and  cankerous 
wood  in  the  cherry  gives  a  proof  of  the  softness  of  the  tissue  in  the  canker 
excrescence.  Normal  wood  has  6O.9  per  cent,  of  dry  substances ;  the 
overlying  canker  wood,  only  45.1  per  cent. 

From  the  fact  that  the  canker  excrescence  frequently  exceeds  consid- 
erably the  thickness  of  the  two  or  three  year  old  branch  which  bears  it,  we 
may  conclude  that  the  excrescence  which  is  never  found  on  the  green  shoot 
of  the  current  year.  i.  e.,  begins  only  in  the  woody  twig,  must  grow  very 
rapidly.  With  such  rapid  development  of  the  tissue,  it  is  not  surprising 
that  the  fluctuations  between  cloudy,  wet  weather  and  periods  of  drought 
can  so  manifest  themselves  that,  within  one  summer,  alternate  zones  of 
thin-walled  and  thick-walled  wood  are  produced  in  the  canker  excrescence. 
This  is  found  if  the  darker  zone,  extending  from  the  pith  (m)  in  Fig.  135, 
is  traced  further.  It  corresponds  to  the  thick-walled  wood  elements  and, 
in  the  normal  part  of  the  trunk,  indicates  the  autumn  wood  in  contrast  to 


590 


the  more  alamdaiU  sijriiig  wood  but  always  within  the  canker  excrescence 
prosenchyma  wood  in  contrast  to  parenchyma  wood.  The  illustration 
shows  the  last  formed,  dark  rings  in  the  health}-  part  divided  radialh' 
toward  the  diseased  part,     n  indicates  a  diagonall\  cut,  dead  branch. 

This  lu.xuriance  of  growth, 
which  manifests  itself  by  the 
formation  of  the  radiating  canker 
excrescence,  ma}'  not,  howe\er, 
lead  universally  to  the  conclusion 
that  the  growth  of  the  tree  as  a 
whole  is  always  luxuriant.  On 
the  contrary,  a  regular  occur- 
rence of  canker  knots  is  found  in 
weak,  slender  trees  in  certain 
localities. 

Cankered  and  abo  blighted 
trees  usuall}-  show  a  \er}  luxuri- 
ant lichen  growth.  At  the  central 
place  of  attachment  of  such 
lichen  cushions  it  ma}-  often  be 
proved  that  the  cork  layers  of  the 
branch  have  been  separated  and 
the  thailus  cords  shoxed  in  be- 
tween them.  In  fact  I  could 
obserxe  cases  in  which  the  lichen 
thailus  penetrated  the  whole  pro- 
tect i\e  cork  laver  f)f  the  branch 
and  reached  the  collench\-matous 
l)ark  cells,  some  of  which  still 
contained  chlorophyll.  The  lichen 
growth  may,  therefore,  not  be  as 
injurious  as  the  yellow  and  green 
forms  are  generally  declared  to 
be.  How  much,  however,  the 
spread  of  the  lichen  depends  upon 
some  indi\  idual  peculiarity  of  the 
tree  is  still  unknown  to  us  (prob- 
abl}-  a  greater  tenderness,  poros- 
it}-  and  torn  condition  of  the 
bark  ),  as  is  explained  by  an  obser- 
vation on  grafted  older  trunks  of  hVaxinus.  The  stock,  possibly  one  to  one 
and  a  half  meters  tall,  appeared  only  scantily  covered  with  lichens  while 
the  grafted  scion,  which  at  times  bore  a  1.2  to  15  year  old  crown,  was  closely 
covered  by  lichen  growth.  As  a  rule,  cankered  places  on  old  ash  trees, 
standing  on  wet  ground,  are  coxered  with  lichen. 


Fi.^-.      1?S.     .Up 


ipp 


591 


In  regard  to  the  juvenile  condition  of  cankered  places,  I  mentioned 
under  Frost  Tears  that  I  considered  such  small  tears  to  be  the  initial  stages 
of  the  canker  excrescences.  In  the  adjacent  picture  I  give  an  illustration 
of  two  branches  in  natural  size,  as  I  found  them  on  an  apple  tree,  suilering 
from  canker.  In  Fig.  136  a  is  shown  an  oval  depressed  part  of  the  bark 
near  a  bud.  The  growth  which  took  place  after  the  injury  has  so  in- 
creased the  tension  at  the  dead  spot  that  the  dry-  bark  at  its  centre  has  split. 
At  h  we  see  a  somewhat  further  advanced  stage.  The  dead  bark  in  the 
middle  of  the  wound  has  already  been  raised  by  the  overgrowth  edges,  ap- 
pearing at  the  side  and  united  with  one  another.  The  places  indicated  at  c 
and  c'  in  Fig.  136  show  conspicuous,  protruding  knots,  with  a  uniform  new 
bark  coxering.  At  r  are  the  dried  scaley,  somewhat 
distended  edges  of  the  primary  bark  of  the  branch, 
which  has  been  ruptured  by  frost.  In  this,  the  places 
are  not  near  a  bud  ;  c  is  in  the  middle  of  an  internode 
and  c'  on  the  side  opposite  the  bud.  In  Fig.  136  i/ 
t]-!c  wound  has  attacked  the  tissue  surrounding  a 
bud.     The  bud  is  dead  and  the  region  depressed. 

The  wound  surface  is  here  very  great,  the  bark 
/■',  under  which  air  has  penetrated,  is  still  connected 
with  its  healthy  surroundings  and  that  newly  pro- 
duced on  the  edge  of  the  dead  spot  has  caused  a 
widening  of  the  branch,  as  is  very  frequent  in  blight 
wounds. 

Reproductions  of  open  canker  of  the  apple  tree, 
as  well  as  closed  canker,  show  that  the  region  of  the 
trunk,  bearing  buds  or  young  sprouts,  is  preferred  in 
the  formation  of  canker.  Such  a  preference  of  the 
region  below  a  short  twig  is  shown  in  the  adjacent 


fie u re  of 


small  pear  branch  (Fig.  137).     Directly 


Fig.      137.      Preference 

shown  by  frost  for 

the  base  of  the 

branch. 


underneath  the  short  twig  at  a  wt  find  a  deep,  already 
overgrown  frost  tear.  At  h,  the  region  of  the  short- 
ened branch  ring  w  ith  its  short  internodes  and  many 

weak  buds,  the  bark  has  been  split  by  many  small  tears  and  dried  like  scales. 
The  young,  upper  part  {c)  of  the  branch  has  remained  healthy.  In  such 
bark  splits  frequently  the  strongest  overgrowth  edges  are  found  which  often 
rei)resent  a  single  enclosed  knot  covered  \^'ith  uniform  bark,  but  having  often 
two  lip-like  excrescences  touching  one  another  and  usually  running  longi- 
tudinally. Such  wound  edges  at  times  appear  folded  toward  the  twisted 
central  cleft,  the  original  bark  tear,  from  there  falling  away ;  they  then 
resemble  the  canker  wounds.  The  bark  tears  do  not  always  represent 
longitudinal  clefts  and,  accordingly,  the  overgrowth  does  not  always  occur 
in  the  form  of  two  protruding  lips  but  rather  as  knotty,  spherical  elevations 
with  a  crater-like  central  depression.  On  a  branch  9  mm.  thick,  I  found 
canker  knots  13  mm.  high  and  35  to  45  mm.  broad.     Other  branches,  just  as 


592 

thick  and  two  years  old,  at  times  showed,  only  \en-  weakl}-  callused.  uni- 
formly closed  protuberances,  covered  with  new  hark,  which  l)reak  out  from 
rhe  cleft  in  the  old  bark. 

The  studies  here  cited  determine  that  each  canker  spot  has,  as  its 
initial  sta^e,  a  wound  which  extends  as  a  narrow  radial  tear  into  the  cam- 
bium and  kills  it  slij^jhtl}-  back  from  both  sides.  This  wound  must  be 
produced  shortly  before,  or  at  the  time  w  hen  the  trunk  of  the  tree  develops 
the  greatest  growth  activity,  since  the  wound  surface  will  attemi)t  at 
once  to  form  a  covering  by  means  of  very  luxuriant  overgrowth  edges. 
'J1ic  luxuriance  of  these  overgrowth  rolls  manifests  itself  in  the  fact  that. 
especially  in  the  closed  form  of  canker,  a  partition  of  rhe  annual  ring 
usually  occurs,  the  edges  of  which  chiefl}-  consist  of  parenchyma  wood. 
The  edges  of  the  wound  are  very  susceptible  because  of  this  porous  struc- 
ture, so  that  they  succumb  with  ease  to  injurious  attacks. 

We  must  consider  frost  as  the  cause  of  these  forms  of  disease  because 
it  has  been  possible  to  produce,  by  the  action  of  artificial  frost,  the  same 
initial  stages  as  are  found  in  canker  wounds. 

How-ever,  a  number  of  \  er}'  reliable  observers  have  determined  that  it 
is  possible  by  the  injection  of  a  (capsule)  fungus,  Nectria  ciitissii}ia\  to 
produce  wounds,  the  forms  of  which  resemble,  perfectly  those  of  the  open 
canker  of  the  apple.  I  can  confirm  these  statements  by  my  own  experi- 
ments. One  has  indeed  a  right  to  speak  of  a  fungous  canker  but  the  above 
named  parasite  is  not  able  to  attack  an  uninjured  axis.  It  can  spread  de- 
structively only  if  it  gets  into  a  bark  wound.  All  inoculation  exi)eriments 
agree  in  this.  ( )n  the  other  hand,  the  same  Xectria  is  found  in  apple  trees, 
beeches  and  other  varieties  of  deciduous  trees  without  causing  any  canker 
excrescences  whatever.  Therefore,  it  cannot  be  termed  the  specific  incitor 
of  canker  excrescences  but  will  give  rise  to  these  only  occasionally  when 
very  definite  secondary  conditions  co-operate  simultaneously.  Besides  the 
presence  of  a  fresh  wound  surface,  it  depends  also  upon  the  specific  pecu- 
liarity of  the  tree,  i.  e.,  the  cultural  variety,  which  must  possess  the  ability 
to  respond  to  the  wound  stimulus  with  ciuickly  developing,  very  luxuriant 
overgrowth. 

This  ability  is  so  ty[)ical  that  in  general  practice  one  speaks  of 
"Varieties  with  a  canker  tendency."  Besides  this,  experience  has  shown 
that  the  tree  easilv  becomes  cankered  in  certain  places  and  kinds  r)f  soil. 
These  are  the  so-called  frost  holes,  having  a  marshy  soil  consistency,  an 
impervious  sub-soil,  etc. 

These  are  well-established  facts.  If  we  now  keep  in  view  the  fact 
that  Nectria  ditissima  must  have  some  wound  for  infection,  we  must  ask 
whence  came  these  w-ounds.  I-'rom  observations  made  in  nature  and  from 
the  results  of  experiments  with  artificial  frost,  we  are  convinced  of  neces- 
sity that  frost  injuries  are  the  most  easily  accessible.     Paparozzi  holds  to 


1   See  literature  in  the  second  volume  of  this  manual,  p.  20'J. 


593 

the  same  standpoint  for  the  canker  of  pear  trees'.  Tf  the  frost  wounds  are 
flat  surfaces  such  as  will  be  found  later  under  "Blight,"  the  Nectria  will 
infest  the  tree  without  its  formation  of  luxuriant  overgrowth  edges.  Tf, 
however,  narrow  frost  tears,  extending  into  the  cambium,  are  produced 
into  which  the  Nectria  find  entrance,  the  tree  responds  with  the  formation 
of  canker  excrescences  in  case  climate,  habitat  or  specific  characteristics 
make  it  capable  of  so  doing. 

Accordingly,  the  fungous  canker  also  appears  to  be  essentially  depend- 
ent upon  frost  injury  and  its  combatting  or  avoidance  will  have  to  be 
carried  on  with  due  consideration  of  the  danger  from  frost. 


b.     Crotch  Cankkr  in  Fruit  and  Forest  Trees. 

"Crotch  canker,"  which  is  of  frequent  occurrence  in  forest  and  fruit 
trees,  should  be  mentioned  as  an  especial  form.  It 
consists  of  frost  wounds  found  at  the  bases  of  the 
branches,  or  twigs,  which  belong  to  the  group  of 
open  cankers  and  are  formed  from  black,  dead 
surfaces  differing  in  size  with  luxuriant,  irregular 
overgrowth  edges.  The  angle  where  the  branch 
joins  the  main  trunk  is  separately  attacked  in 
many  varieties.  In  the  so-called  ''bifitrcations."  or 
forkings,  where  the  difference  between  the  main 
and  the  lateral  branch  disappears  so  that  two  ecfually 
strong  branches  grow  out  from  one  point,  the  ex- 
posed and  blackened  place  in  the  wood  is  usually 
elevated  at  both  sides  and,  accordingly,  the  over- 
growtli  edge  is  formed  from  the  material  of  both 
branches  (cf.  Fig.  138).  Aside  from  the  more 
sensitive,  imj^orted  trees,  our  indigenous  forest 
trees,  according  to  Nordlinger-,  are  also  exposed  to 
injuries  at  the  crotch,  especially  when  young;  thus, 
for  example,  beeches  in  shady  positions  and  on  poor 

soil,  in  which  the  intemodes  at  some  distance  from  the  crotches  are  also 
often  covered  with  frosted  surfaces.  The  annual  growth  of  the  oak  also 
suff'ers  on  poor  soils  and  the  ash  is  found  to  be  injured  if  the  tree  stands  in 
depressions  with  a  heavy  clay  soil.  In  such  damp  places  I  found  the  over- 
growth unusually  luxuriant  but  so  covered  with  thick,  split  bark,  overgrown 
with  lichens,  that  it  had  become  irrecognizable. 

Opposed  to  the  theory,  which  Hartig  represents,  that  crotch  canker  is 
conditioned  by  spring  frosts,  Nordlinger  thinks  the  cause  is  frost  at  the 
beginning  of  winter.  He  bases  his  opinion  on  the  investigation  of  the  wood 
ring  and  on  the   fact  that,  in  thousands  of  cases,   crotch  canker  is  very 


Crotch  canker 


1  Paparozzi.  G.,  II  cancio  del  pero.  Roma,  Offizina  poligraflca;  cit.  Bot.  Cen- 
tralbl.  1904,   v.  XXVIII,  p.  94. 

-  Die  Septemberfroste  1877  unci  der  Astwurzelschaden  (A.st\vurzelkrebs)  an 
Biiumen.  Centralbl.  f.  das  ges.  Forstwesen.  Wien  1878,  Part  10. 


594 

abundant  hii^h  up  in  the  crown  and  in  shady  phiccs.  i.  c.  those  less  exposed 
to  spring  frosts. 

The  especial  susceptibility  to  frost  of  the  base  of  the  branch  is  ex- 
plained by  the  fact  that,  on  account  of  the  greater  number  of  buds  originally 
set  there,  more  parenchymatous  medullary  bridges  are  present,  which 
traverse  the  wood  ring.  Tlie  itarcnch}mat()us  wood  is  more  tender  and 
contains  more  starch.  'J"o  this  shcjuld  also  be  ascribed  the  fact  that  bark 
beetles  like  to  settle  in  the  crotches  and  that  wood  mice,  as  Xordlinger 
states,  fre(|uently  eat  only  the  base  of  the  lateral  branches  in  poplar  suckers 
[ropulns  monilifera).  Therefore  the  frost,  i.  e.,  the  s])ring  frost  kills  the 
base  of  the  branch  most  easily. 

In  old.  weakly  growing  trunks,  the  luxuriance  of  the  o\ergrowth 
edges  decreases  considerably  and  can  become  so  slight  that  only  narrow, 
circular  overgrowth  edges  are  present,  which  push  out  slowly  from  under 
the  dead  bark.  This  blight  corresponds  to  that  of  the  crotch  injurv,  since 
in  open  canker,  the  first  stage  is  not  a  cleft  but  a  c()llai)sing,  drying  dead 
bark  surface.  Hence,  the  expression  "crotch  hlujht"  fre(|uently  used  by 
many  practical  workers. 

c.     Canki:r  on  Cherry  Treks. 

In  sweet  cherries  are  usually  found  semi-cylindrical  protuberances  on 
the  twigs,  or  older  branches.  The  outside  of  these  swellings,  often  thicker 
than  one's  fist,  not  infrequently  seem  depressed,  as  in  blight ;  the  dead 
bark  is  split  and  partially  stripped  from  the  blackened  wood  body,  still 
remaining  attached  as  larger  scales  with  up-rolled  edges  (cf.  Fig.  139). 

The  barrel-shaped  sw'elling  on  the  branch  represents  an  abnormal  de- 
velopment of  the  overgrowth  edges  {n  and  n' )  of  the  wound  (sp)  which 
does  not  close  entirely,  as  is  also  found  in  the  "closed  canker  of  the  ai^ple." 
In  the  latter,  however,  the  overgrowth  tissue  is  a  sudden,  unusually  lux- 
uriant widening  of  the  annual  ring,  while,  in  the  cherry,  the  swelling  of  the 
normal  side  of  the  twig  shows  a  gradual  transition  to  the  excrescent  oxer- 
growth  edge.  On  this  account,  the  closed  canker  of  the  a[)])lc  has  the  form 
of  knots  but  the  completely  developed  canker  of  the  cherry  a  gradually 
increasing  barrel-shaped  thickening.  Besides  this  typical  form,  various 
transitions  are  found  from  the  closed  canker  knots,  on  the  one  hand,  to 
the  flat  wound,  on  the  other,  which  is  termed  blight. 

Conical  swellings  are  found  at  the  base  of  older  branches  of  trees, 
suffering  from  canker,  which  can  offer  all  the  transitional  forms  up  to  the 
typical  canker  swelling.  The  initial  stages  are  found  on  one  side  of  the 
branch  in  the  form  of  a  small  frost  wound  alongside  the  first  annual  ring. 
An  especial  emphasis  should  be  laid  here  on  the  fact  that  the  enormous 
overgrowth  tissue  seems  often  to  be  developed  from  a  medullary  bridge. 
This,  therefore,  points  to  some  direct  injury  to  the  bud.  The  development 
of  the  overgrowth  edges  is  continued  in  subsequent  years,  when  only  paren- 


595 


chyma  wood  is  ff)rmed  in  which  starch  is  rapidly  and  abundantly  deposited. 
If  the  canker  swelling  has  become  considerably  extensive,  the  branch  dies, 
as  a  rule,  above  this  swelling;  in  this,  stroma- forming  fungi  (usually  from 
the  family  of  the  Valseae)  greatly  co-operate.  They  appear  in  the  form 
of  small  warts. 

If  the  young  branches  (i  to  2  years  old)  of  trees  sufifering  from 
canker  are  examined,  blight-like  places,  often  se\eral  centimeters  long,  are 
found,  with  lip-like  overgrowths  instead  of  individual  buds,  while,  on  the 
[)arts  of  the  branch  above  and  below 
these  places,  the  buds  have  developed 
to  short  shoots.  It  is  evident  from 
this  that  the  injury  to  the  branch 
must  take  place  before  the  breaking 
of  the  bud. 

Since,  however,  no  injury  of  any 
kind  can  be  ascertained  in  the  year  in 
which  the  liranch  is  formed,  but  will 
lie  found  only  in  the  following  spring, 
it  must  have  arisen  in  the  winter  or 
at  the  beginning  of  spring;  the  as- 
sumption is.  therefore,  pertinent  that 
the  bud,  as  it  unfolds  in  sprouting,  is 
killed  by  the  frost  and  that  the  accu- 
mulated plastic  material  is  now  used 
in  the  formation  of  the  excrescent 
edges  of  the  wound.  Since  the  tissue  of 
these  overgrowth  edges  remains  as 
soft  as  the  parenchyma  and  is  almost 
always  found  filled  with  starch,  it  is 
clear  that,  in  the  following  winter,  its 
edges  succumb  very  easily  to  injury 
from  frost  and  new  excrescences  are 
produced  from  the  deeper  lying  zones 
which  remain  healthy.  A  consider- 
ation of  the  cross-section  in  Fig.  139 
makes  clear  the  whole  process.  This 
shows   that   the   clefting   of   the   axis 

has  begun  at  a  short  distance  from  the  pith  body  (/;;)  and  in  the 
second  annual  ring.  The  third  annual  ring  has  already  furnished 
luxuriant  overgrowth  edges  (/)  which,  in  turn,  split  the  following  year 
(sp').  These  secondary  clefts  cause  secondary  overgrowth  (/').  The 
barrel  shaped  canker  swelling,  however,  is  formed  chiefly  by  the  ex- 
crescent wound  edges  of  the  main  cleft,  which  are  radiatingly  arranged 
{k).  Thus  an  annual  ring  inside  the  canker  swelling  is  divided  into 
several    rings,    as    in    the    closed    canker    of    the    apple.      The    bark  body 


I'^S.    139.     Cherry    canker    frost    cleft 

with  overgrowth  edges  in  longitudinal 

view  and   cross-section. 


596 


(r)    also    forms  corresponding^  excrescences   and.   in   places,   develops   thick 

bark  scales. 

In  the  canker  of  the  cherry,  as  in  all  canker  diseases,  only  scattered 

individuals  are   found  diseased  in  large  plantations.     I  often  found  in  the 

healthy  shoots  of  these  cankered  examples 
abnormally  broadened  medullary  rays,  a  ])he- 
nomenon  which  may  be  observed  also  in 
other  kinds  of  trees.  I.  therefore,  surmise 
that  the  inclination  to  become  diseased  i^'itli 
canker  may  he  found  in  the  indii'idnal  ten- 
dency tozuard  a  zi'idcnin;!  of  the  medullary 
rays. 

Thk  C'ankkk  (Scab)  of  thk  Gkapkvine. 

In  the  older  wood  of  grapevines  near 
the  surface  of  the  soil,  about  lo  to  30  cm. 
abo\e  it.  are  found  scattered,  small  spherical 
or  large  barrel-shaped,  out-pushings  of  the 
wood  from  the  bark,  with  a  beadv.  irregular 
upper  surface,  split  lengthwise  into  fibres. 
Fig.  140  shows  a  beady  canker  swelling 
between  the  strips  of  bark  which  are  drawn 
in  white.  In  small,  isolated  outgrowths,  their 
production,  according  to  (jothe's^  investiga- 
tions, is  clearly  recognizable  as  the  over- 
growth tissue  of  longitudinal  clefts.  The 
clefts  a])pear  at  the  cdi::,c  of  the  annual  ring, 
from  which  it  must  be  concluded  that  they 
were  produced  at  the  time  when  the  de- 
\elopment  of  the  next  annual  ring  began, 
caused  b}-  the  d}ing  back  in  spots  in  the 
cambial  zone  in  the  spring.  In  regard  to  the 
production  of  the  excrescences,  I  have  stated 
some  dififering  observations  of  my  own, 
under  the  head  of  the  disease  to  be  treated 
next. — Canker  of  the  Spirea. 

The  injury,  which  killed  the  cambium. 
has  also  caused  a  considerable  circular  sur- 
face on  the  old  wood  to  turn  a  deei)  brown. 
The  overgrowth  beginning  at  the  healthy 
place,  which  often  ciuickly  closes  the  cleft,  is  characterized  by  an  excrescent 
luxuriance  of  the  wood  and  bark.  The  woody  edges,  curling  out  towards 
one  another,  consist  of  soft,  ductless  parenchyma  wood,  without  any  real 


Flsf.    140.     clunker   excrescences 
in  the  graj)evinc. 


1   Mitteilungen  liber  den  schwarzen  Bienner  und  den  Grind  der  Reben. 
und  Leipzig,  H.  Voigt,  1878,  p.  28  ft. 


597 

prosenchymatous  elements,  i.  e.,  they  exhibit  the  characteristic  structure 
of  the  excrescent  wound  wood.  If  the  overgrowth  edges  have  united  into 
a  connected  annual  ring,  this  grows  further  in  such  a  way  that  it  is  sub- 
divided by  medullary  rays.  The  direction  of  these  medullary  rays  continues 
that  of  the  medullary  rays  of  the  wood  formed  the  previous  year.  There- 
fore, this  wood  has  undergone  only  a  temporary  interruption  in  the  brown 
dead  tissue. 

The  changes  and  tissue  excrescences  described  are  never  found  in 
wood  of  the  current  year. 

(iothe  thinks  the  bead-like  appearance  of  the  tissue  excrescence,  whicli. 
growing  extensively  radially,  splits  the  old  bark,  is  explained  by  a  complete 
"overlapping,  inward  growth"  of  the  overgrowth  rolls,  which  are  present 
most  abundantly  at  places  on  the  vine  lying  about  30  cm.  above  the  surface 
of  the  soil.  Examination  shows  that,,  starting  at  such  places,  the  number 
and  extent  of  these  swellings  decrease  away  from  as  well  as  towards  the 
soil;  close  to  it.  and  about  one  meter  away  from  it,  they  occur  very  rarely. 
With  a  slight  development  of  the  disease,  the  attacked  trunks  may  vegetate 
for  several  years  and  then  still  produce  bearing  wood.  With  a  greater 
development  of  the  canker  swelling,  the  wood,  lying  above  it,  dies. 

The  rapidity,  with  which  the  canker  swelling  is  produced,  is  proved  by 
the  fact  that,  on  August  8th,  i)lants  were  found  in  which  the  grafting  tajie 
lay  embedded  0.75  cm.  in  the  tissue  excrescences.  Therefore,  the  entire 
canker  swelling,  2.5  cm.  thick,  can  only  have  been  produced  after  the  time 
of  grafting  (in  May),  for  it  can  not  be  assumed  that  a  scion  would  have 
been  inserted  in  a  diseased  vine. 

Gothe  has  proved  by  the  following  experiment  that  the  injuries  to  the 
cambial  ring  take  place  in  the  spring.  In  April,  when  the  vines  were 
pruned.  12  strong  bearing  vines  were  tapped,  between  two  nodes,  with  a 
dull  iron,  in  such  a  way  that  an  injury  to  the  cambial  layer  could  be  as- 
sumed. Cilass  tubes  were  then  shoved  over  the  injured  places  and  the 
openings  closed.  The  first  traces  of  the  swellings  could  be  proved  as  earlv 
as  June  8th,  while  on  specifically  scabb}-  vines  the  tissue  excrescences  did 
not  appear  until  June  20th.  Up  to  autumn,  perfectly  normal  scab  struc- 
tures continued  to  form  in  the  glass  tubes,  with  also  the  same  anatomical 
structure  as  naturally  formed  excrescence  edges. 

Spring  frost  may  be  considered  as  the  cause  of  these  excrescences  in 
nature.  Most  of  the  literature  which  proves  the  appearance  of  grape 
canker  after  spring  frosts  also  favors  this  assumption^  It  is  also  strength- 
ened by  the  discovery  that  grape  canker  occurs  only  in  the  so-called  frost 
holes.  Gothe  cites  in  this  connection,  an  example  from  a  vineyard  which 
began  on  a  small  slope,  passed  through  a  hollow  and  rose  again  on  the 
opposite  slope.  On  both  slopes  the  plants  were  healthy,  but  in  the  hollow 
were  found  to  have  been  attacked  by  the  disease.     In  a  subsequent  test,  the 


1   Gothe    cites    v.    Babo.    Weinljau,    p.    305;     Dornfeld,    Weinliausohule, 
Kohler,  Der  VVeinstock  und  dor  Wein,  p.  20'.;   du  Breuil,   L.es  Vignobles. 


598 

f)Ijserver  found  that  the  disease  had  occurred  on  20  other  vines,  which  stood 
in  depressions  in  the  soil. 

The  fact  that  the  grape  canker  appears  at  a  definite  height  on  the  vine 
is  explained  by  the  various  differences  between  the  heat  maximum  and 
minimum  to  which  the  vines,  at  different  heights,  are  often  exposed  at  the 
time  of  spring  frosts. 

Draining  of  the  soil  might  prove  the  most  effective  method.  Kohlcr 
has  already  announced  fa\()rat)le  results  in  his  above-mentioned  works, 
liesides  this,  attention  should  be  given  to  the  planting  of  hardier  varieties 
and  especially  the  choice  of  suitable  i)ositions  (moderately  moist,  porous 
and  warm  soil). 

It  is  not  inconcei\able  that  the  scab,  without  the  action  of  frost,  may 
be  produced  by  an  accumulation  of  plastic  materials,  as  Blankenhorn  and 
Miihlhauser  beliexe  they  ha\  e  observed  as  the  result  of  too  severe  cutting 
back'.  It  is  certain  that  the  beginnings  of  the  swellings,  occurring  in  tlie 
form  of  medullary  ray  excrescences,  can  appear  in  the  vines  in  which  in 
tlie  spring  the  bark  has  been  raised  in  places  from  the  wood  of  the  pre\ious 
year.  Such  canker  excrescences,  as  said  above,  can  mature  without  any 
injury  from  frost,  just  as  canker-like,  excrescent  overgrowth  edges  are 
found  in  luxuriantly  growing  pomaceous  varieties.  P)Ut  in  such  cases,  the 
deep,  extensive  browning  of  the  wood  body  is  lacking. 

c.     Canker  on    Spiraea. 

A  disease,  not  yet  described,  sliowing  great  relation  to  the  canker  oi 
tlie  gra])e.  attacks  the  bases  of  tlie  stem  of  Spiraea  opulifolia.  The  disease 
seems  to  occur  more  conmionly  only  in  regions  with  very  cold  winters.  The 
material  which  I  had  for  observation  came  from  East  Prussia. 

Other  wood,  at  least  two  years  old,  with  strong  annual  rings  shows  at 
the  stem  bases  unusually  abundant  hemispherical  swellings  of  the  wood, 
scattered,  or  in  row's  like  chains  of  beads,  or  in  masses.  (Fig.  141  ,-/,  k, 
kk).  Tlie  size  of  these  swellings  varies  from  a  few  millimetres  up  to  1.5 
to  2  cm.  in  diameter.  The  swellings  are  brown,  darker  than  the  outermost 
Ijark  layers,  which  they  rupture,  and  loosened  in  tatters.  They  are  often 
cleft  or  depressed  in  the  centre  like  a  funnel  and  provided  with  thick  granu- 
lated, torn  surfaces.  No  single  bark  layer  can  be  raised,  since  the  tissue 
of  the  swelling  is  brittle  and  easily  breaks  off  in  pieces. 

In  cutting  away  a  considerable  swelling,  or,  as  one  is  justified  in  saying, 
canker  knot,  it  is  found  that  lamellae  or  firmer  material  radiate  out  from  a 
more  or  less  broad  base.  However,  the  lamellae  neither  extend  through 
the  whole  thickness  of  the  canker,  nor  are  they  separated  sharply  from  the 
tinder-like,  decayed,  darker  ground  tissue.  This  itself  is  to  be  considered 
an  excrescent  continuation  of  the  last  annual  rinif,  which  becomes  more 
and  more  delicate  toward  the  periphery. 


1  cf.  Wurzburger  Weinbaukongress. 


Fig-.  141.     Cankei-  on  Spiraea. 


6oo 

In  Fi<,^  141  B,  which  gives  a  cross-section  of  the  canker  knot  (k)  from 
I'ig.  141  ./,  ;;;  indicates  the  pith  body;  a,  the  uninjured  annual  ring  of  the 
first  year's  growth;  b,  the  cleft  ring  of  the  second  year;  c,  the  wood  of  the 
third  year,  which  is  growing  out  into  the  canker  swelling  {k)  ;  i  represents 
the  firmer  tissue  islands  and  stripes  in  the  tinder-like  ground  tissue. 

In  the  cases  which  lia\c  been  obser\ed  up  to  the  present,  the  main  part 
of  the  canker  knot  has  seemed  to  be  the  production  of  a  single  year  and,  in 
fact,  a  one-sided  woody  excrescence  over  a  place  which,  even  in  the  pre- 
\ious  year,  had  formed  a  wedge-shaped  zone  of  porous,  parenchymatous 
wood  tissue,  its  pointed  end  toward  the  interior.  In  so  far  two  years  are 
necessary  for  the  comi)letion  of  the  canker  knot.  If  the  above  mentioned, 
wedge-shaped  zone  is  traced  backward  to  the  annual  ring  of  the  previous 
year,  it  will  be  seen  that  this  originates  in  a  brown,  slender  place  in  the  first 
spring  wood. 

The  adj(jining  anatomical  picture,  b'ig.  141  C,  will  facilitate  the  expla- 
nation. The  whole  figure  C  is  a  radial  section  of  the  second  annual  ring 
from  a  Spirea  stem  and  contains  the  tissue  zone  which  is  preparing  to 
develop  into  the  real  canker  swelling.  The  line  /  to  ff  represents  the  strip 
of  changed  tissue,  which  in  its  further  development  in  the  following  year, 
will  have  become  a  complete  canker  knot.  The  tissue  shown  at  a  is  the 
autumn  wood  of  the  first  annual  ring.  Xo  disturbance  has  been  observed 
in  the  wood  body  of  this  first  annual  ring,  just,  as  in  the  canker  of  the  grape, 
the  first  annual  ring  has  a  perfectly  normal  structure.  The  wood  of  the 
second  annual  ring  (/')  at  first  began  a  normal  develo])ment  and  continued 
it  ui)  to  //. 

At  this  time  occurred  some  disturbance  wliich  produced  the  cleft  {d), 
and  browned  its  edges  {c').  The  time  this  split  was  produced  must  have 
lieen  that  of  the  greatest  formation  of  new  wood  for,  only  a  few  cell  rows 
farther,  we  find  that  the  split  is  closed  at  h,  and  the  annual  ring  has  grown 
further  with  the  formation  of  groups  of  normal  parenchymatous  elements 
(p).  Only  a  single  cell-row  (k)  forms  a  radial  stripe,  with  shorter  cells 
containing  wider  lumina.  Now  the  abnormal  wood  stripe,  instead  of  dis- 
appearing as  the  annual  ring  matures  and  increases  in  width,  grows  broader, 
since  more  and  more  cells  take  part  in  the  changed  form  of  construction 
(kh).  Thus  the  disturbance  advances  until  the  second  annual  ring  is  lin- 
ished  and  then  begins,  to  a  renewed  extent,  in  the  spring  zone  of  the  third 
annual  ring  {c-c). 

V.ven  when  the  second  annual  ring  is  finished,  the  stripes  of  the  begin- 
nings of  the  canker  may  be  seen  to  project  as  slight  elevations  above  the 
periphery  of  the  remaining  wood  ring.  In  the  spring  of  the  third  year  the 
new  formation  at  this  place  is  so  luxuriant  that  the  rapidly  growing  canker 
knot,  strengthened  by  the  equally  rapidly  excrescent  part  of  the  bark  (k  I), 
ruptures  the  normal  liark  (r)  at  sp  and  now  grows  further,  as  it  were,  as 
a  foreign  structure,  in  order,  after  some  weeks,  to  end  its  growth,  being  a 
complete  canker  knot  1  to  2  cm.  thick. 


6oi 

Similar  formations  are  found  in  the  canker  of  the  (/rape.  Only  I  have 
found  as  yet  that  the  disturbance,  setting  in  at  the  beginning  of  the  second 
year,  and  corresponding  to  the  holes  (d),  consists  of  a  broader  tangential 
elevation,  circular  in  form.  It  give  the  impression  that,  at  the  beginning 
of  the  period  of  growth,  the  bark  was  raised  from  the  wood  body  for  a 
considerable  distance.  My  repeated  experiments  with  artificial  frost  show 
that  this  process  can  actually  occur  and,  in  fact,  it  is  met  with  rather  fre- 
quently in  various  trees.  As  a  result  of  this  lifting  of  the  bark,  a  tangential 
hole  is  produced  on  the  grapevine,  usually  at  the  place  where,  on  Spirea, 
the  slender,  radial  cleft  is  found.  The  raised  bark  forms,  first  of  all,  wood 
parenchyma  and  this  soft  wood  l)ody  passes  over  very  gradually,  in  the 
course  of  the  following  summer,  into  normal  wood.  Here,  however,  some 
of  the  broad  medullary  rays  are  found  aboxe  the  raised  part  which  have 
developed  especially  and  at  the  end  of  the  year  project  as  delicate  tissue 
caps. 

In  the  grapevine,  as  in  Spirea  in  canker  formation,  these  are  not  neces- 
sarily overgrowth  edges,  as  is  always  the  case  in  the  canker  of  the  apple; 
in  the  former,  tissue  cushions  of  a  w^ood  body  which  has  become  parenchy- 
matous develop  to  canker  knots.  These  cushions  at  first  appear  uninjured 
and  are  at  any  rate  caused  by  some  previous  disturbance.  This  explains 
the  theory  expressed  by  Blankenhorn,  on  the  canker  of  the  grapevine,  viz.. 
that  the  stoppage  of  plastic  materials  (for  example,  with  too  strong  orun- 
ing),  can  cause  the  canker  excrescence. 

The  formation  of  the  canker  excrescence  often  indicates  some  modi- 
fication, inasmuch  as  the  canker  cushions,  produced  in  the  first  year,  are 
partially  killed  by  the  frost.  Then  the  central,  most  delicate  part  suffers  and 
represents  a  black,  dried  core.  In  the  following  spring  only  the  edges 
grow  further,  just  as  do  overgrowth  edges,  and  line  the  cleft,  as  is  shown 
in  Fig.  141  B.  It  has  been  said  that  the  parts  of  the  edges  of  the  growing 
canker  knot  continue  growing  "after  the  manner"  of  overgrowth  edges. 
Actual  overgrowth  edges,  spirally  cur\ed,  are  found  only  rarely  (as  in  the 
canker  of  the  grape). 

Fig.  141  B  shows  that  the  wood  ring  of  the  third  year  passes  over 
imperceptibly  into  the  canker  swellings.  Therefore,  the  canker  swelling 
is  actually  a  wood  formation  but  this  wood,  because  of  the  enormous  rapid- 
ity of  the  tissue  formation,  is  a  structure  so  soft  and  so  similar  to  the 
likewise  excrescent  bark  tissue,  which  is  dying  back  from  the  outer  side, 
that  it  is  often  difficult  to  determine  the  boundary  between  them.  This 
porous  wood,  which  I  have  found  so  very  soft  only  in  the  canker  of  the 
rose,  forms,  on  the  dead  swelling,  the  brown,,  tinder-like  ground  mass,  of 
which  we  spoke  at  the  beginning.  The  firmer,  lighter  colored  parts  are  the 
islands  of  thick-walled  w^ood  cells  and  ducts  (Fig.  141  B,  i)  increasing  in 
breadth  and  thickness  at  the  periphery.  In  canker  knots  of  different  sizes, 
the  groups  of  ducts  (i)  are  sometimes  found  in  the  form  of  wedge-like 
lamellae,  becoming  thicker  toward  the  outside,  sometimes  (as  in  Fig.  14JB) 


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in  the  form  of  spherical  ((roups  witli  a  shcath-like  arraiiijt'ment  of  their 
elements.  The  groups  not  infrequently  unite  and  in  this  way  cause  a 
greater  firmness  but  no  complete  wood  ring  has  ever  been  observed.  It  is 
these  isolated  parenchyma  and  duct  groups  which  in  ])runing  so  greatly 
resist  the  knife,  that  they  are  torn  loose  from  their  connection  with  the 
other  tissue  before  lieing  cut  through.  Hence  the  easy  crumbling  of  the 
canker  knot. 


Fig.  142.     Rose  Canker.     Concentric  overgrowth  edges  may  be  recognized,  ri 
like  terraces  around  a  central,   dead  wood  surface. 


f.     Canker  of  the  Rose. 

Tn  the  culture  of  the  newer  climbing  roses,  which  (according  to 
Crepin-Briissel)  have  resulted  from  a  crossing  of  Rosa  Indica  with  R. 
multiflora  and  are  called  Polyanthus  varieties,  we  have  become  acquainted 
with  a  phenomenon  which  comes  under  the  head  of  canker  excrescences. 
The  adjoining  Fig.  142  A  and  B,  represents  such  canker  swellings  as  are 


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found  at  the  base  of  the  strong  stems  of  Crimson  Ramblers  in  Germany. 
Their  appearance  on  the  lower  part  of  these  rose  stems,  which,  as  is  well 
known,  grow  most  luxuriantly  in  (Germany,  reminds  one  of  the  same  occur- 
rence in  the  canker  of  the  grapevine.  As  in  all  forms  of  canker,  we  find 
here  also  that  the  region  of  the  axis  is  preferred  where  branches  (A,  a) 
are  produced  and  the  base  has  strongly  thickened  or  split  open  into  curled 
excrescences  {B,  iib).  As  an  explanation  of  this  phenomenon,  it  need 
only  be  remembered  that  the  wood  ring  is  broken  and  especially  susceptil)]e 
to  disturbances  at  that  part  of  the  normal  axis  where  a  branch  starts,  for 
the  pith  body  is  widened  at  the  place  of  insertion  of  the  twig  into  a  pith 
bridge,  transecting  the  wood  ring  and  passing  over  into  the  lateral  branch. 
In  such  a  developing  branch  the  eyes  stand  closest  together  at  the  base; 
they  may  often  be  but  little  developed,  because  the  leaves  are  still  bract-like 
or  incomplete,  but  the  parenchymatous  medullary  bridges,  which  traverse 
the  wood  ring,  are  present. 

The  canker  spot  on  the  main  axis  in  the  present  case,  as  in  the  "open 
canker  of  the  apple,"  shows  a  central  wound  surface  with  an  exposed  brown 
wood  body  (Fig.  142  A  and  B,  w).  This  surface  is  encircled  by  terrace-like, 
rounded  overgrowth  edges  {n).  These  wound  edges,  however,  do  not 
retain  their  uniform  wall-like  character,  as  in  the  canker  of  the  apple,  but 
develop  into  irregularly  knobbed,  or  beaded,  heaped  up  tissue  masses.  In 
other  cases,  the  canker  of  the  rose  occurs,  like  the  canker  knot  in  Spiraea, 
in  boil-like,  united  and  elongated  wound  edges,  which  line  a  long  cleft, 
starting  from  the  base  of  the  branch.  All  excrescent  tissues  ultimately 
rupture  the  bark  (r). 

An  insight  into  the  production  of  these  excrescences,  which  are  not 
exceeded  in  luxuriance  by  any  other  canker  swelling,  is  obtained  from 
the  above  reproduced  cross-section  of  a  rose  stem,  at  the  place  where  it  has 
formed  a  small,  isolated  bead-like  elevation  (cf.  b^ig.  143).  We  perceive 
that  the  stem  has  developed  normally  in  the  first  year;  a  normal  wood  ring 
(A)  surrounds  the  pith  body  which  has  broad  medullary  rays  {mst)  and 
which  ruptures  later  (v).  In  the  second  year,  as  the  first  cell  rows  {gr) 
of  the  new  wood  ring  were  in  the  midst  of  developing,  some  disturbance 
must  have  made  itself  felt  in  the  form  of  some  break  in  the  tissue,  for  the 
new  wood  ring  {hp),  for  the  most  part,  has  taken  on  the  character  of  the 
parenchyma  wood  and  only  in  places  (/?')  has  it  retained  the  normal  wood 
structure,  characterized  by  the  formation  of  ducts  and  thick-walled  wood 
cells.  The  cause  of  this  breaking  up  of  the  tissue  has  been  a  split  in  the 
bark,  traces  of  which  may  be  seen  in  the  lip-like,  small  indentation  at  the 
upper  side  of  the  figure.  The  cork  layers  {k)  of  the  bark,  which  cover 
this,  have  been  split  and  the  overgrowth  tissue  {zv)  swelling  out  from  both 
sides,  which  has  been  covered  in  turn  with  a  cork  mantel,  has  coalesced  into 
a  closed  mass  in  the  immediate  proximity  of  the  tear  (which  is  not  shown 
in  the  drawing).  If  this  tissue  is  traced  backward  toward  the.  healthy 
(upper)    side   of  the  branch,   starting   from  the   most  luxuriant  place   of 


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excrescent  tissue  (7c),  it  is  found  that  this  gradually  dwindles  away  and 
inside  the  bark  bej^ins  to  take  on  a  normal  character  (/;/.)  Here  the  ar- 
ranjjemcnt  of  the  hard  bast  cords  is  still  approximately  normal  but  their 
structure  has  been  changed  greatly.  The  majority  of  the  bast  cells  ha\e 
a  yellow,  swollen  content  and  easily  browned  walls.  Nevertheless,  they 
are  distinguished,  as  strong,  light-colored  groups  from  the  deep  brown  bark 


Fis".  143.     First   stases  ot    the  rose  cankei-. 


parenchyma  which  is  cut  off  from  the  outer  coUenchymatous  bark   layers 
f)y  the  suljse(|ucnt]y  produced  layer  of  plate  cork  {k'). 

The  drawing  shows,  however,  that  the  ring  of  bast  cells  (^)  is  removed 
farther  from  the  wood  body  the  further  it  advances  into  the  tissue  of  the 
excrescence.  It  is,  therefore,  pressed  away  from  the  wood  body  by  the 
increase  of  this  body.     At  the  same  time  the  bast  ring  is  seen  to  have  been 


005 

pushed  back  further  from  the  outer  collenchymatous  layers.  Therefore, 
cell  increase  must  have  taken  place  in  the  primary  bark. 

The  question  should  now  be  asked  as  to  whether  the  tissue,  which 
presses  the  bast  ring  away  from  the  wood,  is  exclusively  a  product  of  the 
secondary  bark  or  whether  the  wood  cylinder  itself  has  contributed  to  this. 
We  find  the  answer  in  the  tissue  group  [hp')  which  represents  the  paren- 
chyma wood.  We  find  such  groups  of  parenchymatous  wood  within  a  soft, 
thin-walled  tissue,  when  bark  zvonnds  are  healed  by  the  formation  of  new- 
tissue  from  the  youngest  sapwood  layers,  remaining  on  the  wood  body.  We 
learn  further,  by  studying  the  false  annual  ring  (cf.  False  Annual  Rings) 
and  the  healing  processes  of  inner  frost  tears,  to  recognize  the  formation 
of  parenchyma  wood  from  the  broken  sap  wood  layer.  Also,  in  the  pro- 
cesses of  grafting  and  especially  those  of  budding  and  bark  grafting  we 
find  that  cicatrization  tissue  has  been  formed  from  the  youngest  sap  wood, 
if  the  actual  cambial  zone  has  been  injured.  If  the  cambium  is  retained  in 
an  injury  but  the  bark  mantle  is  broken  by  a  tear  in  the  bark,  the  cambium 
develops  into  a  tissue,  at  first  parenchymatous,  which,  at  the  edge,  gradu- 
ally passes  over  into  a  normal  wood  structure,  according  to  the  amount  in 
which  the  normal  bark  pressure  is  restored  (cf.  Wound  Healing). 

The  same  new  growth  can  also  take  place  on  the  inner  side  of  the  bark 
if  this  is  raised  from  the  wood  c}'linder  without  an  entire  interruption  of 
its  nutrition.  I  have  carried  out  the  experiment  with  cherries  in  sucli  a 
way  that  the  still  smooth  bark  of  the  young  trunks  was  loosened  in  strips, 
connected  at  their  upper  ends  with  the  uninjured  bark  mantel  left  on  the 
axial  cylinder.  At  the  places  where  the  upraised  strips  passed  over  into 
the  uninjured  bark,  I  found  the  same  callus  formed  on  the  inside  which 
later  was  differentiated  into  bark  and  wood.  It  has  therefore  been  deter- 
mined experimentally  that  exposed  -xvood  can  produce  ne-z^'  bark  and  that 
upraised  bark  tatters  can  produce  neiv  zcood  when  still  attached  at  their 
upper  end  to  the  wood  body. 

In  this  way.  the  process  in  rose  canker  becomes  easily  understandable. 
In  the  first  spring,  a  tear  appears  in  the  bark  which  extends  to  the  cell  rows 
of  the  spring  wood  of  the  new  annual  ring  already  formed  and  results  in 
the  lateral  raising  of  the  bark  from  the  cambium  as  shown  in  the  holes  (/). 

At  first  the  constricting  influence,  wdiich  the  cork  girdle  (k)  usually 
exercises  on  bark  and  young  wood,  is  wholly  overcome  because  of  this  cleft, 
which  results  in  a  luxuriant  increase  of  the  young  wood  (on  the  under  side 
of  the  figure)  where  the  cambial  zone  has  not  been  destroyed,  and  the  lux- 
uriant increase  of  the  j)arenchyma  of  the  inner  bark  where  this  had  been 
raised  from  the  young  wood  (at  /  on  the  upper  side  of  the  figure).  The 
new  structures,  whether  formed  from  bark  tatters,  or  }'oung  wood,  are 
uniformly  callus-like  and  pass  over  imperceptibly  into  one  another.  It  is 
these  new  structures  which  have  ruptured  the  previously  continuous  bast 
ring  (b,  b'),  have  pressed  outward  the  most  strongly  injured  part  (b')  and 
caused  its  death  after  splitting  it  off  from  the  outer  bark. 


6o6 


Tlie  main  (|ueslion  is,  in  what  way  can  the  first  radial  ckava<j;c  have 
taken  place.  And  the  only  answer  to  this  can  be ;  as  the  result  of  frost. 
For  we  again  iind  here  the  browning  of  the  pith  crown,  the  tearing  and 
widening  of  the  medullar}-  rays,  the  phenomena  of  elevation  and  cleavage 

of  the  tissue  which  I  have  been 
able  to  i)roduce  experimentally 
b}-  the  action  of  artificial  frost. 
CJnly.  I  ha\e  not  been  able  to 
produce  artificially  the  secondary 
phenomena,  viz..  the  luxuriant 
tissue  increase.  This  probably 
is  based  upon  the  fact  that  in 
using  artificial  frosts  I  have  not 
yet  found  the  proper  juvenile 
developmental  condition.  This 
must  be  the  time  when  the  cam- 
bial  activity  has  just  begun,  as  is 
evident  from  the  small  number 
of  cell  la}ers  just  formed  by  the 
new  annual  ring.  If  the  dis- 
turbances occur  later,  capacity 
for  reaction  in  the  tissue  is  less 
and  the  excrescent  cell  increase 
does  not  take  place.  Ciothe's  ex- 
periments show  how  very  deter- 
minative the  time  of  injury  is. 
As  already  mentioned,  he  pro- 
duced excrescences  resembling 
the  canker  of  the  grape,  by  a 
continued  tapping  of  the  grape- 
\  ine  in  the  early  spring.  The 
grape  canker  is  closely  related 
ontogenetically  to  the  canker  of 
the  rose. 

g.     Canki:k  of  the 
Blackberry. 

It  is  a  noteworthy  fact  that, 
with  the  exception  of  grape 
canker,  all  the  other  canker  ev- 
er esc  enees  are  fuiind  in  the  family  of  the  Rosaeeae.  In  the  canker  of  the 
blackberry,  cauliflower-like,  hard,  glistening,  white  tissue  masses  with  a 
beaded  warty  surface  are  produced  on  the  older  wood  (cf.Fig.  144  k). 
These  tissue  masses  sometimes  form  isolated  spheres ;  sometimes  collect  in 
elongated,  wart-like  cushions,  as  in  Spiraea.     The  region  of  the  eye  is  the 


Fig 


Uln'i-ry. 


6oy 

preferred  place  of  production.  The  bark  is  split  and  partially  thrown  back 
like  wings. 

With  an  abundant  appearance  of  the  canker  swellings,  first  of  all,  the 
foliage  turns  yellow,  then  the  stem  begins  to  die  back  slowly  from  the 
browned  eyes.  By  July,  as  a  rule,  the  diseased  branches  on  the  same 
shoot,  side  by  side  with  bright,  perfectly  green  ones,  have  died  back  entirely. 

If  healthy  plants  are  examined  for  such  cankered  stems,  either  small 
reddish,  or  brown,  long  ridges  are  found,  or  gaping  tears  often  one  centi- 
metre long.  I  observed  the  same  phenomenon  also  on  many  petioles.  The 
sloping  edges  of  such  tears  are  covered  also  with  cork.  On  these  edges, 
small  beady  excrescences  appear  in  places  which  consist  of  parenchyma  and 
are  formed  from  the  primary  bark  close  to  the  outside  of  the  hard  bast 
cords. 

In  the  Rosaceae  this  tissue  region  proved  to  be  extremely  easily  stimu- 
lated. I  found  that,  after  very  different  injuries  to  the  bark,  which  gener- 
ally did  not  extend  to  the  hard  bast,  strong  branches  responded  to  the 
wound  stimulus  by  a  parenchymatous  increase  close  outside  the  hard  bast 
cords.  Often,  in  the  canker  of  the  blackberry,  a  place  of  predisposition  for 
the  formation  of  canker  may  he  noticed,  for.  in  the  spots  where  a  wart-like 
excrescence  had  appeared,  even  in  young  branch  shoots,  the  mechanical 
rings  formed  from  the  hard  bast  cords  and  other  thick-w^alled  connective 
elements  are  proved  to  be  unthickened.  A  thin-walled  parenchyma  had 
appeared  instead  of  the  prosenchymatous  and  sclerenchymatous  tissues. 

The  parenchymatous,  excrescent  tissue  in  the  primary  bark  increases 
very  rapidly  and  ruptures  the  overlying  normal  bark  layers.  In  the  interior 
of  the  canker  wart,  a  porous  wood  body  is  formed  which  is  rich  in  ducts. 
The  formation  of  wood  elements  is  repeated  in  the  peripheral  parenchyma 
layers  of  the  excrescence  zone  first  produced  since  meristematic  aggrega- 
tions arise  from  which  develop  tracheal  wood  elements,  arranged  like  bowls 
or  shells. 

The  beginning  of  canker  in  the  blackberry  therefore  is  a  parenchy- 
matous excrescence  in  the  primary  bark  body  which  grows  outward,  with 
a  cauliflower-like  ramification.  Only  later  does  the  tendency  to  hyper- 
trophy extend  backward  into  the  inner  bark,  finally  attacking  also  the  wood 
ring  which,  at  first,  seems  to  have  a  normal  structure.  As  soon  as  the 
swellings  become  older  and  the  wood  body  participates  in  their  formation, 
it  increases  to  3  or  4  times  its  normal  size.  \Ve  find  similar  processes  in 
dropsy,  in  the  formation  of  tuber-gnarl.  etc.  The  canker  is  more  rare  in 
Rubus ;  as  yet  I  have  found  it  only  in  four  cases  and  always  in  narrowly 
restricted  places. 

C0RRE.SP0X])ING    FEATURES    IN     CaNKER    SweLLINGS. 

In  a  survey  of  all  the  known  material  relating  to  closed  canker  corre- 
sponding features  are  found.  ("Open  canker"  forms  a  transition  to  blight 
and  is  included  here).  The  production  of  a  small  tear  forms  universally 
the  beginning  of  the  disease.     It  may  be  seen  in  all  cases  that  the  injury  must 


6o8 


lia\c  taken  place  in  tlic  early  sprinj^  and  lliat  the  riclil\-  collected  material 
enabled  the  parts  surrounding-  the  wound  to  form  enormous  excrescences 
most  quickly.  The  parenchymatous  character  of  the  new  structures  causes 
a  great  sensitiveness  to  injurious  atmospheric  influences  and  especially  to 
frost.     Low  temperatures,  therefore,  are  able  to  injure  the  canker  tissue  in 

the  next  period  of  growth.  The  injured 
tissue  complex  can  respond  repeatedly  with 
excre^cenl  tissue,  because,  with  its  paren- 
ch}'niatous  nature  in  the  pre\  ious  period  of 
.s';rowth.  it  has  stored  up  \ery  abundant  re- 
ser\c  substances  in  the   form  of  starch. 

The  canker  forms  in  the  indixidual 
genera  of  the  Rosaceae  differ  onl\-  in  the 
manner  of  reaction  to  the  wound  stimulus 
and  agree  in  that  they  prefer  the  bud  and 
its  immediate  surroundings  as  the  place  of 
production.  The  reason  for  this  may  be 
sought  in  the  division  of  the  trunk  at  tlie 
place  of  insertif)n  of  a  bud.  The  wood 
ring  is  always  more  slender  here  and  hnall\ 
tra\ersed  by  a  parenchymatous  pith  bridge. 
The  initial  stages  of  the  canker  knot, 
so  far  as  observed,  i.  e.,  the  small  tears 
usually  arising  near  the  buds,  have  been 
produced  by  artificial  frost,  but  not  the 
luxuriant  overgrowth  structures.  This  cir- 
cumstance may  possibly  be  traced  back  to 
the  fact  that  a  period  in  the  spring  had 
been  chosen  which  was  too  late  for  the 
action   of   the  artiiicial    frosts. 

In  the  health}-  branches  of  cankered 
trees  an  alinormallv  increased  formation  ot 
the  mcdullar\'  rays  has  often  been  obserxed, 
and  this  nia\  indicate  the  explanation  of 
the  tendency  to  canker  excrescences  of 
certain  cultural  varieties,  or  diff'ercnt  indi- 
viduals in  certain  habitats,  since  those  ex- 
amples will  answer  most  easily  to  a  wound 
stimulus  by  hypertrophy,  if  their  medu! 
lary.  or  rather  bark  rays,  grow  luxuriantly 
in    a    healthy    condition. 

El.I<;ilT    (."^I'liACELUS). 

In  contrast  to  the  term  "canker"  which  in  general  [)ractice  is  used  for 
die  heterogeneous  phenomena  of  a  gradually  extending  disease,  one  under- 
stands pretty  generally  by  the  term  "Blight"  the  occurrence  of  dead,  black- 


J 


PART  VIII. 


MANUAL 


OF 


Plant  Diseases 

BY 

PROF.  DR.  PAUL  SORAUER 


Third  Edition—Prof.  Dr.  Sorauer 

In  Collaboration  with 

Prof.  Dr.  G.  Lindau       And       Dr.  L.  Reh 

Private  Docent  at  the  University  -  Assistant  in  the  Museum  of  Natural  History 

of  Berlin  in  Hamburg 


TRANSLATED  BY  FRANCES  DORRANGE 


Volume  I 
NON-PARASITIC  DISEASES 

BY 

PROF.  DR.  PAUL  SORAUER 

BERLIN 


WITH  208  ILLUSTRATIONS  IN  THE  TEXT 


PART  VIII. 


MANUAL 


OF 


Plant  Diseases 


BY 


PROF.  DR.  PAUL  SORAUER 


Third  Edition—Prof.  Dr.  Sorauer 

In  Collaboration  with 

Prof.  Dr.  G.  Lindau        And       Dr.  L.  Reh 

Private  Docent  at  the  University  Assistant  in  the  Museum  of  Natural  History 

of  Berlin  in  Hamburg 


TRANSLATED  BY  FRANCES  DORRANCE 


Volume  I 
NON-PARASITIC  DISEASES 

BY 

PROF.  DR.  PAUL  SORAUER 

BERLIN 


WITH  208  ILLUSTRATIONS  IN  THE  TEXT 


Copyrighted.   1917 

By 

FRANCES  DORRANCE 


THE    RECORD   PRESS 
Wilkes-Barre,    Pa. 


6o9 

ish,  extensive  spots  in  the  bark  which  have  dried  on  the  wood.  In  smooth 
barked  trees,  instead  of  large,  connected  bhghted  surfaces,  numerous  small 
depressed  places  in  the  bark  are  noticed,  appearing  often  on  one  side  of  the 
tree.  These  resemble  finger  marks  and  are  usually  called  frost  plates. 
These  injuries  are  abundant,  or  scarce,  according  to  the  susceptibility  of 
the  variety  to  frost  and  the  conditions  of  the  places  of  growth.  In  stone 
fruits,  the  phenomena  of  blight  are  found  most  frequently  in  cherries  and 
plums;  in  the  more  sensitive  peaches  and  apricots,  the  trunk  usually  suffers 
as  a  whole. 

In  pomaceous  fruits,  pears  undoubtedly  tend  most  easily  to  injuries 
from  bHght.  Of  forest  trees,  the  beech  and  oak  count  as  especially  sensi- 
tive and  in  damp  places  the  ash  and  acacia  also.  The  edible  chestnut  is 
found  in  central  Germany  only  in  isolated  localities.  Among  conifers,  the 
fir  seems  more  sensitive  to  frost  than  the  spruce.  The  larch  suffers  as  soon 
as  it  lacks  sufficient  light  and  air.  The  hnden  and  maple  are  rarely  found 
to  be  injured.  Blight  spots  are  found  most  rarely  in  the  older  birch,  elm, 
willow,  poplar,  hornbean,  and  especially  the  pine. 

The  dying  of  the  bark  is  to  be  considered  as  a  direct  effect  of  frost.  It 
penetrates  to  different  depths  and  can,  accordingly,  produce  a  different 
appearance  in  the  different  blight  wounds.  Thus,  for  example,  frost  fre- 
quently attacks  only  the  youngest  layers  of  the  bark  and  sap  wood,  includ- 
ing the  real  cambium.  The  older,  outer  layers  of  the  bark  die  only  from 
lack  of  nourishment,  since  the  bark,  killed  by  frost,  turns  dark  in  a  short 
time  after  thawing.  We  find  in  the  spring  (especially  in  pears)  depressed, 
sharply  outlined  places,  often  only  very  small  in  extent  and  at  first  only  on 
different  sides  of  the  trees,  or  branches.  These  places  soon  become  dry 
and  adhere  to  the  wood  (Fig.  145  p).  They  are  the  above-mentioned 
"frost  plates"  found  by  many  fruit  tree  growers.  A  cleft  appears  at  the 
boundary  between  the  dried  part  of  the  bark  and  the  healthy  part,  which  is 
raised  up  by  the  growth  in  thickness  of  the  trunk.  The  dead  part  of  the 
bark  is  again  cut  off  from  its  surroundings  by  this  cleft  and  loses  its  ar- 
resting influence  (Fig.  145  r). 

The  arrestment,  exerted  by  such  a  dead  place,  lies  in  the  increased 
pressure  of  the  bark  mantel  so  long  as  this  bark  mantel  is  still  connected 
with  the  dead,  dry,  inelastic  tissue.  The  bark  pressure  will  be  greatest 
near  the  dead  places  and  the  number  of  newly  formed  elements  the 
smallest. 

We  find  this  at  the  beginning  of  the  healing  processes.  The  tree  en- 
deavors to  cover  the  dead  places  by  the  formation  of  overgrowth  edges 
from  the  healthy  parts  of  the  bark.  This  can  take  place  in  two  ways, 
according  to  the  kind  of  blight  injury.  If  the  branch,  at  the  time  of  the 
frost,  already  has  some  older  wood,  which  is  browned  on  the  blighted  side 
but  not  split  off,  then  the  overgrowth  edges  often  gradually  push  between 
the  dead  bark  and  the  wood  body  and  slowly  lift  the  scale-like,  dry 
brown  mass  of  the  bark.    With  each  successive  year,  the  overgrowth  edges 


6io 


approach  more  and  more  closely  to  one  another  from  the  sides  until  they 
finally  unite,  cover  the  blackened  place  in  the  wood  and  thus  push  out  the 
previously  attached  bark  and  throw  it  off. 

In  Fig.  146,  which  represents  a  blighted  young 
pear  trunk,  we  see  at  the  top,  the  old,  blackened, 
exposed  wood  body  which  originally  was  covered  with 
bark  in  a  fresh  condition  ;  it  is  left  light  in  the  drawing. 
The  bark  on  the  whole  side  of  the  tree  has  been  killed 
by  frost,  dried  up  and  thrown  off  from  the  healthy 
[)art  by  the  overgrowth  edges  which  appear  after  frost. 
The  swollen  place  at  the  base  of  the  drawing  illustrates 
the  broadening  of  the  flattened  trunk,  which  occurs 
frequently  at  blighted  places  because  of  the  in- 
creased formation  of  wood  by  the  uninjured,  adjacent 
tissue. 

On  thin  twigs,  the  frost  plates  are  often  very 
small,  but  the  wood  under  the  dried  bark  is  found  to 
be  split  radially.  The  cleft,  which  closes  after  the 
abatement  of  the  frost,  is  now  rapidly  overgrown ; 
the  dead  bark  is  thrown  off  at  once  and  the  over- 
growth edges  unite.  In  this,  the  union  takes  place 
after  the  manner  of  frost  ridges,  i.  e.,  the  edges  rise 
up  like  ridges  above  the  normal  plane  of  the  annual 
ring,  while  the  broad  wounds  which  are  closed  very 
slowly  show  the  axial  cylinder  to  be  flattened  at  the 
frozen  place. 

In  both  cases,  however,  the  overgrowth  edges  are 
distinguished  by  the  fact  that  they  arise  under  the  high 
pressure  of  the  dead  bark  and,  on  this  account,  are 
smallest  at  the  outermost  ends  and  pointed  like  wedges. 
This  -wedge-like  grozvth  of  the  overgrowth  edges, 
which  spread  out  over  the  dead  surface,  is  a  character- 
istic of  Might  in  contrast  to  canker.  The  overgrowth 
edges  of  canker  increase  in  thickness  towards  the  place 
of  injury  and,  like  rolls,  sink  down  into  the  open  split 
■ivhich  forms  the  beginning  of  the  canker. 

It  may  easily  be  seen,  that  the  tissues  of  the  over- 
growth edges  dift'er  according  to  the  pressure  condi- 
tions, under  which  they  arise.    This  has  been  discussed 
more  in  detail  under  canker. 
In  Fig.  147,  the  dark  place  B  corresponds  to  the  frost  plate    p  in  Fig. 
145;  ?  is  a  piece  of  dead  bark,  the  healthy  part  of  which  {R),  recognizable 
by  its  white,  glistening,  hard  bast  bundles  {hh) ,  is  separated  from  the  dead 
tissue  by  a  diagonal  cork  zone,  adjoining  the  normal  cork  covering  (/v)  at 


Fig-.  146.  Young-  pear 
trunk  with  different 
kinds  of  blight  spots. 


6ii 


B.  The  annual  ring,  produced  after  the  frost,  is  marked  /.  If  this  is  fol- 
lowed back  to  the  place  of  injury,  it  is  seen  to  diminish  suddenly  to  a  point 
and  to  be  entirely  absent  under  the  dried,  dead  place  in  the  bark  {f,  t). 
Only  the  next  annual  ring  would  be  able  to  push  between  these.  The 
structure  of  these  pointed  overgrowth  edges  resembles  much  more  the 
normal  wood  because  of  the  very  scantily  formed  parenchyma  wood  and 
the  rapidly  appearing  thick-walled  wood  cells  together  with  the  ducts,  than 
does  the  lip-like  wood  parenchyma  overgrowth  edges  of  the  canker  (cf. 
"Open  canker"). 

In  the  adjoining  Fig.  147 
we  see,  above  the  pith  bridge 
(m),  the  normal  annual  rings, 
interrupted  by  darker,  sickel- 
shaped  zones  (ps),  which  here 
appear  gray.  These  zones  con- 
sist at  times  of  thinner  walled, 
ductless,  shortened  parenchyma 
cells,  and  at  times  of  wood 
parenchyma,  richer  in  starch. 
In  luxuriantly  growing  varie- 
ties the  radii  of  the  medullary 
rays,  which  here  are  straight, 
appear  somewhat  bent  and  dis- 
place the  longitudinally  elon- 
gated wood  cells  and  ducts 
from  a  diagonal  to  a  horizontal 
direction. 

It  was  stated  above  that  the 
frost  plates  should  be  consid- 
ered as  narrowly  limited  scald 
injuries  of  relatively  small  ex- 
tent in  all  directions,  which 
could,  however,  be  found  dis- 
playing all  transitions  up  to 
large,  blasted  surfaces  cover- 
ing the  whole  side  of  the  tree. 
Besides  occurring  in  pears, 
such  frost  plates  may  also  be 

found  in  the  red  beech.  On  branches  of  a  beech  thickly  covered  by  such 
plates,  the  browning  of  the  contents  of  individual  cells,  scattered  through 
the  pith,  could  be  proved  to  be  the  final  radiation  of  the  frost  action  in  its 
furthest  extension  into  the  healthy  tissue.  These  cells  undoubtedly  have  a 
different  content  from  the  other  pith  cells,  which  have  remained  colorless 
and,  in  cell  contents,  probably  approach  most  nearly  those  of  the  medullary 
crown,  which  likewise  easily  become  brov/n. 


Fig.  147.     Cross-section  through  a  pear  stem 
at  a  blight  spot,   produced  by  frost. 


6l2 

The  browning  does  not  extend  into  the  surrounding  tissue,  as  in  wound 
rot,  for  the  cells  already  existant,  as  well  as  those  formed  later  in  the  imme- 
diate proximity  of  the  tissue  browned  by  frost,  remain  clear-walled  and 
healthy.  The  browned  medullary  cells  contain  as  much  starch  as  do  those 
not  attacked,  so  that  the  brown  color  can  not  arise  from  a  change  in  the 
starch  but  from  some  other  substance.  The  pith  does  not  suffer  in  every 
case.  Often  the  wood  in  2  to  3  year  old  branches  is  so  browned  that  a 
yellow,  gum-Hke  filling  of  the  ducts  extends  up  to  the  medullary  crown  and 
the  medullary  rays  also  appear  brown  almost  to  the  centre;  the  pith  itself, 
however,  having  no  diseased  discoloration  whatever.  Such  differences 
take  place  in  different  internodes  of  the  same  branch.  Nevertheless,  the 
rule  holds  that  the  initial  stages  of  browning  are  found,  on  an  average,  in 
scattered  cells  of  the  pith,  especially  those  of  the  pith  crown ;  that,  at  first, 
only  the  contents  and  then  later  the  walls  themselves  become  discolored  and 
that  this  discoloration  of  the  contents  seems  to  consist  of  a  browning  and 
thickening  of  the  cell  fluid.  The  gum-like  solid  masses  can  break  in  sec- 
tioning into  angular  pieces.  I  believe  the  filling  of  the  ducts  must  be  traced 
back  in  part  to  the  hardening  of  the  fluid  contents  already  existing,  in  this 
way  easily  explaining  the  often  drop-like  formation  of  the  filling  substance. 

With  increasing  cold  the  browning  of  the  pith,  as  a  rule,  follows  that 
of  the  medullary  rays  and  bast  parenchyma  groups  in  the  bark.  In  branches 
of  the  red  beech  frost  action,  limited  to  individual  vascular  bundles,  can 
often  be  recognized;  the  discoloration  is  restricted  to  the  inner  half  of  two 
main  medullary  rays,  attacking  first  the  part  of  the  bundle  which  belongs 
to  the  medullary  crown  and  often  ending  suddenly  with  the  boundary  of  an 
annual  ring. 

At  times  the  wall  of  the  duct  may  be  found  unstained  or  only  discol- 
ored on  one  side,  while  the  contents  seem  completely  discolored.  It  was 
mentioned  above  that  the  secondary  membrane  can  also  participate  in  the 
filling  of  the  ducts  and  wood  cells.  At  first  this  swells  up  and  at  times,  in 
fact,  completely  fills  the  lumen  of  the  wood  cell,  or  of  the  narrow  duct, 
which  then  seems  colorless  and  refracts  the  light  uniformly.  Besides  this, 
cells  and  ducts  are  found  which  have  turned  a  deep  brown ;  their  cell  con- 
tents often  lie  in  the  form  of  drops  or  rings  against  the  wall,  but  sharply 
separated  from  it.  In  other  cases  there  is  no  separation  between  the  cell 
contents  and  the  cell  wall  and  here  the  participation  of  the  wall  in  the 
change  is  certain.  It  also  may  happen  that  only  an  inner  layer  of  the  cell 
wall  turns  brown,  swells  up  and  finally  becomes  rigid.  This  swollen  layer 
then  has  not  space  enough  on  the  inner  side  of  the  cell,  or  of  the  duct,  and 
folds  inward  so  that  a  colorless  cavity  is  found  between  the  brown  wall 
layer,  which  has  been  pushed  inward,  and  the  outermost,  unchanged  portion. 

In  the  browning  of  the  cambium,  which  usually  occurs  only  on  one  side, 
the  contents  are  only  slightly  browned  and  the  cell  wall  does  not  discolor  at 
all  until  later.  The  spring  wood,  directly  adjoining  the  autumn  wood,  seems 
to  be  most  sensitive.     It  is  evident  in  the  bark,  that  the  parenchymatous 


6i3 

cells,  extending  in  the  form  of  an  arch  from  bark  ray  to  bark  ray,  and 
already  elongated,  suffer  less  than  the  inner,  small  celled  tissue  which 
bounds  them. 

The  observations,  here  mentioned,  illustrate  frequent,  isolated  cases 
but  not  phenomena  of  universal  occurrence.  Finally,  a  case  in  the  sweet 
cherry  should  be  mentioned  as  especially  noteworthy.  The  pith  of  a  one 
year  old  branch  seemed  spHt  at  one  side  up  to  and  beyond  the  centre  and 
the  cells  of  the  periphery  of  the  pith  grew  out  like  filaments  into  the  result- 
ing cavity,  similar  to  the  woolly  stripes  of  the  apple  core.  No  gummosis 
was  present.  The  case  was  observ^ed  in  the  so-called  "frost-wrinkles."  It 
is  interesting  because  it  shows  that  the  activity  of  growth  in  the  pith,  which 
in  general  occurs  only  in  soft  wood  trees  (Tilia),  can  be  reawakened  here. 

In  the  above  mentioned  phenomena  of  scald  is  also  found,  as  a  rule, 
an  increase  of  the  gum  centres  in  the  Amygdalaceae  and  of  the  resin  centres 
in  conifers,  with  an  increase  of  the  parenchyma  masses  (Fig.  147  pz)  be- 
tween the  normal  parts  of  the  annual  ring,  just  as  in  canker.  In  canker, 
it  can  also  be  proved  that  the  breaking  up  of  the  bark  due  to  a  weakening 
of  the  mechanical  ring  corresponds  to  the  breaking  up  of  the  wood  by 
parenchyma  wood  in  the  same  radius.  The  hard  bast  bundles  are  absent 
from  the  bark  of  the  overgrowth  edges  just  as  are  the  real,  thick-walled 
wood  cells  in  the  wood  of  these  edges. 

Aggregations  of  Parenchyma  Wood. 

In  canker  excrescences,  we  have  seen  how  tender  and  perishable  the 
wood  ring  becomes  as  soon  as  it  passes  over  into  the  overgrowth  edges  of 
a  narrow  cleft  at  the  time  of  the  greatest  growth  activity  in  the  spring. 
Because  of  the  rapidity  of  the  production  of  such  large  tissue  masses,  the 
wood  ring  does  not  have  time  to  mature  prosenchymatous  elements  but  at 
first  is  formed  of  parenchymatous,  thin- walled  elements  which,  to  be  sure, 
have  some  advantages  as  a  storage  tissue  for  reserve  substances,  but  show 
very  slight  power  of  resistance  to  parasitic  and  atmospheric  influences.  It 
is  therefore  easily  understandable  that  even  in  healthy  trees  the  appearance 
of  parenchyma,  instead  of  prosenchyma  wood,  deserves  especial  attention 
from  a  pathological  standpoint.     Such  cases  may  be  found  everywhere. 

The  aggregations  of  parenchyma  wood  can  occur  in  the  trunk  in  the 
form  of  scattered  nests,  or  in  ring-like  bands,  differing  in  length  and  width. 
They  have  been  variously  named.  We  find  an  enumeration  of  such  cases 
in  de  Bary^  ,  who  sees  in  them  an  hypertrophy  of  the  medullary  rays. 
Rossmassler  calls  them  "Repetitions  of  the  pith;"  Nordlinger,  "pith  spots," 
while  Th.  Hartig-  speaks  of  "cell  passages."  The  most  mature  form  is 
found  in  the  so-called  "moon  rings."  These  are  brown,  or  white,  bands  of 
parenchyma  wood,  usually  extending  in  a  ring  partially  or  entirely  around 
the  trunk.     This  parenchyma  wood  appears  at  times  to  be  decayed  like 

1  De  Bary,  Vergleichende  Anatomie  der  Vegetationsorgans  1877,  p,.  567. 

2  Hartig-,    Th.,    Vollstandige    Naturgeschichte    der    forstlichen    Kulturpflanzen. 
1852,  p.  211. 


6i4 

tinder.  These  decayed  tissue  masses  not  infrequently  give  a  cellulose 
reaction.  Such  tissue  is  often  found  traversed  by  mycelium.  Th.  Hartig 
describes  the  fungus  as  Nyctomyces  candidus  and  A'',  utilis.  Rob.  Hartig 
ascribes  the  mycelium  observed  in  oaks  to  Stereum  hirsutum  Willd\  In 
other  tree  genera,  other  fungi  are  found  which  destroy  the  wood  and  which 
are  treated  more  thoroughly  in  the  second  volume,  p.  385  ff-. 

In  cross-sections  of  the  wood  structures  termed  "pith  spots"  appear  as 
isolated,  sharply  bounded,  somewhat  crescent-like,  browned,  decayed  spots, 
which,  like  passages,  may  be  followed  downward  to  different  distances  in 
the  trunk.  We  owe  a  thorough  study  of  these  to  Kienitz-Gerlolf^,  who 
observed  that  in  willows,  mountain  ashes  and  birches  it  is  caused  by  the 
feeding  of  an  insect  larva.  According  to  a  review  by  Karsch*  Tipula 
suspecta,  Rtzb.  is  concerned  here.  This  larva  feeds  "on  the  cells  of  the 
cambium  and  the  youngest  wood  at  the  time  of  the  formation  of  the  annual 
ring."  The  passages,  made  by  it,  are  closed  as  follows : — "the  cells,  break- 
ing through  the  edges  of  the  wound,  grow  quickly  and  divide  with  delicate 
cross-walls.  At  the  same  time,  a  complete  closing  of  the  cambial  ring  takes 
place  and,  from  now  on,  the  normal  wood  and  normal  bark  are  formed  over 
the  wound  surface,  while  the  cavity,  perfectly  independent  of  the  new 
cambium,  is  closed  by  the  increase  of  cells^.  These  injuries,  due  to  filamen- 
tous diptera  larvae,  which  bore  their  way  into  the  cambial  zone,  especially 
at  the  base  of  the  trunk  and  the  root  neck,  sometimes  even  higher  up  in  the 
shaft,  and  in  water  sprouts  in  May  and  June,  are  primarily  considered  as 
producers  of  pith  spots  or  "brown  chains"  only  in  the  varieties  of  trees 
named.  Kienitz  remarks  that  similar  structures  in  other  trees,  especially 
conifers,  do  not  arise  from  the  diptera  larvae  above  mentioned. 

In  regard  to  the  pith  spots  of  the  birch,  v.  Tubeuf"  confirms  the  inves- 
tigations of  Kienitz  and  mentions  thereby  that  G.  Kraus  explains  these  cell 
aggregations  as  normal  structures.  De  Bary,  as  was  said  above,  speaks  of 
hypertrophies  of  the  medullary  rays  and,  at  the  first  glance,  one  also  gets 
the  impression  that  the  pith  spots  are  caused  by  a  widening  of  the  medullary 
rays.  These  are  seen  actually  to  become  broader  before  they  enter  the 
aggregations  of  parenchyma  wood  and  their  cells  take  on  the  polyhedric, 
thick-walled,  greatly  pitted  appearance  of  the  cells  of  the  pith  spot  which 
are  filled  at  times  with  starch  and  brown  tannic  substances.  In  fact,  it  is 
often  found  that  the  medullary  rays,  when  entering  the  pith,  are  broadened 
and  unite  laterally.  But,  supported  by  my  "barking  experiments,"  I  con- 
sider the  newly  formed,  filling  tissue  to  be  a  product  of  some  cell  increase 
which  can  take  place  not  only  in  the  medullary  rays  but  in  all  the  tissue 


1  Hartig,  Rob.,  Zersetzungsorscheinungen  des  Holzes,  p.  129. 

2  Paging  in  the  German  oiiginal. 

8  Kienitz,  M.,  Die  Entstehung  der  Markflecke.     Eot.   Centralbl.   1883,  Vol.  XIV, 
p.  21  ff.    Here  also  bibliography. 

4  Bot.  Jahresbericht.  Jahrg.  XI,  Part  2,  p.  518. 

5  Bot.  Jahresber.  1883,  Vol.  I,  p.  182. 

6  V.  Tubeuf,  Die  Zellgange  der  Birke  und  anderer  Laubhijlzer.  Frostl.  naturwiss. 
Zeitschr.  1897,  p.  314. 


6i5 

forms  composing  the  annual  ring.  The  growth  of  the  medullary,  or  the 
bark  rays,  only  exceeds  that  of  other  tissues  in  all  processes  of  ivound  heal- 
ing; it  thereby  becomes  predominate. 

Also  if,  in  the  above  mentioned  "moon  rings,"  the  boundaries  between 
the  already  destroyed  parenchyma  wood  of  the  annular  bands  and  the 
healthy  tissue  are  investigated,  not  infrequently  a  striking  widening  of  the 
medullary  rays  is  found,  especially  in  oaks. 

In  conifers,  especially  pines,  a  still  more  extreme  form  of  disturbance 
may  be  found,  the  so-called  "ring-barking."  At  times,  when  the  trunk  is 
split,  a  complete  cylinder,  beginning  at  the  healthy  central  portion  of  the 
trunk,  separates  from  the  apparently  equally  healthy  peripheral  wood,  as 
from  a  shell.  This  takes  place  because  the  tissue  is  destroyed  in  one,  and 
indeed  only  one  annual  ring,  becomes  rotten  and  traversed  by  mycelium. 

This  form  of  ring  barking  is  distinguished  by  its  sound,  healthy  core 
from  the  one  studied  by  Robert  Hartig^  in  the  pine,  in  which  a  wound 
parasite,  Trametes  Pini  (Brot.)  Fr.  causes  the  destruction  of  the  core  but 
does  not  extend  into  the  healthy  sap-wood.  Hartig  describes  the  rapid 
advance  of  the  mycelium  in  the  medullary  rays  and,  after  having  discussed 
the  destruction  of  the  wood  caused  by  the  mycelium,  the  dissolution  of  the 
incrusting  substances  and  the  retention  of  the  cellulose  in  the  wood  fibres, 
says  that,  "as  the  result  of  the  collapse  of  the  wood  which  is  connected  with 
this  decay  and  loss  of  water,  not  only  are  radially  extending  cracks  formed 
but  often  the  outermost  annual  layers  are  loosened  as  a  mantel  from  a 
thicker  or  thinner  core.  Thus  annular  clefts  are  produced  which  can  have 
led  to  the  name  of  "ring  barking."  We  are  here,  therefore,  concerned  with 
a  form  of  very  extensive  red  rot,  or  heart  rot.  According  to  v.  Tubeuf, 
the  fungus  appears  also  in  spruces  and  has  been  observed  in  larches  and 
white  firs  and,  in  America,  in  the  Douglas  fir.  Emphasis  should  be  laid 
on  the  fact  that  this  mycehum  spreads  "very  easily  in  one  certain  annual 
zone-  and  the  diseased,  white  tissue  aggregations,  which  now  consist  only 
of  cellulose,  may  be  found  abundantly  in  the  spring  wood"^.  This  seems  to 
me  to  indicate  that  the  fungus  finds  greater  resistance  in  the  adjacent  annual 
rings,  i.  e.,  the  annual  ring  already  attacked  must  necessarily  have  been 
more  porously  constructed.  Accordingly,  bands  of  parenchyma  wood 
might  contribute  especially  not  only  to  infection  of  branch  wounds  by 
Trametes  and  other  wood  destroyers,  but  also  to  their  distribution  in  the 
trunk. 

False  Annual  Rings. 

Double  Rings,  Etc. 

Its  is  a  well  known  fact*  that  the  size  and  constitution  of  every  annual 


1  Hartig,  R.,  Wichtig-e  Krankheiten  der  Waldbaume.    Berlin  1874,  p.  55. 

2  V.    Tubeuf,    Pflanzenkranlclieiten    durch    Icryptogame    Parasiten    vei-ursacht. 
Berlin  1895,  p.  471. 

8  Hartig-,  R.,  Lehrbuch  der  Pflanzenkrankheiten.     Berlin  1900,  p.  172. 
*  Kiister,  E.,  Pathologische  Pflanzenanatomie.    Jena  1903.  p.  25,  etc.     Here  also 
pertinent  bibliography. 


6i6 

ring  in  woody  plants  depends  upon  the  amount  and  kind  of  leaf  activity. 
This  has  been  thoroughly  treated  in  forestry  literature.  Every  considerable 
interruption  in  the  activity  of  the  leaf  apparatus  makes  itself  felt  in  the 
wood  and  can  lead  to  the  omission  of  wood  formation  in  one  side  of  the 
tree,  or  at  the  base  of  the  trunk  and  in  the  root.  If  the  cambium,  which  had 
been  active  in  the  spring,  is  incited  to  renewed  increase  in  the  same  year 
after  a  period  of  inactivity,  it  begins  the  formation  of  a  new  spring  wood 
which  passes  over  into  autumn  wood,  sometimes  more  slowly,  sometimes 
more  quickly.  In  this  way  a  new,  normal,  annual  ring  is  produced.  In 
such  cases  are  found  semi-circular  double  rings,  or  others  encircling  the 
whole  girth  of  the  trunk. 

We  owe  exact  studies  on  this  subject  to  Kny^,  who  determined  espe- 
cially clearly  in  Tilia  parvifolia  that,  after  the  sprouting  of  the  buds  on 
shoots  which  had  been  entirely  defoliated  by  caterpillars,  a  second  annual 
ring  was  formed.  The  boundary  between  the  newly  formed  spring  wood 
and  the  wood  ring  produced  before  defoliation  is  sharp.  In  Ratzeburg's- 
study  we  find  repeated  examples  of  the  dependence  of  the  formation  of  the 
annual  ring  on  the  time  of  defoliation.  Since  diifcrent  insects  can  cause 
complete  defoliation,  at  different  times  of  the  year,  a  weakening  of  the 
growth  of  wood  is  found  sometim.es  in  the  same  year,  but,  at  other  times, 
not  until  the  following  year  (when  the  deposition  of  reserve  substances  is 
scanty). 

In  1886,  I  was  able  to  add  the  action  of  frost  to  the  causes  which  can 
bring  about  the  formation  of  false  annual  rings.  In  1895  R.  Hartig^  pub- 
lished a  treatise  in  which  he  described  frost  rings  in  the  oak  and  fir  and 
considered  also  a  different  mechanical  effect,  viz.,  a  drooping  of  the  shoots 
due  to  a  loss  of  turgidity.  This  bending  of  the  shoots  became  permanent 
and  could  be  found  the  following  year.  The  drooping  can  also  occur  as  a 
result  of  the  destruction  of  the  pith  parenchyma.  In  the  last  edition  of 
Hartig's  text  book*,  frost  rings  from  the  wood  of  a  pine  and  of  a  spruce 
are  illustrated  with  the  remark  "in  older  parts  of  the  trunk  of  the  pine  it 
was  found  that  a  so-called  double  ring  was  produced  in  each  year  of  late 
frosts.  I  later  confirmed  the  fact  also  in  spruces  and  other  conifers,  that 
a  late  frost  not  only  injuries  the  youngest  shoots  but  even  produces  the 
'double  rings'  formed  in  parts  of  the  trunk  which  were  ten  years  old." 

O.  G.  Petersen^  describes  and  illustrates  a  similar  disturbance  in  the 
structure  of  the  annual  ring  of  beech  trees  which  had  suft'ered  severely  from 
frost  on  the  17th  to  i8th  of  May,   1901,  in  Holland.      Nordlinger^  had 


1  Kny,  L.,  iiher  die  Verdoppelung  des  Jahresringes.  Sep.  Verhandl.  d.  Bot.  Ver. 
d.  Prov.  Brandenburg-  1879.     Here  also  discussion  of  earlier  theories. 

2  Ratzeburg,  Waldverderbnis,  I,  p.  160,  2.S4;  II,  p.  154,  190. 

8  Hartig,  R.,  Doppelringe  als  Folge  von  Spatfrost.  Forstl.  naturw.  Zeitschrift 
1895,  p.  1-8. 

4   Lehrbuch  der  Pflanzcnkrankheiten.     Berlin,  Springer  1900,  p.  220,  221. 

n  Petersen,  O.  G.,  Natterfrostens  virkning  paa  Bogens  ved.  Sep.  Det  forstlige 
Forsogsvaesen,  I.    1904. 

6  Nordlinger,  Die  fetten  und  die  mageren  Jahre  der  Baume.  Kritische  Blatter 
C.  Forst-  und  Jadgwissenschaft,  1865,  Vol.  47,  Part  2. 


6i7 

already  observed  in  the  normal  wood  formation  a  ring-like  break  in  the 
form  of  a  line  of  reddish  tissue.  Corresponding  reports  and  observations 
may  be  found  elsewhere  which,  however,  do  not  contain  any  new  points  of 
view.  Studies  on  canker  phenomena  increased  our  understanding  of  the 
disturbances  in  the  formation  of  annual  rings.  I  have  proved  in  the  apple 
canker  that  an  annual  ring,  which  is  simple  and  normal  on  the  healthy  side 
of  the  branch,  may  be  subdivided  on  the  canker  side  into  several  ring  zones. 
My  recent  studies  on  the  oak  have  shown  how  such  a  breaking  up  of  the 
tissue  may  take  place. 
Experimental  Production  of  Parenchyma  Wood  by  Frost  Action. 

The  cases  of  the  production  of  parenchymatous  wood  tissue  instead  of 
normal  parenchyma,  described  in  the  preceding  chapter  as  "pith  spots," 
"parenchyma  wood  bands,"  "ring  shells,"  etc.,  arise  from  a  variety  of  causes 
which,  however,  as  a  whole,  agree,  in  that  the  cambium  in  different  parts  of, 
or  to  the  whole  extent  of  the  annual  ring,  is  more  or  less  freed  from  the 
pressure  of  the  bark  girdle  binding  it.  It  may  be  concluded  from  subse- 
quent observations  that  frost,  and  especially  spring  frosts,  furnish  one  of 
the  most  essential  and  frequent  causes  of  such  a  loosening  of  the  bark  girdle. 

In  1904,  in  May,  a  frost  had  so  greatly  injured  the  younger  oak  shoots 
near  the  edges  of  different  forest  plantations,  where  these  bordered  on  open 
meadows,  that  a  number  of  branch  tips  were  completely  frozen  while  only 
the  leaves  of  others  had  blackened  and  dried;  later  they  continued  their 
growth  at  the  tips.  When  these  shoots,  within  a  few  weeks,  had  again 
formed  new  leaves,  they  were  cut  for  investigation.  They  showed  great 
dift'erences  in  structure,  among  others  that  illustrated  in  Fig.  148. 

We  recognize  an  irregularly  pentagonal  medullary  body  (ni)  sur- 
rounded by  slender  wood  rings  (h)  more  strongly  developed  on  one  side. 
This  wood  ring,  however,  on  the  outside,  does  not  adjoin  a  regular  cambial 
zone,  as  is  the  case  in  the  normal  branch,  but  passes  over  suddenly  into  a 
porous,  wide-celled  parenchyma  wood  (ph)  which  becomes  thicker  walled 
toward  the  bark  and  only  rarely  leaves  recognizable  a  cambial  boundar}' 
zone  between  itself  and  the  bark.  That  this  girdle  (ph)  formed  of  porous 
tissue  still  belongs  to  the  wood  ring  and  has  arisen  from  it,  is  proved  by  the 
short-celled,  vascular  elements  (g')  scattered  in  the  zone  of  thin-walled 
cells  which,  in  the  structure  of  their  thickening  layers,  seem  similar  to 
those  of  the  ducts  in  the  normal,  first  formed  wood  ring,  or  resemble  them. 
This  presence  of  short  ducts,  or  duct  cells,  and  the  condensing  of  the  whole 
zone  of  thin-walled  cells  at  its  periphery  by  the  occurrence  of  thick-walled 
elements,  resembling  the  true  wood  cells,  shows,  therefore,  that  this  branch, 
injured  by  frost,  had  re-adapted  itself  to  the  normal  formation  of  the  wood 
ring  a  short  time  after  the  cessation  of  the  frost  action  and  the  formation 
of  the  parenchyma  wood. 

If  this  bra.nch  had  been  allowed  to  continue  growth  until  frost,  we 
would  then  have  had  a  second  false  annual  ring,  as  has  been  observed  by 
earlier  investigators  and  was  discussed  in  the  preceding  chapter. 


6i8 

The  bast  ring  (&)  has  been  less  affected ;  only  the  contents  of  the  young 
bast  cells  are  usually  found  to  be  brown,  corresponding  to  the  filling  of  the 


Pig-.  148.     A  healed  internal  frost  wound  on  a  young  oak  branch,  caused  by  injury 

from  a  May  frost. 

,-  canibial  zone,  z  zigzagr  line  with  swollen  cell  walls,  g  vessels  in  the  normal  wood. 

Explanation  of  the  other  letters  to  be  found  in  the  text. 

different  ducts  of  the  wood  ring  with  a  reddish  yellow,  gum-like  substance. 
The  bark  parenchyma  contains  single,  brown  groups.  No  special  phenomena 


6i9 

of  discoloration  are  visible  in  the  collenchymatous  outer  layer  of  the  bark 
but  may  be  found  in  the  pith  crown,  which  appears  to  be  entirely  brown. 
This  browning  decreases  with  the  distance  towards  the  heahhier  base  of 
the  branch  at  which  the  sections  were  made.  At  the  base  of  the  branch 
we  find  only  scattered  cells,  with  yellow,  swollen  contents. 

A  difference  in  direction  of  the  holes  thus  produced  becomes  noticeable 
in  the  abundantly  recurring  cracks.  Within  the  pith  disc  may  be  found 
the  greatest  radial  extension  of  the  holes  which  is  seen  to  be  connected  with 
a  pecuUar,  radiating  formation  of  the  pith.  This  is  found  to  be  distended 
into  a  pentagon,  produced  by  the  passing  of  the  vascular  bundles,  com- 
posing the  wood  ring,  out  from  the  wood  ring.  As  indicated  above,  the 
cause  of  this  extension  of  different  bundles  lies  in  the  fact  that,  in  each  of 
the  five  corners  of  the  pith,  the  vascular  .systems,  destined  for  the  five  next 
higher  leaves,  are  about  to  make  their  way  outward  through  the  bark  into 
the  leaves.  The  pith  body  for  the  leaf  lying  next  above  the  part  of  the 
branch  here  illustrated,  is  naturally  furthest  distended  and  is  adapting  itself 
to  passing  over,  as  a  pith  connection  (mb),  into  the  next  bud.  The  bundles 
of  the  two  higher  leaves,  lying  only  one  or  two  internodes  above  the  place 
of  the  cross-section,  still  lie  within  the  complete  wood  ring,  but  even  they 
have  already  formed  noticeable  distentions  of  the  axial  cylinder  (at  the  right 
in  the  figure).  The  bundles  for  the  4th  and  5th  leaves,  following  the  spiral 
of  the  leaf  insertion,  still  lie  entirely  within  the  wood  ring  and  indicate 
their  lateral  appearance  only  by  a  slight  outward  convexity  (at  the  left  side 
of  the  figure).  Between  them  the  pith  body  is  continued  only  in  the  form 
of  a  broadened  medullary  ray  and  has  not  widened  into  an  actual  pith 
connection. 

The  holes  (/),  produced  by  the  rupturing  of  the  tissue,  correspond  in 
size  to  the  amount  of  distention  of  the  pith.  The  larger  these  are,  and  the 
nearer  they  stand  to  the  buds  belonging  to  them,  the  stronger  is  the  radial 
splitting.  Differing  from  those  in  the  pith,  we  find  the  holes  (/')  in  the 
bark  extending  tangentially.  They  are  produced,  in  part,  by  the  throwing 
off  of  the  peripheral  collenchyma  of  the  parenchyma,  rich  in  chlorophyll,  in 
part,  however,  by  the  rupturing  of  individual  parenchyma  cells.  It  should 
be  noticed,  that  the  formation  of  holes  in  the  bark,  as  also  the  formation  of 
thin-walled  tissue  (ph-lg),  is  much  greater  on  the  side  of  the  branch  where 
the  bundle  has  separated  most  widely  from  the  main  vascular  system  than 
on  the  opposite  side.  Moreover,  this  also  explains  the  fact  that,  in  the 
investigation  of  branches  injured  by  frost,  as  a  rule,  one  side  is  found  more 
greatly  affected  than  the  other.  The  natural  conclusion,  that  the  action  of 
the  frost  has  been  greater  on  one  side  is  usually  erroneous.  For,  if  a  num- 
ber of  successive  internodes  are  examined  by  series  of  sections,  the  investi- 
gator will  be  convinced  that  sometimes  one  side  of  the  same  branch  shows 
a  greater  injury  from  frost,  sometimes  the  other,  according  to  the  position 
of  the  bud,  near  which  the  section  was  made.  The  closer  to  the  bud,  the 
stronger  the  action  of  the  frost  in  the  branch. 


620 

After  numerous  vain  attempts,  the  above  described  disturbances  in 
tissue,  and  processes  of  healing,  could  at  last,  in  the  spring  of  1905,  be 
produced  artificially.  In  April  potted  specimens  of  4  to  5  year  old  oaks 
w^ere  brought  into  a  greenhouse  for  forcing.  The  tender  young  shoots 
were  exposed  in  May  for  one  night  to  a  temperature  of  4  degrees  C.  below 
zero  in  a  freezing  cylinder.  The  plants  were  then  left  out  of  doors  and 
investigated  the  middle  of  June.  Here,  exactly  as  in  the  observations  made 
the  previous  year  on  naturally  frozen  oaks,  the  branches,  injured  by  frost, 
showed  very  different  forms  of  disturbance.  Among  them  were  some 
resembling  typically  the  natural  injuries  described  above;  only  the  processes 
of  healing,  which  here  begin  clearly  at  the  medullary  rays,  were  much  less 
extensive,  which  may  be  traced  to  the  fact  that  potted  specimens  always 
develop  more  weakly  and  slowly  than  forest  trees  growing  in  open  ground. 
The  observation  was  also  made,  that  the  clefts  in  the  tissue  seemed  to  be 
less  extensive,  the  older  and  stronger  the  branch  was  at  the  time  of  the 
frost  action.  I  conclude  from  this  that  injury  from  frost  only  leads  to 
the  formation  of  parenchyma  wood  within  an  annual  ring  when  it  affects 
very  young,  tender  shoots  at  the  time  of  the  greatest  growth  in  length. 
Besides  this,  favorable,  warm  weather  must  follow  the  frosty  nights  so  that 
cell  increase  can  continue  at  its  former  rate.  The  building  material,  in  the 
form  of  mobilized  reserve  substances,  is  present  in  the  branch,  injured  by 
frost,  in  the  same  amounts  as  before  the  action  of  the  frost,  but  the  newly 
produced  cell  elements  develop  differently  because  the  conditions  of  tension 
in  the  branch  and  the  resulting  pressure  on  the  cambium  have  become  dif- 
ferent, due  to  the  breaking  up  caused  by  frost. 

The  Theory  of  the  Mechanical  Action  of  Frost. 

The  phenomena,  which  came  to  light  in  the  above  described  natural 
and  artificial  frost  injuries  to  young  branches,  however  they  may  vary,  can 
be  traced  to  simple  mechanical  processes.  In  this  we  still  refer  to  the  above 
illustration  of  the  oak  branch  in  which  we  see  that  the  pentagonal  wood 
ring,  surrounding  the  medullary  disc,  passes  over  suddenly  into  a  light  zone 
of  delicate  tissue  (Ig)  and  this  gradually  forms,  toward  the  perihpery, 
tougher  elements,  which  have  the  character  of  normal  wood  (h). 

The  illustrations  2  to  6  in  Fig.  149  serve  to  orient  the  place  of  origin  of 
the  thin-walled  tissue.  These  show  enlarged  portions,  drawn  cell  for  cell 
from  the  right  side  of  the  above  figure  (Fig.  148)  at  the  region  of  the  sec- 
tion, lying  between  Ig  and  b.  In  all  the  drawings,  the  upper  angle  is  the  one 
toward  the  pith,  the  under  angle  the  one  toward  the  bark  which,  in  fact 
(Fig.  149  2,  4,  6)  even  shows  bark  elements.  The  uppermost  cell  groups, 
in  part  designated  by  h,  form  the  boundary  of  the  wood  ring  which  was 
present  before  the  action  of  the  frost.  These  pass  over  directly  into  the 
thin-walled  tissue  (Ig)  of  the  thin-walled  stripe  (Fig.  149  2,  5).  In  this, 
the  medullary  rays,  which  in  normal  wood  are  only  one  to  two  cells  broad 
(Fig.  149,  5  m  s)  have  become  enlarged  and  irregularly  many-celled.    They 


621 


Fig-.   149.     Cell  groups  from  the  transitional  region  between  the  normal  wood  ring- 

and  the  stripe  of  thin-walled,  loose  parenchyma  wood,  produced  by  frost.     Taken 

from  the  zone  Ig-b  in  Fig-.   148.     z,  in  Fig.  2  and  5,  indicates  the  zigzag  lines  with 

their  swollen  cell  walls. 


622 

contract  to  their  former  breadth  only  wliere  the  porous  tissue  passes  over 
into  the  secondary  wood  (Fig.  149  2,  ?,  A')  with  reg-ular  ducts  {g'').  Then 
a  normal  cambial  zone  is  formed  again  (Fig.  149  2  c~)  which,  at  the  time 
when  the  medullary  rays  were  broadened  excessively,  had  become  irrecog- 
nizable,  since  cell  division  took  place  absolutely  irregularly  in  different 
regions  of  the  ring  of  thin-walled  tissue.  As  soon  as  the  formation  of  the 
regular  cambial  zone  begins  again,  die  loose  bark  tissue  also  differentiates 
itself  in  such  a  way  that  juvenile  bast  groups  (Fig.  149,  7  h  and  6  b  h') 
again  becomes  recognizable. 

The  fact,  that  no  dead  tissue  of  any  kind  is  present  between  the  wood, 
matured  before  the  action  of  the  frost  (h),  and  the  looser,  thin-walled 
tissue  (Ig),  proves  that  the  young  wood,  the  sap  wood  ring,  has  passed  over 
directly  into  the  parenchyma  wood  of  the  ring  of  thin-walled  tissue.  Never- 
theless, this  parenchyma  has  retained  its  connection  with  the  wood  body. 
On  this  account,  it  is  not  suq^rising  that,  after  the  cessation  of  the  causes 
which  had  brought  about  this  parenchymatous  formation  of  wood,  the  tissue 
gradually  re-assumes  the  normal  wood  character  and  adapts  itself  to  the 
formation  of  a  secondary  wood  ring  (Fig.  149  2  and  ?  h').  In  fact,  indi- 
vidual elements  of  the  sap  wood,  the  thickening  of  which  had  advanced 
somewhat  further  at  the  time  when  the  formation  of  parenchyma  wood 
began,  had  continued  the  thickening  of  their  walls.  On  this  account,  we 
find  isolated  tracheal  elements  (Fig.  149  4,  fr)  in  the  centre  of  the  paren- 
chyma wood. 

The  zone  of  thin-walled,  porous  tissue  (Ig)  in  the  cross-section  of  the 
oak  branch  (Fig.  148)  is,  therefore,  only  a  modified  wood  ring  which  has 
passed  over  into  an  excessive  new  cell  formation.  Since  such  a  cell  increase 
can  arise  only  from  elements  which  still  possess  their  cambial  nature,  it 
must  necessarily  be  concluded  that  the  very  youngest  cambial  zone  elements, 
i.  e.,  the  sap  wood,  have  produced  this  parenchyma  wood.  As  a  matter  of 
course  the  real  anatomical  cambium,  together  with  the  young  bark,  has  par- 
ticipated in  this  cell  increase  and,  in  this  way,  produced  the  abundant  tissue 
in  which  it  is  not  possible  to  distinguish  where  the  transition  from  wood  to 
bark  takes  place. 

We  now  ask  what  may  be  the  cause  of  the  formation  of  this  profuse 
tissue  zone?  The  answer  can  only  be  found  in  the  removal  or  weakening 
of  the  constricting,  compressing  influence,  exercised  by  the  bark  girdle,  as 
a  whole,  on  the  youngest  tissue,  i.  c.,  the  cambial  region. 

This  cause  is  indicated  by  the  holes  in  the  bark  tissue  (Fig.  148  /',  at 
the  right).  Such  tangential  holes  in  the  healthy  tissue  are  produced  by  the 
upraising  of  the  tissue  lying  above  the  hole  from  that  lying  beneath  it.  It 
can  only  be  raised,  however,  if  it  has  not  enough  room  on  this  underlying- 
parenchyma  which  is  caused  by  a  greater  tangential  distention.  Conse- 
quently, a  stronger  tangential  strain  has  occurred  in  these  outermost  tissue 
layers  than  in  the  adjacent  inner  layers  of  the  bark. 


623 

Caspary's  measurements  in  freezing  should  be  recalled  here.  The 
peripheral  layers  contract  earlier  and  more  strongly  than  do  the  central 
layers.  This  contraction  with  cold  is  stronger  tangentially  than  radially 
and  greater  in  the  delicate  parenchyma  than  in  the  prosenchyma  wood.  Con- 
sequently, with  the  action  of  frost,  there  must  take  place  everywhere  within 
a  woody  axis  a  preponderance  of  tangential  strain  over  radial  contraction 
and,  under  certain  circumstances,  this  must  increase  to  a  radial  splitting  of 
the  tissue. 

If  the  wood  ring  is  thought  of,  first  of  all,  as  isolated,  this  preponder- 
ating tangential  contraction  in  places  of  least  resistance  would  necessarily 
lead  to  such  clefts  as  would  correspond  to  the  gaping  frost  cracks  in  old 
trunks.  Therefore,  inner  clefts  must  be  produced  from  purely  mechanical 
causes  and.  in  fact,  in  the  medullary  rays  and  medullary  transverse  connec- 
tions. Such  are  actually  shown  in  the  illustration  of  the  oak  branch,  injured 
by  natural  frost  (Fig.  148). 

If  we  noM^  consider  the  primary  wood  ring  in  its  relation  to  the  adjoin- 
ing bark  girdle,  we  must  refer  again  to  the  fact  that  the  bark  girdle,  of 
which  the  peripheral  cells  are  larger  tangentially  than  radially,  contracts 
more  strongly  tangentially  and,  therefore,  is  strongly  torn  in  this  direction 
during  the  action  of  frost.  If  the  frost  grows  less,  this  cracking  may  cease, 
indeed,  but  its  effects  remain,  for  the  tissue  which  may  thus  be  str.etched, 
is  not  absolutely  elastic  and  does  not  contract  to  its  former  volume.  In 
this  way  each  frost  action  leaves  behind  an  excessive  lengthening  of  the 
peripheral  tissue  layers  in  proportion  tO'  the  adjacent  layers  which  lie  more 
toward  the  inside.  The  bark  body,  as  a  whole,  therefore,  is  longer  and 
either  does  not  have  room  enough  on  the  wood  cylinder  so  that  in  places 
it  is  raised  up  from  it,  or  it  at  least  curves  outward,  i.  e.,  it  decreases  its 
constricting  influence  on  the  camhial  elements  of  the  wood  cylinder. 

The  cambial  zone  responds  to  this  with  a  formation  of  parenchyma 
wood,  as  may  be  seen  in  every  wound  in  which  the  bark  is  raised.  If  the 
bark  girdle  closes  together  again  into  a  connected  layer  the  cambial  cylinder 
of  the  branch,  by  growth  in  thickness,  must  again  resist  the  constricting 
effect  of  the  bark  and,  on  this  account,  again  forms  normal  wood  elements. 

Thus  the  formation  of  the  parenchyma  wood  bands  in  young  branches 
comes  under  the  same  law  of  unequal  contraction  which,  in  old  trunks, 
leads  to  the  production  of  gaping  frost  clefts. 

The  Rupture  of  the  Cuticle. 

The  experiments  on  potted  specimens  of  forced  oaks,  mentioned  in  the 
previous  section,  proved  the  fact,  not  known  until  then,  that,  on  superficially 
browned,  or  still  green  leaves,  i.  e.,  those  outwardly  but  little  affected,  a 
repeatedly  interrupted  black,  very  fine  line  is  formed  on  the  under  side, 
which  gives  the  impression  of  very  fine  particles  of  soot  which  had  settled 
on  it  in  places.  With  a  higher  magnification,  it  is  seen  that  this  line  consists 
of  small  raised  places  in  the  outermost  cuticular  layer  which,  because  of  its 


624 

granular  condition,  retains  the  air.  and  therefore  appears  black.  The  small 
granular  papillae  still  remained  when  the  leaf  was  destroyed  by  sulfuric 
acid;  in  which  treatment  the  leaf  curled  up  like  a  worm  and  the  epidermis 
of  the  upper  side  puffed  out  in  places. 

This  result  agrees  with  discoveries  which  had  been  observed  earlier  in 
beech  trees  after  natural  late  frosts,  and  which  we  could  prove  also  on  oaks 
in  the  open.  In  the  production  of  such  scarcely  perceptible  rupturing  of 
the  cuticle,  some  special  conditions  must  also  have  co-operated  which  were 
present  accidentally  in  the  experiments  but  do  not  seem  to  be  always  effec- 
tive in  other  experiments  or  in  nature,  for,  soon  after  late  frost,  such  injured 
oak  leaves  could  be  found  in  some  localities  but  not  in  others.  Probably  3 
definite  condition  of  turgor  in  the  leaf  is  connected  with  it  and  this  will  be 
dependent  again  on  the  constitution  of  the  cell  contents  at  any  given  time. 

A  conception  of  the  fine  differences,  which  are  decisive  in  frost  inju- 
ries, is  obtained  from  the  observation  that  dead  particles  of  tissue,  injured 
by  frost,  may  be  found  at  times  in  the  centre  of  the  mesophyll  of  the  leaf, 
which  apparently  is  but  little,  if  any  injured.  The  fact  that,  in  experi- 
ments, these  cuticular  breaks  appear  only  on  the  under  sides  of  the  leaves 
may  be  traced  perhaps  to  a  constitution  different  from  that  of  the  upper 
.cuticular  covering,  for  it  is  found  that  in  the  action  of  sulfuric  acid,  the 
upper  covering  turned  a  bright  lemon  yellow,  which  color  shade  was 
scarcely  perceptible  in  the  cuticle  of  the  under  side. 

I  would  like  to  lay  especial  value  upon  the  discovery  that,  under  certain 
circumstances,  a  rupturing  of  the  cuticular  glaze  can  be  produced  by  light 
frost.  In  other  breaks  in  the  cuticle  (in  pomes)  fungus  spores  were  found 
lying  in  the  line  of  the  break  and  it  may,  therefore,  not  be  out  of  place  to 
assume  that,  in  these  protected  places,  such  fungus  spores  have  the  best 
opportunity  to  germinate  and  to  sink  their  germinating  tubes  into  the  organs. 
In  this  zvay  might,  therefore,  he  explained  the  attacks  upon  apparently  per- 
fectly healthy  leaves  and  fruit  by  fungus  infection  after  a  light  spring  frost. 
Voglino's^  reports  might  be  referred  to  here.  In  1903,  after  some  frost  in 
April,  he  found  that  the  fungous  parasites  had  an  especially  large  distribu- 
tion in  plants  injured  by  frost. 

Thus  is  explained  also  the  phenomenon  of  the  so-called  rust  etchings 
in  connected  rings  and  irregular  surfaces  on  our  fruit.  They  are  cork 
formations  which  have  set  in,  in  the  cuticular  tears,  as  a  result  of  the 
processes  of  healing,  while  the  normal  cork  etchings  on  the  fruit  usually 
begin  at  the  stomata,  or  rather,  the  lenticels. 

Protective  Measures  Against  Frost. 

(a)   Snow  Covering. 

The  process,  universally  used  for  protecting  plants  against  frost,  con- 
sists in  surrounding  them  v.ith  substances  which  are  poor  conductors  of 


1  Voglino,  P.,  L'azione  del  freddo  suUe  piante  coltivate,  specialmente   in  rela- 
zione  col  parassitlsmo  dei  funghi.     Attl  accad.  di  Torino  XLVI. 


625 

heat.  Grapevines,  roses,  etc.,  are  covered  with  earth  or  leaves,  or  the 
trunks  are  wrapped  in  moss,  straw  and  the  like.  All  these  means  are  good 
but  in  cold  winters,  with  a  moderate  snowfall,  one  should  not  delay  throw- 
ing the  snow  from  the  streets  on  to  the  covered  plants.  It  is  well  known 
that  wrapped  tnmks  of  roses,  for  example,  often  freeze;  this  is  explained 
by  investigating  the  temperature  under  the  covering  material  with  a  ther- 
mometer. It  is  found  to  deviate  but  little  from  the  temperature  of  the  outer 
air.  On  the  other  hand,  if  the  soil  under  the  snow  covering,  possibly  15  cm. 
deep,  is  investigated,  it  is  found  to  be  considerably  warmer.  Goppert's 
investigations^  are  the  best  on  this  subject.  In  February,  1870,  the  tempera- 
ture was  very  low.  The  thermometer  fell  on  the  4th  to  12.6  degrees  below 
zero,  on  an  average,  and  yet  in  this,  the  temperature  was  only  3  degrees 
below  zero  under  the  snow  covering,  10  cm.  deep.  The  temperature  of 
the  air 

on  Feb.  5  was  14  7  degrees  below  zero,  the  temperature  under  the  snow  4.6  degrees 

below  zero, 
on  Feb.  6  w-as  17.6  degrees  below  zero,  the  temperature  under  the  snow,  5  degrees 

below  zero, 
on  Feb.  7  was  16.7  degrees  below  zero,  the  temperature  under  the  snow,  5.5  degrees 

below  zero, 
on  Feb.  8  was  16.7  degrees  below  zero,  the  temperature  under  the  snow,  6.5  degrees 

below  zero, 
on  Feb.  9  was  15  4  degrees  below  zero,  the  temperature  under  the  snow,  6  degrees 

below  zero, 
on  Feb.  10  was  14.9  degrees  below  zero,  the  temperature  under  the  snow,  6  degrees 

below  zero, 
on  Feb.  11  was  15.8  degrees  below  zero,  the  temperature  under  the  snow,  5  degrees 

below  zero, 
on  Feb.  13  was  5.7  degrees  below  zero,  the  temperature  under  the  snow,  2  degrees 

below  zero, 
on  Feb.  16  was  2.8  degrees  below  zero,  the  temperature  under  the  snow,  1.5  degrees 

below  zero. 

The  soil  under  the  snow  covering  was  frozen  36  cm.  deep,  but  its  tempera- 
ture, even  on  the  cold  5th  of  February,  at  a  depth  of  5  cm.,  was  only  one 
degree  below  zero. 

It  would  scarcely  be  possible  to  find  more  eloquent  proof  of  the  useful- 
ness of  a  snow  covering.  This  explains  the  possibility  of  polar  vegetation. 
The  greatest  degrees  of  cold  in  the  polar  zone  as  yet  observed  (40  to  47 
degrees  below  zero)  affect  only  the  trunks  of  the  trees  which  project  above 
the  snow,  but  not  the  roots.  Perennial,  herbaceous  plants  are  just  as  little 
afifected.  These  stand  in  a  soil  with  a  temperature  under  the  snow  cover- 
ing of  only  a  few  degrees  below  zero.  The  snow  covering,  to  be  sure,  does 
not  arrest  freezing  but  does  prevent  loss  of  warmth  through  radiation,  the 
penetration  of  greater  degrees  of  cold  and  a  rapid  change  in  temperature. 
But,  even  with  us,  the  existence  of  many  plants  is  more  often  connected 
with  snow  covering  than  we  think.  The  freezing  of  seed  would  occur 
much  more  frequently  when  a  long  damp  and  moist  autumn  favors  plant 
development,  if  the  snow  covering  were  not  deposited  on  them,  which  keeps 
off  radiation  and  the  great  fluctuations  in  temperature,  so  frequent  in  our 
latitudes.     We  see  often  enough  how  easily  insufficiently  protected,  or  fully 


1   Bot.  Zeit.  1871,  No.  4,  p.  54. 


626 

exposed  parts  of  plants  freeze,  if  struck  by  sudden  strong  sunshine.  The 
cell  contents,  suddenly  struck  in  a  condition  of  rigidity,  the  result  of  cold, 
are  found  poor  in  water  content  and  drawn  back  from  the  cell  wall,  and  do 
not  have  time  to  distend  again,  by  absorbing  water,  into  their  normal  rela- 
tion with  the  cell  wall,  and,  thereby,  the  surrounding  tissues.  In  this  way, 
the  disorganization  of  the  cell  begins.  These  arc  the  processes  which  occur 
with  spring  frost  and  are  especially  advantageous  for  garden  plants. 

(b)   The  Use  of  Water. 

Especially  herbaceous  plants  which  are  suddenly  exposed  to  frost  are 
benefited  if  the  hard  frozen  parts  of  the  plants  are  watered  with  right  cold 
water  and  then  shaded.  The  water  on  the  plants  freezes  to  an  ice  crust, 
thus  raising  slowly  the  temperature  of  the  plant  itself  to  zero,  and  it  can 
gradually  be  warmed  further  above  this  temperature,  after  the  thawing  of 
the  crust. 

On  the  same  principle  of  gradual  warming  rests  the  plunging  of  frozen 
potatoes  and  roots  into  a  vat  full  of  cold  water  and  the  piling  of  frozen 
cabbage  heads  in  heaps  which  are  then  covered  with  straw  mats. 

In  spring  and  autumn,  when  the  air  temperature  does  not  fall  to  zero 
but  the  plants,  because  of  their  radiation  of  heat  under  a  bright  sky,  cool 
down  below  zero,  become  covered  with  frost  and  freeze,  they  may  be  pro- 
tected by  substances  arresting  radiation.  Covers  and  mats  are  spread  over 
the  plants,  also  very  thin  cloths  are  effective  here  and,  if  no  other  covering 
material  is  at  hand,  a  thin  layer  of  brush  is  very  useful;  even  perpendicular 
walls  have  proved  excellent  protection  against  frost.  They  are  effective, 
on  the  one  hand,  by  keeping  off  the  wind  and,  on  the  other,  by  decreasing 
radiation  from  the  plants.  In  trees,  trained  against  stone  or  wooden  walls, 
in  addition  to  the  very  considerable  decrease  in  radiation  of  the  trees  on  the 
side  next  the  wall,  the  wall  itself  gradually  gives  up  its  stored  heat  to  the 
benefit  of  the  trees. 

A  less  effective,  but  not  entirely  rejectable,  protection  against  frost  is 
recommended  by  ®lder  authors  and  is  practical  in  gardens  in  spring.  The 
trunks  of  trees  are  wound  with  straw  rope  one  end  of  which  dips  into  water. 
Straw  and  tow  ropes  are  suspended  in  all  directions  over  beds  of  blooming 
spring  plants  some  distance  above  the  surface  of  the  soil,  their  ends  being 
held  fast  by  stones  in  a  vessel  filled  with  water. 

To  understand  the  favorable  effect  of  this  process,  one  should  remem- 
ber the  great  latent  warmth  in  the  water.  If  the  water  in  the  saturated 
straw  ropes  freezes,  heat  is  set  free  which  is  advantageous,  since  it  prevents 
the  penetration  of  the  cold  to  the  underlying  parts  of  the  plants.  Thus 
plants,  near  larger  bodies  of  water,  freeze  less  easily.  One  measure  used 
with  good  results  for  potted  plants,  at  a  time  when  night  frost  may  be 
feared,  consists  in  a  decreased  watering,  whereby  the  tissue  of  the  plant 


627 

contains  less  water  when  it  is  exposed  to  the  frost.  A  more  abundant 
evaporation  removes  more  heat  from  the  plant  and,  therefore,  heavily 
watered  plants  will  cool  down  more  than  those  which  are  less  turgid. 

(c)     Effect  of  Wind. 

Winds  can  also  act  favorably  inasmuch  as  a  storm  begins  with  warmer 
weather,  which  hastens  evaporation,  thus  removing  the  water  from  the 
tissues.  Experimental  proofs  are  furnished  by  Aderhold's  experiments^ 
with  artificial  rain.  In  each  of  six  specimens  of  pears,  which  had  been  kept 
for  several  months  in  summer  in  a  "rain  chamber,"  five  examples  were 
found,  after  a  winter  frost,  to  be  completely  frozen  and  the  sixth  partially 
frozen,  while  of  the  check  plants,  which  had  stood  in  a  dry  chamber,  only 
2  were  frozen  and  4  were  uninjured. 

Nevertheless,  no  general  rules  can  be  formed  in  regard  to  the  action  of 
wind.  Each  locality  has  its  own  special  requirements.  If,  for  example, 
the  statement  is  made  that  winds  act  favorably,  this  refers  only  to  those 
cases  where  no  such  permanent  eflfect  of  the  wind  is  concerned,  as  is  seen 
on  sandy  coasts.  There  the  action  of  the  roots  is  the  determinating  factor. 
Even  if  they  do  not  freeze,  they  still  cannot  take  up  any  more  water,  while 
the  aerial  portions  still  transpire  strongly.  Plants  can  directly  dry  up  under 
such  conditions.  The  discoveries  of  Hofker-Dortmund"  are  noteworthy 
in  this  connection.  He  protected  the  aerial  portions  less,  but  covered  the 
soil,  which  in  autumn  had  been  loosened  up  about  his  plants,  with  manure 
or  damp  peat  mould  and  watered  the  evergreen  bushes  on  sunny  frosty 
days.  Because  of  the  covering,  the  frost  could  not  penetrate  very  far  and 
the  roots  could  constantly  supply  water  to  the  aerial. portions.  In  decorative 
planting,  where  the  finer  varieties  of  conifers  are  abundantly  used,  it  seems 
advantageous,  in  very  windy  regions,  to  use  the  bluegreen  forms  instead  of 
the  pure  green  ones.  Some  growers  maintain,  in  fact,  that  the  former  are 
more  resistant. 

Care  should  further  be  taken  that  the  base  of  trees  or  plants,  which 
throughout  the  year  have  possibly  been  protected  by  a  moss  growth,  piles 
of  leaves,  forest  litter  and  the  like,  are  not  exposed  in  the  autumn  in  clear- 
ing up,  etc.  It  has  been  found,  in  fact,  that  portions  of  plants  matured 
under  the  protection  of  soil  or  leaves,  contain  a  sap  which  freezes  more 
easily  than  that  of  portions  constantly  exposed  to  the  air.  Sutherst^  has 
proved  this  for  celery,  carrots,  and  the  hearts  of  cabbage  heads.  Besides 
this,  even  if  the  constitution  of  the  cell  sap  is  not  a  determinating  factor, 
at  least  the  transportation  of  water  is  decreased  in  the  roots  and  trunk 


1  Aderhold,  R.,  Versuche  liber  den  Binfluss  haufigen  Regens  auf  die  Neigung 
711  r  Erkrankung  von  Kulturpflanzen.  Arb.  aus  der  Kais.  Biol.  Anst.  f.  Land-  u. 
Forstwirtscliaft.    Vol.  V,  Part  6,  1907.  * 

2  Hofker,  Windschutz  und  Winterschutz.  Prakt.  Ratgeber  i.  Obst-  u.  Garten- 
bau  1907,  p.  61. 

3  Sutherst,  W.  F.,  Der  Gefrierpunkt  von  Pflanzensaften.  Biedermanns  Cen- 
tralbl.  1902,  p.  401. 


628 

which  have  been  robbed  of  their  protective  surroundings ;  they  thereby  cool 
more  quickly,  thus  increasing  the  danger  of  dryingV 

The  importance  of  leaving  the  dead  litter  of  the  plants  (leaves,  bunches 
of  grass,  flower  stalks  of  the  past  year  and  the  like) on  seed  beds  and 
bushes  until  late  spring  is  not  sufficiently  appreciated.  Not  only  is  their 
effect  as  a  protection  against  frost  concerned  here,  hut  also  as  a  protection 
against  the  drying  spring  winds.  Almost  every  year  we  make  the  discovery 
that  plants  have  come  well  through  a  severe  winter  and  evergreens  have 
retained  their  leaves,  but  if  windy,  dry  weather  sets  in  a  few  days  after  the 
snow  has  melted,  the  leavjes,  which  had  remained  juicy,  dry  up.  It  is 
possible  that,  with  this  rapid  drying  of  the  tissues,  a  similar  change  may 
take  place  in  the  protein  of  the  protoplasma;  Gorke^  proved  this  recently 
to  be  due  to  frost  action.  The  result  in  many  plants  is  a  complete  case  of 
leaf  casting  disease,  which  is  absent  where  protection  has  been  afforded  by 
the  litter  of  the  previous  year.  Often  our  most  common  perennial  blos- 
soming bushes,  grain  seeds,  tree  seeds,  etc.,  are  not  destroyed  until  dried 
in  the  spring. 

d.  Smudge.. 

All  these  preventative  methods  may  not  be  used  universally  in  agricul- 
ture, but  the  use  of  smudges  which  Mayer^  has  rescued  from  oblivion,  may 
deserve  still  more  consideration  from  the  agriculturalist.  It  was  previ- 
ously repeatedly  recommended  by  Goppert*  and  Meyen^  and  supported  by 
experiments.  Fires  which  develop  a  good  deal  of  smoke  are  ignited  on 
the  pieces  of  ground  where  injury  from  frost  is  feared.  This  process, 
which,  according  to  Boussingault,  had  been  largely  used  by  the  old  Incas 
in  upper  Peru  and  is  said  to  have  repeatedly  found  extensive  use  among 
the  older  peoples,  is  now  used  again  as  a  protection  in  vineyards.  Accord- 
ing to  Goppert,  Olivier  de  Serres  in  1639  and  later  Peter  Hogstrom  in 
1757  endeavored  to  determine  experimentally  the  effectiveness  of  the  pro- 
cess. In  Wiirtemburg  as  early  as  in  1796  and  in  Wiirzburg  in  1803,  regu- 
lations existed,  according  to  which  in  the  autumn,  when  danger  from  frost 
occurred,  growers  were  obliged  to  light  smudges  for  the  vineyards.  In 
Griinberg,  Silicia,  this  method  was  used  for  a  long  time,  but  it  was  given  up 


1  Kosaroff,  P.,  Einfluss  verschiedener  ausserer  Faktoren  auf  die  "Wasserauf- 
nahme  der  Pflanzen;  cit.  Just's  Jahresbericht  1897,  I,  p.  75. 

2  Gorke,  H.,  tiber  chemische  Vorgang-e  beim  Erfrieren  der  Pflanzen.  Land- 
wirtschaftliche  Versuchsstationen  L,VX,  1906,  p.  149;  cit.  Bot.  Centralbl.  1907. 
Vol.  104,  p.  358.  The  author  explains  the  cause  of  death  from  cold  as  follows: 
The  sap  gradually  becomes  such  a  concentrated  solution,  due  to  the  oliniination  of 
water  from  the  cell,  in  the  form  of  ice.  that  a  precipitation  of  the  soluBle  protein 
bodies  takes  place.  He  bases  his  theory  on  experiments  with  juices  extracted 
from  healthy  and  frozen  plant  parts.  Fresh  vegetable  sap  contained  considerablv 
more  water  soluble  pi'otein  than  that  which  had  been  frozen.  The  degree  of  cold 
at  which  a  precipitation  of  the  proteins  takes  place  in  extracted  sap  varies  greatly 
in  the  different  plant  species.  In  summer  barley  and  rye  it  fluctuates  between  7  to 
9  degrees  below  zero.  In  winter  barley  and  rye,  between  10  to  15  degrees  below 
zero;  in  the  needles  of  Picea  excelsa  it  reaches  40  degrees  below  zero.  Reactionary 
changes  can  also  co(iperate  in  freezing.  The  phosphoric  acid,  for  example,  as  an 
aid,  is  weaker  at  higher  temperatures,  and  is  stronger  when  cooled  down. 

3  Lehrbuch  der  Agrikulturchemie  1871,  I,  p.  382. 

4  Warmeentwicklung  1830,  p.  230. 
6   Pflanzenpathologie  1841,  p.  323, 


629 

from  a  lack  of  general  co-operation,  despite  the  fact  that,  for  twenty  years, 
it  had  been  used  with  good  success  by  one  proprietor.  General  co-operation 
in  any  region  is  necessary,  for  otherwise  a  single  proprietor  frequently  does 
a  service  to  his  neighbor  upon  whose  fields  the  wind  drives  the  smoke, 
without  obtaining  any  service  in  return.  Special  regulations  for  the  use  of 
smudges  are  not  necessary.  Any  clear  night,  toward  morning  but  before 
sunrise,  the  fires  are  lighted  and  fed  with  damp  litter,  moss,  straw,  etc.,  in 
which  care  is  taken  that  the  thickest  possible  smoke  is  carried  over  the  fields. 
Naturally  the  warmth  produced  by  the  fire  is  not  effective  here;  it 
cannot  be  felt  even  a  short  distance  away  from  the  centre  of  the  flame,  but 
the  smoke,  like  the  straw  mats  spread  by  gardeners  over  the  plants,  or  like 
clouds,  is  beneficial  since  it  prevents  too  great  cooling  from  radiation.  We 
know  from  Tyndal's  discoveries  that  a  number  of  substances,  like  carbonic 
oxid  gas,  carbonic  acid,  marsh  gas,  ammonia,  hydrogen  sulfid  and  volatil 
oils,  in  the  finest  possible  distribution  in  the  air,  reduced  to  a  very  small 
amount  its  capacity  for  letting  through  rays  of  warmth.  Water  vapor^ 
has  a  like  eifect.  Tyndal  determined  that  this  took  up  an  amount  of  heat 
fifteen  times  greater  than  that  taken  up  by  the  whole  (impure)  air  in  which 
it  was  distributed.  The  process  is,  therefore,  as  follows: — During  the  day, 
the  sun  sends  its  heat  to  us  in  radiant  and  dark  rays,  part  of  which  the  soil 
reflects,  but  absorbs  the  greater  part,  which  it  retains  until  the  air  becomes 
cooler  than  the  soil.  When  this  condition  appears  an  equilibrium  of  heat 
tends  to  set  in,  since  the  earth  now  gives  up  its  heat  to  the  cool  air  in  the 
form  of  dark  rays.  If,  however,  the  lower  layers  of  the  air  are  stronglv 
laden  with  one  of  the  above-mentioned  gases,  or  with  water  vapor,  the  vapor 
itself  takes  up  the  warmth  radiating  from  the  soil,  instead  of  conducting  it 
into  the  upper  regions  of  the  air.  Tyndal  shows  how  great  the  amount  of 
heat  is,  which  is  taken  up  by  the  lower  layers  of  air.  "If  we  consider  the 
earth  as  a  source  of  heat,  at  least  10  per  cent,  of  the  heat  given  oft"  by  it  is 
held  within  ten  feet  of  the  upper  surface."  By  this  absorption  of  the  dark 
rays  of  heat  the  lower  layers  of  the  air,  rich  in  water,  form  a  protective 
mantel  about  the  earth  which,  as  a  result,  does  not  cool  down  so  far  as  it 
otherwise  would.  The  smoke  produced  by  the  fire  is,  therefore,  an  artificial 
covering,  full  of  water  vapor,  which,  in  combination  with  the  still  partially 
unknown  products  of  distillation,  decreases  the  permeabiHty  of  the  atmos- 
phere for  the  dark  rays  given  out  by  the  surface  of  the  field. 

We  omit  a  special  enumeration  of  the  commercial  smoke  candles  and 
bricks  recently  made  for  the  purpose  of  producing  smoke  at  the  time  of 
frost,  since  new  ones  will  always  appear  with  the  advance  in  technic ;  refer- 
ence to  the  existence  of  such  articles  is  sufficient.  It  need  only  be  mentioned 
that,  recently,  in  smoking  vine3^ards,  the  smudging  material  was  carried 
about  in  carts^  in  order  to  overcome  the  blowing  of  the  column  of  smoke 
by  suddenly  changing  winds.     The  use  of  smoke  carts  is  said  to  be  the  most 

1  Tyndal,  Die  Warme  betrachtet  als  eine  Art  der  Bewegung-.  Deutsche  Ausgabe 
von  Helmholtz  und  Wiedemann  1867. 

2  Burger,  Raucherlvarren.     Prakt.  Ratg.  im  Obst-  u.  Gartenbau  1906,  p.  128. 


630 

extensive  in  the  town  of  Colmar,  where  a  smoke  department  has  developed 
and  has  been  well  organized  ever  since  1884.  Colmar  lies  on  a  plain  and 
the  danger  from  frost  is  greater  on  plains  than  in  higher  regions,  as  was 
shown,  for  example,  in  1903  in  frosts  in  Florence.  Here  Pas'serini^  found 
fruit  trees  and  asparagus  greatly  injured  at  an  elevation  of  40  m.  above 
sea  level,  but  perfectly  healthy  100  m.  higher.  In  Colmar  iron  carts  were 
used,  which  contained  possibly  16  litres  of  fluid  tar.  After  the  tar  had 
been  ignited  they  were  drawn  back  and  forth  over  one  field  and  then  taken 
to  the  next  place  (possibly  150  m.  distant).  When  the  temperature  fell  to 
1  degree  above  zero,  the  smoke  department  was  notified  and,  at  a  tempera- 
ture of  zero  degrees,  the  signal  for  lighting  was  given  by  means  of  gunshots. 
As  a  rule,  this  began  in  the  night  between  two  and  three  o'clock.  The  very 
heavy  expense  to  which  the  administration  was  put,  because  of  the  smoke 
department,  was  paid  by  a  tax  on  the  harvested  grapes. 

W't  have  cited  this  special  case  because  we  believe  that  only  such  an 
organization  can  have  such  sweeping  results. 

Frost  Prediction. 

On  account  of  the  expensiveness  of  producing  smudges  for  the  protec- 
tion of  plants,  threatened  by  late  frosts,  it  is  naturally  of  the  greatest  im- 
portance to  be  able  to  judge  in  advance  approximately  whether  night  frost 
will  occur. 

On  this  account,  it  is  advisable  to  make  use  of  the  frost  curve  con- 
structed by  Lang  (Miinich)  (Cf.  Fig.  150).  This  is  based  on  psycho- 
metric observations.  If,  in  spring,  the  temperature  falls  in  the  afternoon 
and  the  sky  becomes  clear,  with  a  cessation  of  wind,  the  probability  of  night 
frost  increases.  For  the  use  of  the  figure,  two  exactly  corresponding 
thermometers  are  necessary.  The  mercury  bulb  of  one  is  so  wrapped  in 
gauze  that  the  under  end  of  the  gauze  dips  into  water,  thus  keeping  the 
cover  of  the  ball  moist.  This  thermometer,  because  of  the  constant  evap- 
oration of  water,  will  stand  lower  than  the  one  beside  it  showing  the 
ordinary  air  temperature.  From  the  difference  between  these  temperatures 
the  relative  humidity  and  the  position  of  the  dew-point  can  be  reckoned, 
i.  e.,  the  temperature  at  which  the  water,  contained  in  the  air  as  dew,  mist, 
or  rain,  will  be  precipitated.  In  order,  however,  that  these  precipitations 
of  water  vapor  may  become  effective  as  a  protective  mantel  against  frost 
danger  produced  by  radiation,  the  formation  of  dew  and  mist  must  take 
place  at  a  temperature  above  zero;  therefore,  the  point  of  condensation 
must  lie  above  zero.  If  this  is  not  the  case,  and  the  air  is  dr}^,  a  night  frost 
may  be  expected. 

The  mechanical  manipulation  will,  therefore,  be  as  follows :  the  height 
of  the  dry  thermometer  is  read  first  of  all,  then  the  difference  between  this 
and  the  one  with  the  moist  mercury  bulb  is  reckoned.     The  height  of  the 


1   Passerini.  N.,  Sui  danni  prodotti  alle  piante  dal  ghiacciato  dei  giorni   19-20 
April,  1903.    Bull.  soc.  botan.  ital.  1903,  p.  308. 


631 

dry  thermometer  is  found  on  the  horizontal  Hne  and  the  amount  of  differ- 
ence on  the  perpendicular  scale.  If  the  two  lines,  starting  from  these 
points  in  the  scale,  intersect  at  the  right  of  the  curved  line  which  represents 
the  nocturnal  frost  curve,  i.  e.,  intersect  among  the  dotted  lines  of  the  scale ; 
then  no  night  frost  is  to  be  feared.  If,  however,  the  point  of  intersection 
appears  at  the  left  of  the  hypothenuse  of  the  triangle,  i.  e..  outside  the 
dotted  lines,  night  frost  may  be  expected  with  certainty,  in  case  the  weather 
does  not  change  suddenly  and  warm  air  currents  do  not  cause  the  formation 
of  mist  or  clouds.  If,  for  example,  in  the  afternoon,  we  find  8  degrees  C. 
on  the  dry  instrument  and  4  degrees  C.  on  the  moist  thermometer,  this 
gives  a  difference  of  4  degrees.     The  point  of  intersection  of  the  perpen- 


Frosty  Nights 


O    ]    Z    3     ^     5      6       7      8      9      fO    ti     7Z   J5    74    15 
Height  of  the  dty  Thermometer 

Fig.  150.     Curve  for  finding  night  frosts;    according  to  Dr.   Lang,   Municii. 


dicular  temperature  line  8  with  the  horizontal  line  of  a  difference  of  4 
would  be  outside  the  dotted  lines,  i.  e.,  at  the  left  of  the  nocturnal  frost 
line;  therefore  a  night  frost  would  be  probable. 

Hardy  Fruit  Varieties. 

The  more  we  recognize  how  manifold  are  the  often  outwardly  imper- 
ceptible changes  due  to  frost,  which  becomes  apparent  only  in  their  after 
effects,  the  more  important  becomes  the  search  for  varieties  of  fruit 
resistant  to  frost.  If,  however,  we  compare  the  experiences  of  fruit  grow- 
ers, it  becomes  evident  that  the  climatic  conditions  of  different  regions  may 
modify  the  character  of  the  variety  in  such  a  way  that  a  variety  recom- 
mended in  one  place  as  hardy  is  susceptible  to  frost  in  another,  because  of 
earlier  development  or  lesser  maturation  of  the  branches.     On  this  account. 


632 

we  will  name  some  varieties  recommended  as  hardy  for  different  localities, 
some  with  a  continental  climate,  others  influenced  by  the  sea.  In  this  list 
the  injury  to  the  blossom  from  May  frosts  is  decisive,  the  condition  of  the 
wood  less  important,  because  injuries  to  it  come  under  consideration  usually 
only  in  less  frequent,  heavy  winter  frosts,  while  blossoms  are  exposed  every 
year  to  the  danger  of  freezing. 

The  difference  between  northeastern  and  northwestern  Germany  must 
be  taken  into  consideration  for  German  plants.  In  the  eastern  provinces 
the  influence  of  Russia  is  felt,  especially  in  Posen  and  upper  Silesia,  because 
of  the  invading  periods  of  late  frost.  Nevertheless,  we  can  record  experi- 
ences which  show  that  certain  varieties  of  the  more  sensitive  pears  furnish 
good  table  fruit  even  in  Posen.  Radowski^  lists  from  winter  pears  which 
have  stood  the  test  in  unfavorable  years :  Mecheln,  Rihas  Seedless, 
Madame  Verte,  Winter  Nelis,  New  Fulvie,  Winter  William  and  Dechant 
of  Alengon, 

In  upper  Silesia  the  following  have  stood  the  test- :  Amanli's  Butter 
pear,  William's  Christ  pear,  Bonne  Louise  d'Avranches,  Red  Bergamot, 
English  Summer  Butter  pear.  New  Poiteau,  Pastor  pear  and  Diel's  Butter 
pear. 

Of  the  varieties  of  apple  which  have  grown  well  in  the  district  Rybnik, 
the  following  are  preferred:  Red  Astrachan,  Oldenburg,  Kaiser  Alex- 
ander, White  Clear  apple,  Danziger,  Hawthomden,  Winter  Gold  Pearmin, 
Landsberg,  Baumann,  London  Pippin  and  Kasseler. 

The  English  varieties  from  the  region  around  Kosel  have  been  espe- 
cially warmly  recommended :  Lord  Derby,  The  Queen,  Lord  Grosvenor, 
Lane's  Prince  Albert,  as  well  as  Cellini,  Hawthornden  and  Bismarck.  The 
following  are  suitable  for  exposed  positions  and  sandy  soil :  Brunswick 
Milk  apple,  Red  Astrachan,  and  Oldenburg.  According  to  Mathieu  the 
following  are  especially  suitable  for  the  climatic  conditions  of  central  Ger- 
many: White  Astrachan,  Oldenburg,  Red  Eiser  apple.  Kaiser  Alexander, 
Red  Cardinal  and,  for  second  choice,  Red  Astrachan,  Prinz  (Downing), 
Baumann  and  Boiken.  Of  pears,  the  following  have  stood  the  test: 
Winter-Apothecary,  Barons  B.,  Dotted  Summer  Thorn,  Green  Magdalene, 
Small  Long  Summer  Muscatel,  Roman  Butter  pear.  Spar  pear,  Good 
Gray  and  Archduke  pear^.  Although  the  danger  from  frost  is  especially 
great  for  pears,  yet  a  May  frost  at  the  time  of  blossoming  does  not  always 
destroy  the  crop.  Experience  shows  that  good  crops  are  often  obtained 
despite  this,  because  generally  only  the  opened  blossoms  suffer  and  those, 
developing  later,  produce  so  much  the  finer  fruit.  Besides  frost,  a  continu- 
ous rain,  at  the  time  of  the  blossoming  fruit  trees,  is  especially  to  be 
dreaded. 


1  Radowski-Schrimm,  Wintorbirnen  fiir  den  Osten  Deutschlands.  Prakt.  Ratg. 
i.  Obst-  u.  Gartenb.   17  Dez.  1905. 

-  Langer,  G.  A.,  Die  Bedeutung  der  Obstsortenwahl,  fiir  die  ortlichen  und 
klimatischen  Verhaltnisse.     Deutsche  Gartnerz,  1905.    No.  38. 

3  Jahresbericht  d.  Sonderausschusses  fiir  Pfianzenschutz.  1900  Arb.  d.  D.  Landw. 
Ges,  Part  60,  p.  247. 


633 

For  the  German  climate,  the  following  varieties  of  plums  have,  on  an 
average,  best  stood  the  test:  Queen  Victoria,  Yellow  Mirabelle  (of  Metz), 
Double  Mirabelle  of  Nancy,  the  German  prune  and  the  green  Reine  Claude. 

Of  cherries,  the  following  varieties  survive  the  frosty  days  of  spring 
in  spite  of  their  early  blossoming:  the  common  sour  cherry,  Ostheimer 
Weichsel,  Double  Glass  cherry,  large,  long  Loth  cherry,  and  the  Red  Mass 
cherry. 

For  a  more  moist  climate,  the  varieties  might  first  come  under  consid- 
eration which  would  stand  the  test  in  Schleswig-Holstein.  As  such  should 
be  named  the  Peach  Red  Summer  apple,  Degener  apple,  Bath  Beauty,  Red 
June  apple.  Summer  Spice  apple.  White  Summer  Kalvill,  William's  Favor- 
ite, the  White  Clear  apple,  originating  from  the  Baltic  provinces  of  Russia, 
and  the  English  varieties,  Mr.  Gladstone  and  Irish  Peach  (Summer  Peach 
apple)  ^ 

The  majority  of  the  above-named  varieties  are  early  apples  and  we 
think  that  the  cultivation  of  early  varieties  must  be  recommended  for  the 
conditions  in  northern  Germany.  To  be  sure,  they  usually  do  not  give  first 
class  fruit,  but,  with  their  shorter  period  of  growth,  they  have  the  advan- 
tage of  maturing  earlier,  the  growth  of  their  branches  thus  passing  over 
into  winter  with  riper  wood  which,  therefore,  is  harder.  In  planting  new 
fruit  orchards,  the  varieties  should  be  considered  first  which  have  already 
stood  the  test  in  a  similar  cUmate  and  under  similar  soil  conditions.  It 
should  not  be  forgotten,  for  example,  that  varieties,  suitable  for  dry  climate, 
usually  develop  poorly  in  places  by  the  sea,  and  conversely. 

In  regard  to  soil  conditions,  reference  should  be  made  to  the  fact  that 
varieties,  which  grow  well  on  light  or  on  heavy  soils,  would  most  advan- 
tageously be  chosen  from  nurseries  which  have  the  same  physical  soil 
constitution  as  is  found  in  the  place  where  the  trees  are  to  stand  perma- 
nently. A  great  difference  between  the  place  of  early  growth  and  the 
permanent  location  in  which  the  tree  is  planted,  easily  causes  an  arrestment 
in  growth  until  the  specimen  has  accustomed  itself  to  the  new  soil  condi- 
tions. The  conditions  are  the  most  difficult  in  marshy  soils,  even  when 
these  have  been  improved  by  mixing  with  lime  and  the  addition  of  ashes,  or 
kainit  and  Thomas  slag.  Stoll-  recommends,  of  the  stone  fruits,  the  com- 
mon sour  cherry  and  (with  good  liming)  the  house  plum.  The  following 
apples  do  well.  Boskoop's  Beauty,  Golden  Noble  apple.  Double  Pigeon, 
White  Winter  Dove  apple,  Boiken  apple,  Orleans  Reinette,  Gray  Holland 
Reinette,  Parker's  Pippin  and  Purple-red  Cousinot.  The  Gravenstein, 
Prinz  and  the  Golden  Pearmain  grow  well  but  are  inclined  greatly  to  canker. 

Only  the  following  pear  varieties  should  be  named :  the  Yat,  Chameu 
Delicious  and  Great  Katzenkopf.  Of  the  small  fruits,  gooseberry  and  cur- 
rants are  planted  on  moor  lands. 


1  Sorauer,  Schutz  der  Obstbaume  gegen  Krankheiten.    Stuttgart,  Eugen  Ulmer, 
1900. 

2  Stoll,  Obstbau  auf  Moorboden.    Proskauer  Obstbauzeitung  1906,  p.  182. 


634 
Snow  Pressure,  Ice  Coating  and  Icicles 

Just  as  certain  regions  are  especially  often  visited  by  hailstorms, 
definite  zones  exist  (if  from  other  causes),  especially  in  the  mountains,  in 
which  injuries  occur  almost  every  year  due  to  pressure  from  the  snow. 
Besides  these  zones,  some  places  in  all  regions  with  an  abundant  snowfall 
must  be  considered  as  especially  endangered.  These  are  depressions  in 
the  soil  into  which  the  snow  can  be  blown  from  above  or  from  the  sides. 
Equal  amounts  of  snowfall  act  differently  according  to  the  weather.  If  it 
is  very  cold  and  windy,  enough  snow  rarely  collects  on  the  branches  to 
cause  injury;  the  crystals  are  too  fine  and  cold  to  stick  to  one  another.  If, 
on  the  other  hand,  the  weather  is  warm  and  quiet,  the  snow  falls  in  great 
flakes  and  balls  easily,  large  masses  cling  in  the  crowns  of  the  trees  and 
bend  or  break  the  branches. 

If  the  trees  stand  on  declivities,  many  injuries  are  noticed  on  the  slope 
opposite  the  windy  side;  whole  strips  of  trees  can  be  overthrown.  This 
occurs  as  a  simple  result  of  snow  pressure,  especially  with  mild  winter 
weather  and  soft,  open  soil,  while,  with  greater  cold,  the  more  brittle  trunks 
will  be  broken  (snow  breakage).  Transplanted  trees,  with  shallow  root 
systems,  are  overturned  more  easily  than  specimens  well  anchored  by  tap 
roots.  Evergreen  trees  are  especially  inclined  to  break  and  of  them  the 
pines  seem  most  brittle.  The  tougher  varieties,  like  firs  and  spruces,  bend 
more  under  the  burden  and  later  right  themselves.  Deciduous  trees  are 
less  injured  if  the  snow  masses  come  after  the  leaves  have  fallen.  Oaks 
and  beeches,  which  often  retain  their  foliage  throughout  the  whole  winter, 
are  more  endangered  than  other  trees,  provided  that  a  previous  moist  and 
cool  summer  has  not  prevented  the  latter  from  passing  into  their  dormant 
period  and  dropping  their  foliage.  Here  too  the  brittleness  of  the  variety 
is  decisive  for  the  kind  of  injury.  The  trunks  and  branches  of  older 
acacias  almost  always  break.  In  birches  and  alders,  also,  breaking  may  be 
found  oftener  than  bending.  Bernhardt^  also  calls  attention  to  the  fact 
that  the  resistance  of  the  tree  variety  changes  according  to  whether  its 
habitat  is  suited  to  its  requirement  or  not.  For  our  fruit  trees,  the  shape 
of  the  crown  also  enters  greatly  into  consideration;  especially  in  apples, 
for  with  their  flat,  outspread  branches,  a  true  splitting  of  the  crowns  is  often 
found.  If  the  tree's  natural  habit  of  growth  does  not  form  a  pyramidal 
crown,  it  is  advisable  to  cultivate  artificially  the  development  of  a  strong 
middle  branch. 

With  avalanches,  occurring  frequently  in  high  mountains,  the  whole 
effect  changes  according  to  the  variety  of  the  trees  and  the  age  of  the  trunk. 
If  the  standing  forest  is  old,  the  trees  are  broken  at  different  heights  and 
thrown  together  in  wild  and  irregular  disorder.  Where  the  trees  are  of 
different  ages,  the  young  trees  are  only  partially  pressed  downward  and, 
for  a  time,  buried  in  the  snow.     After  the  snow  melts,  these  trees  right 


1  Waldbeschadigungen  durch  Wind-,  Schnec-,  Eis-  und  Duftbruch.     Centralbl. 
f.  d.  gesamte  Forstwesen  1878,  p.  29. 


635 

themselves,  or  lean  somewhat  down  hill,  and  slowly  continue  growth. 
Usually  growing  branches  are  found  only  on  the  side  toward  the  valley, 
since  the  rolHng  snow  masses  have  broken  off  those  of  the  opposite  side. 
In  deciduous  forests,  deformed  bushes  develop,  because  of  the  tearing  out 
of  the  roots  or  trunks ;  they  look  as  if  produced  by  the  grazing  of  wild 
animals. 

The  influence  of  the  snow  covering,  and  of  the  accompanying  frosts  on 
seeds  has  been  mentioned  already  in  an  earlier  chapter.  In  regard  to 
changes  in  temperature  in  the  soil,  reference  should  be  made  to  Wild  and 
\Vollny\  The  ice-water,  produced  by  the  melting  of  the  snow,  can  not  be 
without  effect,  as  soon  as  it  reaches  green  meadows  and  seeded  fields. 
Kiister-,  for  example,  has  shown  that,  as  a  result  of  cooling  with  ice-water 
in  the  chlorophyll  grains  of  Funaria  leaves,  a  vacuole  formation  is  started 
which  results  in  the  green  pigment's  lying  at  the  edge  of  the  vacuoles  in  the 
form  of  crescents. 

Ice  coating  and  icicles.  The  injuries  from  ice  formed  on  trees  are 
more  rare.  A  quickly  melting  coating  of  smooth  ice  is  usually  considered 
non-injurious.  Nevertheless,  in  general  many  growers  ascribe  the  produc- 
tion of  blasted  specks  to  the  deposition  of  ice  on  smooth  barked  branches 
and  trunks.  If,  with  Nouel,  the  production  of  smooth  ice  is  considered 
as  the  solidifying  of  the  rain  drops  due  to  the  impact  of  striking  the  tree,  the 
drops  having  already  been  cooled  below  zero  degrees,  it  can  be  assumed 
that  the  cold  of  the  ice  acts  injuriously.  From  the  experiences  collected 
from  artificial  frost  experiments,  I  am  of  the  opinion  that  the  smooth  ice 
covering  can  act  injuriously,  because  of  changes  in  tension  in  the  ice-covered 
tissue.  It  may  be  proved,  in  very  light  spring  frosts,  that  clefts  arise  in 
the  bark  tissue  of  herbaceous  shoots  without  any  extensive  browning  of 
the  cell;  therefore,  without  the  chemical  action  of  the  frost  having  made 
itself  felt.  Such  injuries  to  the  tissues  are  also  possible  from  smooth  ice, 
if  it  remains  for  some  time  on  the  plant  and  especially  if  it  outlasts  the 
fluctuations  in  temperature  frequently  occurring  with  the  formation  of 
smooth  ice. 

It  is  possible  to  distinguish  from  the  usual  formation  of  smooth  ice, 
the  ice  and  mist  coverings  which  might  be  compared  with  snow  pressure 
because  they  depend  upon  different  processes  of  formation.  As  character- 
istic of  the  phenomenon,  we  will  consider  a  description  by  Breitenlohner", 
who  made  extensive  observations.  On  January  2y,  1879,  precipitation 
began  in  the  middle  of  the  day,  in  A.  forest  near  Vienna  with  a  complete 
cessation  of  wind  and  with  misty  weather,  under  an  increasing  air  pressure 
and  low  temperature.  This  precipitation  was  half  way  between  a  drizzle 
and  mist  and  soon  hardened  to  smooth  ice.     A  one-sided  ice  covering  3  to 


1  Bot.  Jahresber.  1898,  I,  p.  584-85. 

2  Kiister,   E.,   Beitrage  zur  Physiologie  u.   Pathologie   der  Pflanzenzelle.     Z.   f. 
allg-em.  Physiologie  1904,  Vol.  4. 

3  Breitenlohner,  Der  Eis-  und  Duftanhang  im  Wiener  Walde.     Forsch.  auf  d. 
Gebiete  d.  Agrikulturphysik  1879,  p.  497. 


636 

5  mm.  thick  was  produced  on  the  trees,  the  temperature  of  which  in  all 
parts  lay  under  zero.  The  period  of  the  still  frost  lasted  5  to  6  days  in 
this  Viennese  forest ;  the  ice  covering  remained  9  days  and  increased  until 
the  thinnest  branches  grew  to  the  size  of  a  ship's  rope;  the  beech  trunks 
broke,  while  the  young  copse  wood  was  bent  to  the  ground.  Since  only  the 
surface  of  the  soil  was  frozen,  the  trees  were  also  overthrown.  The 
needles  of  the  conifers  especially  favored  the  formation  of  ice  and  firs 
became  ice  pyramids,  since  the  icicles,  often  20  cm.  long  on  the  upper 
branches,  were  frozen  to  the  lower  branches. 

In  low  positions,  the  covering  was  actually  transparent,  smooth  ice;  on 
the  heights,  however,  the  chief  part  consisted  of  a  mixture  of  ice  and  mist. 
In  the  same  way,  the  size  of  the  ice  particles  decreased  gradually  from  the 
edge  of  the  forest  toward  the  centre,  where  the  covering  was  neither  ice 
nor  mist  but  had  a  firm,  ray-like  consistency,  until  finally,  deep  in  the  forest, 
it  appeared  as  a  typical  mist  covering,  which  became  thinner  and  thinner 
the  deeper  one  penetrated  into  the  forest.  In  order  to  form  a  conception 
of  the  amount  of  ice  thus  produced,  which  also  occurred  simultaneously  in 
Germany  and  France,  the  weight  of  the  ice,  hanging  on  a  single  branch, 
was  determined  with  the  following  results :  for  the  one  part  weight  in  a 
leafless  cherry  branch,  the  ice  was  36.7  parts;  in  the  Zerr  oak,  44.1 ;  in  the 
red  beech,  85.3;  in  the  fir,  31. i ;  in  the  spruce,  51.3;  in  the  pine,  99.0  parts. 

Breitenlohner,  in  explaining  the  phenomenon,  calls  attention  to  the 
fact  that  the  observations  of  meteorological  stations,  at  the  time  of  the  ice 
covering,  showed  the  action  of  a  south  wind;  therefore,  a  moist,  warm 
equatorial  current  above  a  cold  polar  stream  filled  the  valleys.  The  contact 
of  the  equatorial  with  the  polar  air  waves  led  to  the  unusual  form  of  precipi- 
tation. This  remained  fluid  because  the  lower,  cold  stream  of  air  was  not 
very  thick  vertically,  so  that  the  precipitation,  coming  from  a  warm  current, 
had  to  pass  only  a  short  way  through  cold  air. 

Where  the  cold  layer  of  air  had  a  greater  vertical  thickness,  the  pre- 
cipitation took  on  a  solid  form  and  covered  the  vegetation  as  hoar  frost. 

The  precipitation,  formed  after  the  contact  of  two  layers  of  air,  which 
differ  in  temperature  and  moisture,  can  retain  its  consistency  as  fluid  water 
even  below  zero  degrees,  since  moist  winds  are  splendid  heat  producers  and 
carry  an  amount  of  latent  warmth  in  water  vapor  which  is  freed  during  the 
continued  condensation.  Only  when  the  cooling  agent  exceeds  a  certain 
amount  is  the  mist  changed  into  frost  vapor  and  then  the  moisture  eUm- 
ination  consists  of  ice  needles.  The  peripheral  trees,  exposed  to  the  free 
currents  of  air,  catch  and  hold  the  mist,  while,  in  the  interior,  the  choked 
air  causes  the  formation  of  the  typical  mist  covering. 

This,  therefore,  would  be  analogous  to  hoar  frost,  occurring  with  late 
or  early  frosts,  and,  therefore,  cannot  be  considered  to  be  frozen  dew. 
Dew  is  condensed  water  vapor,  which  is  precipitated  in  drops  on  the  parts 
of  the  plant  cooled  down  below  the  condensation  point  of  the  air  by  radia- 
tion.    These  drops  unite.     Water  vapor  is  usually  abundantly  present  in 


637 

the  air  and,  as  Stockbridge^  proves,  can  arise  as  vapor  during  the  summer 
months  from  the  soil  which  in  the  night  is  warmer  than  the  air.  If  there 
is  a  strong  dew  covering,  it  can  be  considered  rather  as  a  means  of  protec- 
tion against  the  freezing  of  the  plants.  If  this  dew  freezes,  a  crystalline 
coating  is  produced  which  is  identical  with  the  ice  covering.  Hoar  frost, 
on  the  other  hand,  is  produced  when  the  point  of  condensation  of  the  air 
lies  below  zero  degrees.  This  degree  of  temperature  is  reached  through 
radiation  and  evaporation  from  the  plant;  therefore,  the  mist  molecules 
attach  themselves  to  one  another  in  a  firm  crystalline  form  (soil  or  summer 
hoar  frost).  The  covering  of  frozen  mist,  or  winter  hoar  frost,  is  pro- 
duced by  the  flowing  of  the  equatorial  current  into  the  slowly  displaced 
polar  current;  the  change  is  dangerous  because,  with  longer  duration,  so 
thick  a  covering  of  frozen  mist  can  be  produced  that  the  strongest  trees 
break  under  its  load. 

In  nurseries,  the  prompt  and  careful  beating  of  the  branches  with 
sticks  will  prevent  such  an  injurious  accumulation  of  ice.  This  naturally 
cannot  be  carried  out  in  forests. 

In  summer  frosts,  the  cultural  conditions  are  often  of  decisive  signifi- 
cance. It  should  be  taken  into  consideration,  in  tilled  soil,  that  the  plant 
body  cools  down  more  rapidly  than  does  the  soil  which,  in  the  night,  acts  as 
an  equalizing  source  of  heat  and  prevents,  more  or  less,  the  formation  of 
hoar  frost.  This  effect  will  be  the  greater,  the  larger  the  water  content  of 
the  soil  which  thus  retards  the  cooling  down.  On  damp  fields  the  dew, 
which  moderates  the  cooling  of  the  leaves,  is  formed  earlier  and  more 
abundantly  than  on  dry  soils.  On  the  other  hand,  cultural  regulations 
which  prevent  the  rising  of  heat  from  the  drier  soil  layers,  such  as  the 
loosening  of  the  soil,  or  a  strawy  manure,  favor  frost". 


1  Journal  of  science,  Vol.  I,  p.  471;  cit.  Naturforscher  1879,  No.  32. 

2  Petit,  M.,  Einfluss  einiger  Kulturverfahren  auf  die  Bildung-  von  Reif.  Anna!, 
agron.  1902,  No.  7,  cit.  Centralbl.  f.  Agrikulturchemie  1903,  p.  557. 


CHAPTER  XII. 


excf:ss  of  heat. 


Death  from  Heat. 

Supported  by  numerous  psychological  works^  we  have  arrived  at  the 
conclusion  that,  in  judging  injuries  produced  by  excess  of  heat,  the  same 
points  of  view  make  themselves  felt  as  in  judging  those  due  to  lack  of 
heat.  In  our  cultivated  plants  we  are  confronted  by  constantly  changing 
organizations.  Not  only  has  each  species  its  special  requirements  as  to  the 
amount  of  heat  which  it  can  endure,  but,  even  within  a  wide  range  of  heat, 
the  different  individuals,  in  each  species,  and  indeed  their  different  develop- 
mental stages,  behave  quite  differently.  The  individual  susceptibility  to  a 
degree  of  heat,  exceeding  tlie  optimum  amount,  varies  according  to  the 
habitat,  the  supply  of  water  and  nutritive  substances  and  the  action  of  the 
other  vegetative  factors  so  that  definite  figures  as  to  admissable  temperature 
values  can  only  have  a  limited  validity. 

We  see,  from  this,  that,  in  our  plantations,  the  plants  can  accustom 
themselves  to  higher  amounts  of  heat  up  to  a  certain  degree.  Their  struc- 
ture becomes  different,  their  development  more  rapid,  but  their  life  pro- 
cesses, as  a  whole,  still  take  place  within  the  latitude  of  health.  In  regard 
to  the  different  susceptibility  of  the  different  organs,  according  to  their 
momentary  developmental  stage,  we  favor  the  theory  that  the  part  of  the 
plant  is  the  more  resistant  to  an  excess  of  heat,  the  richer  the  tissues  are 
in  cyptoplasm  and  the  relatively  poorer  in  water.  Death  from  heat,  like 
death  from  frost,  is  produced  by  the  irreparable  destruction  of  the  mole- 
cular structure  of  the  cytoplasmic  body.  We  do  not  know  in  what  way 
this  takes  place,  nor  how  far  a  coagulation  of  certain  protein  bodies  co-oper- 
ates in  it.  The  more  porous  the  cytoplasmic  body  is  within  its  specific 
composition,  due  to  the  in-layering  of  abundant  water,  the  more  easily  such 
a  destruction  takes  place.  On  this  account  we  find  that  organs,  rich  in 
water,  die  more  quickly  from  excess  of  heat.  Death  from  heat  is  often 
preceded  by  a  "heat  rigor,"  from  which  the  plants  can  recover^  when  the 
super-maximal  temperature  abates,  and  can  begin  their  growth  again.     The 


1  Pfeffer,  W.,  Pflanzenphysiologie,  2d  ed.,  Vol.  II,  Leipzig  1904. 


639 

longer  the  plant  is  left  in  a  condition  of  rigor,  the  more  slowly  can  it  take 
up  its  activity  again^.  We  will  become  acquainted  with  other  main  points 
on  the  subject  of  difference  in  susceptibility  in  the  following  actual  occur- 
rences. 

Poor  Development  of  Our  Vegetables  in  the  Tropics. 

When  cultivated  plants  from  the  temperate  zones  are  carried  to  tropical 
regions  very  great  disturbances  become  noticeable  at  times  in  the  ontogeny 
of  the  plants,  which  severely  impair  the  cultural  aim.  This  lies  in  the  unde- 
sired  abbreviation  of  the  different  phases  of  growth,  especially  in  the 
shortening  of  the  period  of  leaf  development,  and  of  the  production  of 
reserve  substances  which  are  used  up  too  early  for  the  development  of  the 
reproductive  apparatus.  This  is  especially  marked  in  the  case  of  plants  in 
which  the  period  of  growth  has  been  prolonged  by  continued  cultivation  in 
soil  abounding  in  nutritive  substances,  i.  e.,  rich  in  nitrogen,  and  the  leaf 
apparatus  has  been  developed  luxuriantly  (varieties  of  cabbage,  lettuce, 
etc.).  We  find  cases  of  this  nature  reported  in  older  works.  Thus,  for 
example,  Duthie  cites  such  a  case  from  Saharanpur-.  His  experiments  in 
India  on  plant  structures  show,  with  a  few  exceptions,  a  too  rapid  ripening 
of  the  seeds  of  European  plants.  While  the  beet  {Beta  vulgaris  var.  rapa) 
takes  i8  months  in  England  to  complete  its  development,  it  needs  in  India 
only  8  months.  In  the  cultivated  forms  of  German  asters,  the  effect  of  a 
change  of  climate  manifests  itself  in  the  non-ripening  of  the  seed.  The 
blossoms  of  Brachycome  and  Petunia  change  and  all  become  white.  The 
process  seems  to  me  to  represent  the  opposite  of  the  process  of  the  redden- 
ing of  plant  parts  in  spring,  due  to  a  lack  of  heat. 

Similar  phenomena  have  been  reported  from  tropical  America.  Leh- 
man' found  in  Western  Colombia  that  cabbage,  lettuce,  onions  and  carrots 
did  not  develop  sufficiently  for  cultural  purposes.  While  seeds,  imported 
from  Europe,  furnish  in  the  first  year,  in-corresponding  localities,  excellent, 
tender  vegetables  with  a  desired  amount  of  development,  seeds  from  these 
individuals  give  ])lants  which,  in  cabbage  and  lettuce,  show  only  traces  of 
head  formation  while  the  onions  grow  out  into  stalks  a  finger  thick  without 
any  tenderness,  or  flavor.     The  plants  here  have  no  dormant  period. 

In  the  level  equatorial  regions  this  phenomenon  occurs  sooner  and 
more  noticeably  than  in  the  higher,  mountainous  regions  and  between  the 
loth  to  15th  parallels  of  latitude.. 

Postponement  of  the  Usual  Seed  Time  in  Our  Latitudes. 

We  must  here  consider  the  phenomenon,  not  infrequently  observed, 
that  vegetables,  sown  too  late  in  the  year,  come  into  the  hot,  dry  season  too 


1  Hillirig-,  H.,  iJber  den  Einfluss  supramaximaler  Temperatur  auf  das  Wachstum 
der  Pflanzen.  Inauguraldissertation.  I^eipzig-  1900;  cit.  Just,  Bot.  Jahresber,  1901, 
II,  p.  203. 

2  Gardener's  Chronicle  1881,  I,  p.  627. 

3  Lehmann,  Uber  eine  physiologische  Erscheinung  bei  der  Gemiisekultur  im 
tropischen  Amerika.     Deutsche  Gartnerzeitung  1883,  p.    260. 


640 

soon,  while  still  developing  their  vegetative  organs.  The  leaf-body  becomes 
hard  and  the  tuber-like  swellings  soon  become  woody.  Annual  seed-bear- 
ing plants  (grains  and  summer  blossoms)  ripen  prematurely.  Peas,  sown 
too  late,  succumb  very  early  to  rust  (Uromyces).  Kraus^  has  already 
advanced  the  theory  that  the  turgidity  of  the  tissue  decreases  with  too  high, 
temperatures. 

Haberlandt,  in  his  experimental  plants,  has  found  a  splendid  example 
of  the  influence  of  drought  in  fungous  attacks  on  plants.  Of  three  pots 
sown  with  wheat  and  left  standing  side  by  side  during  the  whole  period  of 
growth,  the  one  where  the  plants  were  watered  only  enough  to  keep  up 
life,  were  so  attacked  by  mildew  (Erysiphe  graminis)  that  the  greater  part, 
at  any  rate,  of  the  blame  for  the  whole  failure  of  the  harvest  must  be 
ascribed  to  the  fungus.  The  pot,  standing  nearby  and  abundantly  watered, 
was' almost  entirely  shunned  by  the  parasite-.  Still  more  decisive  is  the  case 
which  I  observed  with  Podosphaera  leucotricha  Salm.  Half  of  a  number 
of  young  apple  trees  in  pots  stood  in  a  conservatory,  the  other  half  out  of 
doors  back  of  this  conservatory.  All  the  specimens  had  retained  through- 
out the  winter  the  oidia  form  from  the  previous  year.  The  trees  in  the 
conservatory  exposed,  without  any  protection,  to  the  summer  heat  were 
twisted  out  of  the  shape  from  the  extensive  spread  of  the  mildew,  which 
developed  to  the  perithecial  fruiting  stage.  Those  standing  back  of  the 
conservatories,  in  half  shade  and  in  moving  air,  lost  the  mildew.  Hell- 
riegel's^  experiments  prove  how  much  the  production  of  plants  suffers  from 
a  wrong  time  of  sowing,  even  without  the  action  of  parasitic  enemies. 
Barley  sown  in  April,  May,  June,  August  and  September  in  pots  with  the 
same  mixture  of  nutritive  substances  and  soil  moisture,  under  otherwise 
entirely  similar  conditions,  behaved  absolutely  diiiferently.  That  sown  in 
April  developed  very  regularly  grown,  excellent  plants,  bearing  ripe  seeds 
at  the  end  of  88  days.  The  seed  sown  at  the  end  of  May  grew  into  plants 
which,  at  first,  also  developed  very  vigorously,  but  as  a  long  period  of  heat 
occurred  toward  the  middle  of  July,  at  the  time  the  heads  push  out  from 
the  upper  leaf  sheath  the  stalk  was  retarded  in  its  growth  in  length.  Up  to 
the  premature  death  of  the  plants  (after  yy  days)  the  kernels  had  matured 
only  incompletely  and  remained  flat ;  they,  therefore,  had  become  ripe  pre- 
maturely. The  latter  sowings  showed  an  increasing  lengthening  of  the 
period  of  growth  (the  September  seed,  for  example,  required  240  days)  and 
resulted  in  quite  incompletely  ripened  grain. 

In  regard  to  forest  plantations,  experience  also  shows  that  the  losses 
from  transplanting  of  young  forest  trees  vary  according  to  the  time  it  takes 
place.  Experiments  in  Mariabrunn*  gave  the  smallest  loss  in  spring  trans- 
planting. For  spruce  trees  the  number  of  dying  examples  of  an  April  to 
June  planting  increases   only  to  decrease   again   in   autumn   transplanting 


1  Molekularkonstitution  des  Protoplasms.     Flora  1S77,  p.  534. 

2  Biedermann's  Centralbl.  1875,  II,  p.  402. 

3  Grundlagen  des  Ackerbaues  1883,  p.  352. 

4  Deutsche  Forstzeitung-  November  13,  1892. 


641 

(September  and  October).  The  same  behavior  was  shown  in  the  case  of 
the  pine,  which  gave  a  still  more  significant  percentage  of  loss.  In  decidu- 
ous trees,  as  is  well  known,  autumn  transplantation  is  preferred. 

Sunburn  of  Leaves  in  Nature. 

The  death  of  the  tissue,  resulting  from  the  action  of  the  sun,  is  here 
meant.  In  such  cases,  however,  light  and  warmth  act  together.  We  do 
not  know  how  much  must  be  ascribed  to  each  factor  in  such  phenomena  of 
death.  The  opinion  of  noted  foresters,  that  all  the  light  in  the  plant  cell 
passes  over  into  the  dynamic  force  of  heat  and  becomes  effective  in  this 
form,  is  not  ver\^  probable.  My  evaporation  experiments  with  a  decrease 
of  light,  and  a  simultaneous  increase  in  temperature,  indicate  rather  that 
at  least  a  part  of  the  light,  as  such,  becomes  effective,  and  influences  the 
process  of  assimilation.  A  part  without  doubt  is  converted  into  heat  and 
acts  in  that  way.  Upon  this  hypothesis,  it  is  also  probable  that  a  plant 
would  behave  differently  with  the  same  amount  of  heat,  according  to 
whether  it  is  subjected  to  this  in  a  dark,  or  in  a  lighted  place. 

In  general,  temperatures  between  40  to  50  degrees  C.  are  fatal ;  yet 
Askenasy^  has  observed,  with  Crassulae,  that  they  can  endure  uninjured 
such  amounts  of  heat.  Askenasy  was  convinced  in  midsummer  that  the 
inner  parts  of  Sempervivum,  at  an  atmospheric  temperature  of  31  degrees  C. 
in  the  shade,  had  undergone  a  heating  up  to  48  to  51  degrees  C.  The 
warmth  within  the  plants  seemed  higher  in  some  varieties,  lower  in  others, 
than  on  their  outer  surfaces.  The  temperature  of  the  outer  surface  of  the 
leaf,  in  different  days,  did  not  stand  in  any  direct  relation  to  the  atmospheric 
temperature.     Sempervivum  arenariuni  showed,  for  example, 

at  31.0  degrees  C.  on  the   15th  of  July,  at    3:00  P.  M.,  48.7  degrees  C. 
"  28.2       "         "     "     "      i6th  "      "       "     3  :oo  P.  M.,  46.0 
"28.1       "         "     "     "      i8th  "      "       "  12 :30  P.  M.,  49.0 

Thin-leaved  plants,  standing  nearby,  had  a  much  lower  temperature. 

The  phenomena  of  sunburn  are  observed  most  frequently  in  hot-house 
plants  which,  in  spring,  are  set  out  of  doors.  The  leaf  is  not  always  killed 
but  often  only  reddened  or  browned.  In  curled  leaves  only  the  convexity, 
on  the  upper  side,  becomes  colored  and,  instead  of  being  green,  is  reddened 
to  a  copper  color  (roses).  In  the  course  of  a  few  weeks  such  a  plant  can 
recover  even  when  left  in  this  place. 

I  tested  experimentally  a  similar  case  in  spotted  specimens  of  Canna 
indica,  the  greatest  number  of  which  in  cloudy  weather  were  taken  from 
the  hot  house,  in  which  they  had  been  forced  up  to  the  unfolding  of  the 
first  blossoms,  and  were  set  out  of  doors.  Some  pots  stayed  two  days 
longer  in  the  hot  house  and  were  then  sunk  in  the  earth  in  the  middle  of  the 
day  beside  the  specimens  set  out  earlier.     In  the  afternoon  the  upper  leaves 


1  Askenasy,  tjber  die  Temperatur,  welche  Pflanzen  im  Sonnenlichte  annehmen. 
Bot.  Zeit.  1875,  p.  441. 


642 

appeared  striped  with  white,  since  the  parts  of  each  intercostal  field  farthest 
from  the  ribs,  conducting  water,  showed  dead  tissue.  The  white  stripes 
were  broadest  at  the  edge  of  the  leaf  and  dwindled  gradually  toward  the 
midrib  so  that  it  was  clearly  evident  that  the  burning  of  the  leaf  occurred 
earliest  and  strongest  in  those  regions  which  lay  farthest  away  from  the 
water  conducting  system  of  the  large  vascular  bundles. 

The  epidermis  did  not  seem  essentially  changed  in  the  white  places, 
but  the  palisade  parenchyma  which  no  longer  had  chloroplasts  was  greatly 
changed,  while  a  transitional  zone  toward  the  healthy  tissue,  provided  with 
large  chlorophyll  bodies  arranged  along  the  walls,  showed  a  content  still 
green  but  cloudy.  In  tissue,  which  had  become  white,  the  cell  walls  of 
which  had  remained  clear,  glycerin  contracted  only  a  small  amount  of  the 
contents  so  that  it  was  necessary  to  conclude  that  in  this  short  time  a  large 
part  of  the  contents  had  been  used  up  in  respiration.  In  the  places  most 
greatly  injured,  the  epidermis  was  raised  here  and  there,  like  blisters,  from 
the  flesh  of  the  leaf  (hum  blisters)  and  the  destruction  of  the  chlorophyll 
had  extended  even  to  the  under  side  of  the  leaf.  After  some  weeks  it  was 
possible  to  observe  a  regeneration  of  the  chloroplasts*  in  the  burned  leaves 
in  the  above-mentioned  transitional  zones.  Thus,  a  healing  process  had 
taken  place  exactly  as  after  slight  injuries  from  frost.  The  presence  of 
mycelium  could  now  be  demonstrated  beneath  the  burn  blisters  in  which 
part  of  the  epidermal  cells  seemed  to  have  collapsed. 

Rowlee^  observed  a  collapse  of  the  epidermal  cells  even  after  an  8  hour 
exposure  to  electric  arc  light  which  acted  on  the  leaves  of  heliotrope  at  a 
distance  of  one  metre;  other  plants  (for  example  Ficiis  elastica),  under 
similar  conditions,  remained  unchanged. 

In  fleshy,  long-lived  leaves,  the  healthy  tissue  is  separated  from  the 
burned  tissue  by  a  cork  zone,  as  is  shown  in  the  subjoined  illustration  of  a 
Clivia  leaf  injured  in  August  from  sunburn.  It  is  easy  to  observe  that  the 
position  of  the  leaf  determines  the  place  of  production  of  the  burned  spot, 
since  only  those  places,  perpendicular  to  the  source  of  heat,  turned  a  yellow- 
ish gray  and  collapsed.  On  the  following  day  the  burned  spot  was  per- 
fectly brown  and  brittle.  The  youngest  leaves  were  uninjured.  The 
boundary  between  dead  and  living  tissue  becomes  sharp,  as  soon  as  the 
burned  spot  extends  through  the  whole  thickness  of  the  leaf.  If,  however, 
only  the  upper  side  of  the  leaf  is  injured,  a  faded,  transitional  zone  is  found. 
In  this,  the  chloroplasts  turn  the  color  of  verdigris,  while  the  remaining  cell 
contents  show  a  yellow  green.  Therefore,  there  may  occur  here  first  of  all 
the  disappearance  of  the  xanthophyll,  while  the  cyanophyll  remains  com- 
bined in  the  chloroplasts.  Thus,  the  contours  of  the  mass  of  chlorophyll 
grains,  which  at  first  refracted  the  light  equally  strongly,  become  less  sharp 
and   a  large  amount   of  very  fine    granules   give   it   a   sandy   consistency. 


1  Rowlee,  W.,  Effect  of  electric  light  upon  the  tissues   of  leaves.     .Just's  bot. 
Jahresber,  1900.    II,  p.  287. 


643 

Finally,  the  chloroplasts  form  groups,  a  dirty  tea-green  to  a  blackish  green 
in  color,  which  assume  a  cord-like  form  because  the  cell  collapses.  These 
content  masses,  which  lie  against  a  wall,  bleach  very  quickly  in  sunshine 
and  cause  the  yellowish  gray  color  of  the  burned  place.  The  cell  walls  do 
not  lose  their  cellulose  character,  as  is  proved  by  testing  them  with  chlor 
zinc  iodide. 

The  healthy  tissue  begins  at  once  to  cut  itself  oft"  from  the  injured 
tissue  by  a  cork  zone  {k)  whereby  the  cells  of  the  transitional  zone  (hr), 
which  have  remained  rich  in  contents,  at  first  somewhat  enlarged  by  an 
undulation  of  their  walls  {h,  z),  show  enlarged  intercellular  spaces  and 
gradually  die. 

When  the  burned  spot  becomes  somewhat  older,  it  turns  a  deeper 
brown,  in  which  the  epidermal  cells,  which  have  not  collapsed  {e),  partici- 
pate even  up  to  the  healthy  tissue.     The  cork  zone   {k)   is  produced  by  a 


Fig-.  151.     Cross-section  through  a  sunburn  spot  in  a  leaf  of  Clivia  nobilis. 


division  and  elongation  of  the  mesophyll  cells  which  have  remained  alive  at 
the  edge  of  the  burned  place.  The  normal  cells,  back  of  these  (/>)  usually 
remain  somewhat  poorer  in  chlorophyll.  The  callous  appearance  of  the 
peripheral  zone  (w)  of  the  normal  leaf  part  at  the  edge  of  the  'burned 
place  should  be  noted ;  this  is  explained  by  the  distention  of  the  cells,  which 
develop  the  cork  zone,  and  of  the  mesophyll  {h)  lying  in  front  of  them, 
which  had  been  injured  but  did  not  die  at  once. 

Sunburn  Spots  in  Conservatories. 

Complaints  of  the  occurrence  of  burned  spots  on  the  leaves  of  tender 
plants  in  conservatories  abound,  especially  in  spring,  and  opinions  as  to 
their  production  differ  greatly.  Sometimes  bubbles  in  the  glass  are  held 
responsible  for  this.  Sometimes,  it  is  thought  that  the  drops  of  water, 
which  remain  on  the  upper  surface  of  the  leaf  after  the  plants  are  sprinkled, 
act  as  burning  glasses  or  become  so  warm  from  the  sunshine  that  they  injure 


644 

the  tissue.  Jonsson's^  experiments  have  proved  that  the  bubbles  in  the 
glass  are  actually  the  cause.  He  observed  the  light  image  of  the  sun's  rays 
produced  on  the  leaf  by  such  bubbles  and  the  changed  position  of  such 
spots  resulting  from  the  change  of  the  sun's  position.  This  explains  also 
the  not  infrequently  observable  phenomenon  that  such  burned  spots  appear 
in  regular  lines. 

One  experiment  proved,  however,  that  sprinkling  can  also  act  danger- 
ously, when  a  drop  of  water  remained  hanging  on  the  under  side  of  the 
cover  glass,  fastened  at  some  distance  above  the  surface  of  the  leaf.  In 
this,  traces  of  burned  spots  could  be  produced,  while  drops  of  water  lying 
directly  on  the  leaf  caused  no  injury. 

To  avoid  such  disadvantages,  it  would  be  advisable  in  general  practice 
to  choose  better  grades  of  glass  at  least  for  those  hot  houses  in  which  valu- 
able foliage  plants  are  kept. 

Defoliation. 

Phenomena  of  scorching  are  not  here  concerned  but  rather  the  precipi- 
tous maturity  of  the  tissues.  In  cases  observable  out  of  doors,  a  great 
dryness  of  the  soil  is  usually  combined  with  the  direct  action  of  the  sun. 
Special  experiments  with  burning  glasses  show,  however,  that  even  in 
damp  soil  the  leaves  are  thrown  oflf  which  are  most  strongly  injured  by 
burned  spots.  Wiesner-  found  that,  in  "the  falling  of  leaves  due  to  heat," 
those  which  usually  fall  come  from  the  inner  part  of  the  crown  of  the  tree, 
rather  than  from  its  periphe^\^  He  thinks  that  these  outer  leaves,  as  a 
result  of  their  greater  radiation  of  heat,  do  not  become  so  warm  as  the 
leaves  found  in  the  enclosed  places.  We  might  seek  the  reason  for  this  in 
the  different  vitality  of  the  organs.  Those  exposed  to  the  greater  amount 
of  light  produce  more  substance  and  their  cells  are  richer  in  cytoplasmic 
material.  They  have,  therefore,  with  an  abnormally  increased  evaporation 
and  respiration,  more  reser\^e  substances  and  are  longer  lived  than  leaves 
of  the  same  period  found  in  the  inner  part  of  the  tree  crown.  Young 
organs  in  themselves  are  more  resistant. 

In  cases  occurring  out  of  doors,  the  place  of  growth,  together  with  the 
water  supply,  acts  decisively.  Among  forest  trees,  this  is  seen  best  in  oaks 
and  larches  in  young  plantations  where  individual  specimens,  already  show- 
ing completely  dried  bunches  of  leaves,  are  always  to  be  found  betv/een 
green  trees  which  have  been  uninjured,  or  only  slightly  changed. 

In  one  young  larch  plantation,  I  found  that  the  specimens  most  greatly 
injured  had  lost  almost  all  their  needles  from  the  upper  branches.  Onlv  the 
very  young  shoots,  the  tips  of  which  seemed  twisted  and  a  fox  red,  still  held 
needles  which  hung  downward  like  red  tassels.     The  youngest  needles  of  all 


1  Jonsson,     Benst,     Om    Brannflakar    pa   vilxtblad.      Botaniska     Notiser     1891. 
Zeitschr,  f.  Pflanzpnkrankh.    1892,  p.  358. 

2  Wiesner,  Jul.,  t)ber  den  Hitzelaubfall.     Ber.  d.  D.     Bot..  Ges.  1904,  Vol.  XXII, 
p.  501. 


645 

seemed  faded,  flattened  and  papery  dry.  Their  extremely  scanty  cell  con- 
tents formed  a  colorless  ball,  lying  free  in  the  inner  part  of  the  cell  and 
turning  yellow  with  iodine.  In  the  older  needles,  the  cell  walls  of  which 
had  remained  perfectly  colorless,  the  abundant  cell  contents  appeared  in  the 
form  of  pale  grayish  red,  or  yellowish  brown,  uniform  masses  lying  against 
the  wall.  The  appearance  resembled  that  produced  under  the  influence  of 
acid  gases.  In  spruces  too  the  discoloration  of  the  needles,  produced  by 
intense  summer  drought,  is  very  similar  to  that  produced  by  sulfurous  acid. 

A  similar  dropping  of  the  leaves,  due  to  heat  and  drought,  may  also 
occur  not  infrequently  in  other  conifers,  especially  when  suddenly  left 
standing  alone.  My  experiments  with  spruces  showed,  in  regard  to  the 
process  of  dropping  needles,  that  when  the  rays  from  a  lens  were  focussed 
at  the  base  of  the  needles,  these  could  be  loosened  at  once  with  a  slight  pres- 
sure even  if  they  showed  no  discoloration.  When  the  needles  were  injured 
at  points  higher  up  they  remained  attached.  In  the  burned  places  the  cell 
contents  had  contracted  into  a  band-Hke,  green  to  brownish-green  mass  in 
the  centre  of  the  cell,  and  even  their  granular  structure  could  still  be  per- 
ceived. The  contracted  content  masses  lay  usually  in  the  same  position  in 
the  different  cells,  i.  e.,  in  the  direction  of  the  long  diameter  of  the  needle. 

Injuries  to  the  bud  from  sunburn  are  comparatively  rare.  This  is  to  be 
attributed,  in  part,  to  the  protection  of  the  covering  of  the  buds  by  a  hairy 
felt,  gum,  resin,  cork  layers,  or  the  like,  which  often  are  found  to  be  espe- 
cially effective;  in  part,  also  to  the  abundant  cytoplasmic  contents  of  the 
young  tissue  which,  therefore,  are  changed  with  greater  difficulty.  In  the 
tropics,  special  protective  precautions  may  often  be  found.  According  to 
Potter^,  for  example,  in  Artecarpus,  Heptapleurum,  Canarium  ceylanicum, 
and  others,  the  stipules  of  the  older  leaf  organs  serve  as  a  protection  for 
the  young  leaves  until  they  become  strong,  or  the  entire  old  leaf  at  first 
forms  a  protective  covering  for  the  young  one  ( Uvaria  purpurea,  Gos- 
sypium,  etc.) 

In  peach  forcing  in  England,  a  dropping  of  the  peach  buds  has  been 
observed.  In  places,  where  a  damp  cloth  was  stretched  over  the  plants  as 
a  protection  against  the  action  of  the  sun,  no  dropping  of  the  buds  was 
found^. 

Sunburn  in  Blossoms  and  Fruits. 

In  injuries  to  blossoms,  no  absolutely  high  degree  of  temperature  is 
necessary;  even  the  usual  temperatures  can  become  injurious  for  shade 
loving  plants  in  an  unfavorable  place  of  growth.  The  tuberous  Begonias 
form  the  best  known  example,  the  blossom  edges  of  which  easily  become 
brown,  if  the  plants  cannot  benefit  from  the  evaporation  from  moist  soil. 

An  unusual  excess  of  heat  affects  fruit  in  two  ways.  On  the  one 
hand,  it  produces  premature  ripening,  i.  e.,  the  appearance  of  the  processes 


1  Potter,  M.  C,  Observations  on  the  Protection  of  Buds  in  the  Tropics.     Journ. 
Linn.  Soc.  XXVIII,  1891,  p.  34,3. 

2  Gardener's  Chronicle  1893,  XIII,  p.  693. 


646 

of  ripening  at  a  time  when  the  fruit  should  really  be  storing  up  reserve 
substances.  The  result  is  that  the  cells  of  the  fruit  flesh,  insufficiently  filled 
with  reserve  substances,  end  their  life  prematurely,  resulting  in  a  specked 
condition  and  premature  decay  when  stored.  In  grains,  a  premature 
ripening  of  the  blades  causes  a  distinct  injury  to  the  kernel  from  an  insuffi- 
cient formation  of  starch'. 

•  The  other  form  of  injury  consists  in  the  direct  killing  of  the  tissues, 
by  sunburn,  on  the  exposed  places  of  juicy  fruits.  Such  burned  spots  fre- 
quently resemble  places  injured  by  hail  because  the  killed  tissue  cannot 
stretch  proportionately  during  the  process  of  swelling  of  the  fruit  and 
therefore  tears.  In  the  increasing  cultivation  of  the  tomato,  we  now  find 
abundant  examples  which  remain  unrecognized  only  because  fungi  usually 
infest  the  burned  places  of  the  fruit.  The  cases  are  then  described  as 
parasitic  diseases. 

Injury  to  Grapes  from  Sunburn. 

This  is  of  great  agricultural  significance.  According  to  Muller- 
Thurgau's  observations-  an  injury  to  grapes  will  be  observed  when  hot, 
clear,  sunny  days  occur  suddenly  after  a  longer  period  of  cold,  damp 
weather.  It  is  found  then,  almost  as  a  rule,  that  the  berries  of  the  free 
hanging  clusters,  exposed  to  the  direct  rays  of  the  sun,  lose  their  green 
color,  become  pale,  then  turn  brown  and  finally  shrivel.  The  stem  of  the 
cluster  also  begins  to  suffer  where  it  is  directly  touched  by  the  sun's  rays. 
The  berries,  hanging  to  it,  shrivel  but,  in  this  case,  do  not  lose  their  green 
colon.  In  the  blue  varieties,  the  berries,  which  come  in  contact  with  the 
sun's  rays,  remain  green,  becoming  darker  than  those  of  the  white  varieties 
and  turn  almost  black.  In  some  years,  whole  bunches  are  found  shrivelled 
up  like  raisins,  producing  in  places  a  considerable  injury^.  That  it  is 
actually  an  excess  of  the  heat  which  kills  the  berries  in  this  case  is  shown 
by  the  fact  that  grapes,  which  were  warmed  in  a  tin  case  to  50  degrees  C, 
took  on  exactly  the  same  appearance  as  specimens  attacked  by  sunburn  out 
of  doors.  The  state  of  ripeness,  as  well  as  the  water  content  of  the  organs, 
and  also  the  humidity  of  the  surrounding  air,  exercises  a  decisive  influence 
on  the  burning.  Unripe  Riesling  and  Sylvaner  berries  were  not  injured 
when  warmed  to  42  degrees  C,  for  two  hours  but  were  injured  at  44  degrees 
C;  after  an  equal  length  of  time. 

Direct  measurements  showed  that  the  berries,  on  which  the  sun  shone, 
were  warmer  than  the  surrounding  air.  While  a  thermometer  in  the  air 
showed  24  degrees  C.  in  the  shade  and  another  36  degrees  C.  in  the  sun,  the 
temperature  in  the  grapes,  exposed  to  the  sun,  increased  to  40  degrees  C. 

It  was  found  further  that  Riesling  grapes  from  good  warm  positions 
were  poorer  in  water  and  suffered  less  from  sunburn,  than  those  from 


1  D6h6rain   et  Dupont,  Uber  den  Ursprung  dcr   Starke  des  Weizcnkorns;    cit. 
Biedermann's  Centralbl.  1902,  p.  324. 

2  Der  Weinbau  1883,  No.  35. 

3  Jahresber,  d.  Sonderaussch.  f.  I'flanzenschutz  1892.     Arb.  d.  D.  Landw.  G. 


647 

inferior  vineyards.  Besides  the  small  water  content,  the  advanced  ripeness 
of  the  berries  is  a  condition  which  acts  as  a  protection  against  sunburn. 
The  early  Malinger  and  the  early  Burgundy,  which  ripen  even  in  the  middle 
of  August,  for  example,  showed  no  injury  whatever  from  the  hot  August 
sun  while  more  than  50  different  varieties  of  grapes,  standing  close  by, 
which  ripened  later  and  therefore  were  still  hard  and  green  in  August,  had 
suffered  more  or  less.  Measurements  of  the  temperature  in  green,  unripe, 
hard  berries  of  Riesling,  Sylvaner,  Elbling  and  late  Burgundy  showed 
injury  at  43  degrees  C,  while  the  fairly  ripe  berries  of  the  early  Malinger 
and  early  Burgundy  could  be  warmed  for  some  time  up  to  55  degrees  C. 
without  injury  and  the  flesh  of  the  Malinger  grapes  was  killed  only  at  a 
temperature  somewhat  above  62  degrees  C. 

The  discovery  by  practical  workers  that  sunburn  is  found  most  fre- 
quently when  wet,  cold  weather  precedes  hot  days,  is  explained,  on  the  one 
hand,  by  the  greater  water  content  of  the  berries  and,  on  the  other,  by  a 
lesser  evaporation  and,  consequently,  a  lesser  cooling  when  the  air  is  moist. 
In  regard  to  the  influence  of  drought,  Miiller  made  an  experiment  on  two 
Riesling  grapes,  one  of  which  was  placed  in  a  glass  vessel  lined  with  moist 
blotting  paper,  the  other  in  one  containing  some  calcium  chlorid,  and  both 
placed  in  a  tin  case  which  could  be  heated.  The  grapes  in  moist  air  were 
completely  killed  at  a  temperature  of  41.5  degrees  C,  while  those  in  the  air, 
dried  by  the  calcium  chlorid,  were  scarcely  injured.  Two  thermometers, 
one  of  which  hung  free  while  the  bulb  of  the  other  was  stuck  into  a  grape 
berry,  were  put  in  a  similar  tin  case,  and  warmed  up  to  40  degrees  C.  The 
thermometer,  covered  by  the  grape,  constantly  stood  approximately  4  de- 
grees lower  than  the  other  when  the  temperature  increased  slowly  as  well 
as  when  it  decreased.  This  may  well  be  conditioned  only  by  the  evapora- 
tion of  the  grape. 

The  phenomenon  of  Seed  cracking  can  set  in  as  the  result  of  sunburn. 
Since,  however,  different  causes  of  this  phenomenon  exist,  it  would  be 
better  to  consider  it  later  by  itself. 

At  times  so  called  "rusty  grapes"  are  found,  i.  e.,  those  of  which  the 
skin  has  formed  fine  cork  lamellae.  This  has  been  thought  to  be  a  protec- 
tive means  against  sunburn^. 

Protection  of  the  grapes  by  the  leaves  is  the  best  precautionary  method 
and  it  is  wrong  to  think  grapes  are  helped  by  the  removal  of  their  foliage. 

Sun  Cracks. 

In  forest  and  other  trees,  at  times  in  spring,  the  bark  cracks.  This 
phenomenon  has  been  named  Sun  cracks  by  de  Jonghe,  while  Caspary- 
considers  them  due  to  the  action  of  frost.  Surface  dying  of  the  bark  is 
distinguished,  as  sunburn,  from  simple  torn  wounds.    Illustrations  are  found 


1  Zeitschr.  f.  Pflanzenkrankh.    1902,  p.  111. 

2- Bot.   Zeit.    1857,    No.    10;    "Bewirkt   die    Sonne   Risse   in  Rinde    und  Holz   dei- 
Baume?" 


648 

in  R.  Hartig^  and  Nordling-.  The  latter  distinguishes  still  another  "winter 
sunburn"^  in  which  the  injury  to  the  trunk  is  found  only  at  its  base.  The 
reflection  of  the  sun's  rays  from  the  upper  surface  of  the  soil  is  assumed  to 
be  the  cause.  R.  Hartig's  illustration  shows  the  lower  end  of  the  trunk  of 
a  red  beech  sapling  with  sun  cracks*.  Since  these  phenomena,  as  yet,  have 
only  been  observed  in  the  late  winter  and  strict  experimental  proofs  are  still 
lacking,  we  maintain  the  opinion  expressed  earlier  that  the  cracks  are  pro- 
duced by  differences  in  tension  which  arise  with  a  sudden  sharp  change  in 
temperature  without  the  necessity  of  a  warming  of  the  tissue  from  the  sun 
until  it  dies,  as  is  the  case  in  sunburned  places.  Hartig's-^  measurements  of 
a  spruce  in  August  show  how  much  the  parts  of  the  plants  are  warmed 
above  the  temperature  of  the  air.  With  an  air  temperature  of  37  degrees 
C.  he  found  55  degrees  C.  in  the  cambial  region  of  the  southwest  side ;  only 
45  degrees  C.  on  the  south  side ;  39  degrees  C.  on  the  east  side ;  37  degrees 
C.  on  the  north  side.  The  measurements  were  made  in  the  afternoon 
after  4  o'clock. 

Influence  of  Too  Great  Soil  Heat. 

Sachs"  has  already  furnished  abundant  material  in  regard  to  the  deter- 
mination of  the  temperature  requirements  of  different  plants  and  especially 
with  respect  to  the  germination  of  seeds  which  had  been  exposed  to  a  high 
temperature  of  air  and  water.  In  the  latter  connection  it  is  evident  that 
dry  seeds  endure  a  higher  temperature  without  being  injured  than  those 
already  sprouted  and  that  probably  all  plant  tissue  (within  boundaries 
required  by  the  species)  is  in  every  case  the  more  resistant  to  heat  the  less 
the  water  content  of  the  cells  is  proved  to  be.  Corroborative  works  have 
been  furnished  by  Haberlandt,  Wiesner,  Fiedler,  Krasan,  Just,  Nobbe, 
Iloehnel  and  recent  authors,  in  regard  to  which  reference  must  be  made 
to  Pfeffer's  Physiology. 

Just's'^  experiments  show,  for  example,  that  unfavorable  results  may 
be  experienced  when,  in  germinating  seed,  the  temperature  is  increased 
above  the  optimum  given  for  any  special  variety.  He  found  in  these  ex- 
periments, that  a  prolongation  of  the  germinating  time  and  a  slower  devel- 
opment of  the  seedling  is  produced  by  too  high  temperatures,  just  as  in 
seeds  which  are  too  old. 

Prillieux's^  older  work  is  of  importance  in  regard  to  the  anatomical 
changes.  In  bean  and  pumpkin  seeds,  sown  in  pots  in  which  a  high  soil 
temperature  was  maintained  by  heated  wires,  the  following  results  were 
found :  the  young  seedlings  grew  but  little  and  with  difficulty ;  however, 


1  Lehrbuch  der  Baumkrankheiten,  1st  ed.,  p.  188. 

2  Lehrbuch  des  Forstschutzes,  1884,  p.  332. 

3  Baumphysiologische  Bedeutung  des  kalten  Winters   1879-80;    cit.   Illustrierte 
Gartenzeitung  1881. 

4  Lehrbuch  der  Pflanzenkrankheiten,  3d  ed.  1900,  p.  230. 

5  Ibid.,  p.  228. 

6  Experimental-Physiologie,  p.  64  ff. 

7  Cohn's  Beitriige  zur  Biologie  der  PHanzen.     Vol.  II,   p.  311. 

8  Prillieux,  Alterations  produites  dans   les  plantes  par  la  culture  dans  un  sol 
surchauffe.     Ann.  so.  nat.  Ser.  VI  Botanique,  t.  X,  p.  347. 


649 

they  looked  swollen ;  in  the  places  where  the  swelling  of  the  little  stems  was 
most  intensive,  gaping,  usually  horizontal  wounds  were  found  which  ex- 
tended to  the  pith.  In  contrast  to  normal  plants  of  the  same  age,  those  of 
the  over-heated  soil  were  only  half  as  long  but  approximately  three  to  four 
times  as  thick  in  diameter  at  the  place  of  the  greatest  swelling.  Here  too 
the  epidermal  cells  were  two  to  three  times  as  broad  as  in  normal  plants. 
The  stomata  showed  the  same  difference  only  to  a  slighter  degree.  The 
hairs  were  not  changed.  The  bark  parenchyma  was,  to  be  sure,  four  times 
as  thick  but  no  cell  increase  had  taken  place;  the  cells  of  the  pith  paren- 
chyma showed  still  greater  radial  distention ;  but  actual  cell  increase  could 
be  proved  only  in  the  bast  parenchyma.  Prillieux  cites  further  that  the 
nuclei  behave  similarly.  They  hypertrophy  and  increase  in  such  a  way  that 
even  three  or  four  may  be  found  in  a  single  cell.  Nuclear  division  takes 
place  by  fragmentation.  Such  a  cell  increase  is  perceived  also  in  the  short, 
curved  and  twisted,  but  not  swollen,  roots  of  the  changed  plants.  The  large, 
deformed  nuclei  show  usually  very  irregular  nucleoli,  occurring  more  than 
one  in  a  cell,  in  which,  not  infrequently,  vacuoles  appear  when  colored  black 
with  osmic  acid.  In  fragmentation  of  the  nuclei,  first  a  fold  usually  ap- 
pears at  one  side  and  seems  to  constrict  the  nucleus.  Later  a  cytoplasmic 
wall  is  formed  between  the  two  resulting  nuclei.  The  two  halves,  thus 
produced,  become  inflated  and  tend  to  separate,  which  separation,  however, 
does  not  always  actually  become  complete.  It  also  seems  that  this  cleavage 
of  the  nucleus  takes  place  within  an  already  existing  cytoplasmic  covering, 
belonging  to  the  original  nucleus,  which  does  not  rupture  until  later. 

This  increase  of  the  nuclei  and  the  tender  bast  element  may  indeed 
indicate  the  way  in  which  a  higher  soil  temperature,  which  approximates 
the  optimum,  can  act  favorably.  Cell  increase  and  the  conducting  of  the 
plastic  material  may  be  hastened.  As  is  well  known,  horticulture  makes 
good  use  of  the  beneficial  influence  of  the  higher  soil  temperature  by  means 
of  hotbeds.  Yet  just  here  the  observation  may  be  made,  that  a  too  high  soil 
temperature  is  not  favorable  for  the  many  plants  from  a  cooler  climate. 
They  do  not  grow  more  rapidly  but  easily  decay.  The  assimilatory  energy 
slackens  and  the  weakened  organism  is  attacked  by  bacteria  and  fungi. 
Hellriegel's  experiments^  show  how  much  assimilation  falls  when  the  soil 
temperature  becomes  too  high.  Comparative  cultures  in  roasted  quartz 
sand  gave  yields  for 

rye 
at  8°       10°       15°       20°      25°      30°    40°  C,  constant  soil  temperature 

Fresh  weight 191.5  176.3  269.4  456.6  376.0  408.0  240.1 

Dry    substance    .  .      23.9     22.8     32.4     49.5     42.4     47.0     31.2 

wheat 

Fresh  weight   98.6  130.8  241.0  260.5  342.0  402.2  296.0 

Dry    substance    . .      15.8     20.8     29.5     30.8     43.9     46.9     40.3 

barley 
Fresh   weight  ....    151.9  156.0  383.4  408.5  435.2  365.,0  230.5 
Dry    substance    .  .     17.1     18.0     34.4     36.7     42..0     35.0     26.3 


1  Beitr.  zu  den  naturwissenschaftlichen   Grundlagen  des  Aclterbaues.     Braun- 
schweig 1883.     Vieweg  &  Sohn. 


650 

The  results  refer  to  young  plants  and  show  clearly  how  the  production 
falls  off  toward  an  upper  and  lower  limit  starting  from  an  optimum  tem- 
perature for  the  roots.  At  the  same  time  the  figures  also  throw  light  upon 
the  difference  in  the  warmth  needed  by  the  different  species.  Wheat  (at 
least  when  young)  requires  the  highest  soil  temperature.  Wheat  developed 
the  most  energetic  assimilatory  activity  at  30  degrees  soil  temperature,  while 
rye  developed  best  at  20  degrees  and  barley  at  25  degrees  C. 

Also  in  this  young  stage,  when  adjustment  to  conditions  is  easiest,  the 
plants  clearly  show  the  disturbing  influence  of  too  high  a  soil  temperature. 
Aside  from  the  retardation  of  germination,  a  considerable  difference  was 
shown  in  the  habit  of  growth  of  the  seedlings  in  that  their  stems  and  leaves 
at  high  temperatures  became  thin  and  delicate  while,  at  lower  soil  tempera- 
tures, the  specimens  appeared  short,  thick  and  more  fleshy. 

The  experiments  by  v.  Bialoblocki^  gave  the  same  results  and  showed 
also  considerable  diff'erences  in  the  formation  of  the  root  system.  The 
barley  plants,  which  were  kept  growing  constantly  at  10  degrees  C,  soil 
temperature,  had  formed  their  roots  from  a  few  large,  strikingly  strong, 
splendidly  white  branches  of  the  jDrimary  and  secondary  series,  of  which  the 
latter  were  unusually  short  and  covered  with  small,  wart-like  protuberances 
(latent  eyes  of  the  tertiary  series).  The  individuals,  standing  in  the  soil  at 
30  degrees  C,  constant  temperature,  had  developed  unusual,  richly  ramified 
brown  root  fibres,  as  thin  as  threads,  which  had  become  matted  to  a  thick 
felt.  At  40  degrees  C.  the  character  of  the  root  ball  was  the  same  but  its 
extent  was  very  small ;  a  small  felt  was  formed  in  the  upper  soil  layers. 

Tolsky-  also  found  in  oats  a  stronger  development  of  the  individual 
roots  at  a  lower  temperature  and  recently  Kossowitsch-'  confirmed  these 
results.  The  rate  of  penetration  of  the  oats  roots  into  the  soil  was  retarded 
thereby.  A  soil  layer  of  about  30  cm.,  at  the  increased  temperature,  was 
penetrated  14  days  after  seeding  but,  at  the  lower  temperature,  only  after 
30  days. 

Also  in  other  experimental  plants  (mustard  and  flax)  the  weight  of  the 
air  dried  roots  was  the  greatest  at  a  low  temperature.  The  amount  of 
evaporation  of  plants  grown  under  such  conditions  was  less  than  for  speci- 
mens of  similar  development  which  had  grown  at  the  normal,  or  higher 
temperature. 

Failure  of  the  Pineapple. 

The  fact,  that  pineapples  grown  in  European  conservatories  surpass 
imported  fruit,  because  of  increased  flavor,  has  extended  their  cultivation 
in  private  gardens  in  some  regions  (for  example,  Silicia).  The  greatest 
danger  in  their  cultivation  lies  in  their  "Durchtreiben,"  i.  e.,  a  continued 
leaf  growth  at  a  time  when  the  plant  should  enter  its  rest  period  in  order 

1  Landwirtschaftliche  Versuchsstationen  1871,  Vol.  XIII,  p.  424. 

2  Journ.  f.  experim.  Landwirtschatt,  1901,  p.  730. 

3  Kossowitsch,  P.,  Die  Entwickelung  der  Wurzeln  in  Abhangigkeit  von  der 
Bodentemperalur  in  der  ersten  Wachstumsperiode  der  Pflanzen.  Journ.  f.  experim. 
Landw.  1903;  cit.  Centralbl.  f.  Agrkulturchemie  1904,  p.  451. 


EDGAR    lULLib 

651 

to  set  fruit.  The  cause  lies  in  the  untimely  supply  of  heat  and  water  during 
the  rest  period  of  the  plant,  which  needs  three  years  for  its  development. 
After  the  plants  from  the  sprouts  (suckers)  of  already  fruited  plants  have 
grown  for  two  years  in  hot  beds,  they  are  planted  in  the  autumn  of  the 
third  year  in  beds  close  under  the  glass  of  greenhouses  which  are  built  flat 
purposely  for  pineapple  growing.  These  beds  are  kept  at  a  high  soil  tem- 
perature by  bottom  heat.  When  the  plants  are  well  rooted  at  a  temperature 
which  should  he  between  25  to  2^  degrees  C.  the  heat  must  be  decreased  at 
least  10  to  12  degrees  C.  and  a  marked,  dry  period  begin.  Only  if  the 
plants  have  thus  been  given  a  complete  rest,  may  the  forcing  begin  again  in 
February,  when  the  former  degree  of  heat  in  the  soil  is  allowed  to  act  again 
on  the  plants  and  the  soil  very  soon  well  watered  with  warm  water.  If, 
after  4  to  6  weeks,  the  leaves  of  the  plants  begin  to  spread  out  and  to 
become  colored  at  the  heart,  it  may  be  concluded  that  the  fruit  is  setting. 
For  fear  that  the  decrease  of  temperature  may  injure  the  pineapple  the 
moisture  and  heat  are  often  not  sufficiently  reduced  and  the  result  is  a 
continued  growth  of  the  plant  with  the  exclusive  production  of  leaves. 

According  to  reports  made  by  Cousins^  the  same  phenomena  appear  in 
the  cultivation  of  the  pineapple  in  the  tropics. 

The  Glassiness  of  Orchids. 

Two  cases  may  be  briefly  mentioned  here  in  which  plants  of  Oncidium 
developed  young  shoots,  nearly  all  of  which  showed  a  glassy,  translucent 
consistency.  A  few  days  after  the  appearance  of  the  glassy  places,  at  the 
base  of  the  bulbs,  the  shoots  fell  over  and  decayed.  Since  parasites  could  not 
be  found  in  the  initial  stages  of  the  disease  and  the  slendemess  of  the  older 
shoots  indicated  great  heat  and  moisture,  the  plants,  without  any  further 
treatment,  were  brought  into  a  cooler,  brighter  conservatory.  After  a  few 
weeks,  the  phenomenon  had  disappeared. 

Failure  in  Forcing  Blossom  Bulbs. 

Often,  after  very  hot  summers,  gardeners  complain  that,  contrary  to  all 
expectations,  the  blossom  bulbs  develop  poorly;  that,  when  the  usual  tem- 
perature was  used,  the  blossoms  pushed  unsatisfactorily  out  of  the  bulbs 
and  these  began  to  decay.  Bulbs  set  out  later  than  usual  for  forcing  and 
cultivated  with  less  heat,  however,  gave  perfect  blossoms. 

From  the  dift'erent  cases  with  which  I  have  become  familiar,  I  have 
formed  the  following  theory:  if  a  period  of  warm  weather  occurs  in  the 
early  summer,  when  the  bulb  fields  are  in  the  midst  of  their  most  vigorous 
development,  the  foliage  is  killed  prematurely  by  heat  and  the  bulb  becomes 
ripe  prematurely.  Under  such  circumstances,  the  material  which  later,  in 
forcing,  should  furnish  the  starch  dissolving  enzymes,  seems  to  be  formed 
in  insufficient  amounts.     If,  in  forcing  the  bulbs  in  winter,  the  usual  high 

1   Revue  cult,  colon.  1902,  No.  92. 


652 

temperature  is  made  use  of  at  the  customary  time,  the  stimulus  of  the  heat 
for  these  prematurely  ripened  bulbs  is  too  great,  since  they  require  a  slower, 
more  gradual  sprouting  with  lower  temperature.  If  this  requirement  is  not 
taken  into  consideration,  the  reserve  substances  are  not  used,  as  normally, 
in  nourishing  the  inflorescence  and  the  bulbs  decay. 

Another  case  in  which  similarly  the  usual  forcing  method  fails,  be- 
cause the  temperature  usually  found  to  be  best  proves  to  be  too  high,  is  seen 
in  the  "falling  over  of  tulips."  In  certain  early  varieties  (pink  blooming), 
it  has  been  observed  that  the  peduncles  break  over  before  the  blossoms  open. 
A  glassy  spot  i  to  2cm.  long,  appears  below  the  node  out  of  which  leaves 
spring  in  these  varieties  (several  centimeters  above  the  neck  of  the  bulb). 
The  gradual  shrivelling  of  this  spot  causes  the  breaking  over  of  the  stem. 

investigation  proved  an  abundance  of  starch  throughout  the  whole 
bulb  body  along  with  an  unusual  amount  of  peroxydases.  In  forcing,  it 
was  found,  however,  that  with  a  high  increase  of  temperature,  the  starch 
was  insufficiently  dissolved,  i.  e.,  too  little  constructive  material  was  sup- 
plied to  those  forced  aerial  parts.  The  medullary  tissue  of  the  stalk,  poor 
in  contents,  was  torn  at  this  glassy  place,  because  of  the  rapid  elongation, 
thus  destroying  the  rigidity  of  the  stalk.  Bulbs,  from  the  same  shipment, 
which  were  set  out  some  weeks  later,  i.  e.,  nearer  their  natural  time  of 
developing  and  in  the  same  temperature,  developed  normally.  It  is  thus 
seen  how  the  same  temperature  in  the  conservatory  can  act  favorably  at 
one  time,  unfavorably  at  another,  according  to  the  weather  of  the  previous 
year  and  the  constitution  of  the  bulbs,  and  it  is  advisable  at  the  beginning 
of  the  time  of  forcing  to  make  some  preliminary  tests. 

In  lilies  of  the  valley,  the  same  circumstance  of  unusually  rich  starch 
production  with  an  insufficient  supply  of  starch  dissolving  enzymes  mani- 
fests itself  in  the  scanty  development  of  the  blossom  sprays.  At  first  only 
a  few  of  the  lowest  blossoms  of  the  sprays  develop  and  only  after  these 
have  withered  do  the  upper  bells  open.  For  this  reason,  forced  lilies  of 
the  valley  often  become  unsalable  as  market  plants.  For  such  cases  the 
process  used  by  Garden  Inspector  Weber^  of  Spindlersfeld  can  be  recom- 
mended. He  watered  the  pips  with  water  at  44  degrees  C.  before  planting. 
At  any  rate,  the  dissolving  of  the  reserve  svtbstances  was  hastened  by  this. 

It  is  evident  from  these  examples  that  the  dormant  plant  parts  must 
have  reached  a  definite  condition  of  maturity  for  success  in  forcing,  which 
condition  is  characterized  by  a  sufficient  supply  of  starch  dissolving  enzymes. 

Seed  Which  Has  Suffered  From  Self  Heating. 

Without  going  into  the  much  mooted  question  whether  the  self-heating 
of  unripe  seed,  or  of  seed  stored  in  a  moist  condition,  takes  place  from  the 
effects   of  oxydases,  or  from  micro-organisms,  as  in  hay',  or  from  both 


1  "Gartenflora,"  Berlin,  1907,  Part  2,  p.  26. 

2  Miehe,  H.,  tJber  die  Selbsterhitzung-  des  Heues.     Ai-b.  d.  Deutsch.  Landw.  Ges. 
Part  111,  1905,  p.  76. 


653 

processes,  we  will  consider  here  only  the  utilitarian  value  of  the  heated  seed. 
We  will  mention,  as  example,  an  observation  made  by  Bolley\  who  found 
in  overheated  wheat,  stack-burned  as  well  as  bin-burned,  that  the  embryo 
was  browned,  or  entirely  killed.  If  the  grains  develop  at  all,  the  tips  of  the 
leaves  usually  die  and  the  roots  have  no  hair  covering.  The  injured  grains 
have  lost  their  clear  color  and  appear  pale  or  browned.  The  testa  is  pale 
and  wrinkled ;  the  flavor  of  the  grain,  as  a  rule,  is  sweetish  and  the  germin- 
ating power,  even  in  grain  which  looks  good,  is  weakened. 

The  injury  to  the  germinating  power  takes  place  so  much  the  more 
rapidly  the  less  ripened  the  seed  was  when  stored  or  the  less  draughty  the 
place  of  storage,  since  wind  can  dissipate  the  water  vapor.  According  to 
Jodin's  experiments-  the  use  of  a  drying  substance  (slacked  lime)  has 
proved  to  be  advantageous. 


1  Bolley,  H.  L.,  Conditions  affecting-  the  value  of  wheat  for  seed.  Agric.  Exp. 
Sta.  North  Dakota;   cit.  Zeitschr.  f.  Pfianzenkrankh.  1894,  p.  22. 

-'  Jodin,  v.,  Sur  la  resistance  des  grraines  aux  temperatures  elevees.  Compt. 
rend,  1899;  cit.  Bot.  Jahresber.  1900.    II,  p.  420. 


CHAPTER  XIII. 


LACK  OF  LIGHT. 


Etiolation. 


The  disease,  which  is  produced  by  deficient  illumination,  or  entirle  lack 
of  light,  is  called  etiolation  (etiolement).  The  different  stem  members  in 
the  majority  of  green  plants  become  uncommonly  long  and  weak.  Accord- 
ing to  the  variety  to  which  they  belong,  the  leaves,  as  well  as  the  internodes 
of  the  stem,  either  become  very  long,  slender  and  limp  (the  majority  of 
monocotyledons),  or  develop  only  very  slightly  and  remain,  for  their  whole 
life,  in  a  condition  similar  to  that  in  the  bud  (most  dicotyledons). 

A  bleaching  of  the  green  parts  of  the  plants,  i.  e.,  an  arrested  develop- 
ment, or  decay  of  the  existing  chloroplasts,  is  connected  with  this  change 
in  form.  We  find  exceptions  only  in  the  gymnosperms,  of  which  the  major- 
ity are  unusually  little  susceptible  to  the  removal  of  light.  At  any  rate, 
according  to  Burgerstein^  the  absorption  of  the  endosperm  becomes  slower, 
the  epinastic  spread  of  the  cotyledons  less  energetic  and  incomplete  than  in 
the  light,'  but — with  the  exception  of  Gingko  hiloha  and  Ephedra — the  seed- 
lings did  turn  green,  Cycas  and  Zamia,  on  the  other  hand,  cannot  form 
any  chlorophyll  in  complete  darkness,  even  with  a  favorable  temperature. 
Among  conifers,  the  larches  need  the  light  most  since  they  become  only 
slightly  green  when  it  is  excluded,  while  the  Cupressineae  become  com- 
pletely green. 

The  difference  in  the  formation  of  the  leaves  of  etiolated  plants  is 
explained  by  the  fact  that  the  leaf,  for  the  most  part,  must  nourish  itself 
and  that  the  cellulose  material,  which  it  needs  for  the  new  formation  and 
maturing  of  the  leaf  cells,  can  be  formed  only  by  the  action  of  the  light  on 
the  very  spot.  If  the  nutriment  is  suppressed,  the  leaf  cells,  already  formed 
in  the  bud,  elongate  with  the  absorption  of  water,  on  which  account  the 
leaf  itself  will  become  somewhat  larger,  but  all  further  growth,  depending 
on  cell  increase,  will  be  impossible.  The  more  the  leaf,  in  its  later  enlarge- 
ment in  the  Hght,  depends  on  cell  increase,  the  smaller  it  remains  when  the 


1  Burg-erstein,  A.,  t)ber  das  Verhalten  der  Gj^mnosp'^rmen-Keimlinge  im  Lichte 
imd  im  Dunkeln.     Just's  bot.  Jahresb.  1900,  II,  p.  250. 


655 

light  is  shut  away.  Further,  it  will  develop  so  much  the  less,  the  fewer  the 
cells  originally  formed  as  leaf  primordia  at  the  tip  of  the  stem;  a  clasping 
leaf,  on  this  account,  will  develop  further  than  a  whirl  leaf  can,  because, 
in  the  primordia  of  the  former,  the  whole  circumference  of  the  stem  is 
active,  while  in  those  of  the  latter,  the  cells  at  the  same  height  on  the  stem 
must  be  divided  among  as  many  leaves  as  the  whirl  numbers.  A  further 
point,  which  must  be  of  influence  on  the  development  of  the  leaf  in  the 
dark,  is  the  distance  of  the  leaf  primordia  from  the  soitrce  of  the  reserve 
substances.  Those  produced  first,  and  lying  nearest  a  reserve  substance 
store,  remove  more  material  from  the  supply  and,  on  this  account,  become 
larger  than  those  produced  later  and  higher  up  on  the  etiolated  stem.  Thus 
the  development  of  the  etiolated  leaf  is  dependent  on  the  individual 
primordia  and  on  the  amount  of  nutrition  to  be  found  in  its  immediate 
proximity. 

The  primordia  of  the  monocotyledon  leaves,  in  the  majority  of  cases, 
are  formed  like  a  roll,  surrounding  the  stem,  below  the  vegetative  cone  and 
in  the  immediate  proximity  to  reserve  substance  stores,  when  these  are 
present,  from  which  the- dissolved  constructive  material  has  to  pass  only  a 
short  distance  through  the  shortened  axis  (grasses). 

Having  discussed  the  etiolation  phenomena  of  the  leaf,  the  unusual 
elongation  of  the  etiolated  stem  members  remains  to  be  explained.  We  will 
follow  in  this  the  statement  made  by  Kraus^.  As  a  rule,  etiolated  stems  are 
thinner  than  normal  ones,  caused  by  a  lesser  number  of  cells,  and  this 
deficient  activity  in  the  cambium  of  the  stem  is  explained  by  the  assumption 
that  some  of  the  nutritive  substances,  worked  up  by  the  leaf,  which  pass 
over  into  the  stem  through  the  petiole,  pass  further  in  a  radial  direction  and 
help  to  nourish  the  cambium  of  the  internode  of  the  stem.  If  this  source  of 
nutrition  fails,  i.  e.,  the  leaf,  which  in  the  dark  remains  in  the  form  of  a 
scale,  is  not  in  a  position  to  obtain  material  for  cell  increase,  the  stem  mem- 
ber remains  as  it  is  without  any  actually  new  cell  formation.  The  thicken- 
ing of  the  cell  walls  is  also  suppressed.  In  normal  stems  the  parenchyma 
cells  of  the  bark  and  the  prosenchyma  cells  of  the  wood  become  thickened 
during  their  growth  in  length.  The  pith  cells,  however,  begin  to  grow 
thicker  only  when  elongation  is  approximately  at  an  end,  i.  e.,  at  the  latest 
moment,  since  they  are  only  reached  by  the  cellulose  micella,  wandering  in 
a  radial  direction  from  the  leaf  into  the  interior  of  the  stem,  when  it  is  no 
longer  used  to  thicken  the  wood  or  bark  cells.  In  etiolated  stems,  because 
of  the  lack  of  nutrition,  the  thickening  of  the  cell  is  only  indicated,  so  that 
it  is  almost  lost  in  those  which  lie  between  the  different  vascular  bundles 
and,  in  the  normal  condition,  develop  into  wood  cells.  On  this  account, 
frequently  no  closed  wood  ring  is  found  in  the  etiolated  plants.  The  loss 
in  thickness  suffered  by  these  cells  is  compensated  for  by  their  greater 
length,  which  exceeds  that  of  the  normal   cell   from  two  to   four  times. 


1   Kraus,   C,  Tiber  die  Ursachen  d.  Formveranderungen   etiolierender   Pflanzen. 
Prlngsheim's  Jahrb.  f.  wiss.  Bot.,  Volt  VII,  Part  1,  2,  p.  209  ft. 


656 

This  excessi\e  length  is  explained  by  the  modified  tension  conditions  in  the 
stem  members. 

The  bark,  if  loosened  from  the  growing  part  of  the  stem,  contracts; 
the  isolated  pith  body,  on  the  other  hand,  becomes  considerably  longer.  It 
is  evident  from  this  that,  in  the  stem,  the  pith  is  really  the  elongating  factor, 
while  the  rest  of  the  tissue  represents  the  restraining  factor.  Only  when 
the  stem  is  still  very  young  can  the  pith  satisfy  the  impulse  for  elongation 
because  the  surrounding  tissues  are  still  thin-walled  and  very  easily 
stretched.  They  can,  therefore,  most  easily  follow  passively  the  strain 
which  the  pith  exercises.  Gradually,  however,  the  elasticity  of  the  outer 
tissue  is  entirely  lost  and  the  longer  pith  is  now  restrained  by  the  thick- 
walled  bark  and  wood  elements.  In  the  latter  developmental  stage,  shorti}' 
before  the  stem  member  ceases  growing,  the  differences  in  the  tissue  are 
equalized,  for  now  the  pith  cells  grow^  broader  rather  than  longer,  as  a  result 
of  the  restraining  influence  of  the  bark  layers  and,  in  this  form,  become 
stable  since  the  porous  thickening  layers  are  now  formed  in  the  cell  wall. 

Therefore,  the  longer  the  bark  elements  remain  elastic,  so  much  the 
longer  can  the  pith  follow  its  impulse  to  elongate  and  draw  the  other  tissues 
out  wdth  it. 

The  etiolating  plants  often  resemble  juvenile  organs  and  the  condition 
of  etiolation,  up  to  a  certain  degree,  can  be  designated  as  a  permanent  juven- 
ile form. 

After  discussing  the  morphological  changes,  we  have  still  to  consider 
some  metabolistic  processes.  First  of  all  we  will  mention  the  investiga- 
tions of  E.  Schulze  and  N,  Castoro^  on  Liipiniis  alhus.  In  etiolated  seed- 
lings, the  protein  content  decreases  constantly,  while  asparagin  increases ; 
tyrosin  and  leucin  decrease.  At  any  rate,  seedlings  grown  in  the  light 
retain  for  a  long  time  a  high  amount  of  asparagin  but  contain  very  little 
amino  acid. 

Palladin's-  experiments  make  it  evident  that  the  decreased  current  of 
transpiration  in  etiolated  plants  causes  a  too  slight  absorption  of  mineral 
elements,  especially  calcium.  A  lack  of  calcium  salts,  however,  even  in 
leaves  rich  in  proteins,  prevents  all  further  development. 

Wiesner^  has  shown  by  numerous  experiments  that  plants  gro\vn  in 
the  dark  are  less  resistant  to  atmospheric  influences.  He  found,  for 
example,  that  seedlings,  grown  in  the  light,  are  much  more  resistant  to  the 
action  of  rain  and  water  in  any  form,  than  seedlings  developed  in  the  dark. 

Observations  made  by  Maige*  on  Ampelopsis  and  Glechoma  show  how 
the   material   differences   come   to   expression   in   growth.     Diffused   light 

1  Schulze,  E.,  u.  Castoro,  N.,  Beitrage  zur  Kenntnis  der  Zusammensetzung  und 
des  Stoffwechels  der  Keimpflanzen.  Zeitschr.  f.  phys.  Chemie,  Vol.  XXXVIII.  Cit. 
Botan.  Centralbl.  1904.  No.  47,  p.  540. 

2  Palladin,  W.,  Eiweissgehalt  der  grunen  und  etiolierten  Blatter.  Ber.  d. 
Deutsch.  Bot.  Ge.s.  Vol.  IX,  p.  194.  ■ —  ErgTiinen  und  Wachstum  der  etiolierten 
Blatter.     Ibid.  p.  229. 

3  Wiesner,  J.,  Der  Lichtgenuss  der  Pflanzen.  Leipzig  1907,  W.  Engelmann. 
p.  260.  '    "*. 

4  Maige,  Influence  de  la  lumiere,  etc.  Compt.  rend.  1898,  p.  420.  Cit.  Bot. 
.lahresber.  1898.     I,  p.  587- 


657 

furthers  the  formation  of  the  leaf  shoots  and  can,  in  fact,  cause  the  trans- 
formation of  an  inflorescence  bud  into  a  climbing  branch.  Direct  sunshine 
has  an  exactly  opposite  effect. 

Green's  experiments^  are  very  important  for  pathology  and  especially 
for  the  point  of  view  which  we  would  represent,  that  a  whole  series  of 
diseases  is  caused  by  a  change  in  enzymatic  functions.  He  confirms  the 
observations  of  Brown  and  Morris  that  the  supply  of  diastase  in  the  foliage 
is  diminished  after  a  period  of  bright  illumination.  The  ultra  violet  and 
adjoining  visible  rays  are  especially  important  in  producing  such  an  enzy- 
matic decrease.  Such  an  enzymatic  destruction  by  light  may  be  compared 
with  the  well-known  killing  of  bacteria  by  light. 

Shading. 

In  agriculture,  the  injuries  produced  b}^  direct  etiolation  are  much  less 
frequent  and,  on  this  account,  less  significant  than  the  lower  grade  of  occur- 
rences which  arise  from  an  insufficient  supply  of  light;  i.  e.,  too  strong 
shading,  and  make  themselves  felt  in  the  decreased  production  of  useful 
substances.  Stebler  and  Volkart-  have  made  measurements  of  the  removal 
of  light  caused  by  different  trees.  With  a  clouded  sky,  they  found  a 
decrease  of  light  from  the  pine  of  50  per  cent. ;  from  the  birch,  56  per  cent. ; 
from  the  cherry,  78  per  cent. ;  from  the  oak,  pear  and  apple,  82  per  cent.  ; 
and  from  the  beech,  95  per  cent. 

Since  each  plant  has  its  definite  need  of  light,  cases  also  occur  in  which 
cultivation  gives  an  excess  of  light,  while  the  natural  habitat  would  furnish 
the  plant  with  only  a  subdued  amount.  This  is  found  in  many  of  our  hop 
fields  and  in  strawberry  culture^.  In  such  cases,  shade  causes  an  increased 
production  but,  in  the  majority,  reduces  the  amount  of  dry  substance  and 
weakens  the  color  of  the  foliage  and  blossoms.  The  question  of  shading 
may  be  of  especial  importance  for  our  colonial  plants.  In  Java,  as  well  as 
in  our  East  Africa  colonies,  coffee  plantations  suffer  very  frequently  and 
Zimmerman*  ascribes  this  to  a  lack  of  shade  trees  which  would  prevent 
over-production  by  the  coffee  trees ;  for  example,  in  Usambara,  this  has 
already  caused  great  injury.  It  is  probable  that  the  consequent  lessened 
strength  of  illumination,  besides  the  protection  from  the  wind  and  decrease 
of  temperature,  especially  favors  the  thriving  of  coft"ee. 

The  decreased  harvest  from  plants  which  need  light,  due  to  the  influ- 
ence of  the  shade  of  trees,  arises  not  only  from  the  limited  amount  of  light 
but  also  from  the  lesser  warming  of  the  soil.     E.  v.  Oven's  experiments^ 

1  Green,  .J.  Reynolds.  On  the  action  of  light  on  diastase.  Phil.  Trans,  of  the 
R.  Soc.  of  I^ondon.     Ser.  B.  Vol.  188;    cit.  Bot.  Jahresber.  1897.     I,  p.  89. 

-  Stebler,  F.  G.,  u.  Volkart,  A.,  Der  Einfluss  der  Beschattung-  auf  den  Rasen. 
Landwirtsch.  Jahrtaucher.  d.  Schweiz.  Bern  1904;  cit.  Bot.  Centralbl.  1908,  Vol. 
101,  p.  60. 

3  Taylor,  O.  M.,  and  Clark,  V.  A.,  An  experiment  in  shading-  strawberries.  New 
York  Agrie.  Exp.  Sta.  Geneva  Bull.  246.  1904. 

4  Zimmerman,  A.,  Einige  Bemerkungen  zu  dem  Aufsatze  von  Fr.  Wohltmann, 
usw.  Berichte  iiber  Land-  u.  Forstwirtschaft  in  Deutsch-Ostafrika.  Vol.  I,  Part  5, 
1903. 

5  V.  Oven,  tJber  den  Einfluss  des  Baumschattens  auf  den  Ertrag-  der  KartofCel- 
pflanze,     Naturw.  Zeitschr.  f.  Land-  u  Forstwirtschaft.     1904,  p.  469. 


658 

show  how  great  the  differences  can  be.  He  found  an  average  temperature  of 
22.26  degrees  C.  at  9  A.  M.  on  ten  days  in  August,  in  soil  on  which  the  sun. 
shone,  but,  under  a  cherry  tree,  a  temperature  of  19.06  degrees  C.  In  1884, 
Wollny^  had  already  measured  the  influence  of  soil  shading  due  to  weeds 
in  a  potato  field  and  found,  at  a  depth  of  10  cm.  in  the  soil,  that  the  temper- 
ature averaged  2.6  degrees  C.  less  than  on  a  field  cleared  of  weeds. 

Besides  the  temperature,  the  amount  of  water  in  the  soil  is  of  impor- 
tance. Gain's  measurements-  show  how  much  the  soil  moisture  influences 
the  size  of  the  leaf.  He  reckoned  the  length  of  the  organs  set  in  a  dry 
habitat  at  100,  the  dimensions  on  damp  soil  for  barley  were  240;  for  poppies 
550;  for  potatoes  150. 

If  the  plants  continue  to  have  too  little  water,  their  maturing  is  natu- 
rally delayed ;  their  productivity  is  also  considerably  reduced.  In  this 
connection  Bimer's  experiments^  should  be  mentioned.  He  found  that  the 
ripening  of  potato  plants  was  delayed  8  days  in  a  soil  with  a  40  to  30  per 
cent,  saturation  capacity;  18  days  in  a  30  to  10  per  cent,  saturation  capacity 
in  contrast  to  plants  with  an  abundant  soil  moisture  (80  per  cent,  saturation 
capacity).  With  the  same  high  moisture  content  of  the  soil,  Wollny  har- 
vested 80  g.  of  tubers  from  pot  plants,  while  he  obtained  only  39  g.  with 
half  the  water  content  of  the  soil  and  only  19.5  g.  with  20  per  cent,  satura- 
tion capacity. 

In  growing  herbaceous  plants  with  shallow  spreading  roots,  the  yield  is 
markedly  decreased  by  the  deeper  lying  tree  roots.  In  v.  Oven's  investiga- 
tions, the  water  content  under  a  cherry  tree  amounted  to  20.24  per  cent.,  in 
the  unshaded  vicinity,  however,  it  amounted  to  21.78  per  cent.  According 
to  Wollny,  2.86  per  cent,  more  water  was  withdrawn  from  a  potato  field  by 
the  weeds  than  by  the  potatoes  alone. 

V.  Oven  describes  the  influence  of  shade  on  the  plant  itself,  according 
to  his  own  observations  and  those  of  other  scientists.  The  stem  members 
become  longer;  the  leaves  more  slender  and  the  ripening  is  retarded.  The 
epidermis,  the  sheath  of  the  vascular  bundles,  the  walls  of  the  ring  ducts 
and  medullary  parenchyma  are  not  so  thick  and  the  lignification  is  less. 

The  cause  of  the  lengthened  period  of  growth  of  plants  in  the  shade 
must  be  looked  for  in  the  lesser  intensity  of  metabolism,  which  manifests 
itself  in  the  weaker  respiration,  since,  according  to  our  experiments,  the 
amount  of  assimilatory  activity,  under  otherwise  equal  conditions,  deter- 
mines the  degree  of  transpiration,  and  this  also  explains  the  essentially  lesser 
evaporation,  and,  on  this  account,  the  higher  water  content  in  shaded  plants. 

Of  the  numerous  experiments,  which  determine  a  reduction  of  the 
harvest  due  to  shade  and  which  v.  Oven  cites,  in  addition  to  his  own,  one 
by  Wieske  on  a  wheat  field  is  of  interest.  The  plants,  which  were  shaded 
for  the  greater  part  of  the  day  by  fruit  trees,  gave  a  grain  yield  decreased 

1  Wollny,  Forschungen  auf  dem  Gebiete  der  Agrikulturphysik,  Vol.  VII,  p.  349. 

2  Bot.  Centralbl.,  Beihefte.   Vol.  IV,  p.  418. 

3  Bimer  in  Biedermann's  Centralbl.     1881,  p.  154. 


659 

about  30  per  cent.,  and  a  straw  yield  about  32  per  cent,  less  than  the  un- 
shaded plants  in  the  same  fields. 

The  results  which  PagnouP  obtained  are  especially  noteworthy.  In 
experiments  with  sugar  beets,  he  found  a  strong  falling  off  in  sugar  content 
with  an  increase  of  the  leaf  substance  per  gram  of  root  body  and,  for  pota- 
toes, a  decreased  tuber  yield  with  a  significant  falling  off  of  dry  substance. 
Besides  this,  however,  he  proved  that  the  nitrate  content  for  beets  and 
potatoes,  grown  under  blackened  glass,  was  more 'than  ten  times  as  great  in 
the  leaves  and  roots  as  in  plants  grown  in  the  sunshine.  Therefore,  the 
physiological  activity  was  changed  in  the  shade  since  the  nitrates  were  not 
sufficiently  used  up. 

Some  of  v.  Oven's  experiments  took  up  the  measurement  of  the  inten- 
sity of  the  light  which  remained  after  the  sun's  rays  had  passed  through  a 
tree  crown.  It  was  shown  by  the  Bunsen-Roscoe  method,  that  the  propor- 
tion of  full  daylight  to  the  amount  of  light  under  fruit  trees  was  about  i  to 
0.3.  The  shade  of  apple  trees  reduces  the  intensity  of  the  light,  on  an 
average,  from  i  to  0.234;  the  shade  of  pear  trees  from  i  to  0.233;  that  of 
cherry  trees  from  i  to  0.345. 

For  practical  purposes,  the  lesson  may  be  drawn  from  existing  obser- 
vations that  the  cultivation  of  fruit  trees  between  field  plantations,  so  widely 
recommended,  is  unprofitable  for  northern  regions.  For  southern  countries, 
in  which  an  excess  of  light  and  heat  may  at  times  injure  the  plants,  the 
method  will  be  advantageous.  We  find  this  theory  confirmed  by  the  fact 
that  in  Italy  the  fields  are  divided  by  rows  of  mulberry  and  olive  trees,  as 
well  as  by  grapevines.  According  to  Linsbauer^  the  cultivation  of  grapes 
in  Italy  (on  pergolas)  and  in  Austria  (on  low  stakes)  has  been  determined 
by  adaptation  to  the  light  conditions.  In  southern  regions,  thedonger  dura- 
tion of  the  sunshine  permits  the  shading  method  of  growth  on  arbors,  while, 
in  northern  countries,  the  shorter  period  of  sunshine  must  be  fully  used. 

Like  Frank-Schwarz,  we  reproduce  illustrations  of  beech  leaves  from 
vStahl's  well-known  studies  on  the  structure  of  shade  leaves.  In  Fig.  152' 
may  be  seen  a  beech  leaf  grown  in  the  sun,  in  Fig.  153,  one  grown  in  half 
shade;  and  in  Fig.  154,  another  matured  in  strong  shadow.  We  see  from 
these  how  the  leaf  decreases  in  size  with  deficient  illumination.  The  pali- 
sade cells  (pp)  are  formed  in  a  less  characteristic  way,  the  spongy  paren- 
chyma (schp)  becomes  especially  reduced  and  the  vascular  bundle  cords 
weaker ;  a  more  feeble  bud  development  is  coordinated  with  the  lesser  leaf 
development. 

The  formation  of  the  tissue,  especially  the  differentiation  in  the  paren- 
chyma tissue^,  depends  upon  the  light  intensity  in  the  spring.     Hesselman* 


1  Annales  agronomique.s,  Vol.  VII,  189];    cit.  v.  Oven. 

2  "Wiesner,  Lichtgenuss  der  Pflanzen.     1907. 

3  MacDougal,    D.  F.,    The    Influence    of    Light    and    Darkness,    etc.;     cit.    Bot. 
Centralbl.    1903.     Vol.  XCII,  p.  296. 

4  Hesselmann.  H.,  Zur  Kenntnis  des  Pflanzenlebens  schwedischer  Laubwiesen. 
Beih.  Bot.  Centralbl.     Vol.  17,  1904,  p.  311. 


66o 

found  that  the  plants,  completing  their  development  in  a  constantly  reduced, 
but  not  especially  small  amount  of  light,  show  a  much  scantier  formation  of 
the  assimilatory  tissue  than  those  specimens  which  have  a  good  deal  of  light 
in  the  spring  but  are  strongly  shaded  in  summer.  With  an  equal  amount 
of  leaf  surface,  plants  grown  in  the  sun,  with  their  matured  palisade  paren- 
chyma, transpire  considerably  more  strongly  than  those  grown  in  the  shaded 
According  to  Ricome"-,  the  palisade  cells  are  said  to  be  taller  but  narrower, 
the  vascular  bundles  more  abundant  in  the  petioles.  The  same  difference  is 
found  between  specimens  grown  out  of  doors  and  in  conservatories^. 

Investigations  made  by  Count  zu  Leiningen*  give  us  a  satisfactory  in- 
sight into  the  amount  of  work  performed  by  light  and  shade  leaves.     He 


Fig-.  152.     Cross-section  through  a  beech 

leaf     matured     in     the     sun.        (After 

Stahl.) 


Fig.   153.     Cross-section   through 

a  beech  leaf  from  a  half  shaded 

position.      (After  Stahl.) 


Fig. 


154.     Cross-section    through    a    beech    leaf   from    a    very    shady    place. 
(After  Stahl.) 


pp  palisade  pareiich\ 


spoiijry  parciichx 


found  in  the  beech,  reckoned  on  the  same  amount  of  leaf  surface,  a  con- 
siderably smaller  content  in  pure  ash  (with  the  exception  of  silicic  acid)  in 
sun  leaves  than  in  shade  leaves ;  the  nitrogen  content  was  corresponding. 
We  explain  this  condition  of  affairs  as  follows : — the  root  system  provides 
the  leaves  with  equal  amounts  of  mineral  substances ;  it  now  depends  upon 


1  Bergen,  J.,  Transpiration  of  sun  leaves  and  shade  leaves  of  Olea  europaea 
and  other  Orval-leaved  evergreens.     Bot.  Gaz.     Vol.   38,  1904,  p.  285. 

-'  Ricome,  R..  Action  de  la  lumifere  sur  des  plantes  6tiol6es.  Rev.  gen.  de  Bot. 
1902,  t.  XIV,  p.  26. 

3  Klister,  Review  of  "BM^lian,  Influence  de  la  culture  en  serre,  etc.,"  in  Holl- 
rung's  Jahresber.  iiber  Leistungen  auf  d.  Geb.  der  Pflanzenkrank.  Vol.  VII,  1905, 
p.  7.  (Further  notes  on  Sun  and  Shade  Leaves,  cf.  Kuster,  E.,  Pathologische  Pflan- 
zenanatomie  1903,  p.  24,  etc.) 

4  Leiningen,  Wilhelm,  Graf  zu,  Licht.  und  Schattenblatter  der  Buche.  Naturw. 
Zeitschr.  f.  Land-  u.  Forstwirtsch,     1905,  III  Year,  Part  5. 


66i 

how  these  are  made  use  of.  The  more  vigorously  a  plant  grows,  the  more 
organic  substances  it  produces  per  gram  ash.  Therefore,  a  lesser  assimil- 
atory  activity  must  be  concluded  each  time,  if  the  analysis  proves  a  high 
ash  content  in  proportion  to  the  dry  substances.  In  the  present  case,  the 
scanty  amount  of  light  is  the  factor  reducing  production. 

Sensitiveness* to  shade  is,  at  any  rate,  connected  with  a  definite  limit  of 
value  for  each  plant  variety,  but,  as  in  all  factors  of  growth,  these  values 
can  shift  individually  to  a  certain  degree,  so  that,  in  the  same  species,  there 
may  be  races  very  sensitive  to  shade  in  which,  in  Nordhausen's^  opinion, 
certain  reduction  phenomena  become  herditary. 

Each  leaf  in  the  plant  has  its  special  sensitiveness  to  shade,  according 
to  the  light  conditions  under  which  it  was  produced,  and  its  position  on  the 
axis.  The  shade  produced  by  leaves  higher  up  is  the  most  important.  The 
amount  of  assimilation  and  respiration,  as  weU  as  of  transpiration,  is  deter- 
mined by  this.  In  Griffon's  experiments^,  for  example,  it  was  found  that 
a  leaf,  as  thick  as  that  of  Prunus  Laurocerasus  is  not  able,  in  direct  sunlight, 
to  completely  prevent  the  carbon  dioxid  decomposition  in  the  leaf  of 
IJgustrum  ovalifolium.  Under  two  such  leaves,  however,  the  development 
of  carbon  dioxid  took  place.  Under  such  conditions,  therefore,  assimilation 
was  so  reduced  that  respiration  exceeded  it. 

It  naturally  depends  also  upon  what  color  the  shaded  plant  parts  are, 
i.  e.,  which  light  colors  can  still  pass  through  them. 

According  to  Teodoresco"  the  leaf  tissues  develop  most  poorly  ingreen 
light;  they  are  found  to  be  better  in  red  light;  the  best  development,  how- 
ever, is  found  in  blue  light,  and,  therefore,  the  greatest  enlargement.  The 
chlorophyll  grains  are  also  smaller  in  green  Hght,  less  numerous  and  not  so 
regularly  distributed  as  in  red  and  blue  light. 

The  product  of  the  activity  of  the  chloroplasts,  corresponding  to  their 
development,  is  proved  especially  favorable  in  the  most  strongly  refrangible 
rays.  Palladin*  exposed  etiolated  cotyledons  of  Vicia  in  sugar  solutions  to 
white  and  colored  light  and  found  that  the  assimilation  of  the  sugar,  as  well 
as  the  formation  of  active  proteids,  took  place  most  vigorously  in  the  more 
strongly  refrangible  light  rays  and,  therefore,  respiration  was  more  intensive. 

If  the  leaf,  because  of  a  scanty  light  supply,  cannot  work  any  longer, 
it  falls  off,  just  as  under  the  action  of  all  other  factors  which  suppress  its 
assimilatory  activity ^  This  explains  the  regular  "summer  leaf  fall,"  which, 
naturally,  is  different  from  leaf  fall  due  to  heat.     Wiesner"  explains  the 

1  Nordhausen,    M.,    tJber    Sonnen    unci    Schattenblatter.      Ber    d     Deut'sch     Bot 
Ges.  Vol.  XXI,  1903,  p.  30.  ... 

2  Griffon,    Ed.,    L'assimilation    chlorophyllienne    dans   la    lumiere    solaire    qui   a 
traverse  des  feuilles.     Compt.  rend.  CXXIX,  Paris  1899,  p.  1276. 

3  Teodoresco,  E.,  Influence  des  diffgrentes  radiations,  etc.;   cit.  Bot.  Jahresber 
27.  Jahrg".  1901.     Part  II,  p.  133. 

4  Palladin,  W.,  Influence  de  la  lumiere,   etc.;    cit.   Bot.   Jahresber.   Jahra-    1899 
II,  p.  134. 

5  Vochting-,  H.,  fiber  die  Abhangigkeit  des  Laubfalls  von  seiner  Assimilations - 
tatigkeit.    Bot.  Zeit.  1891,  Nos.  8  and  9. 

6  Wiesner,    Jul.,    tJber    Laubfall    infolge    Sinkens    des    absoluten    Lichtgenusses 
(Sommerlaubfall).     Ber.  d.  Deutsch.  Bot.  Ges.  Jahrg.  XII,  Part  1,  1904,  p.  64. 


662 

"summer  leaf  fall"  in  that  the  lowering  of  the  daily  light  intensity,  follow- 
ing the  beginning  of  summer,  brings  about  a  lowering  of  the  (absolute) 
amount  of  light,  for  the  plant  concerned,  below  the  minimum,  whereby  an 
immediate  loosening  of  the  leaves  is  caused. 

The  amount  of  bloom  for  each  plant  depends,  of  course,  upon  the 
abundance  of  the  carbon  assimilation,  hence  shaded  speqimens  bloom  less. 
Exclusively  diffuse  light  delays  the  time  of  blooming  and  can  prevent  the 
complete  ripening  of  the  fruit,  so  that  the  seed  will  atrophy'. 

There  are  cases  where  plants,  with  a  previously  abundant  assimilation, 
are  placed  in  the  shade  before  their  blossoms  develop.  In  the  dark,  the 
blossoms  appear  later,  as  a  rule.  Their  color  is  paler  and  at  times  white; 
their  size  and  amount  of  substance  less  and  the  peduncles  not  infrequently 
longer-.  If  however,  the  leaves  are  left  in  the  light  and  only  the  branches, 
bearing  the  blossom  buds,  are  darkened,  then,  according  to  Kraus^  the 
flowers,  with  a  few  exceptions,  develop  completely. 

We  have  considered  in  the  previous  section  the  thin-walled  condition  of 
the  cell  elements  in  etiolated  plants. 

The  Lodging  of   Grain. 

The  lodging  of  the  stalks  for  a  long  period  effects  a  loss  in  quantity 
and  quality  of  the  harvest.  It  is  the  more  dangerous  the  more  the  bending 
of  the  stalk  approaches  actual  breaking  over.  Investigators  were  inclined 
earlier  to  assume  one  single  cause  for  this  lodging  until  later  observations 
determined  that  very  different  factors  can  come  into  effect  and  that,  accord- 
ing to  the  causes,  the  breaking  over  of  the  stalk  takes  place  sometimes  at 
the  base  in  the  soil,  sometimes  close  above  this  point,  or  higher  on  the  stalk. 

Thus  we  know  now  that  frost  injuries  often  produce  weakening  of  the 
stalks  which  without,  or  (usually)  with  the  later  co-operation  of  some  fun- 
gus, initiates  their  falling  over.  Further,  eating  by  insects,  breaking  from 
the  wind,  hail,  long  continued  rainfall,  not  infrequently  cause  a  direct  falling 
of  the  stalks. 

While,  however,  the  majority  of  the  factors  named  cause  a  lodging  of 
the  grain  in  spots  so  that  stalks  remain  standing  upright  between  these 
places,  the  actual  lodging  most  feared  by  the  agriculturalist  is  the  one 
occurring  in  continuous  areas,  due  to  weak  development  of  the  bases  of 
the  stalks. 

L.  Koch"*,  who  has  definitely  shown  by  experiments  that  this  results 
from  a  lack  of  light,  produced  artificially  the  phenomena  of  lodging  by 
shading  the  stalks.     The  experiments  made  earlier  by  Gronemeyer°  were 


1  Passcrini,  N.,   Sopra  vegetazione  di   alcune  piante  alia  luce   solare  diretta  e 
diffusa,     cf.  Just's  Jahresber.  1902,  II,  p.  628. 

2  Beulayg-ue,  Einfluss  der  Dunkelheit  auf  die  Entwicklung  der  Bliiten.     Bieder- 
mann's  Centralbl.  1902,  p.  102. 

3  Kraus,    tjber    die    Uisachcn    der   Formverilnderungen    etiolierender    Pflanzen. 
Pring-sheim's  Jahrb.  f.  wiss.  Bot.,  Vol.  VII,  p.  209. 

4  Koch,    Ludwig-,    Abnormc    Andeiungeaa    wachsender    Pflanzenorgane    durch 
Beschattung. 

5  Gronemeyer  in  Agronom.     Zoil.  1SG7,  No.  34. 


663 

thus  confirmed.  The  weakness  of  the  stalks,  which  conditions  the  falling 
over  in  lodging  is  found  actually  in  the  lower  stem  members  and  the  second 
internode  (reckoned  from  the  base  of  the  stalk)  is  the  one  usually  bent  over. 

To  be  sure,  the  first,  lowest  stem  member  is  also  weak,  but,  as  a  rule,  it 
is  too  short  to  bend  over ;  on  the  other  hand,  the  second  is  the  most  elongated 
and  the  least  thickened.  The  cells  of  this  internode  in  lodged  grain  show  a 
considerable  over-elongation  and  scanty  thickening  in  proportion  to  the 
corresponding  cells  of  the  normal  stem.  This  deficient  thickening  is  espe- 
cially noticeable  in  those  cells  which,  in  the  blade,  fill  the  space  between  the 
outer  membrane  and  the  vascular  bundle  sheath,  and  actually  conditions  the 
firmness  of  the  stalk. 

Lodging  of  grain,  therefore,  is  produced  when  the  lower  internodes  of 
closely  planted  grain  are  insufficiently  lighted.  Too  great  shading  also  acts 
disadvantageously  in  the  very  early  developmental  stages  of  the  plant  by  the 
over-elongation  of  the  cells  and  the  scanty  thickening  of  the  walls,  which, 
as  said  above,  takes  place  usually  in  the  second  internode  from  the  bottom. 
This  bad  condition  will  occur  more  strongly  in  the  places  in  the  internodes 
where  the  leaf  sheath  surrounds  the  stalk  most  closely.  This  takes  place 
near  the  base  of  the  stem  and  the  phenomena  of  etiolation  are  found  most 
clearly  and  intensively  here. 

Formerly  a  lack  of  silicic  acid  was  assumed  as  one  reason  for  the 
lodging  of  grain.  This  may  now  be  explained  as  erroneous,  since  it  has 
been  shown  by  water  cultures  of  grain  plants,  that  minimal  amounts  of 
silicic  acid  are  sufficient  to  produce  a  normal  plant  and  since  analyses  of 
lodged  grain,  compared  with  grain  which  had  not  lodged,  have  shown  but 
little  difference  in  silicic  acid  content.  In  normal  plants  also,  as  Pierre  has 
shown  for  wheat  and  Arendt  for  oats,  the  lowest  internodes  of  the  stalk 
are  the  poorest  in  silicic  acid,  of  which  the  greatest  quantity  in  any  case  is 
found  in  the  leaves.  These  can  be  7  to  18  times  as  rich  in  silicic  acid  as 
the  lower  stem  members. 

Connected  with  the  lack  of  light  is  the  second  point,  given  as  a  cause 
for  lodging,  namely,  that  the  disease  may  be  traced  to  an  excessive  supply 
of  nitrogen  in  the  soil.  At  any  rate,  this  is  one  cause  inasmuch  as  a  too 
luxuriant  development  of  the  leaf  apparatus  is  thus  produced,  essentially 
increasing  the  shading.  Such  a  cause  is  given,  however,  by  every  circum- 
stance which  conditions  a  too  thick  stand  from  the  seed,  i.  e.,  for  example, 
too  abundant  seeding,  too  abundant  water  supply,  etc. 

Experiments  made  by  Ritthausen  and  Pott^  show  the  change  in  the 
maturing  of  fruit  due  to  different  nitrogen  fertilizers  and  the  tendency  of 
the  plant  to  lodge.  While  the  grains  of  summer  wheat  are  well  matured  with 
an  abundant  supply  of  nitrogen  but  remain  small  and  glassy  hke  the  seed,  the 
grains  from  plots  not  fertilized  with  nitrogen,  lodge  after  less  heavy  rain- 
storms.    Kreusler  and  Kern  confirmed  the  above  statements'.     We  may 


1  Landwirtsch.  Versuchsstationen  1873,  p.  384. 

2  Centralbl.  f.  Agrlkulturchemie  1876,  I,  p.  401. 


664 

have  in  pure  phosphoric  acid  fertilization  a  means  of  decreasing  the  dangers 
of  a  too  large  supply  of  nitrogen.  At  least,  the  results  obtained  by  the 
above-named  authors  with  wheat  and  barley  showed  that  a  fertilization  with 
phosphoric  acid  alone  (Baker  guano  with  18.97  P^r  cent,  soluble  Pg  Or.) 
resulted  in  a  reduction  of  the  nitrogen  content  of  the  grain. 

But,  aside  from  the  composition  of  the  grain,  which  is  changed  by  an 
increased  nitrogen  supply,  the  whole  amount  of  the  harvest  must  be  taken 
into  consideration,  which  had  suffered  not  a  little  from  a  too  luxuriant  and, 
therefore,  too  thick  and  dark  a  growth  of  the  plant.  Experiments  based 
mostly  on  the  conditions  occurring  in  practice,  since  they  show  the  influence 
of  shading  from  the  sides,  have  been  cited  by  Fittbogen'.  Under  otherwise 
perfectly  similar  nutritive  conditions,  he  shaded  barley  plants  by  means  of 
a  cylinder  of  rye  stalks,  fastened  side  by  side  and  placed  around  the  barley 
plants,  and  raised  it  in  proportion  to  the  growth  in  height  of  the  experi- 
mental plant,  which  was  constantly  illuminated  at  the  tip.  The  plants, 
therefore,  had  light  for  production  but  still  in  insufficient  amounts.  On 
this  account,  they  produced  only  about  two-thirds  as  much  dry  substance  as 
plants  illuminated  on  all  sides,  in  spite  of  the  4  to  6  weeks  longer  growth 
which  were  needed  for  complete  ripening.  The  dry  substance,  however, 
was  also  distributed  much  less  favorably  in  the  different  harvest  products. 
While,  with  a  normal  illumination,  47  per  cent,  of  the  dry  substance  in 
summer  barley,  as  a  whole,  was  found  in  the  grain,  and  53  per  cent,  in  the 
straw  and  chaff,  from  shaded  plants,  only  39  per  cent,  of  grain  was  har- 
vested for  61  per  cent,  of  straw  and  chaff,  and  the  kernels  were  also  poorer 
in  cjuality.  In  regard  to  the  water  used,  it  v^^as  found  that  plants  shaded  on 
the  sides,  in  spite  of  the  at  least  6  weeks  longer  growing  time,  had  used  only 
one-tenth  more  water  in  the  hottest  months  (July  and  August).  Therefore, 
in  the  same  unit  of  time  they  absolutely  transpired  considerably  less  than 
the  normally  illuminated  specimens,  corresponding  to  the  lesser  production 
of  dry  substances.  On  the  other  hand,  the  plant  will  have  evaporated  rela- 
tively a  great  deal  of  water  for  we  find,  in  shaded  .plants,  that  more  than 
500  g.  of  water  were  used  per  gram  of  dry  substance,  while  normally  lighted 
specimens  have  respired  only  something  over  300  g.  for  the  same  amount  of 
dry  substance.  Therefore,  we  find,  in  this  vegetative  factor,  the  same  eft"ect 
on  transpiration  as  in  others  (soil  solutions,  carbon  dioxid  content  in  the 
air,  etc.)  A  supply  of  one  vegetative  factor  kept  below  the  optimum,  in- 
creases the  relative  use  of  water  per  gram  dry  substance  produced. 

The  loss  due  to  lodging  will  be  decreased  in  many  cases  by  the  fact 
that  grain  possesses  the  ability  to  right  itself.  The  process  of  righting 
consists  in  the  ability  of  the  nodes  to  show  phenomena  of  growth  at  a  time 
when  the  internodes  have  already  lignified.  According  to  de  Vries'  expla- 
nation", a  new  formation  of  osmotically  effective  substances  takes  place  in 


1  Vortrag  aus  dem  Klub  der  Landwirte  am  14.  Dez.  1875. 

'■!■  De  Vries,   tJber  die  Aufrichtung  des  gelagerten  Getreides.     Landwirtschaftl. 
.JahibiiL-her  von  Thiel.  IX,  1880,  Part  3. 


665 

the  parenchyma  cells  of  the  under  half  of  the  node,  which  carries  out  the 
bending,  vtnder  the  force  of  gravity,  because  the  stalk  with  its  node,  is  bent 
toward  the  horizontal.     These  parenchyma  cells  attract  water. 

However,  supported  by  the  investigations  of  G.  Kraus\  we  would  like 
to  assume  that  no  considerable  formation  of  osmotically  effective  substances 
(acids)  takes  place,  but  rather  a  longer  retention  of  such  substances  on  the 
convex  side,  as  a  result  of  a  decreased  oxidation  of  the  organic  acids.  At 
least  Kraus  proves  that  as  much  acid  is  present  on  the  convex  as  on  the 
concave  side  in  the  occurrence  of  geotrophic  and  heliotrophic  bending. 

The  only  actually  successful  precaution  lies  in  thinner  seeding,  the 
quantity  of  which  must  be  modified  according  to  the  consistency  of  the  soil. 
On  sandy  soils  the  seeding  must  be  thicker  than  on  loamy  soils,  and  thicker 
with  a  poorer  fertilization  than  with  an  abundant  supply  of  nitrogen. 
Planting  with  the  drill  is  found  to  be  the  most  useful  because  the  best  dis- 
tributed stand  of  plants  is  obtained  thereby. 

If,  however,  the  seeding  has  already  taken  place  and  a  close  stand, 
luxurious  development,  and  moist  weather  give  rise  to  a  fear  of  a  subsequent 
lodging,  the  attempt  should  be  made  to  remove  a  part  of  the  leaf  apparatus 
by  strong  harrowing,  rolling,  or  prudent  mowing  and  uprooting,  in  order  to 
provide  a  sufficient  access  of  light. 

In  regard  to  cultural  regulations,  we  must  refer  to  the  recently  pub- 
lished, very  thorough  work  of  C.  Kraus",  based  on,  experimental  studies, 
because  the  precautionary  regulations,  according  to  the  difiFerent  causes  of 
lodging  here  mentioned,  must  also  differ  greatly.  On  general  principles,  it 
is  not  only  a  question  of  growing  strong  plants  as  resistant  as  possible  to 
disturbances  in  equilibrium,  but  also  to  take  pains  that  the  plants,  me- 
chanically well  developed  above  and  below  the  soil,  find  the  indispensable 
support  within  the  soil  of  a  properly  developed  root  system.  The  task  of 
breeding  now  follows  these  two  directions.  Even  the  weather  at  the  time 
of  seeding  acts  determinatively  for  the  position  of  nodes,  regulating  essen- 
tially the  anchorage  of  the  plant  in  the  soil.  According  to  Schellenberg^, 
the  node  lies  higher  if  the  seed  develops  in  cloudy  weather.  It  is,  therefore, 
more  advantageous  (even  for  winter  grain)  when  the  seeds  sprout  in  clear 
weather. 

In  weak  stemmed  plants,  inchned  to  lodge,  there  occurs  also  at  times 
a  decay  of  the  parts  entirely  removed  from  the  light,  which  causes  consid- 
erable loss  in  the  lodging  of  fodder  peas.  The  sowing  of  some  horsetooth 
maise  with  these  is  recommended  as  a  precaution.  The  peas  can  climb  up 
the  stems  of  the  maise  and  its  leaves  also  furnish  good  fodder. 

The  sowing  of  gold  of  pleasure  (Camelina  sativa)  possibly  6  liters  per 
hectare,  is  also  recommended  to  prevent  the  lodging  of  peas,  sweet  peas, 
etc.     This  plant,  which  is  perfectly  hardy,  ripens  about  the  same  time  as 


1  Sitzung-ber.  d.  naturf.  Ges.  zu  Halle  1880;   cit.  Bot.  Centralbl.  1882,  I,  p.  107. 

2  Kraus,  C,  Die  Lagerung-  cler  Getreide.     Stuttgart  1908,  Eugen  Ulmer. 

3  Schellenberg,  H.   C,  Untersuchung-en  iiber  die  Lag-e  des  Bestockung-sknotens 
beim  Getreide.     Forsch.  auf  d.  Gebiete  d.  Landwirtsch.   Frauenfeld  1902. 


666 

peas  and  the  kernels  may  be  easily  separated  from  the  peas  by  sifting,  while 
the  grain,  generally  grown  with  peas  (summer  rye  and  oats),  is  sifted  out 
with  much  more  trouble  and  exhausts  the  soil  more  for  the  following  winter 
crop. 

Here  also,  as  in  grain,  breeders  are  now  directing  their  attention  to 
resistance  to  lodging.  The  Bulletins^  published  by  the  German  Agricul- 
tural Society  have  proved  to  be  most  advantageous  in  this  direction.  They 
contain  the  latest  results  of  cultural  experiments  with  the  different  varieties 
of  our  cultivated  plants. 

Lack  of  Light  as  Predisposition  to  Disease. 

When  it  conies  to  the  attacks  of  jjarasites,  the  mechanical  resistance  of 
the  membranes  of  etiolated  plants  will  be  less.  However,  the  atmospheric 
influences  become  weaker  and  their  fluctuations,  reaching  directly  the  cyto- 
plasmatic  cell  body,  can  disturb  its  functions  even  if  the  etiolated  plant 
should  work  in  the  same  way  and  with  the  same  energy  as  one  which  has 
sufficient  light. 

The  last  is,  however,  by  no  means  the  case. 

The  first  indication  of  a  change  in  function  is  found  in  the  moving  of 
the  chlorophyll  grains  toward  the  side  walls,  in  the  dark.  At  the  same  time 
another  significant  change  begins,  viz.,  the  closing  of  the  stomata.  Accord- 
ing to  Schwendener-  this  phenomenon,  already  observed  in  complete  dark- 
ness, also  sets  in  with  a  sudden  decrease  in  the  intensity  of  illumination.  It 
is  possibly  not  a  result  of  the  lowering  of  the  temperature  connected  with 
the  decrease  of  light,  for  an  increase  in  temperature  within  the  usual  fluc- 
tuations causes  no  opening  of  this  apparatus.  Connected  with  this  also  is 
the  fact  that  a  longer  suppression,  or  reduction  of  the  exchange  of  gases, 
can  bring  about  changes  in  the  cell  contents,  due  to  a  lack  of  oxygen,  that  is, 
for  example,  a  tendency  to  the  formation  of  alcohol.  These  disturbances 
will  occur  so  much  the  more  easily,  the  more  intense  the  capacity  for  growth 
and  the  greater  the  need  for  ventilation.  Therefore,  very  young  organs  will 
feel  this,  while  old  leaves,  grown  for  many  years,  with  a  lesser  need  of  light, 
endure  longer  limitation  in  the  exchange  of  gases.  Nature  indicates  this 
also  by  the  wall  thickening  of  the  guard  cells,  increased  with  advancing  age, 
which,  according  to  Schwendener,  is  so  strong  at  times  that  no  further 
opening  of  the  stomata  can  be  possible. 

In  regard  to  lessened  transpiration,  I  found  in  young  seedlings  of 
Phaseolus,  dependent  upon  their  cotyledons,  such  a  difference  between 
etiolated  and  normal  plants  that  the  former,  on  an  average,  transpired  in 
the  same  period  of  time,  0.21  g.  per  sq.  cm.  leaf  surface;  the  latter,  0.29  g.^ 
The  production  of  dry  substance  in  a  plant,  under  otherwise  equal  condi- 


1  Mittel.  cler  Saatzuchtstelle   iiber  wichtige  Sortenversuche  1905-1907  usw. 

2  Schwendener,  tjber  Bau  und  Mechanik  der  Spaltiiffnungen.  Monatsber.  d.  Kgl. 
Akad.  d.  Wiss.  zu  Berlin,  July,  1881;   cit.  Bot.  Zeit.  1882,  p.  234. 

3  Sorauer,   Studien   iiber  Verdunstung.     Aus  WoUny's   "Forschung-en   auf  dem 
Gebiete  der  Agrikulturphysik."    Vol.  I,  Part  4-5,  p.  116. 


667 

tions,  parallels  the  transpiration.  Investigation  showed  that  not  only  the 
absolute  production  of  the  young  plants  was  essentially  more  energetic  in 
the  light,  but  that  also  a  square  centimeter  of  leaf  surface  developed  a 
greater  amount  of  substances.  A  weakening  of  the  light,  by  means  of  col- 
ored media,  through  which  the  rays  must  pass,  acts  similarly  to  the  removal 
of  light  by  placing  it  in  the  dark.  In  yellow  light,  assimilation  and  transpi- 
ration are  more  energetic  than  in  blue  light;  at  least  the  majority  of  experi- 
ments favor  this^. 

The  energy  of  production  of  plants  and  also  the  mode  change  with  the 
decrease  of  light  and  this  change  is  expressed,  not  only  in  the  metamorphic, 
but  also  in  the  metabolic  structure. 

The  well-known  experiment  of  covering  lea,ves  in  the  light  with  a 
stencil  pattern,  which  leaves  free  some  rather  larger  surface  figures,  remov- 
ing the  green  from  these  leaves  after  some  days  by  means  of  alcohol,  and 
then  wetting  them  with  iodine  solution,  is  a  simple  illustration  of  the  action 
of  light.  All  parts  of  the  leaf,  which  have  been  exposed  to  the  light,  look 
blue  because  of  the  action  on  the  starch  which  had  been  formed  in  the  light. 
This  experiment  is  of  interest  inasmuch  as  it  shows  how  locally  limited  the 
action  of  light  is.  Only  the  part  which  had  been  illuminated  formed  starch 
and  no  starch  passed  over  into  the  darkened,  adjacent  part.  The  most 
important  thing,  according  to  this,  is  that  the  green  parts  of  the  plant  must 
themselves  work  over  their  constructiv^e  materials  if  they  should  continue 
to  live. 

It  has  been  mentioned  already  that  the  mobilized  reserve  substances 
pass  into  the  young,  entirely  darkened  shoots  a  certain  distance  from  the 
tubers  and  seeds.  If  the  distance  is  too  great,  however,  the  shoots  finally 
die  from  starvation.  They  breathe  up  more  respiratory  material  than  they 
receive  in  the  form  of  sugar,  etc.  Some  of  Miiller-Thurgau's^  experiments 
show,  for  example,  that  the  starch,  when  dissolved,  passes  over  into  sugar, 
which  is  used  up  partly  for  construction  and  partly  in  respiration.  Grape 
leaves,  which  contain  2  per  cent,  sugar  and  as  much  starch,  were  cut  off  and 
their  petioles  put  in  water.  The  container  was  set  in  a  room  at  zero  de- 
grees. Nine  days  later  all  trace  of  the  starch  had  disappeared.  Since  the 
respiration  of  the  grapevine,  however,  at  zero  degrees  is  very  slight,  the 
sugar,  produced  by  the  solution  of  the  starch  m  the  dark,  cannot  have  been 
used  up.  in  respiration  and  must,  accordingly,  have  accumulated  in  the  leaf. 
As  a  fact,  investigation  shows  4  per  cent,  sugar  in  the  leaves. 

Thus,  placing  in  the  dark  wall  promote  the  formation  of  sugar  in  the 
organs  as  against  the  formation  of  starch.  If,  as  is  frequently  the  case  in 
growing  plants  out  of  doors,  an  actual  temperature  decrease  takes  place 
with  the  decrease  in  light,  it  means  a  blocking  of  sugar  in  the  assimilator}' 
tissues. 


1  Compare  Hellriegel,  Beitrage.  p.  378.     Nobbe,  Versuchsstationen  XXVI,  p.  354. 
Flahault,  Bot.  Centralbl.  1880,  p.  932.     Deherain,  Bot.  Zeit.  1873,  p.  494,^ 

2  Miiller-Thurgau,  tJber  den  Einfluss  dei'  Belaubung-  auf  das  Reifen  der  Trau- 
ben.    Weinbaukongress  zu  Durkheim  a.  d.  H.  1882. 


668 

Anyone  who  has  cultivated  fungi  in  nutrient  solutions  knows,  however, 
how  favorably  a  supply  of  sugar  acts  on  the  development  of  many  parasitic 
fungi. 

Cloudy,  cool  days,  therefore,  not  only  weaken  the  assimilation  in  the 
green  parts  of  the  plants  but,  at  the  same  time,  by  reducing  the  respiratory 
processes,  bring  about  an  accumulation  of  sugar  in  the  leaf  cells  and,  there- 
fore, make  possible  the  production  of  a  more  favorable  substratum  for 
parasites. 

The  acid  content  of  the  various  plant  parts  is  also  very  different  in 
the  dark  from  that  found  when  the  organ  is  favorably  illuminated. 

The  observation,  that  many  plants  (Crassulaceae)  taste  sour  at  night' 
but  not  noticeably  so  during  the  day-  is  very  odd.  In  etiolated  plants,  Wies- 
ner  could  recognize  an  abundance  of  organic  acids^  in  the  leaves  of  many 
monocotyledons,  and  later  De  Vries  observed*  that  the  stems  of  etiolated 
dicotyledons  are  strongly  acid.  When  illuminated,  the  rich  sugar  content 
disappears.  This  has  been,  at  least,  especially  proved  for  the  Crassulaceae, 
in  which,  in  the  night,  De  Vries  could  determine  a  rich  acid  formation  only 
when  the  plants  had  been  abundantly  lighted  during  the  day,  but,  if  the 
supply  of  light  was  limited  to  a  few  hours,  the  acid  content  in  the  night  was 
correspondingly  less. 

An  increase  of  warmth  increases  also  the  decomposition  of  the  acids  in 
the  dark.     Cooler  nights  lead  to  the  storage  of  acid. 

De  Vries  has  proved  this  directly  by  experiments^  It  is  evident,  how- 
ever, from  the  fact  that  the  loss  of  acid  becomes  less  with  each  successive 
day  of  shading,  that  the  disappearance  of  the  acids  is  connected  with  the 
supply  of  material  for  the  formation  of  acid  which  has  been  worked  over 
in  the  light. 

Plants,  therefore,  constantly  produce  acids  and  the  more  energetically 
the  stronger  growing  the  organs  are.  With  light,  the  acids  are  oxidized  as 
fast  as  they  are  produced ;  in  the  dark,  they  are  stored  up.  On  this  account, 
etiolated  plants  are  relatively  rich  in  acids.  The  suppression  of  the  inflor- 
escences increases  the  content  of  free  acids  in  the  leaf.  The  acid  content 
in  the  roots  is  also  subjected  to  great  fluctuations  and,  according  to  Chara- 
bot",  in  plants  cultivated  in  the  shade  it  is,  in  fact,  larger  than  in  the  leaves. 
In  general,  this  acid  content  is  greater  in  etiolated  plants. 

This  accumulation  of  acids  in  and  of  itself  can  offer  those  fungi,  which 
decompose  acids,  the  possibility  of  colonization  and  luxuriant  development ; 

1  Heyne  und  Link  in  Jahrbuch  der  Gewachskunde  von  Sprengel,  Schrader  und 
Link,  1819,  p.  '70-73. 

2  Ad.  Mayer,  Uber  Sauerstoffausscheidung  usw.  Verhandl.  d.  Heidelberger 
naturf.  Gesellsch.  4-8,  1875.  Landwirtsch.  Versuchsstat.  1875,  Vol.  XVIII,  p.  410, 
Vol.  XXI,  p.  277. 

3  Wiesner,  Sitzungsber.  d.  K.  K.  Akad.  d.  Wissensch.  I,  April,  1874,  Vol.  69; 
cit.  Bot.  Zeit.  1874.  p.  116. 

4  De  Vries,  Uber  die  Bedeutung  der  Pflanzensauren  fur  den  Turgor  der  Zellen. 
Bot.  Zeit.  1878,  p.  852.  tjber  die  periodische  Saurcbildung  der  Fettpflanzen.  Bot. 
Zeit.  1884,  Nos.  22  and  23. 

5  Bot.  Zeit.  1884,  p.  340. 

6  Charabot,  E.,  et  Herbert,  A.,  Rechercbes  sur  I'acidite  v6getale.  Compt.  rend. 
1904,  CXXXVIII,  p.  1714. 


669 

however,  an  excessive  increase  of  turgidity  in  the  tissue  can  be  ascribed  to 
this  since,  according  tolDe  Vries,  it  is  especially  the  plant  acids  which  condi- 
tion the  turgidity  of  the  cells. 

The  experiments  of  Viala  and  Pacottet^  on  hlack  rot  (Guignardia 
BidzvelUi)  show  how  very^  determinative  this  acid  content  can  often  be. 
Infection  experiments  in  young  berries  are  successful  only  so  long  as  the 
acid  content  exceeds  the  sugar  content.  Not  only  the  content  in  organic 
acids  is  increased  but  also  the  indifferent  ash  material  is  changed  by  the 
changed  absorption  of  nutrition.  This  is  shown  by  Andre's  experiments- 
He  tried  to  excite  etiolated  plants  to  unusual  activity  'by  increasing  the  tem- 
perature (30  degrees),  but  found  only  an  unusual  increase  in  the  absorption 
of  silicic  acid,  with  an  exclusion  of  other  mineral  elements. 

The  decomposition  and  counter  building  of  the  proteins  in  the  plant 
celP  also  stand  in  the  closest  connection  with  the  above  described  processes 
of  the  formation  and  oxidation  of  the  carbohydrates. 

In  the  germination  and  sprouting  of  buds  on  branches,  roots  and  tubers, 
we  find  products  of  the  decomposition  of  proteins  which  are  similar  to  those 
of  artificial  protein  decomposition,  i.  e.,  asparagin,  glutamin,  leucin,  tyrosin, 
occur  in  very  large  amounts.  According  to  Borodin's  investigations*  these 
amido  compounds  occur  more  abundantly,  the  fewer  the  elements  present 
which  are  free  from  nitrogen  (especially  the  grape  sugar)  and  which  can 
be  used  for  the  breaking  down  of  the  proteins. 

Since  in  etiolated  plants,  as  well  as  in  others  grown  in  the  light  but  in 
air  free  from  carbon  dioxid,  the  new  production  of  carbohydrates  is  sup- 
pressed and  since  these  are  used  up  by  day  in  respiration,  an  accumulation 
of  asparagin  will  take  place.  Among  the  more  recent  observers,  we  wi!l 
mention  Zaleski  (cf.  next  page)  who  found  an  increase  of  asparagin  in 
seedlings  of  Allium  Cepa.  The  above  mentioned  work  by  Schulze  and 
Castoro°  should  be  especially  considered,  from  which  it  is  seen  that,  for 
example,  in  etiolated  seedlings  of  Lupinus  Alb  us  the  content  in  protein 
substances  decreases ;  that  in  aspargin  constantly  increases.  Tyrosin  and 
leucin  decrease. 

As  a  matter  of  fact,  E.  Schulze  found  more  than  half  of  the  whole 
nitrogen  content  in  20  day  old  etiolated  lupin  seedlings  in  the  form  of 
asparagin".  If  now  the  nitrogen  free  part  of  the  protein  molecule  is  used 
up  in  respiration  and  no  new  elements,  lacking  nitrogen,  are  present  to 
reconstruct  normal  protein  in  the  protoplasm,  the  cell  will  undergo  the  most 

1  Viala,  P.,  et  Pacottet,  P.,  Sur  le  developpement  du  Black  Rot.  Compt  rend 
1904.     CXXXIX,  p.  152. 

2  Andre,  G.,  Wirkung  der  Temperatur  auf  die  Absorption  der  Mineralstoffe  bei 
etiolierten  Pflanzen.  Compt.  rend.  1902;  cit.  Biedermann's  Centralbl  f  Agrikul- 
turchemie  1903,  Part  2. 

3  Pfeffer  in  Jahrb.  f.  wissensch.  Bot.  1872,  Vol.  8,  p.  548.  Tagebl.  d  Naturf 
Vers.  z.  Wiesbaden. 

4  Bot.  Zeit.  1878,  p.  802  ff. 

5  Schulze,  E.,  und  Castoro,  N.,  Beitrage  zur  Kenntnis  der  Zusammensetzung-  u. 
des  Stoffwechsels  der  Keimpflanzen:    cit.  Bot.  Centralbl.  1904,  Vol.  XCVI,   p.  540. 

6  Schulze,  E.,  Uber  den  Eiweissumsatz  im  Pflanzenorganismus.  Landwirtsch. 
Jahrbiicher.    1880,  p.  1-60. 


670 

extensive  disturbances.  It  is  probable  that  a  further  decomposition  will 
introduce  phenomena  of  decay  which  produce  the  best  nutrient  substrata  for 
parasites  and  saphrophytes.  The  asparagin  is  worked  up  well  by  the  fungi 
in  the  presence  of  sugar.  VogeP  found  in  the  germination  of  moistened 
cress  seed  that  hydrogen  sulfid  was  produced  in  the  dark,  while,  in  check 
experiments,  in  lighted  places,  the  lead  paper  showed  practically  no  change. 

A  different  process  may  prevail  in  the  leaf  parenchyma  from  that  in 
the  leaf  veins.  In  young  Dahlia  plants  Borodin"  proved  the  presence  of 
saltpetre  in  the  veins  and  in  the  petioles,  but  large  amounts  of  tyrosin  and 
no  saltpetre  in  the  leaf  parenchyma.  Here  the  tyrosin  may  well  be  no 
analytic  product  but  rather  a  synthetic  one;  for  if  the  young  shoots  of 
dahlias  become  etiolated,  no  tyrosin  is  formed,  but  asparagin,  which  does 
not  appear  when  the  plants  are  grown  in  the  light. 

At  times,  at  any  rate,  an  increase  in  proteins  is  found  in  the  dark  but  it 
is  then  caused  by  the  very  abundant  carbohydrates  at  the  jDlant's  disposal  in 
the  stores  of  reserve  substances,  as  IwanofT^  has  shown,  for  example,  fot 
Allium  Cepa.  If  carbohydrates  are  present,  the  leaves,  even  in  the  dark, 
can  change  the  nitrate  nitrogen  into  protein  nitrogen,  as  Zaleski'*  found  in 
the  leaves  of  Helianthus,  which  had  been  placed  in  a  nutrient  solution  con- 
taining nitrates  and  sugar. 

We  have  stated  here  simply  a  series  of  facts  which  show  the  natural 
changes  in  the  plant  body  due  to  a  lack  of  light.  These  explain  sufficiently 
the  decreased  power  of  resistance  of  the  shaded  plant  parts  through  atmos- 
pheric influence,,  as  well  as  parasitic  attacks.' 


1  Vogel,  Ein   aufCallig-er  Unterschied  zwischen  Keimen  am  Tagreslicht  iind  im 
Dunkeln;   cit.  Bot.  Jahresber.  1877,  p.  675. 

2  Sitszungsber.  d,   Bot.   Sekt  Petersburg-.     Naturf.   Ges.    1881;    cit.    Botan.   Zeit. 
1882;  p.  589. 

3  Iwanoff,  M.,  Versuche  iiber  die  Frage,  ob  in  den  Pflanzen  bei  Lichtabschlu.ss 
Eiweissstoffe  sich  bilden.     L/andw.  Versuchsstationon  1901,  p.   78. 

•t  Zaleski,  W.,  Die  Bedingungen  dor  ]i;iweiss])ildung  in  den  Pflanzen.     Charkow 
1900  (Russian);  cit.  Bot.  Centralbl.  1901,  Vol.  87,  p.  277. 


CHAPTER  XIV. 


EXCESS  OF  LIGHT. 


According  to  the  discoveries,  already  made  in  great  numbers,  on  the 
influence  of  heat  on  the  different  vegetable  processes,  it  must  be  supposed, 
from  the  outset,  that  not  only  does  a  minimal  limit  exist  for  the  action  of 
light,  but  that  also  a  special  degree  of  illumination  exists  in  each  plant  for 
each  process  and  for  each  combination  of  the  vegetative  factors,  which  can 
be  termed  the  optimum.  The  exceeding  of  this  degree  introduces  a  retro- 
gression in  production.  In  fact,  the  observation  has  already  been  made  for 
a  number  of  plants  that,  if  the  light  is  increased  above  a  certain  amount, 
the  assimilation,  perceptible  in  the  elimination  of  oxygen,  does  not  increase., 
but  remains  stationary^  or  indeed  may  decrease-.  A  normal  carbon  dioxid 
content  in  the  air  is  presupposed  in  this,  for  even  when  the  air  contains  too 
large  an  amount  of  this  element,  the  elimination  of  oxygen  retrogresses,  as 
has  been  proved  already  by  Boussingault  and,  later,  by  Pfeffer^.  An 
optimum  illumination  may  be  seen  in  the  appearance  of  the  plant  since  this 
loses  its  deeper  green  color,  with  a  considerable, increase  in  the  intensity  of 
light  above  the  optimum ;  then  it  assumes  a  yellowish  color. 

That  the  dark  green  leaves  of  camellias  show  a  yellowed  condition, 
when  moved  from  the  conservatory  into  sunny  places  out  of  doors,  is  well 
known.  The  camellia  is  a  Japanese  plant  which  grov/s  under  trees.  It  is 
content  with  small  quantities  of  light  and,  with  the  strong  rays  of  our 
summer  sun,  soon  loses  more  chlorophyll  through  oxidation  than  can  be 
formed  by  the  process  of  reduction.  The  breaking  down  of  the  chlorophyll 
by  the  taking  up  of  oxygen  (taking  place  also  in  the  dark  in  the  presence  of 
bodies  which  easily  take  oxygen  from  the  air  and  form  ozone,  Turpentine 
oil)  is  known  to  be  connected  with  different  groups  of  rays.  According  to 
Wiesner,  the  yellow  rays,  and  the  green  and  orange  ones  on  both  sides  of 
them,  show  the  greatest  energ>^  in  the  breaking  down  of  the  chlorophyll  in 
the  light. 

Another  example  of  yellow  leaves  with  a  high  intensity  of  light  is 
offered  by  some  varieties  of  coleus  with  yellow  variegated  leaves.     These 

1  Reinke,  Li.,  Untersuchungen  iiber  die  Elnwirkung-en  des  Lichtes  auf  die  Sauer- 
stoffausscheidung  der  Pflanzen.     Bot.  Zeit.  1883,  No.  42  ff. 

2  Famintzin,  Effet  de  I'intensite  de  la  lumiere,  etc.;  cit.  Bot.  Centralbl.  18S0, 
p.  1460. 

3  Pfeffer,  Arbeiten  d.  Bot.  Instituts  zu  Wurzburg-,  ed.  by  Sachs,  Part  1. 


6^2 

produce  leaves  which  at  first  unfold  as  green  leaves  and  later,  when  they 
become  old,  become  light  yellow  in  places.  In  the  same  way,  many  yellow 
garden  varieties  of  woody  plants  only  become  a  bright  yellow  with  strong 
insolation ;  in  the  shade  they  remain  green. 

Ewart^  observed  in  tropical  plants  a  complete  bleaching  of  the  chloro- 
phyll grains  as  a  result  of  an  excess  of  light.  If  the  light  stimulus  increases 
above  the  specific  optimum,  the  optimal  and  maximal  development  of  gases 
at  first  continues  for  a  short  time,  but  then  follows  a  condition  of  exhaus- 
tion^. If  this  excessive  stimulation  does  not  last  too  long,  the  plant  can 
recover  its  normal  activity.  This  over-stimulation  can  also  occur  under 
our  normal  light  conditions,  if  the  plant,  by  nature,  belongs  among  shade 
plants.  Weiss^  cites  a  fine  example  of  this  in  Poly  podium  vulgar  e,  a  de- 
cided shade  plant,  as  contrasted  with  Oenothera  biennis  which  is  distinctly 
a  sun  plant.  With  a  favorable  temperature,  the  latter  produced  about 
three  times  as  much  carbon  dioxid  in  direct  sunlight  as  in  diffuse  light ; 
while  the  former  assimilated  more  energetically  in  dillfuse  light.  Diffuse 
daylight  can,  in  fact,  act  to  arrest  the  growth  of  roots  which  are  accustomed 
to  the  dark,  as  Kny  found  in  lupines,  cow  beans,  and  water  cress*.  In  this, 
he  observed  in  lupines  usually  a  decrease  of  growth  in  thickness  and  a 
retarding  of  the  development  of  the  central  cylinder,  if  the  growth  in  length 
increased. 

The  works  of  Dixon,  Dixon  and  Wigham,  Joseph  and  Prowazek,  Max 
Koernicke  and  Hans  Molisch'^  prove  a  very  decided  arrestment  of  growth 
from  the  use  of  Rontgen  and  radium  rays. 

An  abnormal  thickening  and  a  wrinkled  surface  were  observed  in  pea 
roots,  which  could  be  traced,  apparently,  to  differences  in  internal  tension. 
Contractions  are  produced  by  the  increase  in  the  radial  diameter  of  the  cells 
of  the  inner  bark  parenchyma,  together  with  a  shortening  of  the  longi- 
tudinal diameter.  It  was  found  in  other  experiments  with  vetches  and  horse 
beans  that  the  roots  turned  brown  and  their  growth  was  arrested.  But 
after  8  to  lo  days  they  grew  further,  after  having  thrown  of¥  the  outermost 
tips  in  the  form  of  brown  caps,  and  formed  new  root  tips  directly  behind 
these.  Normal  lateral  roots  were  produced  immediately.  The  arrest  of 
growth 'is  less  in  organs  containing  chlorophyll.  In  seedlings  a  cessation  in 
the  growth  in  length  has  been  observed  but  no  dying  back.  The  leaves 
became  somewhat  smaller  than  in  normal  specimens.     Dixon"   could  not 


1  Ewart,  A.  J.,  The  effects  of  tropical  insolation;  cit.  Just's  Jahresber.  1899, 
I.  p.  87. 

-  Pantanelli,  Enrico,  Abhangiffkeit  der  Sauerstoffau.sscheidiins-  belichtetei- 
Pflanzen  von  iiusseren  Faktoren.     Jahrb.  f.  wiss.  Bot.  1903,  Vol.  XXXIV,  p.  167. 

3  Weiss,  Fr.,  Sur  le  rapport  entre  I'intensit^  lumineuse  et  I'^nergie  assimilatrice 
chez  les  plantes  appartenant  a.  des  types  biologiques  differents.  Compt.  rend.  Paris 
CXXXVII,  1903,  p.  801. 

■*  Knv,  Ij.,  liber  den  Einfluss  des  Lichtes  auf  das  "Wachstum  der  Bodenwurzeln. 
Jahrb.  f.  wiss.  Bot.  1902.  Vol.  28,  p.  421. 

5  Seckt,  Hans.  Die  Wirkung-  der  Rontgen-  und  Radiumstrahlen  auf  die  Pflanzp. 
Sammelreferat.     Naturwiss.  "Wochenschrift;  1906,  No.  24. 

6  Dixon,  Henry,  Radium  and  plants.  Nature,  London  LXIX;  cit.  Just's  Bot, 
Jahresber.  1903,  II,  p.  567. 


^7Z 

find  heliotropic  curvature  in  young  cress  seedlings  at  a  distance  of  one  cen- 
timeter, from  a  glass  tube  containing  5  g.  of  radium  bromid. 

In  bright  sunlight,  we  find  that  parts  of  the  plant  often  not  only  become 
yellow  but  even  turn  brown  and  die^.  That  this  dying  is  a  specific  light 
action  and  not  a  result  of  too  great  an  increase  in  temperature  is  proved  by 
the  fact  that  the  chlorophyll  remains  unchanged^  in  temperatures  var}dng 
■from  30  degrees  below  zero  to  100  degrees  above  zero  and,  on  the  other 
hand,  that  the  destruction  takes  place  with  rays  of  shorter  wave  length 
which  influences  most  of  all  the  processes  of  growth  and  protoplasmic 
movement. 

The  rays  of  a  concentrated  sun  image,  which  have  passed  through 
ammoniacal  copper  oxid  often  cause  death  after  a  few  minutes,  while  the 
same  amount  of  light,  after  passing  through  a  solution  of  iodine  in  carbon 
disulphid  (which  lets  only  the  outermost  red  rays  pass  through)  scarcely 
causes  any  destruction,  or  only  a  \tvy  tardy  one^.  In  this  red  light,  how- 
ever, an  extensive  warming  takes  place,  but  not  in  the  blue  light. 

Among  the  phenomena  arising  from  an  excess  of  light  belongs  also  the 
production  of  shadow  pictures,  i.  e.,  intensive  green  pictures  of  overshad- 
owing organs  on  a  strongly  lighted  leaf  surface.  No  destruction  of  the 
chlorophyll  apparatus  necessarily  takes  place  here,  only  a  change  in  the 
position  of  the  chloroplasts  is  produced. 

Observations,  made  by  Bohm,  Famintzin,  Borodin,  Stahl  and  Frank,, 
proved  that,  in  sunlight  too  high  for  the  special  need  of  the  plants,  the 
chlorophyll  grains  begin  to  move  from  the  cell  walls,  parallel  to  the  upper 
surface  of  the  leaf,  towards  the  walls  at  right  angles  to  them.  The  chloro- 
plasts pass  from  the  episfrophe  to  the  apostrophe  and  thereby  bring  about 
the  lighter  color  of  the  too  strongly  lighted  part. 

A  further  observation  which  can  be  made  easily  is  the  appearance  of  a 
red  color  with  too  strong  lighting  in  the  green  leaves  of  plants  which  turn 
red  in  the  autumn,  as,  for  example,  when  the  under  sides  of  sweet  cherry 
leaves  are  turned  uppermost.  In  the  same  way,  a  decided  brownish  red 
color  may  be  found  in  many  plants,  especially  in  those  with  fleshy  leaves, 
when  brought  in  spring  from  the  shaded  conservatories  into  an  open,  sunny 
place.  Molisch*  has  investigated  such  cases.  He  proved  in  Aloe  and 
Selaginella  that  anthocyanin  is  not  formed  in  the  cells  but  that  the  chloro- 
plasts themselves  turn  red  and  become  green  again  when  put  in  the  dark. 
In  some  varieties  of  Selaginella,  red  or  brownish  red  chloroplasts  were 
observed,  colored  by  carotin,  especially  above  a  place  where  the  stem  had 
broken. 

The  process  most  important  agriculturally  and  most  significant 
hygienically,  however,  consists  in  the  destructive  action  of  the  sunlight  on 


1  Bohm,  Versuchsstationen  1877,  p.  463. 

2  Wiesner,     D'e    naturlichen    Einrichtungen    zum     Schutze,    des     Chlorophylls. 
Festschrift:   cit.  Bot.  .Jahresber.  1876,  p.  728. 

3  Pring-sheim.  Jahrb.  f.  wiss.  Bot.  1879,  Vol.  12,  p.  336. 

4  Molisch,     H.,    tJber    voruberg-ehende    Rotfarbung    der    Chlorophyllkorner    in 
Laubblattern.  B.  der  Deutsch.  Bot.  Ges.  1902,  XX,  p.  442. 


674 

pathogenic  fungi  and  especially  on  bacteria.     Pfeffer^  says,  "It  seems  that 
all  pathogenic  bacteria  are  killed  by  a  sufficient  exposure  to  sunlight." 

That  artificial  light  acts  in  the  same  way  as  sunlight  is  proved,  for 
example,  by  the  experiments  made  by  Dixon  and  A\'igham-  with  radium 
rays.  Cultures  made  with  Bacillus  pyocyaneus,  B.  typhosus,  B.  prodigi- 
osus  and  B.  anthracis  showed  that  the  fi  rays  of  radium  bromid  called  forth 
a  perceptible  arrest  of  growth.  After  5  mg.  of  radium  bromid  had  acted  4 
days  on  the  bacteria,  at  a  distance  of  4.5  mm.,  their  growth,  at  least,  was 
stopped,  if  they  were  not  all  killed. 


1  Pflanzenphysiologie,  2d  ed.,  Part  II,  p.  319. 

2  Dixon,  Henry  H.,  and  Wigham,   J.,  Action  of  Radium  on  Bacteria.     Nature, 
London  LXIX;    cit.  Just's  Jahresber.  1903,  11,  p.  567. 


SECTION  III. 


ENZYMATIC  DISEASES. 


CHAPTER  XV. 


DISPLACEMENT  OF  ENZYMATIC  FUNCTIONS. 


General  Discussion. 

Present  investigations  tend  to  the  theory  of  perceiving,  in  the  majorit> 
of  metabolic  processes,  the  action  of  enzymes.  We  would  like  to  divide 
these  enzymes  into  two  groups,  according  to  their  activity,  which  may  be 
called  constru'ctive  and  destructive.  In  the  process  of  formation  of  the 
vegetative  organism,  we  observe  in  germination,  i.  e.,  in  the  preparation  for 
the  vegetative  development,  a  prevalence  of  the  destructive  activity  since 
the  reserve  substances  are  dissolved  and  carried  over  into  usually  instable 
groups  of  substances,  capable  of  being  transported.  The  activity  of  the 
vegetative  apparatus  leads  gradually  to  the  precipitation  of  reserve  sub- 
stances and  we  term  this  activity  constructive.  Its  final  goal  may  be  recog- 
nized in  the  maturation  of  the  seed. 

From  this  may  be  perceived  an  antagonism  in  the  occurrence  of  the 
most  important  material  groups,  which  antagonism  may  be  determined  by 
the  fact  that,  in  abundant  deposition  of  starch,  the  sugar  content,  as  well 
as  the  amount  of  tannin  and  of  organic  acids,  decreases.  If,  on  the  other 
hand,  sugar,  tannin  and  acids  are  abundantly  present,  the  precipitation  of 
starch  remains  small.  If  the  amount  of  starch  is  large,  the  formation  of 
the  proteids  in  the  cell  from  asparagin  or  other  nitrogenous  compounds  is 
abundant.  In  the  preponderance  of  sugar  and  acids,  the  nitrogenous  com- 
pounds remain  in  an  instable  form.  I  would  like  to  contrast  this  condition 
of  the  plant  parts  as  "immature,"  with  the  "mature"  condition  which  is 
distinguished  by  an  abundance  of  reserve  materials. 

The  different  factors  of  growth  that  influence  constantly  the  plant 
body  sometimes  let  one  group  of  enzymes  prevail,  sometimes  another.  It  is 
not  necessary  that  the  enzymes  be  destroyed.     Their  action  need  only  be 


676 

temporarily  arrested.  Pozzi-Escot'  furnishes  an  example  of  this  when  dis- 
cussing the  Philothion.  "Reductases,"  he  thinks,  which  are  identical  with 
Loew's  catalase,  "are  distributed  everywhere  like  oxydases,  and  act  antag- 
onistically" .  .  .  De  Rey-Pailhade  has  proved  that  reductases  are 
quickly  destroyed  by  an  oxydase  in  the  presence  of  free  oxygen,  and,  con- 
versely, Pozzi-Escot  proves  that,  under  certain  circumstances,  the  action  of 
an  oxydase  can  be  "paralyzed,"  when  the  reductase  is  present  in  great  ex- 
cess. Thus,  in  temporary  fluctuations  in  the  cell  contents,  a  reductase  can, 
for  the  moment,  make  the  oxydase  ineffective,  and  conversely.  Pozzi- 
Escot  perceives  the  most  important  role  of  the  reductases  to  be  their  action 
on  H,  Oo  in  the  processes  of  respiration  as  well  as  in  photo-synthesis. 

Antiferments  occur  in  other  cases,  as  Czapek-,  for  example,  has  dem- 
onstrated. He  found  an  arrestment  in  the  further  oxidation  of  the  homo- 
gentisin  acid,  originating  from  tyrosin,  in  organs  stimulated  geotropically 
or  heliotropically  by  the  presence  of  an  anti ferment. 

In  general,  we  perceive  from  the  results  of  cultivation  and  some  experi- 
mental investigations,  that  light  and  heat  favor  catabolism,  i.  e.,  disposition 
of  groups  of  solid  reserve  material,  while  darkness  and  cold  either  maintain, 
or  cause  an  increase  in  the  amount  of  colloidal  food  materials. 

Under  normal  climatic  conditions,  the  time  at  which  prevailing  condi- 
tions in  the  cell  contents  exhibit  the  conditions  characteristic  of  the 
destructive  activity,  lies  actually  in  the  colder  seasons  of  the  year.  We 
find  processes  of  germination  especially  in  autumn  and  spring,  but,  on  the 
other  hand,  constructive  activity,  i.  e.,  the  deposition  of  reser\^e  materials, 
in  the  summer. 

The  necessary  regular  succession  of  these  periods  depends,  however, 
not  only  on  the  weather  but  also  on  all  the  nutritive  factors,  as,  for  example, 
the  supply  of  water,  the  amount  and  constitution  of  the  nutrients,  and, 
besides  this,  on  differences  in  cultivation,  viz.,  pruning,  etc.  A  number  of 
diseases  offer  examples  for  the  last  point,  i.  e.,  when  the  organism  is  com- 
pelled, by  the  sudden  removal  of  considerable  amounts  of  the  plant  body 
Cbranches  and  leaves),  to  mobilize  again  the  stored  material  at  a  time  when 
the  period  of  storing  should  prevail  and,  thereby,  to  return  to  the  vegetative 
period  for  the  formation  of  new  shoots.  In  regard  to  the  supply  of  food 
we  find,  for  example,  that  excessive  amounts  of  nitrogen  postpone  the 
period  of  storing  up  reserve  materials  since  growth  is  continued  beyond 
the  normal  size. 

Thus,"  the  enzymatic  work  is  postponed ;  the  mobilizing  enzymes  now 
prevail  and  the  plant,  with  organs  in  active  growth,  enters  upon  a  period 
of  weather  which,  in  the  normal  course  of  events,  demands  mature  plant 
parts,  rich  in  reser\^e  materials.  It  becomes,  therefore,  susceptible  to  para- 
sitic and  non-parasitic  attacks. 


1  Pozzi-Escot,  E.,  The  Reducing-  Enzymes.     American  Chem.  Journ.,  Vol.  XXIX, 
1903,  p.  517;  cit.  Bot.  Centralbl.  1904,  No.  49. 

2  Czapek,  F.,  Antifermente  im  Pflanzenorganismus.     Ber.  d.  Deutsch.  Bot.  Ges. 
1903.  Vol.  XXI,  p.  229. 


^77 

It  is,  however,  not  only  the  momentary  displacement  of  the  enzymatic 
functions  which  can  act  disadvantageously  on  the  organism,  but  the  number 
of  subsequent  phenomena  must  necessarily  be  connected  with  it,  which  will 
manifest  themselves  onh^  in  the  next  generation.  If,  for  example,  we  keep 
in  view  the  lengthening  of  the  period  of  growth,  induced,  as  experience 
shows,  by  an  excess  of  nitrogen,  the  immediate  result  is  that  the  production 
of  seed,  which  normally  occurs  at  the  period  of  the  greatest  amount  of  heat 
and  light,  is  carried  over  into  a  cooler  time  when  the  light  is  poor.  The 
seed  thus  produced,  therefore,  does  not  have  sufficient  time  and  proper 
climatic  conditions  to  carry  on  all  the  processes  necessary  for  the  formation 
of  reserve  materials.  The  seed  is  harvested  in  a  condition  in  which  the 
mobilizing  enzymes  are  still  considerably  active  and  it,  therefore,  is  suscep- 
tible to  attacks  by  parasites  affecting  the  fully  matured  seed.  It  has  been 
proved  experimentally  that  immature  seed  is  destroyed  more  quickly  by 
moulds.  Even  if  the  immature  seed  is  not  destroyed,  and  develops  the 
following  season,  the  plant  thus  produced  will  necessarily  be  influenced  in 
its  first  growth  by  the  greater  amount  of  water  content  in  the  seed  and  the 
lesser  amount  of  reserve  materials.  In  this  connection  the  following  gen- 
eration is  the  product  of  the  preceding  one,  and,  therefore,  will  reproduce 
by  inheritance  conditions  of  weakness. 

Everything  that  is  true  of  the  seed,  must  also  hold  good  for  all  other 
permanent  organs.  Ihe  bud  and  the  maturation  of  the  branch  are,  in  the 
same  way,  the  product  of  the  preceding  period  of  growth  and  the  manner 
of  their  further  development  depends  primarily  on  the  degree  of  maturity 
to  which  they  attained  in  the  previous  year. 

Displacements  of  the  enzymatic  functions,  therefore,  are  continued 
from  one  period  of  growth  to  another  and  the  diseases,  subsequently 
described,  are  examples  of  the  inheritance  of  physiological  disturbances. 

Albinism  (Variegation). 

The  phenomenon,  sought  by  gardeners  and  propagated  by  grafting 
(which  may,  in  fact,  be  carried  over  to  the  stock),  manifests  itself  in  the 
whitish  appearance  of  places  which  sometimes  have  a  circular  form  in  the 
diachyma  (mesophyll),  sometimes  appear  as  wedge-shaped  stripes  between 
the  ribs,  and  sometimes  as  connected  zones  along  the  edge  of  the  leaf.  The 
intensity  of  the  white  coloration  varies.  The  most  diverse  transitions  from 
the  purest  white  to  quince  yellow  are  found,  which  in  many  plants  give  still 
further  color  shades  because  of  the  occurrence  of  reddish  tones.  In  this 
way  is  produced  the  phenomenon  called  variegation. 

A  very  well-known  example  of  this  white  spotted  condition  is  found 
in  the  ribbon  grass  of  our  gardens  (Phalaris  arundinacea  L.,  Phalaris  picta 
L.),  in  which  the  white  parts  occur  alternately  as  stripes  between  the  veins. 
A  toy  species  of  the  ash  leafed  maple  (Acer  Negundo  L.)  is  still  more 
striking.  At  times  this  shows  perfectly  white  foliage.  The  family  of  the 
Aroideae  might  be  named  as  examples  of  the  occurrence  of  variegation  as 


678 

well  as  of  white  coloring.  Among  these,  the  calla,  frequently  cultivated  in 
the  house  {Zantedeschia  aethiopica),  shows  leaves  which  often  are  as  pure 
white  as  the  funnel-shaped  blossom  sheath.  The  bright  colored  calladia, 
greenhouse  favorites,  are  related  to  the  Zantedeschia.  Among  them  a  few 
are  only  specked  with  white,  others  have  white  and  red  spots,  and  many 
finally  only  red  spots. 

The  white  spotted  condition  of  the  flowers  and  the  more  rare  albinism 
of  fruit  are  difficult  to  distinguish.  Of  the  latter,  Dufour^  has  described 
interesting  cases  in  grapes. 

There  prevails,  especially  in  practical  circles,  an  earnest  hesitation  in 
accepting  the  theory  which  ascribes  the  white  variegated  leaves  to  the 
phenomena  of  disease.  Yet,  we  believe  that  this  opinion  must  be  defended. 
If  we  investigate  a  considerable  number  of  plants  with  variegated  leaves, 
we  find  all  gradations  in  the  cells  from  the  normal  chloroplasts  to  the  entire 
disappearance  of  the  chloroplastids.  The  parts  of  the  plants  which  appear 
yellowish  often  have  chloroplasts  which  appear  as  yellow,  sponge-like  balls 
or  discs  in  the  cells ;  the  purer  white  the  plants  are,  the  fewer  are  the  even 
colorless  chlorophyll  bodies ;  and  the  more  the  cytoplasm  assumes  the  ap- 
pearance of  a  soft,  uniform  wall  lining.  The  intercellular  spaces  contain 
more  air  and  at  times  are  larger. 

The  assimilation  of  carbon  dioxid  also  ceases  with  the  disappearance 
of  the  chloroplasts.  Cloez-  and  later  Engelmann^  found  that  the  leaves 
assimilate  carbon  dioxid  only  in  proportion  to  their  chlorophyll  content. 
The  diiiferent  gradations  in  the  yellow  variegation  arise  from  lesser  quanti- 
ties of  the  same  chlorophylline  and  zanthophyll,  than  occur  in  the  normal 
green  leaves*  and  their  assimilator}'  activity  is  in  accordance  with  this. 

In  pure  white  leaves  the  chlorophyll  does  not  form  and  the  chloroplasts 
are  poorly  developed.  In  the  yellow  forms,  chloroplasts  are  found  at  least 
in  the  bud  and  often  later  but  the  degree  of  degeneration  of  the  chloroplasts 
depends  on  their  proximity  to  the  pure  white  zone.  The  analyses  given  by 
Church^  serve  as  a  good  confirmation  of  this.  He  used  white  variegated 
forms  of  maple  {Acer  Negundo),  Ivy  (Hcdera  Helix)  and  Holly  {Ilex 
a  qui  folium)  : 


Acer 

Ilex 

Hedera 

They  contained           white      green 
leaved    leaved 

white      green 
leaved    leaved 

white      green 
leaved     leaved 

per  cent,  per  cent. 

per  cent,  per  cent. 

percent,  percent. 

Water    82.83       72.70 

Organic  substances    15.15       24.22 
Ash   2.02         3.08 

74.14      62.83 

23.66       35.41 

2,20         2.47 

78.88       66.13 

18.74       31.63 

2.38         2.24 

1  Defour,  J.,  Panachierte  Trauben.     Extr.  Chronique  ag^ric.  du  canton  de  Vaud; 
cit.  Zeitschr.  f.  Pflanzenkrankh.  1904,  p.  286. 

2  Compt.  rend.  LVII,  p.  834. 

3  Engelmann,  Faibe  und  Assimilation,  Bot.  Zeit.  1883,  Nos.  1  and  2. 

4  Kranzlin,     G.,    Anatomische    und    farbstoffanalytische     Untersuchungen    an 
panachierten  Pflanzen.     Inaug.-Diss.     Berlin  1908. 

5  Church,  Variegated  leaves.     Gardeners'  Chronicle  1877,  II,  p.   586. 


679 

The  green  leaves  show,  therefore,  in  contrast  to  the  white  spotted  ones, 
considerably  greater  amounts  of  dry  substances,  while  in  the  latter  the  ash 
constituents  (as  found  universally  where  disturbances  in  nutrition  make 
themselves  felt)  form  a  greater  percentage  of  dry  substance.  The  nitrogen 
content  in  the  white  leaves  of  the  ivy  and  the  holly  was  greater  in  propor- 
tion to  the  dry  substance.  This  result  is  also  expHcable ;  for,  if  the  chloro- 
phyll apparatus,  without  doubt  necessary  for  the  production  of  starch 
grains  and  other  carbohydrates,  is  only  scantily  present,  the  amount  of  dry 
substances  is  reduced  and  the  absolutely  smaller  amount  of  substances  con- 
taining nitrogen  appears  relatively  increased.  The  fact  that  the  substances 
soluble  in  alcohol  and  ether  in  the  white  leaves  of  ivy  and  holly  amount  to 
about  half  that  in  the  green  leaves  likewise  may  not  be  considered  surprising. 

The  percentages  in  the  composition  of  the  ash  are  very  important. 
They  are  as  follows  : — 

Acer  Ilex  Hedera 

white      green  white      green  white     green 

per  cent,  per  cent,     per  cent,  per  cent,    per  cent,  per  cent. 

Potash    45.05       12.61  35.30       16.22  47.20       17.91 

Lime   10.89       39-93  21.50       34.43  12.92      48.55 

Magnesia    3.95         4.75  3.23         2.43  i.ii  1.04 

Phosphoric  acid...    14.57         8-8o  9.51         7.29  10.68         3.87 

Iron  oxide ?  ?  3. 11         3.11  2.62         2,31 

It  .is  evident  from  these  figures  that  organs  without  pigmentation 
approximate  the  condition  of  young  green  leaves  and  have,  therefore,  failed 
to  develop  in  a  normal  manner.  Griffon^  has  come  to  the  conclusion  that 
plants  without  pigmentation  behave  in  general  like  etiolated  ones,  which  we 
have  also  compared  to  arrested  development.  In  the  yellow  transitional 
stages  the  results  of  variegation  are  very  different.  In  Abutilon  Thomp- 
soni  I  found  the  cell  content  in  many  leaves  still  arranged  as  in  perfectly 
green  parts,  i.  e.,  provided  with  chloroplasts,  their  edges  roundish  angular, 
which  were  normally  arranged  against  the  walls  but  were  a  pale  yellow,  or 
colorless,  and  had  a  strongly  granulated  content.  In  other  cells  the  sub- 
stance of  the  chloroplasts  was  united  into  irregular  Agranular  balls  which 
took  on  a  blue  color  with  iodine,  glycerine,  and  in  part  also  with  sulfuric  acid 
and  which  might  be  called  carotin.  KohP  also  found  carotin  (etiolin),  in 
the  investigation  of  golden  yellow  leaves,  besides  ;^-zanthophyll  and 
phyllofuscin. 

The  difference  in  the  thickness  of  the  leaf,  i.  e.,  the  noticeably  lesser 
thickness  of  the  pure  white  parts  in  contrast  to  the  pure  green  parts, 
decreases  the  more  the  color  tone  varies  from  the  pure  white ;  i.  e.,  the  more 
yellow  the  places  in  the  leaf  become.     Timpe^  also  calls  attention  to  this 

1  Griffon,    Ed.,    L'assimilation    chlorophyllienne    et    la    coloration    des    plantes. 
Annal.  sc.  nat.  VIII,  1899;   cit.  Bet.  .Jahresber.  1899,  I,  p.  151. 

2  Kohl,    F.    G.,    Untersuchungen    iiber    das    Carotin    und    seine    physiologische 
Bedeutung  in  der  Pflanze.     Leipzig-,  Borntrager,  1902,  IX. 

3  Timpe,   H.,  Beitrage  zur  Kenntnis   der  Panachierung.    -Dissertat.,   Gottingen, 
1900. 


68o 

circumstance  and  lays  emphasis  on  the  fact  that  the  slime  cells  are  fewer 
in  the  non-pigmented  parts  of  plants  which  bear  the  mucilage  cells  (Ulmus, 
Crataegus).  On  the  other  hand,  the  content  of  tannin  in  the  white  parts  is 
usually  proved  to  be  greater.  Starch  is  found  rarely  but,  according  to 
Timpe,  in  a  sugar  solution  is  often  formed  more  abundantly  by  the  non- 
pigmented  places  than  by  the  green  ones.  Monocotyledons  store  up  no 
starch  in  a  sugar  solution. 

It  is  stated  by  other  authors  that  the  pure  white  places  contain  no  starch 
since  assimilation  does  not  take  place  there.  These  apparent  contradictions 
are  explained  by  the  transitional  stages  to  a  golden  yellow  color  which, 
indeed,  contain  no  chlorophyll  but  have  zanthophyll  and  carotin  and  elim- 
inate oxygen  in  the  light  (like  etiolated  leaves)*. 

An  interesting  fact  is  that  in  many  plants  a  lack  of  pigmentation  may 
be  communicated  to  the  stock  by  grafting.  Meyer^  reported  experiments 
of  this  kind  with  positive  results  as  early  as  1700-1710  with  Jasminum 
officinale.  "If  a  branch  of  Jasminum  with  variegated  leaves  is  grafted  on 
the  healthy  trunk  of  the  same  Jasminum,  the  other  branches  above  and 
below  the  scion  likewise  bear  variegated  leaves."  Later  Lindemuth^  and 
recently  Baur^  have  studied  the  question  especially.  Baur  has  advanced  the 
theory  that  the  yellow  forms  may  be  considered  to  be  sport  varieties,  or 
mutations,  which  in  part  persist  in  the  seed.  The  pure  white,  however, 
should  be  distinguished  from  these  as  examples  diseased  by  infection.  At 
any  rate,  the  infecting  body  may  be  no  living  creature,  but  an  unknown 
material  something,  a  virus  which  can  increase  in  amount  within  the  dis- 
eased plant.  This  virus  can  be  a  metabolic  product  of  the  diseased  plant 
which  is  able  to  infect  the  young  chloroplasts  in  such  a  way  that  they  cannot 
develop  tc  normal  organs,  but  to  malformations  in  which  then  the  same 
virus  is  formed  anew.  However,  it  may  be  a  metabolic  product  of  the 
diseased  plant  which,  in  a  certain  sense,  has  the  capacity  for  growth,  i,  e., 
can  split  off  substances  from  other  compounds  identical  with  it,  or  can 
synthetically  construct  new  substances  of  this  kind*. 

This  line  of  thought  has  already  been  expressed  in  a  more  precise  form 
by  Pantanelli%  and  later  supplemented.  He  sa3^s^',  "the  albinism  is  not  an 
infectious  disease,  but  a  constitutional  one,  the  first  sign  of  which  occurs  as 
an  abnormal  accumulation  of  destructive  and  primarily  oxidizing  enzymes." 
"The   substances,    causing   the   destruction,    spread    through    the    leptome. 


*  Kohl,  loc.  cit. 

1  Meyen,  F.  J.  F.,  Pflanzenpathologie,  Berlin,  1841,  p.  288. 

-  Lindemuth  Vegetative  BastarderzeuRung  durch  Impfung-.  Landwirtschaftl. 
Jahrbiicher  1878,  Part  6.     Gartenflora  1901,  1902,  1904. 

3  Baur,  Erwin,  Zur  Aetiologie  der  infektiosen  Panachierung-.  Ber.  d.  Deutsch. 
Bot.  Ges.  1904,  Vol.  XII,  p.  453.  Further  statements  on  the  infectious  chlorosis  of 
the  Malvaceae  and  other  simila.  phenomena  in  Ligustrum  and  Laburnum.  Ber.  d. 
Deutsch.  Bot.  Ges.  1906,  Part  8,  p.  416. 

*  Baur,  E.,  tJber  die  infekti()se  Chl.orose  der  Malvaceen.  Sitzungsber.  d.  Kgl. 
Preuss.  Akad.  d.  Wiss.  January  11th,  1906. 

5  Pantanelli.  E.,  Studii  su  I'albinismo  nel  regno  vegetale.  Malpighia.  Vol. 
XV-XIX  (1902-5). 

6  Pantanelli,  E.,  tJber  Albinismus  in  Pflanzenroich.  Zeitschr.  f.  Pflanzenkrank- 
heiten  1905,  p.  1. 


68i 

bundles,  either  because  of  an  energetic  influence  due  to  adjacent  and  com- 
municating protoplasts,  or  of  a  material  transportation  by  means  of  sieve 
tubes  and  analogous  elements  throughout  the  entire  body ;  they  reach  at  last 
the  developing  petioles  and  then  the  main  ribs  of  the  leaves.  Here  they 
influence  all  the  parenchyma  cells  with  which  they  are  connected  clearly 
more  energetically  or  because  of  a  poor  nutritive  provision,  and  removal." 
The  transference  of  the  phenomena  from  the  scion  to  the  stock,  therefore, 
comes  about  if,  in  grafting,  the  leptome  connection  in  the  two  component 
parts  has  been  established. 

This  theory  is  based  on  experimental  studies.  It  has  been  proved  by 
chemical  investigation  that  "the  protoplasm  and  plastids  are  gradually 
attacked  by  abnormal  formations  of  strongly  destructive  enzymes  and 
digested  by  them."  In  some  intensive  cases  of  albinism  no  accumulations, 
however,  of  inorganic,  or  organic  substances,  or  sugar,  may  be  proved. 

A  determination  made  by  Pantanelli  on  Ulmus  leaves  throws  light  oh 
the  behavior  of  the  nitrogen  compounds.  He  pulverized  green  and  non- 
pigmented  leaves  with  the  necessary  precaution  and  let  the  pulp  stand  8 
days  in  a  cylinder.  The  original  amount  of  water  in  the  green  leaves 
averaged  60.67  P^^"  cent.,  that  in  the  non-pigmented  leaves  of  the  same  tree, 
at  the  same  time,  73.8  per  cent. 

The  green  leaves  contained  (in  percentages  of  the  dry  weight). 

In  the  beginning  After  8  days 

Nitrogen  as  a  whole 3.355  per  cent.  3-3250  per  cent. 

Proteid  nitrogen 3-324       "  0.9212 

Non-proteid  nitrogen 0.031       "  2.4050 

Non-pigmented  leaves  contained  (in  percentages  of  the  dry  weight)  : 

In  the  beginning  After  8  days 

Nitrogen  as  a  whole 2.681  per  cent.  2.576  per  cent. 

Proteid  nitrogen   2.274       "  0.604        " 

Non-proteid  nitrogen   0.407       "  1-972 

Autolysis  in  the  sap  of  the  variegated  leaves  is,  therefore,  compara- 
tively more  extensive  than  in  the  green  ones.  The  amount  of  nitrogen  in 
non-pigmented  organs  is  considerably  less,  but  the  percentage  of  non-proteid 
nitrogen  compounds  is  greater.  The  richly  abundant  phosphoric  acid  must 
be  present  jn  some  other  combination  since  lecithin  cannot  be  formed  nor 
the  chloroplast  be  developed.  Also,  according  to  Pantanelli's  investigations, 
an  enzyme  which  breaks  up  the  starch  seems  to  be  present  more  abun- 
dantly in  the  variegated  leaves  than  in  the  green  ones,  at  least  when  they  are 
young. 

In  the  second  edition  of  this  manual  (p.  195),  I  have  already  referred 
to  the  nitrogen  poverty  of  the  non-pigmented  parts  and  there-  expressed 
the  following  opinion : — in  the  normally  nourished  leaf  cell  so  much  cyto- 
plasm is  present  that  not  only  material  can  be  furnished  for  the  develop- 
ment of  the  cell  wall,  but  the  chloroplasts  can  also  be  produced  abundantly. 


682 

If  the  supply  to  the  young  cells  is  cut  off  too  soon,  because  the  material, 
increasing  the  amount  of  protoplasm,  is  supplied  too  scantily,  and  the  cell 
wall  becomes  old  prematurely,  the  cell  can  have  performed  only  the  first 
part  of  its  task,  the  formation  of  the  wall,  and  has  nothing  left  over  for  the 
formation  of  the  apparatus  which  produces  reduction  and  increases  the  dry 
substances,  nor  for  its  maintenance.  This  same  poverty  must  occur  in  the 
normal  cell  if  it  gets  into  conditions  of  growth  which  cause  an  accumulation 
of  destructive,  i.  e.,  amylolytic  enzymes,  whereby  it  is  again  carried  back 
toward  the  young  stage.  If  the  plant  is  brought  under  conditions  which 
favor  normal  vegetative  activity  (shade,  moisture  and  heat)  the  non-pig- 
mented  parts  of  the  axis  tend  to  produce  green  leaves.  A  discovery  of 
Lindemuth's  confirms  this  observation.  He  proved  that  intense  light  actu- 
ally favors  albinism.  Ernst^  mentions  that  in  Caracas  Solanus  aiigerum 
Schlecht.,  common  to  that  region,  is  found  not  infrequently  with  variegated 
leaves.  This  occurs,  however,  only  on  poor  soil.  Specimens  with  stroayly 
variegated  leaves,  transplanted  to  better  soil,  become  green.  With  Urtica 
dioica,  Beijerinck-,  even  in  one  year,  succeeded  in  bringing  back  the  green 
form  from  the  variegated  form  by  means  of  cuttings. 

Tissues,  with  a  less  concentrated  cell  sap  are,  however,  less  resistant. 
Actually,  the  white  leaved  parts  of  the  plants  are  more  sensitive  to  heat, 
frost,  and  drought,  and  die  sooner.  We  find  more  abundant  examples  in 
the  white  leaved  Acer  Negundo,  in  which  even  the  bark  of  the  branches 
becomes  variegated.  Almost  every  year,  summer  sunburn  and  winter  frosts 
kill  the  most  exposed  branches.  Such  cases  also  occur  in  conifers\  In 
the  same  way  seedlings  with  white  cotyledons  and  plumules  are  very  easily 
destroyed.  Not  infrequently  I  have  found  pure  white  seedlings,  or  white 
ones  with  a  reddish  tinge,  in  larger  sowings  of  various  kinds  of  fruits. 
These  were  always  treated  with  special  attention  but  died  after  some  time, 
in  case  they  did  not  begin  to  produce  green  leaves.  Similar  observations 
have  been  made  also  by  others,  for  example,  on  Phormium  tenax  (de  Smet), 
Passiflora  quadrangularis  as  well  as  on  Dahlia  variabilis,  Dianthus  Caryo- 
phyllus,  and  the  Liliacea  (Lindemuth).  A  scarcity  of  reserve  substances 
in  non-pigmented  branches  explains  also  the  further  observation  that  their 
cuttings  grow  with  greater  difficulty  than  those  from  the  green  parts  of  the 
same  individual.  Consider,  for  example,  hydrangeas  with  pure  white 
leaves  and  geraniums  from  the  group  "Miss  Pollack." 

Lindemuth  observed  in  Abutilon  that  the  non-pigmented  leaves  are 
usually  smaller  and  have  a  shorter  life  period.  We  would  recall  in  this 
connection  the  phenomenon,  occurring  not  infrequently,  in  our  wild  plants, 
that  when  one-half  of  the  leaf  is  white,  the  other  half  green,  the  former 
remains  shorter  and  the  latter,  on  this  account,  curves  about  the  white  half 
in  the  form  of  a  sickle.     (Cichorium,  Beta.)     In  marbled  leaves,  the  white 


1  Botanische  Miscellaneen.     Bot.  Zcit.  1876,  p.  37. 

2  Beijerinck,  M.  W.,   Chlorella  variegator,   ein  bunter  Mikrobe;    cit.  Bot.   Cen- 
trabl.     G.  Fischer,  1907,  p.  333. 

3  Zeitsch.  f.  Pflanzenkrankh.  1896,  p.  361. 


683 

fields  of  a  leaf  often  appear  distended,  the  green  ones  wrinkled,  or  blistered. 
The  stems  also  at  times,  in  the  non-pigmented  part,  show  some  shortening, 
as  is  proved  by  the  variegated  Kerria  japonica,  of  which  green  shoots  on 
the  same  stem  and  of  the  same  age  are  at  times  half  a  meter  taller  than 
those  bearing  white  leaves.  Sambucus,  Weigelia  and  others,  behave  in 
this  way. 

in  my  opinion,  albinism  is  a  form  of  arrested  development  which  occurs 
more  rarely  in  wild  plants  but  to  an  increasing  degree  in  cultivated  ones 
and  manifests  itself  in  the  poorer  nourishment  of  the  different  tissue  ele- 
ments. The  result  of  this  is  that,  either  the  chlorophyll  apparatus  does  not 
mature  at  all,  or  soon  falls  victim  to  destructive  enzymes.  The  lack  of  any 
accumulation  of  resen^e  materials,  or,  at  most,  a  scanty  one,  is  connected 
with  this  and  explains  the  increased  collapsibility  of  the  tissues. 

Of  the  causes  producing  albinism,  the  pressure  conditions  in  the  bud 
should  come  first  under  consideration  which  arrest  the  development  of  the 
conducting  system  and  thereby  hinder  the  sufficient  filling  of  the  cells  with 
plastic  material  even  in  the  embryonic  condition.  This  would  explain  the 
phenomenon  of  the  sudden  development  of  a  non-pigmented  shoot  from  the 
bud  of  a  plant  which  had  been  green  up  to  that  time.  In  regard  to  cultural 
influences,  experience  shows  that  a  relative  excess  of  light  acts  favorably, 
for  we  see  that  often  a  condition  of  pure  white  leaves  occurs  very  inten- 
sively with  direct,  strong  insolation  and  is  retained  longest,  but  decreases, 
when  shade  and  a  sufficient  supply  of  water  and  nitrogen  give  the  leaf  time 
to  develop  more  slowly  and  let  its  vegetative  functions  act  longer,  i.  e., 
preventing  a  premature  end  of  life. 

Timpe^  cites  in  his  latest  work  a  phenomenon  which  has  been  repeat- 
edly tested  experimentlly.  He  repeated  the  experiments  first  described  by 
Molisch-  with  the  white  and  green  variegated  species  of  Brassica  oleracea 
acephala  and  obtained  the  same  result,  viz.,  that  the  brilliant  white  color  of 
the  leaf  surfaces,  which  reaches  its  greatest  development  in  winter  in  a 
cold  frame  (up  to  February),  decreases  almost  at  once  and  finally  disappears 
if  the  plants  are  brought  into  a  warm  place.  Molisch  transferred  white 
variegated  plants  from  the  cold  frame  at  4  degrees  to  7  degrees  C.  into  a 
hot  bed  at  12  to  15  degrees  C.  All  the  leaves  already  formed  turned  green 
in  from  8  to  14  days ;  those  newly  formed  appeared  green  at  once.  Returfied 
to  the  cold  frame,  the  specimens  again  formed  leaves  variegated  with  white. 
Here  belongs  also  Weidlich's  statement^  that  Selaginella  Watsoniana  must 
be  cultivated  in  a  temperature  of  10  degrees  C.  if  it  is  to  form  white  tips. 
In  these  cases,  therefore,  the  increase  in  the  vegetative  functions,  producing 
the  loss  of  albinism,  is  conditioned  by  the  increase  of  heat;  while  in  other 
cases,  according  to  the  nature  of  the  plant  and  other  local  nutritive  condi- 
tions, the  variegated  leaves  can  be  brought  back  to  the  optimum  of  their 


1  Tempe,  Heinrich,  Panachierung  und  Transplantation.     Jahrbuch  d.  Hamburg:. 
wis.s.  Anstalten  XXIV,  1906,  Beiheft'^3. 

2  Ber.  d.  Deutsch.  Hot.  Ges.  XIX,  1,  p.  32. 

3  Gartenflora  1904,  p.  585. 


684 

functions  and  to  the  normal  formation  of  chlorophyll  by  decrease  of  light 
and  heat;  or  by  the  increase  of  the  nitrogen  or  potassium  supply,  thus  pro- 
longing the  period  of  growth. 

A  scanty  supply  of  material  frequently  manifested  in  the  increase  of 
tannin  and  the  absence  of  starch,  the  small  size  of  the  cell  and  the  increase 
of  the  intercellular  spaces,  is  also  emphasized  by  Timpe  in  his  carefully 
worked  out  experiments.  He  describes  a  phenomenon  for  Ulmus  which 
seems  strange  to  him  but  is  exactly  the  best  proof  of  our  theory.  In  this 
the  luxuriant  spring  growth  of  shoots  variegated  with  white  developed  per- 
fectly green  foliage  after  the  tree  had  been  set  out;  but  the  midsummer 
growth,  with  a  lack  of  water  and  excess  of  light  and  heat,  again  showed 
the  variegation*. 

If,  however,  albinism  consists  in  the  premature  ending  of  hfe,  i.  e.,  in 
the  suppression,  or  arrestment,  of  the  work  of  the  chlorophyll  apparatus,  the 
destructive  enzymes,  even  if  not  increased  in  absolute  amount,  still  obtain 
a  preponderance  in  the  cell  because  those  which  cause  the  formation  of  the 
reserve  materials,  have  been  too  little  developed  due  to  the  lack  of  chloro- 
phyll activity.  The  equilibrium  otherwise  formed  in  the  cells  containing 
chlorophyll  is  destroyed. 

We,  therefore,  do  not  need  to  assume  the  formation  of  a  "virus" :■ — • 
a  group  of  materials  acting  poisonously,  which  must  be  produced  and 
increased  in  the  plant, — in  order  to  explain  albinism  and  the  phenomena  of 
disease  related  to  it  (the  mosaic  disease,  shrivelling  disease,  etc.).  It  is 
simply  a  change  in  the  functions,  i.  e.,  a  different  direction  of  the  mole- 
cular motion  to  which  we  must  trace  back,  however,  all  metabolic  processes. 
If  this  changed  formation  of  substances  is  a  movement,  it  can  continue  until 
some  other  form  of  molecular  motion  causes  its  arrestment.  II le  non- 
pigmented  part  of  the  plant  is,  therefore,  the  carrier  of  an  abnormal  motion 
in  its  substances  and  on  this  account  it  would  not  seem  strange  if  this  motion 
is  continued  as  soon  as  the  paths,  i.  e.,  the  vascular  bundles  (according  to 
Pantanelli,  the  leptome  parts),  of  two  separated  individuals  are  united,  as 
is  the  case  in  grafting. 

If  we  consider  albinism  not  as  a  phenomenon  coming  from  the  ranks 
of  the  othei"  phenomena  of  variegation  but  only  as  the  most  extreme  case  of 
a  process  representing  a  decrease  in  the  amount  of  chlorophyll,  it  can  no 
longer  seem  strange  that  plants,  variegated  with  yellow  and,  therefore,  less 
irritated,  can  still  be  brought  to  the  production  of  seeds  in  which  the  same 
direction  of  the  metabolic  motion  is  continued,  i.  e.,  that  the  seeds  furnish 
plants  with  yellow  variegation. 

The  Mosaic  Disease  of  Tobacco. 

The  most  recent  authors,  who  have  w^-itten  on  albinism,  have  already 
mentioned  the  relation  of  this  phenomenon  to  the  mosaic  disease  of 
tobacco. 


*  Loc.  cit.,  p.  68. 


685 

This  name  originated  with  Adolph  Mayer,  who  in  July,  1879,  when  the 
disease  had  occurred  to  an  alarming  extent  in  Holland,  received  some  dis- 
eased plants  from  the  Society  of  Agriculture  (Department  Wijk  bij 
Duurstede)  for  investigation.  He  published  the  results  of  his  experiments 
in  1885,  in  a  Dutch  periodical  and  in  the  following  year  in  the  "Landwirt- 
schaftHchen  Versuchsstationen"^  According  to  F.  W.  T.  Hunger^  Van 
Swieten  in  1857  had  first  called  attention  to  the  mosaic  character  of  the 
variegated  leaves  of  tobacco  in  the  Dutch  plantations  but  in  his  later  studies 
on  the  cultivation  of  tobacco  in  Cuba,  did  not  mention  the  disease  which  then 
was  called  "Rost."  At  present  the  disease  may  exist  in  any  country  grow- 
ing tobacco  and,  accordingly,  has  received  any  number  of  names.  Thus 
Hunger  mentions  that  in  Holland  it  is  not  only  called  "Rost"  but  in  places 
"Bunt"  or  "Faule."  In  Germany  the  name  "Mosaikkrankheiten"  holds 
good.  In  places  it  passes  as  "Mauche ;"  in  France  it  is  called  "La  Mosaique" 
or  "Nielle"  or  "Rouille  blanche;"  in  Hungary  it  is  called  "Mozaikhetegsege" 
and  the  Tartars  in  southern  Russia  call  it  "Bosuch."  In  Italy  it  is  described 
under  the  name  "Mai  de  Mosaico,  or  "Mai  della  holla."  In  America,  in 
the  northern  states,  it  is  called  "Calico"  or  "the  Frcnching  disease ;"  in  the 
southern  states,  on  the  other  hand,  "Brindle"  or  "Mongrel  disease"  The 
plantations  in  Java,  Borneo  and  Sumatra  also  suffer  heavily.  The  Javan- 
ese call  the  disease  "Poetih"  while  it  is  known  in  Deli  by  the  Chinese  name 
"Peh-sem"^. 

The  mosaic  disease  may  at  present  be  considered  the  most  dangerous 
disease  of  the  tobacco  plant.  This  explains  why  it  has  been  thoroughly 
studied  recently  from  several  points  of  view  but  the  results  are  often  con- 
tradictory. While  some  investigators,  retaining  the  old  theory  with  great 
tenacity,  wish  to  find  microbes  and  think  they  have  found  them,  others 
defend  the  theory  that  an  infection  disease  is  present  here,  the  cause  of 
which  must  be  sought  in  inexpedient  enzymatic  activity. 

The  diversity  of  opinion  is  explained  partially  by  the  fact  that  different 
phenomena  have  been  included  under  the  mosaic  disease  which  do  not 
belong  together.  On  the  other  hand,  however,  the  disease  can  actually 
appear  under  different  forms. 

We  follow  Delacroix*  in  describing  its  symptoms.  He  distinguishes 
two  stages  :^ — i,  loss  of  color;  2,  changes  in  the  form  of  the  diseased  leaves. 
In  the  first  group  of  symptoms,  the  edge  of  the  leaf  shows  sharply  outlined, 
various  colored  spots  of  a  faded  green,  which  shades  off  into  a  whitish  color 
but  not  into  a  yellow  green  as  in  chlorosis;  the  pale  green  parts  have  spots 
of  dark  green  color,  which  is  even  darker  than  that  of  the  normal  leaf. 
The   dift'erences   in   color  become   more   apparent   when   the   leaf   is   held 

1  Mayer,  Adolf,  Die  Mosaikkrankheit  des  Tabaks.  Landw.  Versuchs&tat.  1886, 
Vol.  XXXII,  p.  450.  Part  III. 

2  Hung-er,  F.  W.,  Untersuchung-en  und  Betrachtungen  uber  die  Mosaikkrank- 
heit der  Tabak.spflanzen.     Zeitsch.  f.  Pflanzenkrankh.  1905,  p.  257. 

3  Hunger,  loc.  cit. 

4  Delacroix,  Georges,  Recherches  sur  quelques  maladies  du  Tabac  en  France. 
Paris  1906,  p.  18.  Extrait  des  Annales  de  I'lnstitut  national  agronomique,  2  ser., 
Vol.  V. 


686 

aj^ainst  the  light,  and,  by  feeling  the  leaf,  it  is  noticeable  that  the  dark  green 
places  are  somewhat  thicker  than  the  pale  ones.  Before  Delacroix,  Iwan- 
ovvski^  had  already  emphasized  the  fact  that  the  lateral  shoots,  developing 
from  the  axes  of  diseased  leaves,  have  the  mosaic  disease.  This  circum- 
stance is  very  important  and  characteristic  of  the  disease  in  which  the  loss 
of  color  occurs  in  the  young  leaves ;  as  a  rule,  mature  leaves  do  not  be- 
come diseased.  Often  the  dark  green  places  become  somewhat  convex  so 
that  the  surface  of  the  leaves  is  somewhat  wrinkled;  in  other,  and  rarer 
cases,  a  reduction  of  the  leaf  surface  sets  in  which  can  increase  to  such  an 
extent  that,  on  the  whole  plant,  only  the  mid  ribs  are  present  but  no  blades. 
This  latter  characteristic  has  been  mentioned  by  Heintzel-  and  Iwanowski, 
but,  according  to  Hunger'  it  is  not  typical  of  the  disease,  for  he  had  also 
observed  it  in  Deli  in  healthy  plants  on  open  ground. 

Therefore,  in  the  mosaic  disease,  we  find  the  same  characteristics  as  in 
albinism;  a  sharp  delimitation  of  the  spots,  a  greater  thickness  of  the  green 
places,  and,  at  times,  a  reduction  of  the  leaf  surfaces,  which,  in  the  varie- 
gated parts,  remain  small.  This  can  also  be  transmitted  artificially  and 
probably  follows  the  same  paths,  i.  e.,  the  leptome.  The  only  difference  is 
that  the  mosaic  disease  can  be  transmitted  considerably  more  easily.  Ever)' 
particle  of  sap  which  falls  from  a  diseased  plant  into  an  injury  in  a  healthy 
one  is  enough,  under  certain  circumstances,  to  cause  infection.  We  will 
cite,  as  example,  the  description  of  an  infection  experiment  made  by 
Koning*.  On  the  5th  of  July  he  cut  the  stem  of  a  perfectly  healthy  plant 
as  far  as  the  vascular  bundles  and  inserted  in  the  cut  a  small  piece  of  the 
spotted  leaf  from  a  diseased  plant.  On  the  20th  of  July  a  dark  fleck  could 
be  seen  near  the  edge  of  a  young  leaf,  between  the  veins.  In  the  course  of 
the  next  few  days,  specks  appeared  also  on  the  other  young  leaves  while 
the  leaf  itself  took  on  "an  uneven,  irregular  appearance  due  to  the  increase 
of  the  palisade  tissue."  The  edge  of  the  leaf  appeared  in  places  to  be 
strangulated,  or  slightly  lobed.  Later  these  spots  dried  up,  after  having 
assumed  a  reddish  brow^n  color.  Koning  perceived  concentric  zones  in  the 
larger  spots,  of  which  the  outermost  zones  were  the  darkest.  Not  infre- 
quently he  found  that  whole  pieces  had  fallen  out  of  the  leaf.  The  latter 
characteristics  are  not  mentioned  by  other  observers,  which  fact  supports 
our  theory  that  the  disease  can  present  different  aspects  in  dififerent  places 
and  in  different  varieties  of  tobacco. 

Koning  gives  only  scanty  notes  on  the  anatomy  of  the  diseased  leaves. 
In  the  very  youngest  stage  of  the  spots,  where  no  differentiation  of  palisade 
and  spong}^  parenchyma  has  set  in.  dark  stripes  appear  between  the  cells 
which  represent  strikingly  large,  air-filled  intercellular  spaces.     These  are 

1  Iwanowski,  D.,  tJber  die  Mosaikkrankheit  der  Tabakspflanzen.  Zeitschr.  f. 
Pflanzenkrankh.  1901,  p.  1  ff. 

2  Heintzel,  Kurt,  Kontagiose  Pflanzenkrankheiten  ohne  Mikroben  mit  beson- 
derer  Beriicksichtigung  der  Mosaikkrankheit  der  Tabaksblatter.  Inaug-  -Dissert. 
Erlangen  1900. 

n    Tvoc.  cit,  D.  274. 

4  Koning,  C.  J.,  Die  Flecken-  oder  Mosaikkrankheit  des  hoUandischen  Tabaks 
Zeitschr.  f.  Pflanzenkrankh.  1899,  p.  65. 


retained  in  the  advancing  development  of  the  tissue.  No  change  can  be 
observed  at  first  in  the  epidermis.  It  shrivels  later,  becomes  brown  and 
dry  when  the  chlorophyll  has  disorganized  in  the  underlying  tissue  and  the 
cells  dry  up. 

In  extensive  plantations  the  infection  of  the  plants  usually  takes  place 
through  contact  with  the  hands  of  laborers  who  produce  wounds  when 
thinning  out  the  plants  and  otherwise  working  among  them.  The  touching 
of  such  places  with  fingers  covered  with  sap  from  diseased  plants  is  enough 
to  inoculate  the  majority  of  the  healthy  plants.  The  process  has  often  been 
tested  experimentally.  In  an  experiment  made  especially  for  this  purpose 
in  Holland,  Koning  determined  80  per  cent,  of  disease. 

The  disease,  moreover,  is  not  restricted  to  tobacco,  for  Woods^  had 
already  reported  that  he  could  call  forth  similar  phenomena  when  pruning 
tomato  plants.  Hunger^  showed  as  an  example  that,  in  the  same  plant 
species,  different  varieties  behaved  differently  according  to  their  origin. 
He  found  in  direct  experiments  with  the  heads  of  plants  in  Buitenzorg  that 
all  the  shoots  (lateral  shoots)  of  50  examples  raised  from  American  seeds 
had  the  mosaic  disease.  Df  25  plants  grown  at  the  same  time  from  German 
seed  9  were  diseased.  On  the  other  hand,  the  shoots  of  the  25  specimens 
raised  from  Indian  seed  showed  no  change. 

In  speaking  of  the  cause  of  this  disease,  we  have  already  mentioned 
that  part  of  the  observers  assume  the  presence  of  micro-organisms  without 
having  seen  them.  Iwanowski,  in  fact,  describes  a  specific  bacterium,  but 
Hunger  found,  in  subsequent  investigations,  that  the  alleged  organism  dis- 
appeared from  the  cell  with  the  use  of  the  chloral  hydrate  phenol  mixture. 
We  can,  therefore,  say  that  no  parasitic  organism  is  known,  as  yet,  for  the 
typical  mosaic  disease,  or,  rather,  the  majority  of  exact  observations  lead 
to  the  theory  that  a  physiological  disease  is  concerned  here,  the  transmission 
of  which  takes  place  by  means  of  carriers  which,  advancing  in  the  infected 
organism,  cause,  in  the  existing  normal  group  of  substances,  the  same 
changes  in  the  arrangement  which  produce  the  disease  and  in  this  way  the 
spread  of  the  disease.  The  different  degrees  of  susceptibility  of  the  differ- 
ent varieties — those  with  thick  leaves  being  much  more  resistant  than  those 
with  thin  leaves — prove  that  some  predisposition  must  exist.  The  highly 
prized  Deli  tobaccos  (those  with  the  tenderest  leaves)  suffer  most.  The 
influence  of  cultivation  is  shown  by  the  fact  that  virgin  soils  give  decidedly 
smaller  percentages  of  sick  plants  than  those  already  used  repeatedly  for 
the  cultivation  of  tobacco  (cf.  Hunger's  field  experiments)^. 

Two  points  of  view  are  now  held  by  the  investigators  who  do  not  rec- 
ognize microbes  as  the  cause  of  the  mosaic  disease.  One  group  believes 
that  the  plant  produces  a  poison,  a  virus,  which  is  capable  of  producing  the 
same  poisonous  substances  in  the  cell  content  of  an  inoculated  plant,  thereby 


1  Woods,  A.  F.,  Observations  on  the  Mosaic  disease  of  Tobacco.     U.  S.  Dept.  of 
Agrriculture,  Bull.  No.  18,  May,  1902. 

2  Loc.  cit.,  p.  287. 

3  Zeitschr.  f.  Pflanzenkrankh.  1905,  p.   289. 


688 

causing  the  disease.  Beijerinck^  appeared  first  among  those  who  hold  this 
opinion.     In  1898  he  described  a  "contagium  vivum  fliddum"  as  the  cause. 

Hunger  says  further-,  "I  consider  the  virus  of  the  mosaic  disease  to 
be  a  toxin  which  is  akvays  produced  in  the  tobacco  plant  during  the  metabo- 
lism of  the  cells  but,  in  normal  cases,  exercises  no  effect,  while  it  accumu- 
lates when  the  metabolism  is  too  strongly  increased  and  then  causes  disturb- 
ances such  as  the  mosaic  form  of  variegated  leaves."  I  assume  that  the 
toxin  of  the  mosaic  disease,  which  is  produced  primarily  by  external  stimuli, 
is  capable,  when  penetrating  into  normal  cells,  of  exercising  a  physiological 
contact  effect  with  the  result  that  the  same  toxin  is  formed  there  secondar- 
ily. In  other  words  the  toxin  of  the  mosaic  disease  possesses  the  pecidiarify 
of  acting  as  a  physiologico-autocatalytic  agent.  In  this  way  the  virus  can  be 
make  its  way  independently  throughout  the  tobacco  plant  and,  reaching  the 
paths  leading  to  the  meristem,  can  exert  its  influence  there  on  the  young 
structures.  This  explains  the  capacity  of  the  diseased  substance  for  in- 
crease. "This  capacity  does  not  depend  on  the  active  reproductivity  of  the 
virus  itself  but  simplv  arises  from  the  passive  reproductive  power  of  the 
living  cell  substances." 

In  contrast  to  the  theory  of  poison  we  represent  a  second  theory  and 
call  attention  to  the  experiments  of  Pantanelli  and  others  who  have  proved 
a  change  in  the  amount  and  action  of  the  enzymes.  HeintzeP  says  (1899, 
p.  45),  "The  enzyme  which  causes  the  mosaic  disease  may,  therefore,  be 
considered  an  oxydase."  Accordingly,  the  cause  of  the  mosaic  disease 
would  be  present  also  in  a  healthy  plant  and  would  have  an  abnormal  action 
only  under  special  circumstances.  Woods*  expresses  exactly  the  same 
theory  since  he  thinks  only  certain  conditions  are  concerned  under  which 
the  oxidizing  enzymes  become  eft'ective — "either  become  more  active,  or  are 
produced  in  abnormally  large  quantities."  The  condition  of  matters  at 
present  is  still  uncertain  and  forbids  a  closer  examination  of  the  relations. 
For  the  theory  which  we  advance  and  have  described  in  the  first  section  of 
this  chapter,  the  question  is  less  important,  whether  an  increase  of  the 
oxydases  actually  takes  place,  or  whether  a  decrease  of  the  reducing  sub- 
stances, always  accompanying  the  oxydases,  whereby  the  same  amount  of 
oxydase  has  an  increased  activity.  Hunger  has  actually  proved  that  the 
leaf  with  the  mosaic  disease  contains  less  reducing  and  tannic  substances 
than  do  healthy  tobacco  leaves'*.  A  scantier  sugar  content  has  been  proved 
in  the  diseased  leaf,  corresponding  to  a  lack  of  chlorophyll;  besides  this, 


1  Beijerinck.  M.  W.,  Over  een  coTitas:ium  vivum  fluiflum  als  oorzaak  van  de 
Vlekziekte  dor  tabaksbladen.  Koninkl.  Akad.  van  "Wetenschappcn  te  Amsterdam. 
Nov.  1898.  tJber  ein  Contagium  vivum  fliiidum  als  Ursache  der  Fleckenkrankheit 
der  Tabaksblfltter.     Centralbl.  f.  Bakeriologic  1899,  Part  II,  No.  2,  p.  27. 

2  Loc.  cit.,  p.  296. 

3  Heintzel,  Kurt,  Kontapriose  Pflanzenkrankheit  ohne  Mikroben,  mit  beson- 
derer  Berlicksichtig-unp:  der  Mnsaikkrankheit  der  Tabaksblatter.  Inaug. -Dissert. 
Erlangren  1900;    cit.  bv  Hun.srer,  loc.  cit.,  p.   269. 

4  Woods,  A.  F.,  The  destruction  of  chlorophyll  by  oxidizing-  enzymes.  Centralbl. 
f.  Bakt.  1899.  Part  II.  Vol.  V,  No.  22,  p.  745. 

■^  Hunger,  F.  W.  T..  Bemerkungen  zur  "Wood'schen  Theorie  tiber  die  Mosaik- 
krankheit  des  Tabaks.     Bull.  d.  I'Inst.  Bot.  de  Buitenzorg  1903,  No.  XVII. 


689 

less  free  organic  acids  are  found\  Accordingly,  the  parts  suffering  wfth 
the  mosaic  disease  lack  the  ability  to  form  sufficient  reserve  substances  ; 
and  thus  the  mosaic  disease,  which,  according  to  Hunger-,  may  also  be 
transmitted  without  the  existence  of  any  injury,  simply  by  contact  with  the 
hand,  or,  in  grafting,  be  transmitted  to  the  stock,  belongs  under  albinism. 

While  we  still  have  no  reason  for  restricting  the  last  named  phenom- 
enon, because  the  white  variegated  plants,  in  spite  of  their  greater  sensitive- 
ness, form  desirable  specimens  for  our  gardens,  yet,  the  need  of  earnest 
regulations  for  combatting  the  mosaic  disease,  is  most  imperative  and  these 
have  often  been  tried.  According  to  Koning  liming  the  soil  has  proved  to 
be  the  best  method.  Hunger  also  proved  good  results  by  fertilizing  with 
bone  meal  and  gives  warning  primarily  against  an  excessive  chemical  ferti- 
lization. In  my  opinion  the  disease  is  a  result  of  inbreeding,  which  can  be 
overcome  successfully  by  decreasing  the  supply  of  nitrogen  and  by  increas- 
ing the  lime. 

Wood  says",  "Overfeeding  with  nitrogen  favors  the  development  of 
the  disease  and  there  is  some  evidence  that  excess  of  nitrates  in  the  cells 
may  cause  the  excessive  development  of  the  ferments  causing  the  disease." 

The  choice  of  seed  also  deserves  especial  attention  as  is  evident  from 
the  statements  of  Bouygeres  and  Perreau*.  These  investigators  took  seed 
from  plants,  in  the  midst  of  a  diseased  field,  which  up  to  the  time  of  har- 
vesting had  remained  free  from  the  mosaic  disease.  They  obtained  98  per 
cent,  of  healthy  plants.  These  were,  at  any  rate,  capable  of  being  infected 
in  wounds  brought  in  contact  with  parts  having  the  disease.  Special  con- 
sideration should  be  given  primarily  to  the  soil.  In  earth,  on  which  tobacco 
had  been  grown  for  some  time,  healthy  seed  very  easily  became  diseased^. 

Pox  OF  Tobacco. 

We  have  mentioned  already,  in  discussing  the  mosaic  disease,  that  other 
phenomena  of  discoloration  have  often  given  rise  to  much  confusion.  An 
example  of  the  latter  is  furnished  by  the  pox  disease.  Iwanowski  and 
Poloftzoff*'  have  called  attention  to  the  difference  between  this  and  the 
mosaic  disease.  For  three  years  they  studied  this  disease  in  Bessarabia, 
having  been  commissioned  by  the  Russian  Department  of  Agriculture. 
According  to  Hunger",  the  disease  manifests  itself  in  the  appearance  of 


1  Hunger,  De  Mozaik-Ziekte  bij  Deli-Tabak.    Deel  I.  Mededeelingen  uit  S'Lands 
Plantentuin  LXIII,  Batavia  1902. 

2  Hunger,  On  the  spreading'  of  the  Mosaik-disease   (Calico)   on  a  tobacco  field. 
Extr.  Bull.  d.  I'Institut  Bot.  de  Buitenzorg  1903,  No.  XVII. 

3  Observations  on  the  mosaic  disease  of  tobacco,  Washington  1902,  p.  24. 

4  Bouygeres   et   Perreau,    Contributions   a   I'etude   de  la   nielle   des   feuilles   du 
tobac.     Compt.  rend.  1904,  CXXXIX,  p.  309. 

5  Behrens,  J.,  Weitere  Beitrage  zur  Kenntnis  der  Tabakspflanze.     Landwirtsch. 
Versuchsstat.  1899,  p.  214  ff  and  482  ff. 

6  Iwanowski    und    Poloftzoff,    Die    Pockenkrankheit   der   Tabakspflanzen.     Mem 
de  I'Acad.  Imp.  de  St.  Petersbourg  1890,  s6r.  VII  v.  XXXVII,, 

7  Hunger,     Zeitschr.    f.     Pflanzenkrankh.     1905,    p.     297.      Here    also    pertinent 
bibliography. 


690 

numerous  small  white  specks  at  times  of  great  drought,  while  in  Deli  the 
mosaic  disease  is  observable  immediately  after  sharp  rainstorms.  The 
cause  is  looked  for  in  conditions  similar  to  those  in  the  mosaic  disease. 

White  Rust  of  Tobacco. 
A  further  phenomenon  has  been  confused  with  the  mosaic  disease 
which  is  called  "White  Rust."'  Delacroix^  has  called  attention  to  the  fact 
that,  in  this  the  mature  leaves,  and  not  the  young  ones,  become  sick  first. 
The  spots  are  more  numerous  but  are  smaller  and  stand  out  in  sharp  relief. 
Ultimately  they  are  bounded  by  a  cork  layer.  The  cause  is  said  to  be 
a  micro-organism.  Bacillus  macnlkola. 

The  Disease  of  the  Peanut  in  German-East  Africa. 
According  to  Karosek-  Arachis  hypogaea,  one  of  the  most  important 
cultivated  plants  of  the  East  African  colony,  is  in  general  but  little  attacked 
by  disease.  In  the  neighborhood  of  Tanga  and  Lindi,  however,  a  phenom- 
enon has  now  appeared  to  a  considerable  extent  which  recalls  the  mosaic 
disease.  The  leaves,  blossoms  and  fruit  remain  small,  the  yield  is  scanty ; 
whitish,  irregular  spots  appear  on  the  leaves,  deforming  them  somewhat. 
The  leaves  finally  become  brown  and  die.  Fungi  have  been  found  and  any 
lack  of  nutrition  is  out  of  the  question. 

The  Shrivelling  Disease  of  the  Mulberry. 

This  disease,  at  present  widely  distributed  through  Japan,  which  surely 
will  be  found  later  in  Europe,  has  only  been  observed  more  exactly  for 
possibly  the  last  twenty  or  thirty  years  and  has  been  studied  earnestly  only 
during  the  last  ten  years.  According  to  Suzuki^,  whose  description  of  the 
disease  we  follow,  it  is  called  Jshikubyo  or  Shikuyobyo  in  Japan.  Like  the 
mosaic  disease,  this  shrivelling  disease  also  occurs  most  extensively  in  the 
tender  leaved  and  quick  growing  varieties.  Within  the  same  cultural 
varieties  the  individuals  suffer  most  strongly  wdiich  receive  too  much  liquid 
fertilizer,  while  trees  planted  in  poor  soil,  or  in  mountainous  regions,  are 
almost  free  from  it. 

The  fact  that  the  disease  became  noticeable  at  about  the  time  when 
the  so-called  "pruning  method"  was  universally  introduced  into  Japan  is  of 
especial  importance.  This  method  consists  in  the  cutting  down  of  the 
trunks,  or  branches,  at  the  time  of  the  most  luxuriant  leaf  development 
(May  to  June),  close  to  the  soil  when  the  plant  is  three  years  old.  The. 
stock  at  once  produces  new,  luxuriant  shoots  which  by  September  have 
become  5  to  6  feet  tall.  These  branches,  in  the  following  summer,  are  cut 
back  again,  either  close  to  the  soil  or  several  feet  above  the  surface.  Speci- 
mens, which  have  been  cut  back  for  a  long  time,  suffer  less  from  the  disease 


1  Delacroix,  G.,  La  rouille  blanche  du  tabac  et  la  nielle,  eta  Compt.  rend. 
1905,  CXL,  p.  G75. 

2  Karosak,  A.,  Eine  neue  Krankheit  der  Erdniisse  in  Deutsch-Ostafrika. 
Gartenflora  1904,  p.  611. 

3  Suzuki,  v.,  Chemische  und  physiologrische  Studien  liber  die  Schrumpfkrank- 
heit  des  Maulbeerbaumes,  eine  in  Japan  sehr  weit  verbreitete  Krankheit.  Zeitschr. 
f.  Pflanzenkrankh.  1902,  p.  203. 


691 

and  it  is  absolutely  unknown  in  regions  where  the  plants,  under  the  old 
cultural  method,  have  not  been  cut  at  all.  Consequently,  we  may  maintain 
with  certainty  that  a  phenomenon  resulting  from  intensive  cultivation  is 
concerned  here.  The  fact  that  the  plants  remain  healthy,  which  were  cut 
back  in  autumn  or  the  early  spring  before  the  opening  of  the  leaves,  favors 
the  theor}^  that  thi's  cutting  during  the  time  of  making  growth  is  the  cause 
of  the  shrivelling  disease.  Diseased  plants  can  be  cured  if  left  unpruned 
for  several  years. 

The  first  indication  of  the  disease  appears  generally  when  the  young 
branches,  breaking  out  from  the  stump  of  the  trunk,  have  reached  a  height 
of  one  foot.  First  of  all,  the  uppermost  surfaces  shrivel  or  show  other 
phenomena  of  weakness.  This  change  advances  gradually  dovvnward, 
while  the  leaves  turn  yellowish  or  dark  green,  or  even  can  retain  their 
normal  color.  This  usually  sets  in  slowly  since,  in  the  first  year,  only  the 
upper  leaves  of  some  shoots  become  diseased.  In  the  course  of  time,  the 
condition  so  spreads  that  the  tree  dies.  There  are,  however,  also  acute 
cases  in  which  all  the  leaves  shrivel  at  the  same  time  in  one  year.  The 
branches  of  the  diseased  plants  are  usually  very  thin  and  develop  very 
numerous  side  branches  and  leaves ;  they  droop  at  times  and  lose  their  stiff- 
ness.    The  roots  begin  to  decay. 

Naturally,  parasites  have  often  been  held  responsible  for  this  disease 
and  the  phenomenon  has  been  declared  to  be  the  result  of  a  parasitic  decay 
of  the  roots  but  the  roots  are  demonstrably  healthy  in  the  first  stages  of  the 
disease  of  the  aerial  parts ;  besides  this,  it  seems  very  remarkable  that  a 
parasite  always  seeks  only  the  trees  treated  with  the  pruning  method. 

With  due  consideration  of  the  preceding  facts,  one  is  forced  to  the  con- 
clusion that  a  continued  disturbance  of  equilibrium  in  the  nutritive  processes 
must  be  the  cause  here.  This  is  confirmed  by  Suzuki's  numerous  analyses. 
He  found,  for  example,  in  the  average  from  ten  experiments  that  in  leaves 
of  plants  suffering  from  the  shrivelling  disease,  when  the  content  of  the 
healthy  leaves  is  set  at  100,  the  water  content  is  94.7  per  cent. ;  the  dry 
substance  116  per  cent.     In  100  parts  dry  substance  the  content  is : — 

(normally  valued  at  100) 

Protein    Si. 8  per  cent. 

Fat    86 

Raw  fibre 81.4  " 

Extractive  substances  free  from  nitrogen 120  " 

Pure  ash   91  " 

Total  nitrogen    81.8  " 

Albuminoid  nitrogen   86.8  " 

Non-albuminoid  nitrogen 66.6 

In  100  parts  ash  content. 

(normally  valued  at  100) 

Si  Oo   I  ^3-1  per  cent.     K,  O 92.3  per  cent. 

SO 97.2       "  CaO 105.5       " 

P.O.     101.6       "  MgO    120.6       " 


692 

Therefore,  a  greater  abundance  of  ash  in  proportion  to  the  organic 
substances  produced,  as  has  been  emphasized  already  as  typical  for  all 
defective  plants. 

The  characteristic  of  the  shrivelling  disease  of  the  mulberry  is  a  con- 
gestion of  starch  in  the  diseased  leaves  and  a  very  scanty  development  of 
the  wood  body,  especially  of.  the  conducting  elements,  the  sieve  tubes.  Be- 
cause of  the  scanty  number  and  small  breadth  of  the  lumina  of  these 
elements,  only  a  ver}'  slow  transportation  of  the  assimilated  material  (here 
especially  sugar)  can  take  place.  Consequently  the  continued  dissolution 
of  the  starch  is  prevented^  Besides  these  anatomical  conditions,  chemistry 
now  proves  the  presence  of  an  abnormally  large  quantity  of  oxydases  and 
peroxydases.  According  to  Woods,  it  is  very  probable  that  the  oxydases 
not  only  destroy  all  the  chlorophyll  but  also  prevent  diastatic  and  proteo- 
lytic action.  On  this  account,  they  might  be  the  cause  of  the  delay  in  the 
transportation  of  the  starch  and  nitrogen  compounds.  At  any  rate,  Shibata- 
maintains,  as  a  result  of  his  experiments,  that  the  diastase  action  is  not  pre- 
vented by  the  oxydase  and  that  a  further  production  of  the  enzymes  would 
be  caused  by  the  entire  elimination  of  the  elaborated  materials.  Later 
experiments  must  make  clear  which  of  these  theories  is  correct.  The  fact 
is  sufficient  for  us  here  that  the  zvhole  amount  of  the  reserve  substances  is 
exhausted  in  the  sick  plants''.  This  is  shown  also  in  the  scanty  filling  with 
starch  of  the  bark  on  the  branches  and  roots  and  of  the  dormant  buds,  and 
manifests  itself  also  in  the  decrease  of  root  pressure  and  the  transpiratory 
intensity  (Miyoshi).  It  is  now  clear  that  if  a  plant  is  continually  forced  to 
use  its  reserve  material  by  the  removal  of  its  foliage,  it  does  not  have  time 
enough  to  mature  the  new  growth,  i.  e.,  to  deposit  sufficient  starch,  albumen 
and  cellulose  in  these  organs. 

The  curing  of  this  disease  will  lie  in  a  return  to  the  normal  fall  pruning. 
As  soon  as  branches  of  diseased  plants  have  developed  their  own  roots  by 
layering,  they  develop  normally  as  Suzuki  has  shown  experimentally. 

Besides  this,  very  similar  phenomena  of  disease  also  occur  in  the  tea 
plant  as  soon  as  the  picking  of  the  leaves  is  carried  on  irrationally. 

The  Sereh  Disease  of  the  Sugar  Cane. 

At  present  the  Sereh  disease,  which  appeared  in  Java  in  the  8o's  of  the 
last  century  and  is  advancing  from  the  West  to  the  East,  is,  indeed,  the 
most  greatly  dreaded  disease  of  the  sugar  cane.  It  has  now  been  observed 
also  in  Reunion,  Sumatra,  Borneo,  Malakka,  the  Mascarrean  Islands,  and 
in  Australia*.    According  to  Kriiger",  whom  we  follow  first  of  all,  the  name 


1  Miyoshi,  M.,  Untersuchung'en  iiber  Schrumpfkrankheit  ("Ishikubyo")  des 
Maulbeerbaumes.     II.     Journ.  Coll.  Sc.  Tokio  1901,  Vol.  XV. 

2  Shibata,  K.,  Die  Enzymbildung  in  schrumpkranken  Maulbeerbaumen.  The 
Botanical  Magazine  XVII,  1903. 

3  Suzuki,  loc.  cit.,  p.  277. 

4  Cit.  Zeitschr.  f.  Pflanzenkrankh.  1901,  p.  297. 

5  Kriig-er,  W.,  ffber  Krankheiten  u.  Feinde  des  Zuckerrohrs.  Ber.  d.  Versuchs- 
station  f.  Zuckerrohr  in  West -Java,  Kagok-Tegal.  Dresden,  Schonfeld's  Verlag, 
1890,  p.  126. 


EDGAR  TULLIS 


PART  IX. 


MANUAL 


OF 


Plant  Diseases 


BY 


PROF.  DR.  PAUL  SORAUER 


Third  Edition --Prof.  Dr.  Sorauer 

In  Collaboration  with 

Prof.  Dr.  G.  Lindau       And       Dr.  L.  Reh 

Private  Docent  at  the  University  AieiBtant  in  the  Museum  of  Naturnt  Hiitory 

of  Berlin  in  Hamburg 


TRANSLATED  BY  FRANCES  DORRANGE 


Volume  I 
NON-PARASITIC  DISEASES 

BY 

PROF.  DR.  PAUL  SORAUER 

BERLIN 


WITH  208  ILLUSTRATIONS  IN  THE  TEXT 


PART  IX. 


MANUAL 


OF 


Plant  Diseases 

BY 

PROF.  DR.  PAUL  SORAUER 


Third  Edition—Prof.  Dr.  Sorauer 

In  Collaboration  with 

Prof.  Dr.  G.  Lindau        And       Dr.  L.  Reh 

Private  Docent  at  the  University  Assistant  in  the  Museum  of  Natural  History 

o(  Berlin  ^n  Hamburg 


TRANSLATED  BY  FRANCES  DORRANGE 


Volume  I 
NON-PARASITIG  DISEASES 

BY 

PROF.  DR.  PAUL  SORAUER 

BERLIN 


WITH  208  ILLUSTRATIONS  IN  THE  TEXT 


Copyrighted.    1920 

By 
FRANCES  DORRANCE 


THE    RECORD   PRESS 
Wilkes- Barr6,    Pa. 


693 

originates  from  the  Javanese  name  for  Andropoijoti  Schoenanthus  (Jav. 
Sereh),  grown  extensively  in  gardens  there.  This  grass  forms  unusually 
greatly  branched  bushes.  In  its  most  highly  developed  form  the  disease  of 
the  sugar  cane  also  appears  in  an  excessive  formation  of  short  lateral  shoots 
which  make  the  plant  look  bushy.  The  root  system  is  poorly  developed  and 
only  slender  roots  spread  out  in  the  soil;  the  majority  remain  short  and 
bushy,  for  their  ti])S  die  and  those  formed  anew  fall  victim  to  the  same  fate. 
Many  parasites  are  found  in  the  dead  tissue ;  among  these,  Tylenchus  Sac- 
chari  Soltw.  is  the  most  common  in  Java.  The  internodes  of  the  stem 
remain  short ;  the  eyes  of  the  leaf  axils  swell  up  round,  while,  in  the  normal 
cane  (with  the  exception  of  a  few  varieties)  they  lie  flat  like  a  shell  in  the 
small  depressions  on  the  stem.  The  growth  of  the  main  shoot  is  sup- 
pressed and,  on  this  account,  the  lower  eyes,  especially  those  below  ground, 
develop  quickly.  In  the  new  shoots,  however,  the  same  process  of  sup- 
pression of  the  apical  growth  is  repeated  immediately  as  well  as  that  of  the 
breaking  of  the  secondary  axes.  In  this  way  the  whole  plant  gets  an  obnor- 
mally  bushy  formation.  The  Javanese  material,  which  I  ordered  for  inves- 
tigation, at  times  showed  such  a  ramification  of  the  lateral  axes  on  tlie 
upper,  higher  parts  of  the  stem  that  groups,  resembling  witches'  brooms, 
were  formed.  All  possible  transitions  between  this  bushy  dwarfing  and  the 
slender  normal  condition  are  found  in  the  different  stages  of  the  disease. 

As  a  result  of  the  great  shortening  of  the  internodes,  the  leaves  stand 
close  to  one  another  like  fans.  The  leaf  sheaths  seem  to  enclose  each  other. 
In  many  cases,  their  death  does  not  take  place  as  it  does  normally  by 
advancing  from  the  edge  towards  the  mid-rib,  but  conversely,  and  the  result 
is  that  they  remain  for  a  long  time  on  the  stem  and  form  nests  for  micro- 
organisms. Their  color  is  usually  darker  than  that  of  the  normally  dead 
leaves  and  while  the  latter  are  tough,  the  abnormal  ones  are  more  brittle 
and  disintegrate  easily.  The  intensive  red  colored  vascular  bundles  are  at 
once  conspicuous  in  a  cross-section  throvtgh  a  node  of  the  diseased  cane. 
This  coloring  matter  may  be  withdrawn  with  alcohol.  The  cell  walls  are 
frequently  swollen  out  of  shape  and  partially  destroyed. 

This  red  coloring  of  the  bundles  occurs  in  cuttings  and  in  older  plants 
in  the  first  stages  of  the  disease,  so  that  it  was  thought  that  they  should  be 
emphasized  as  a  characteristic  especially  deserving  of  consideration. 

We  have  observed  this  red  coloring  of  the  cell  walls  in  many  non- 
parasitic diseases  of  monocotyledons,  and  Busse^  has  been  able  to  produce 
it  artificially  in  the  sorghum  millet  in  German  East  Africa  by  painting  the 
leaf  blades  with  vaseline  or  paraffine  oil.  The  color  spread  still  further  in 
the  xylem  parts  of  the  vascular  bundles  and  was  traced  by  Busse  to  a  dis- 
turbance in  the  respiratory  process.  We  consider  the  red  color  to  be  a 
phenomenon  of  oxidation  which  indicates  a  functional  disturbance  in  the  con- 


1  Busse,  Walter,  Untersuchungen  liber  die  Krankheiten  der  Sorghum-Hii'se. 
Arb.  d.  Biol.  Abt.  f.  Land-  u.  Forstw.  am  Kaiserl.  Gesundheitsamte  1904,  Vol.  IV, 
Part  4,  p.  319. 


694 

ductive  system  due  to  very  different  causes  but  especially  frequent  in  root 
diseases.  It  appears  also  very  clearly  in  the  pineapple  disease,  in  a  parasitic 
disease  of  the  sugar  cane  produced  by  Thielaviopsis  cthaceticus  which  can 
be  transmitted  by  cuttings.  The  greater  the  amount  of  sugar  in  the  stem — 
this  increases  constantly  from  the  base  up  to  about  the  middle  of  the  stem — 
the  more  easily  the  cuttings  become  diseased  by  the  fungi\  The  red  color 
appears  in  the  Sereh  disease  at  times  isolated  in  some  nodes,  while  the  fibro- 
vascular  cords  of  the  underlying  internodes  are  still  uncolored.  It  may  be 
concluded  from  this  that  the  disease  represents  a  general  ailment,  a  constitu- 
tional disease,  which  shows  its  first  visible  symptoms  in  especially  weakened 
places. 

The  cause  of  the  disease  has  been  sought  in  all  kinds  of  influences ; 
exhaustion  of  the  soil,  degeneration  due  to  continual  asexual  propagation, 
abnormal  atmospheric  conditions,  unsuitable  fertilization,  especially  with 
peanut  meal  (Bungkil),  too  deep  planting,  or  too  high  covering  with  earth, 
too  early,  or  too  late  planting,  and  finally  parasites.  Among  the  latter, 
nematodes,  fungi  and  bacteria  come  under  consideration. 

The  conclusions  of  one  scientist  contradict  those  of  another.  Thus, 
for  example,  Kriiger  states  that  he  has  found  bacteria  in  the  ducts  as  a 
constant  accompaniment  of  the  disease,  while  Tschirch-  considers  it  impos- 
sible that  bacteria  can  be  the  cause  of  the  disease  and  sees  the  initial  stages 
in  an  injury  to  the  roots.  Benecke^  sides  with  Kriiger,  Mobius*  opposes  the 
assertion  of  any  existing  degeneration  and  also  seeks  the  cause  in  parasitic 
organisms.  OhP  perceives  the  cause  of  the  Sereh  disease  and  the  disease 
of  the  coffee  tree  in  Java,  in  which  the  leaves  fall,  to  be  the  deforestration  of 
the  mountains  and  subsequent  drought.  Janse*,  in  the  same  way,  traces  the 
disease  to  a  lack  of  water,  since  he  thinks  that  the  gummy  obstruction  of 
the  ducts  prevents  conductivity.  He  connects  the  formation  of  the  gummy 
substance  with  bacteria  (Bacillus  Sacchari).  Went''  considers  the  Sereh 
directly  as  a  gummosis  which  arises  from  the  co-operation  of  a  parasitic 
root  and  leaf  sheath  disease  and  which  may  be  propagated  by  cuttings. 

Wakker*  considers  the  disease  as  a  non-parasitic  gummosis,  associatetl 
with  the  excess  of  water  which  cuttings,  developing  during  the  dry  monsoon, 
suffer  in  the  following  rainy  period. 


1  Cobh,  N.  A.,  Fungus  Maladies  of  tho  Sugar  Cane.  Rop.  Exp.  Stat,  of  the 
Hawaiian  Sugar  Planters'  Association.     Bull.  T>,  Honolulu,  190fi,  Part  1,  p.  218. 

2  Tschirch,  A.,  Vtaer  Sereh,  die  wichtigste  aller  Krankheiten  des  Zuckerrohrcs 
in  Java.     Schweiz.  "Wochenschrift  f.  Pfarmazie  1891. 

3  Benecke,  Franz,  Proefnemingen  ter  Bestrijding  der  "Sereh."  Samarang  1890. 
For  further  treatises  by  this  author  cf.  Zeitschr.  f.  Pflanzenkr.  1891.  p.  3.'^4,  361. 

4  Mobius,  M.,  Over  de  gevolgen  van  voortdurende  vermcnigvuldiging  der 
Phanerogamen  langs  geslachteloosen  weg.  Mededcelingen  van  het  Proefstation 
"Midden  Java"  te  Samarang.  1890. 

s  Ohl.  A.  E.,  Eene  Waterstudie.  Batavia  1891;  cit.  Zeitschr.  f.  Pflanzenkrankh. 
Vol.  I,  p.  365. 

B  Cit.  Zeitschr.  f.  Pflanzenkrankh.  1893,  p.  238. 

7  Went,  F.  A.,  Die  Serehkrankheit;  cit.  Zeitschr.  f.  Pflanzenkrankh.  1894,  ji. 
235  and  1901,  p.  297. 

8  Wakker,  J.  H.,  De  Sereh-Ziekte  S.  A.  Archief  voor  dc  Java-Suikcrindustrie. 
1897,  Afl.  3. 


695 

Thus  the  difference  of  opinion  extends  to  the  most  recent  times^  with- 
out having  led  to  any  positive  reconciUation.  The  reason  probably  lies  in 
the  fact  that  the  characteristics  given  for  the  Sereh  disease  also  occur  in 
other  diseases,  as  will  be  shown,  for  example,  in  the  following  section,  and 
thus  different  investigators  may  have  considered  different  forms  of  the 
disease. 

We  will  emphasize  a  few  facts  from  positive  results,  i.  e.  that  healthy 
cane  can  remain  healthy  in  plantations  suffering  from  the  Sereh  disease,  and 
that  diseased  cane  remains  diseased  in  healthy  fields.  It  should  be  added 
further  that  often  wide  bands  along  the  edges  of  the  fields  appear  diseased 
first,  or  only  the  edges  themselves,  and  that  the  Cheribon  cane,  which  tends 
to  disease  when  planted  in  mountainous  regions,  has  given  healthy  cuttings. 
Some  cuttings  are  practically  immune,  while  others  are  susceptible.  Even 
the  cuttings  of  the  same  variety  from  regions  free  from  the  Sereh  disease 
at  first  remain  healthy,  even  in  infected  regions.  It  is  evident  from  this  that 
the  disease  can  scarcely  be  parasitic  but  falls  under  the  group  of  the  gum- 
moses.  It  can,  therefore,  not  be  contested  that  the  bacterial  gummosis 
conditions  exist  in  the  Sereh  disease,  just  as  in  the  rot  of  our  sugar  beets,  but 
these  forms  also  depend  upon  certain  conditions  of  weakness  of  the  plant 
body  which  we  call  displacement  of  the  enzymatic  functions. 

We  consider  the  causes  of  the  insufficient  ripening  of  the  cane,  i.  e. 
non-deposit  of  reserve  substances,  cane  sugar  in  this  case,  to  be  the  inconsid- 
erate cultivation  of  sugar  cane  with  an  increased  supply  of  fertilizer  and 
water  on  heavy  soil  in  enclosed  positions,  etc.  Actually,  the  loss  in  the 
sugar  content  is  uncommonly  great  in  the  Sereh  disease. 

We  are  not  in  a  position  to  determine  the  process  which  causes  the  lack 
of  reserve  substance.  It  is,  however,  a  matter  of  indifference  in  judging  of 
the  disease,  whether  an  excess  of  destructive  enzymes  is  present  or  a  para- 
lyzation  of  the  constructive  ones.  The  metaboUc  processes,  leading  to  this 
lack  of  cane  sugar,  are  naturally  present  in  the  whole  plant  no  matter  where 
they  make  themselves  felt  symptomatically.  Therefore,  each  smallest  part 
of  the  diseased  cane,  even  if  it  shows  no  symptoms  of  the  Sereh  disease,  is 
actually  predisposed  to  it  and  even  contains  the  carriers  of  the  disease. 
Consequently  each  Bibit  (cutting)  from  the  plant  having  the  Sereh  disease 
is  condemned  to  death  as  soon  as  it  comes  under  conditions  favoring  the 
disease.  It  heals  itself,  however,  and  returns  to  the  normal  enzymatic 
activity  on  tracts  of  land  where  the  Sereh  does  not  break  out. 

From  this  the  best  method  is  clearly  the  choice  of  varieties  immune  to 
Sereh  or,  at  least,  the  cultivation  of  Bibits  in  open,  mountainous  positions 
and  other  locaUties  which  do  not  permit  the  disease  to  occur.  Probably  a 
change  in  cultivation  takes  place  in  such  a  way  that  only  weak  fertilizing 
and  more  porous  soils,  as  well  as  open  positions,  are  used  in  the  cultivation 


1  Hein,  A.  S.  A.,  Hypothesen  en  Ervaring-  omtrent  de  Sereh  ziekte.  De 
Tndische  Mercuur.  Amsterdam  1905;  cit.  Jahresber.  f.  Pflanzenkrankh.  v.  Hollrung, 
Vol.  VIII.  1906,  p.  245. 


696 

of  cane;  these  also  cause  a  standstill  in  the  Sereli  disease  in  distinct  centres 
of  the  disease. 

We  believe  also  that  the  diseases  termed  the  rusts  of  sugar  cane  belong 
here.  ( )f  these,  wc  refer  here  to  the  Powdery  Disease  described  by  Spegaz- 
zini'.  which  occurs  also  with  red  spots  and  a  gummy  secretion  but  becomes 
noticeable  because  of  its  unpleasant  smell.  The  base  of  the  stem  suffers 
especially.  A  bacillus  (Hacilliis  sacchari)  may  be  isolated  from  the  gummy 
slime  which  rcf|uires  an  acid  nutrient  sulistratiun  and  produces  a  protein 
decay  which  gi\es  rise  to  the  otTensi\e  smell  of  the  diseased  cane.  This 
disease  also  occurs  with  .  liidropoiioii  )iiilans  In  regard  to  the  production 
of  the  red  color  in  the  vascular  bundles  and  of  the  gum  in  the  sugar  cane 
by  micro-organisms,  Grieg  vSmith's-  work  is  of  especial  importance.  He 
found  reddened  vascular  bundles  in  otherwise  healthy  cane  as  well  as  in  the 
stems  which  had  become  gummy  because  of  Bacillus  vascularum  Cobb.  The 
red  color  was  produced  by  the  tilling  of  the  large  ducts  with  a  red  gum  just 
as  in  the  Sereh  and  other  sugar  cane  diseases.  He  found  further  a  fungus. 
wliicli  produced  a  shiny,  very  scarlet  color  on  nutritive  media  with  dextrose 
but  no  gum,  and  gum  bacteria  in  the  diseased  ducts,  especially  Bacillus 
Pseudarabinus  n.  sp.  Bact.  Sacchari  ("this  variety  normally  lives  in  the 
sugar  cane")  and  besides  this  Bacillus  vascidarum.  On  sheets  of  nutrient 
agar  with  laevulose,  the  fungus  produces  no  coloring  matter,  but  in  combi- 
nation with  Bacillus  pseudarabinus  a  bright  scarlet  is  produced  and  in  com- 
ftination  with  Bact.  Sacchari,  a  rusty  brown. 

It  will  be  seen  from  these  examples  how  the  constitution  of  the  sub- 
stratum is  able  to  modify  the  ]^arasitic  activity  and  in  what  way.  therefore, 
different  aspects  of  disease  are  produced.  A  preliminary  condition  neces- 
sary for  the  production  of  the  disease  is.  however,  a  deviation  from  the 
normal  metabolic  processes  in  cane,  healthy  up  to  that  lime,  which  favors 
an  increase  of  bacteria  (probably  always  ijresent)  and  which  appears  sooner 
or  Liter  in  the  dilferent  susceptible  \arieties  of  cane  but  remains  suppressed 
in  the  innnune  \arieties. 

Cop.b's  Disf.asf.  of  the  Sugar  Cane. 

According  to  T'Twin  .Smith",  the  .'^ereh  disease  resembles  in  many  ways 
the  disease  of  the  sugar  cane  occurring  in  Australia  (and  es])ecially  in 
jVIauritis,  jaxa  and  lirazil),  which  Cobb  describes.  Hiis  latter  disease  is 
characterized  b)'  diminutive  growth,  shortening  of  the  internodes,  albinism, 
premature  sprouting  of  the  buds,  and  i)ropagation  by  infected  cuttings.  It 
diiTers  essentially.  howe\er,  from  the  .Sereh,  since  the  heart  of  the  cane  stalk 
becomes  lignilied  and  masses  of  yellow  slime  (gum)  occur  constantly  in  the 


1  Spegiizzini,  T^a  g.ingrona  humida  o  polvillo  do  la  carina  de  zucchfjo.  Rivista 
azucarera  1895. 

-'  Smith  R.  Grieg,  Sidney.  Bakteriolog-.  T^ahoratorium  der  Linnean  Soc.  of  New 
Soutli  Wales.     Central))!,  f.  liakt.  usw.  1906.     Vol.  XV,  No  25.  p.  733. 

3  Smith,  Krwin,  Ursache  der  Cobb'schen  Krankheit  des  Zuckerrohres.  Central- 
blatt  f.  Bakteriologie  usw.  1904.    Vol.  XIII.     Part  22,  23. 


697 

blood  red  bundles  of  the  trunk.  It  has  been  proved  by  careful  inoculation 
experiments  that  the  cause  of  the  disease  is  Pseudomonas  (Bacillus  Cobb) 
vascularum. 

Smith  considers  the  red  coloration  of  the  branches  (corresponding  to 
the  brown  coloration  of  bacterial  gummoses)  as  a  reaction  of  the  plant. 
According  to  Prinsen  Geerlings,  a  neutral  uncolored  substance,  dissolving 
with  difficulty,  exists  in  the  cellulose  of  the  normal  sugar  cane,  which  turns 
yellow  with  the  action  of  an  alkali  (like  tannin),  but  becomes  red,  when 
aerated,  and  later  brown. 

The  interesting  result  is  the  definite  proof  that  certain  varieties  of  cane 
(common  green  cane)  in  inoculation  experiments  show  extraordinarily  great 
susceptibility,  while  other  varieties  (for  example,  common  purple  cane) 
become  only  slightly  diseased.  The  sap  of  the  latter  canes  showed  approxi- 
mately a  doubled  acid  content  and  Smith  surmises  that  the  high  suscepti- 
bility to  parasites  depends  "only  on  the  weak  acidity  or  the  minimal  occur- 
rence of  a  specific  arresting  acid."  Cobb  reports  that  where  such  resistant 
varieties  are  grown  the  disease  has  disappeared. 

To  the  same  group  of  diseases  belongs  also  the  disease  of  the  sugar 
beet  which  I  first  described  as  "bacterial  gummosis"  and  later  as  "beet  tail 
rot.""*-  So  far  as  can  be  determined  experimentally,  the  bacteria  have  an 
epidemic  distribution  only  if  continued  heat  and  drought  with  abundant 
nitrogen  fertilization  weaken  the  growth  of  the  beets.  If  wet  weather 
sets  in  with  the  same  excessive  fertilization,  the  yield  in  sugar  becomes 
considerably  less,  but  the  bacterial  gummosis  is  lacking\ 

Peach  Yellows. 

Since  1887  a  disease  of  the  peaches  in  the  United  States  of  North 
America  has  been  studied  very  earnestly.  It  has  caused  uncommonly  great 
injury  to  extensive  orchards.  A  yellow  disease  (chlorosis)  is  concerned 
here  which  is  transmissible  by  grafting-.  This  condition  of  yellow  foliage 
differs  in  this  from  the  similar  phenomena  caused  by  a  lack  of  nutrition, 
frosts,  etc.  In  this  disease,  which  has  constantly  increased  in  the  last  20 
years  and  has  made  the  cultivation  of  the  peach  unprofitable  in  many  places 
(in  the  Delaware  and  Chesapeake  regions),  a  peculiar  red  mottled  condition 
and  a  premature  ripening  of  the  fruit  are  very  characteristic.  To  this 
should  be  added  the  premature  development  of  the  winter  buds  and  the 
extensive  development  of  latent  and  adventitious  buds;  therefore,  a  diseased 
branch  as  in  the  Sereh  disease.  Although  the  fruit,  which  at  times  has  red 
stripes  extending  into  the  flesh,  attains  a  normal  size  in  the  first  year,  it 
becomes  smaller  in  the  following  years  of  the  disease,  and  tasteless,  or  even 
bitter.     The  phenomenon  is  restricted  at  first  to  a  few  branches  and  then 


*     See  V.  2  of  the  Manual,  p.  42. 

1  Zeitschr.  f.  Pflanzenkrankh.  1S92,  p.  2S0.  1S96,  p.  296,  and  1S97,  p.  06.  Blatter 
■  f.  Zuckerrubenbau  1S94,  p.  1. 

-  Smith,  E.  F.,  in  Report  of  the  chief  of  the  Section  of  Veg-etable  Pathology. 
Washing-ton,  1890.  Smith,  Erwin  F.  Additional  evidence  on  the  communicability 
of  peach  yellows  and  peach  rosette.     Washington  1891,  Bull.  1. 


698    . 

extends  gradually  over  the  whole  tree.  At  the  same  time  the  foliage  begins 
to  turn  yellowish  green  in  places  and  weakly  pale  shoots  break  out  from  the 
bark.  The  foliage  developed  in  the  following  spring  appears  yellow,  or  a 
reddish  green,  the  new  shoots  are  stunted  and  their  leaves  roll  and  curl.  At 
times  the  tips  of  all  the  healthy,  slender  shoots  suddenly  show  a  continually 
repeated  formation  of  lateral  axes  which  become  weaker  and  weaker  and 
whole  nests  of  sprouts  are  produced  (usually  in  the  autumn).  Death  occurs 
sooner  or  later.  In  budding  with  healthy  eyes  from  diseased  trees,  a  large 
percentage  of  the  budded  trees  seems  to  be  sick  and,  in  fact,  not  only  the 
shoot  developed  from  the  eye  itself,  but  also  the  stock,  similar  to  the  varie- 
gation in  albinism. 

The  rosette,  which  occurs  also  in  plums,  was  considered  at  first  a 
variety  of  the  peach  disease  here  described,  but  later  Smith  held  it  to  be  a 
specific  disease.  Its  course  is  uncommonly  rapid,  so  that  death  occurs  in 
the  same  year,  or,  at  the  latest,  in  the  following  year.  Here,  too,  the  leaf 
rosettes  are  produced  by  a  strikingly  abundant  development  of  latent  eyes 
and  the  development  of  lateral  shoots,  which  attain,  however,  scarcely  one- 
sixth  the  length  of  normal  shoots.  These  may  develop  other  side  shoots, 
which  again  branch.  Such  nests  of  branches  often  contain  from  200  to  400 
small  leaflets  and  malformed  stipules.  At  the  bases  of  the  shoots  the  leaves 
are  larger  and  better  developed  but  peculiarly  rolled  in  at  the  edges  and 
strikingly  stiff,  because  of  a  certain  rigidity  of  the  mid-rib.  These  leaves 
turn  yellow  in  the  early  summer  and  drop.  In  the  course  of  the  summer 
the  rosettes  dry  up;  the  blossoms  of  the  diseased  shoots,  however,  do  not 
develop  earlier  than  those  of  the  healthy  shoots,  but  rather  somewhat  later. 
On  the  other  hand,  all  the  fruits  which  become  gummy  fall  when  still  green 
and  never  show  the  red  specking  as  in  peach  yellows.  In  both  diseases  the 
line,  lateral  roots  are  found  to  be  shrivelled  and  dead  and  the  rosette  disease 
is  often  accompanied  by  abundant  gum  centres.  This  rosette  disease  may 
also  be  carried  to  the  stock  in  budding.  Only,  as  a  rule,  very  many  more 
normal  lateral  eyes  in  a  shoot  develop  into  rosettes  and,  thereby,  the  bushy 
formation  becomes  denser  than  in  the  peach  yellows. 

Opinions  as  to  the  cause  of  this  disease  are  divided,  yet  the  bacterial 
theory  has  become  less  prominent  since  it  has  been  recognized  that  in  many 
cases  mycelium  and  bacteria  have  not  been  found.  For  this  reason  the 
theory  has  become  much  more  universal  that  a  constitutional  disease  is 
concerned  here,  in  which  substances  due  to  an  abnormal  metabolism  may 
be  transmitted  by  grafting  as  in  albinism  and  the  mosaic  disease.  In  fact, 
here,  the  transmission  probably  takes  place  through  the  pollen,  for  Morse' 
has  observed  that  out  of  three  varieties  of  peaches,  two  became  diseased, 
while  the  third,  the  white  Magdalene,  remained  healthy.  This  variety  could 
not  be  crossed  with  others. 


1  Morse,  E.  W.  On  the  power  of  some  peach  trees  to  resist  the  disease  called 
"yellows."  Bull.  Biissey  Institution,  Cambridge,  1901;  cit.  Ztntschr.  f.  Pflanzenkr. 
1902,  p.  58. 


699 

Of  the  unusually  numerous  practical  experiments  made  especially  by 
Smith^,  it  can  be  only  stated  as  a  result,  that  no  one  has  succeeded,  as  yet, 
in  obtaining  any  indication  of  the  cause.  In  ordinary  years,  a  lack  of  nutri- 
tion, or  its  excess,  can  not  be  considered  as  a  reason  for  the  disease.  Still  it 
may  be  observed  that  rainy,  cool  summers  show  a  decrease  of  the  disease 
and  dry  periods,  an  increase.  Grafting  on  the  Marianna  plum  was  found 
to  be  apparently  a  protection  against  the  rosette  disease,  since  the  eyes  from 
the  diseased  peach  developed  to  healthy  shoots.  Infection  experiments  with 
about  twenty  different  kinds  of  bacteria  and  yeasts,  taken  from  the  tissue  of 
diseased  peaches,  gave  no  other  result  than  a  swelUng  in  a  few  cases  at  the 
point  of  infection  or  an  exudation  of  gum-. 

The  almond  suffers  from  both  of  these  diseases  and  apricots  and  Japa- 
nese plums  from  the  yellows^. 

In  my  opinion,  injuries  are  concerned  here  which  are  produced  by 
intensive  cultivation  and  lack  of  consideration  of  the  soil  requirements  of 
the  peach.  In  the  long  run,  all  heavy  soils,  rich  in  fertilizers,  become 
dangerous  for  the  peach.  In  combatting  this  disease,  it  might  be  well  to 
consider  primarily  cultivation  on  light  soils  and  in  open  places. 

GUMMOSIS  OF  THE  ChERRY. 

The  exudation  of  gum  is  well  known  as  a  widespread  phenomenon 
especially  among  the  stone  fruits  and  can  be  produced  by  very  different 
kinds  of  causes. 

With  us,  the  cherry  and  the  peach  suft'er  most  frequently  from  gum 
exudations.  We  sometimes  find  light  yellow,  transparent  masses,  at  other 
times  brown,  cloudy  solid  ones,  extending  over  a  part  of  the  bark  of  a 
branch  or  the  trunk.  These  masses  are  soluble  in  boiling  water;  insoluble 
in  alcohol  and  cannot  be  crystalized.  When  boiled  with  dilute  sulfuric  acid, 
the  jam  contains  a  sugar  which  can  ferment  and  yields  mucic  acid  when 
treated  with  nitric  acid.  They  belong,  therefore,  to  that  group  which 
organic  chemistry  terms  Gums.  Different  varieties  of  gums  have  been  dis- 
tinguished, according  to  their  capacity  for  swelhng  in  water.  Gum  per- 
fectly soluble  in  cold  water  is  called  Arahin,  which  has  all  the  characteristics 
of  an  acid*.  The  gum  tragacanth  which  swells  up  in  water  to  a  sticky  jelly 
is  a  representative  of  the  Bassorin  group,  and  the  modification  of  Bassorin 
is  called  Cerasin,  which  is  soluble  in  boiling  water.  Cherry  and  plum  gums 
are  a  mixture  of  Arabin  and  Cerasin.  We  may  assume  that  the  gum  formed 
in  gummosis  changes  its  constitution  according  to  the  time  of  its  production 
and  the  character  of  the  tissues  from  which  it  is  produced.  It  may  have 
some  relationship  with  pectin  substances.  Gum  arable  has  the  character  of 
an  organic  calcium  salt. 


1  Smith,  E.  F.     Experiments  with   fertihzers,   etc.;    cit.  Zcitschr.  f.  Pflanzenkr. 
1R94,  p.  177. 

2  Smith,  E.  F.     Additional  notes  on  peacli  rosette.     The  .Tournal  of  Mycology, 
Vol  VII,  No.  3,  1893. 

•T  Cit.  Zeitschr.  f.  Pflanzenkr.nnkh.  1S9G,  p.  ir)6. 

4    Czapek,  Fr.     Bionhemic  d.  I'flanzen.  I.eipzig-,  190;",  Vol.  T,  p.  .'irid. 


70f^ 

We  jjc't  tlic  host  insi.Ljht  into  tlu-  nature  of  the  disease  by  considering 
the  young  gummed  lateral  cherry  branch  illustrated  in  L'ig.  155.  i  and  2. 
Isolated  ducts  are  shown,  first  of  all,  in  the  middle  of  the  normal  wood, 
which  are  entirely  filled  with  gum  (Fig.  155  2a).  This  gum  has  been 
formed  in  part  from  the  secondary  membranes  of  the  ducts.  When  treated 
with  hydrochloric  acid,  whicli  colors  the  walls  of  the  wood  cells  and  ducts  a 
brilliant  carmine,  as  well  as  the  bast  fibre  cells,  the  breaking  down  of  the  still 
red  wall  of  the  duct  into  yellow  gum,  found  licrc  in  drops,  may  be  easily 
recognized.  This  phenomenon  is  fre(iuently  only  a  forerunner,  or  accom- 
{laniment  of  a  mucli  more  extinsi\e  formation  of  gimi,  whereby  large  gum 
centres  are  produced  in  tlie  wood  and  in  the  bark. 

Even  in  one  year  old  branches,  it  is  possible  to  discover  the  first  traces 
of  the  gummy  exudation  liy  examining  closely  cross-sections  of  young 
branches  in  which  gummosis  is  recognizable  to  the  naked  eye  only  in  the 
occurrence  of  extremely  small  black  points.  Ligliter  colored  places  appear 
at  times  in  the  wood  body  which,  with  more  thorough  investigation,  are 
found  to  be  composed  of  parenchymatous  instead  of  prosenchymatous  cells. 
This  abnormal  wood  parenchyma  (Fig.  155  ^  />.)  is  usually  enclosed  by 
normal  wood,  which  separates  it  also  from  the  cambium  (2c).  As  a  rule, 
these  lighter  colored  places,  which  are  usually  deposited  side  by  side,  parallel 
to  the  periphery,  and  usually  se])arated  by  thin  radial  stripes  of  normal 
wood,  are  found  in  dilTercnt  dcNcIopmental  stages.  Some  are  i)erfectly 
unimpaired;  others  show  cells  near  the  centre  which  have  already  changed 
to  gum.  ]n  the  same  cases,  all  the  abnormal  parenchyma  and,  in  the  same 
way,  the  normal  wood,  are  entirely  changed  to  gum  (Fig.  155  2d).  In  this, 
the  intercellular  substances  are  dissolved  first  of  all;  then  follow  the  i)ri- 
mary,  and  finally  the  secondary  membranes  of  the  ducts  and  the  wood  cells. 
In  such  large  gum  holes,  a  peculiar  process  of  growth  of  some  cells  sets  in, 
together  with  the  simultaneous  dissolution  of  the  remainder.  While  the 
wood  cells  and  ducts  especially  undergo  gummosis,  some  medullary  ray  cells 
at  first  grow  longer.  The  starch  which  they  contain  is  dissolved ;  in  a  few, 
two  new  cells  may  be  observed,  which  elongate  in  different  directions.  The 
medullary  ray  cells,  lying  more  toward  tin-  centre  and  somewhat  removed 
from  the  gum  centre,  round  oiT  and  sometimes  elongate.  In  this  way  arise 
many  celled  filaments,  v^hich  remind  one  of  certain  algae  (Trentepohlia) 
(^'ig-  155  "0  ^^^  which  grow  freely  into  the  gurrimy  mass.  They  are 
also  dissolved,  beginning  at  the  outside,  but  this  does  not  take  ])]ace  in  any 
definite  order.  Often  the  cells  at  the  tip  of  the  filament  are  found  dissolved, 
with  the  exception  of  a  thin  remnant  of  the  walls.  In  other  cases  the  cells 
at  the  base  are  dissolved  and  then  the  piece  of  the  filament,  which  has  becf)me 
free,  lies  isolated  in  the  gummy  mass. 

Very  similar  j)rocesses  are  found  in  the  l)ark,  the  thin  walled  bast  cells 
of  which  (Fig.  155  h)  very  easily  succumb  to  gummosis.  The  gum  centres 
are  met  with  much  more  frequently  in  the  bark  than  in  the  wood.     In  rare 


Fig.   155.     Year-old   twig-  ot  sweet  cherry  witli   mature   sum   cavity   and   parencliy 
matous  tissue  agg-regations  in  the  healthy  wood.  " 


702 

cases  I  have  found  the  initial  stages  only  in  the  cambium  itself  and,  in  fact, 
more  frequently  in  the  peach  than  in  the  cherry. 

However,  where  the  initial  stages  can  be  found,  the  evil  is  always 
dangerous  because  it  spreads  further.  Gummosis  produced  in  the  wood  soon 
spreads  to  the  cambium  and  the  bark,  when  it  becomes  very  extensive  in  the 
bark,  and  thus  may  furnish  the  greatest  part  of  the  gum  on  the  exterior  of 
th6  trunk;  the  cambium  also  does  not  escape  later.  The  assertion  that 
gummosis  always  begins  in  the  cambium  is  correct  only  if  by  cambium  is 
meant  the  primordia  of  imperfectly  developed  cells  which  later  fall  victim 
to  liquefication.  The  profess  of  liquefication  itself  can  begin  at  any  place  in 
the  branch  and  long  after  the  formation  of  these  tissues  has  taken  place. 
On  this  account,  we  find  gum  holes  in  the  middle  of  the  wood  body. 

The  ultimate  result  is  essentially  the  same.  At  some  point  in  the  cir- 
cumference of  the  trunk,  the  cambium  is  finally  destroyed  and  the  already 
matured  wood  becomes  more  or  less  diseased.  A  wound  thus  appears 
which  spreads  further  and  further.  This,  however,  is  not  always  recog- 
nizable externally,  for  the  diseased  place  is  not  indicated  by  gum  which  has 
exuded  to  the  outside.  The  gum  comes  to  the  surface  rarely,  or  only  very 
late,  if  the  cambium  is  first  attacked  by  gummosis.  Then  the  solid,  already 
matured  wood  dies  slowly  and,  in  fact,  gradually  more  toward  the  centre  of 
the  trunk,  i.  e.  toward  the  pith  (Fig.  155  2k)  than  toward  the  circumfer- 
ence. This  arises  from  efforts  at  localization,  which  occur  simultaneously 
with  the  disease.  A  case  illustrated  in  the  drawing  (Fig.  155  i  g)  and 
occurring  not  infrequently,  consists  in  the  drying  up  of  the  bark  above  the 
affected  wood,  with  the  exception  of  a  few  bast  bundles,  and  not  its  dissolu- 
tion. At  that  place,  the  part  marked  IV  in  the  figure  is  bridged  over  by 
bark  elements  (Fig.  2  r).  The  formation  of  gum  is  not  very  extensive  but 
the  attempt  of  the  tree  to  heal  the  wound  becomes  more  noticeable.  This  is 
perceptible  in  one-year-old  branches.  Figure  155  i,  illustrating  a  gnm 
pocket  a  year  old,  shows  at  u  the  attempt  of  the  tree  to  overgrow  the  place 
(during  several  years)  :  a  indicates  a  branch. 

A  more  abundant  formation  of  wood  and  bark  on  the  healthy  part  of 
the  trunk,  lying  next  to  the  wound  (Fig.  155  2  h)  makes  the  trunk  thicker 
on  the  wounded  side  than  on  the  healthy  side  (!')  and  above  and  below  the 
wound.  If  the  bark  is  retained  above  the  wound  the  edges  of  the  over- 
growth (Fig.  155  w)  have  raised  the  dry  bark  from  the  dead  wood  and  in 
this  way  a  cavity  forms  of  which  the  back  wall  is  formed  from  the  wood 
and  pith  partially  attacked  by  gummosis  and  the  front  wall  by  the  dry  bark 
(not  drawn  in  the  figure)  and  the  sides  of  the  freshly  formed  callus  («  u). 
The  cavity  thus  produced  is  a  lodging  place  for  insects  and  fungi. 

The  newly  formed  callus,  however,  rarely  remains  intact.  In  the 
majority  of  cases,  small  gum  centres  (Fig.  155  2d')  are  found  in  the  lux- 
uriantly developed  new  tissues.  To  be  sure,  the  living  bark  attempts  to 
enclose  the  diseased  places  by  layers  of  cork,  but  I  have  never  been  able  to 


703 

find  a  case  of  healing.  The  difficulty  in  closing  the  wound  is  explained  by 
the  presence  of  new  gum  centres  in  the  callus. 

We  have  the  following  points  to  emphasize  from  the  consideration  of 
the  cherry  branch  affected  by  gummosis  here  illustrated,  i.  The  pro- 
duction of  parenchymatous  tissue  groups  between  the  prosenchymatous 
elements  of  the  wood.  2.  The  position  of  the  groups  between  two  medul- 
lary rays  which  can  curve  about  the  parenchyma  aggregations,  and,  more 
rarely,  are  able  to  participate  in  their  formation.  3.  The  production  of 
these  groups  independently  of  wounds.  4.  The  liquefaction  of  these  tissue 
aggregations  into  gum  pockets  into  which  the  resistant  medullary  ray  cells 
grow  like  threads.  The  last  circumstance  is  explained  by  the  fact  that  in  the 
same  cambial  ring  zone  of  the  branch,  or  trunk,  the  medullary  cells  develop 
more  rapidly  than  the  tissue  lying  between  them,  and,  therefore,  are  elon- 
gated further  radially  into  the  bark  body  where  they  function  as  parenchy- 
matous tissue.  At  the  time  when  the  process  of  liquefaction  begins,  the 
medullary  ray  cells,  therefore,  are  tougher  and  more  resistant  and  the  first 
gummy  centres  appear  as  holes  between  two  medullary  rays  when  the 
gummosis  is  not  caused  by  wounds. 

The  more  recent  experiments  attempting  to  explain  the  production  of 
gum  exudation^  begin  with  the  phenomena  of  injury.  Beijerinck  and  Rant- 
assert  in  their  very  thorough  work  that  the  gummy  exudation  depends  "on 
the  abnormal  development  of  the  embryonic  wood  tissue  caused  by  the 
wound  stimulus." 

Beijerinck  presents  the  subject  thus :  the  normal  plant  forms  cytolytic 
substances  which  take  part  in  the  formation'  of  ducts  and  tracheids.  The 
physiological  gum,  thus  produced,  is  in  fact  usually  entirely  re-absorbed,  yet, 
under  certain  circumstances,  it  remains  demonstrable  as  such  even  in  the 
cavities  of  the  mature  ducts.  The  "gummy  exudation,  therefore,  depends 
upon  an  abnormal  increase  of  the  action  of  those  cytolytic  substances  under 
the  influence  of  dying  cells,  perhaps  because  an  especially  large  number  of 
these  are  produced  in  necrobiosis.  By  necrobiosis  is  meant  the  cell  activity 
after  the  death  of  the  protoplasm,  while  the  enzyme  bodies  remain  active." 

Ruhland^  opposes  this  theory.  He  calls  attention  first  of  all  to  the  fact 
that  gummosis  can  take  place  in  seeds,  fruits*,  leaves  and  also,  in  the 
phellogen,  on  which  last  point  he  lays  especial  stress.  He  found  considerable 
masses  of  gum  in  the  youngest  phellogen  of  Prunus  Cerasus  and  thinks  that 


1  Compare  the  second  edition  of  this  manual  for  older  points  of  view. 

2  Beijerinck,  M.  W.,  and  Rant,  A.  Wundreiz,  Pai-asitimus  and  Gummifluss  bei 
den  Amygdalaceen.  Centralbl.  f.  Bakteriol.  usw.  1905,  XV,  No.  12.  Rant.  A.  Die 
Gummosis  der  Amyg-dalaceen.     Dissertation,  Amstei'dam,  1906. 

3  Ruhland,  W.  Zur  Physiologie  der  Gummibildung  bei  den  Amyg-dalaceen.  Ber. 
d.  Deutsch.  Bot.  Ges,  1907,  Vol.  XXV,  p.  302. 

4  The  gum  exudation  appears  especially  frequently  in  plums  in  wet  years.  As  a 
rule,  it  forms  in  little  drops  of  gum  as  clear  as  water  which  come  from  wounds  in  the 
fruit  flesh  made  by  insects.  Often  no  insect  injury  can  be  recognized,  and  then  the 
places  bearing  the  drops  are  usually  harder  and  somewhat  flattened.  A  considerable 
accumulation  of  gum  is  found  in  the  fruit  itself  beneath  these  flattened  places.  I 
also  found  gummification  of  the  pits  of  plums  along  the  line  of  union  of  the  halves, 
so  that  under  slight  pressure  the  two  fell  apart. 


704 

"a  universal  [K'culiarity  nl  embryonic  cells  is  concerned  in  this  .i^umniy  disso- 
lution which,  however,  docs  not  extend  so  far  as  dissolution  in  normal  life, 
but  only  when  caused  by  some  further  impetus."  Kuhland  investigated  the 
abnormal  tissue  groups,  which  may  be  observed  in  the  production  of  the  gum 
canal  and  found  cells  enlarged  to  vesicles  with  two  fully  developed  nuclei 
but  without  the  formation  of  any  cell  wall  between  them.  The  process  is 
explained  by  the  adjacent  Fig.  15O. 

Therefore,  the  cell  iilaments,  whicli  extend  into  the  gum  centre,  are 
produced  by  the  "repeated  divisions  of  a  cell  which,  not  diseased,  lies  at  the 
base  of  the  filament,  while  the  daughter  cells,  thus  produced,  only  increase  in 
size  without  division."  The  normal  process  of  wall  formation  is  arrested 
in  the  embryonic  cell  and  tlie  carbo-hydrates,  designed  for  the  formation  of 
cross  walls,  are  transformed  into  gum  substances.  The  reason  for  the 
change  may  be  sought  in  the  fact  that,  because  of  some  injury,  the  embryonic 


Fig-.  156.     Sections  tiiroush  gum-forming-  tissue   (fixed  with  cyirom-iicetiite 
witli  sal'runin-gentian-violet  orange.      (After  liuhiiind.) 


stained 
./  a  cell  filament.  />'  a  yoiiiiR  Rruiu  center:  at  a  and  f>  cell.';  with  two  nuclei 


tissues  are  made  accessiltle  to  the  oxygen  of  the  air;  the  carbo-hydrates, 
really  destined  for  cross-wall  formation,  will  then  pass  over  into  the  gum 
which  is  richer  in  oxygen,  (iriiss^  explains  the  oxidation  by  means  of 
oxygen  carriers  which  are  formed  in  the  tissue  during  growth.  W'iesner- 
had  earlier  assumed  a  ferment  which,  like  diastase,  turns  the  guaiac  emul- 
sion blue  and  is  destroyed  by  boiling.  When  treated  with  Orcin  or  hydro- 
chloric acid,  a  red  or  violet  color  appears  after  a  short  boiling,  and  a  blue 
precipitate  fornis.  In  the  initial  stage  of  gummosis,  only  the  contents  of  the 
I)arenchyma  cells  are  found  to  discolor  in  this  way,  from  which  it  may  be 
concluded  that  the  ferment  has  its  seat  in  the  protoi)lasm.  The  ferment  has 
been  pro\cd  in  tlie  gums  of  seed  and  of  stone  fruit  trees,  in  gum  araliic  and 
other  kinds  of  gum.     Ruhland's  experiments  with  the  removal  of  oxygen, 


1  Oriiss,  tjber  Liosung  u.  Tiildiing  d.  aus  Heinicclliiloso  bestohi^nden  Zc^llvviindc 
und  ihre  Bezieliiuig  zur  Gummosis.    Ril)l.  bot  Heft  39,  Stuttgart  1896,  Erwin  Naegele. 

-  Wiesner,  tjljer  ein  Ferment,  welche'^  in  der  F'flanzc  die  Umwandlung  der 
Cellulose  in  Gummi  und  Schleim  bcwirkt.  Bot.  Zeit.  1885,  No.  37. 


705 

m  which  production  of  the  gum  centres  was  suppressed,  show  that  a  supply 
of  oxygen  seems  to  be  an  absolute  necessity. 

In  our  opinion,  the  necrobiosis  theory  of  Beijerinck  and  Rant  is  unten- 
able, since  gummosis  may  be  found  with(Kit  any  previous  presence  of  dead 
cells  in  very  young  branches  and  one-year-old  seedlings  in  places  which 
represent  still  intact  cell  centres  such  as  in  Fig.  155  2 p.  Therefore,  the 
wound  stimulus  does  not  enter  into  the  ([uestion  here.  We  believe  rather 
that  all  embryonic  and  mature  cells  are  capable  of  forming  gum  as  soon  as 
certain  processes  of  cell  wall  formation,  or  maturation,  are  suppressed.  This 
prevention  of  the  normal  maturing  of  the  cell  wall  can  be  caused  very  well 
by  an  increased  supply  of  oxygen.  This  oxygen,  however,  can  be  directly 
atmospheric  oxygen  only  in  case  of  injury,  but  probably  is  only  rarely 
actually  such,  being  furnished  rather  by  substances  which  carry  oxygen  as 
Griiss  explains.  Substances  of  this  kind  are  present  in  the  iionnal  ijroivtli 
of  trees.  In  an  exudation  of  gum  only  an  abnormal  increase  in  the  amount, 
or  the  length  of  action  of  these  substances  is  involved^  This  increase  can 
take  place  because  of  wound  stimulus.  It  can  also  be  produced  by  different 
parasites  and,  finally,  developed  by  inorganic  poisons.  In  the  latter  connec- 
tion. I  would  mention  my  experiments  in  introducing  a  weak  oxalic  acid 
solution  under  the  bark  of  perfectly  healthy  cherry  trees.  In  the  course  of 
the  summer  profuse  streams  of  gum  were  produced  which  gradually  ceased 
because  of  the  dying  out  of  the  oxalic  acid  action  and  they  did  not  continue, 
for  example,  in  wounds  which  had  received  only  distilled  water  instead  of 
the  oxalic  acid. 

In  regard  to  the  manner  in  \\hich  gum  exudations  can  develop  we  will 
take  as  a  basis  the  theories  formulated  by  Griiss'-. 

In  his  investigations,  this  scientist  has  come  to  the  conclusion  that  the 
hemi-celluloses.  Mannan,  Galactan  and  Araban  are  deposited  directly,  or 
indirectly,  as  reserve  substances.  This  takes  place  directly  in  the  form  of 
thickened  cell  walls  in  the  endosperm  of  the  seed  (Phoenix,  Phytelephas), 
or  in  the  form  of  secondary  thickening  layers  in  libriform  or  wood  paren- 
chyma cells  (different  varieties  of  Astragalus,  Prunus,  Acacia,  etc).  They 
can  be  considered  as  indirect  reserve  substances  if  they  compose  the  cell 
walls  of  cells  containing  starch,  such  as  those  in  the  endosperm  of  the 
Gramincae.  The  hemi-celluloses,  Galactan  and  Araban,  are  changed  by 
enzymes  into  the  gums  Galactin  and  Arabin  and  can  migrate  in  the  tissue 
even  before  they  have  l)ccn  transformed  into  the  sugars  galactose  and 
arabinose. 


1  These  substances  arc  found  in  varying  amounts  in  the  tree  according-  to  the 
individual,  the  place  of  growth,  the  time  of  year,  etc.  This  explains  also  the  different 
results  when  the  gum  exudation  is  produced  by  injuries.  Thus,  for  example,  the 
youngest  tips  of  the  branches  are  not  the  ones  most  endangered  in  this,  but  the 
region  in  which  the  tissue  elongates  most,  i.  e.  the  region  beneath  the  apex.  In 
vegard  to  the  influence  of  the  different  sides  of  the  tree  and  the  seasons,  I  found  in 
incisions  made  monthly  that  the  late  spring  and  the  southern  to.  western  sides  of  the 
tree  are  most  favorable  for  the  development  of  gummosis. 

-   Loc.  cit. 


7o6 

The  oxygen  carriers,  which  form  gums,  are  now  actually  (Icmonslrahle 
as  enzymes  which  are  produced  in  the  sprouting  of  the  buds  and,  in  fact,  are 
present  even  before  the  diastase.  The  latter  will  then  dissolve  the  hemi- 
cellulose,  or  other  gums,  as  Griiss  has  proved  for  tragacanth. 

If  such  enzymes  are  produced  in  excess  or  their  anti-bodies  develop  in 
loo  small  amounts,  they  hinder  the  normal  development  of  the  cell  wall  in 
embryonic  cells,  or  begin  the  process  of  liquefaction  in  the  complete  cell  of 
the  mature  wood,  so  that  pathological  gum  centres  are  produced. 

It  is  not  at  all  improbable  that  an  excess  of  oxalic  acid,  like  the  hydro- 
lyzing  sulfuric  acid  and  other  mineral  acids,  acts  like  the  naturally  formed 
ferments  and  produces  thereby  an  exudation  of  gum.  Such  an  increase  of 
oxalic  acid  action  can  either  be  brought  about  by  its  more  abundant  forma- 
tion, or  through  its  lesser  combination  with  calcium.  Thus,  for  example, 
Mikosch^  calls  attention  to  the  fact  that  almost  no  calcium  oxalate  crystals 
are  found  in  the  tissues  involved  in  this  transformation.  It  is  evident  from 
Benecke's  works-  that  the  content  of  these  crystals  depends  upon  the  nutri- 
tion. He  found  in  his  cultures  that  the  addition  of  nitrates  favors  the 
formation  of  calcium  oxalate;  that  feeding  with  ammonia  decreases  this 
formation. 

Among  the  parasites  producing  an  exudation  of  gum,  Clasterosporium 
carpophilum  (Lev.)  Aderh.  (Coryneum  Beijerinckii  Oud.)  should  be  named 
first  of  all.  Nevertheless,  a  certain  predisposition  of  the  organ  is  necessary 
if  the  fungus  should  become  effective.  Aderhold''  found  in  his  inoculation 
experiments  with  leaves  that  red  fungous  spots  occur  without  the  formation 
of  gums  as,  conversely,  wounds  with  an  abundant  formation  of  gum  could  be 
found  in  the  midribs  of  the  leaves  and  in  the  cambium  of  branches  in  which 
the  fungus  was  absent.  The  other  parasites  behave  similarly ;  Cytospora  leu- 
costoma;  Monilia  fructigena  and  M.  cinerea,  Botrytis  cinerca  and  many 
kinds  of  bacteria*. 

It  is  very  possible  that,  in  some  of  the  parasites  here  named,  oxalic  acid 
is  the  poison  produced  by  them  which  causes  gummosis. 

Before  we  take  up  the  question  of  overcoming  exudations  of  gum,  it  is 
necessary  to  turn  our  attention  to  the  conditions  under  which  the  disease 
appears.  Duhamel's  theory  is  found  most  frequently  confirmed  in  pomo- 
logical  literature.  He  thinks  that  cherry  trees,  which  are  planted  in  too 
strong  soil,  are  most  subject  to  the  disease.  We  find  this  proved  especially 
with  the  peach  and  cherry  if  clayey  soil  is  understood  by  the  term  "strong 
soil."  Exudations  of  gum  are  found  less  frequently  on  warm,  porous  soils 
wliich  can  be  very  rich.     Further,  we  find  exudations  of  gum  abounding  in 


1  Mikosch,  K.  Untersuchungren  iiber  die  Entstehung-  dcs  Kirschgummi.  Sitz- 
ungsber.  d.  Akad.  d.  Wiss.  Wien;  cit.  Bot.  Contmlbl.  1907,  XXVIII,  No.  27. 

-  Bcnccke,  W.  tJbcr  Oxalsaurebi Idling-  in  griincn  Pflanzen.  Bot.  Zeit.  1903,  Vol. 
LXI.  cit.  Bot.  Centralbl.  (Lotsy)  1903,  No.  27,  p.  16. 

■^  Aderhold,  R.  t)bor  Clasterosporium  carpophilum  (LSv.)  Aderh.  und  die 
Beziehungen  desselben  zum  Gummifluss  dcs  Steinobstes.  Arb.  d.  Biol.  Abt.  d.  Kals. 
Gesundheitsamtcs  1902,  Vol.  II,  Part  5. 

4  lluhland,  W.  tJber  Arabinbildung  durch  Bakterien  und  deren  Beziehung  zum 
Gummi  der  Amygdalaceen.    Ber.  d.  Deutsch.  Bot.  Ges.  1906,  Part  7. 


70/ 

larger,  unclosed  wounds  on  the  Ijranches.  In  the  same  way,  we  find  them 
occurring  in  specially  young  peach  branches,  of  which  the  bark  has  been 
greatly  injured  by  bruising  or  rubbing. 

In  my  experiments,  in  wdiich  all  the  eyes  were  removed  in  the  spring 
from  a  considerable  number  of  cherry  trees,  an  exudation  of  gum  occurred 
with  very  few  exceptions.  In  other  experiments,  in  which  the  trunks  had 
been  peeled  for  a  considerable  distance,  gummosis  appeared  in  the  bark  near 
the  upper  girdling  cuts,  in  which  no  new  structures  in  the  forms  of  callus 
had  been  formed.  Finally,  it  is  well  known  that  great  injury  to  the  roots, 
or  crown,  in  transplanting,  as  well  as  poor  grafting,  can  give  rise  to  the 
formation  of  gum. 

All  these  injuries,  in  my  opinion,  do  not  act  through  necrobiosis  but 
because  of  a  simple  wound  stimulus  which  causes  an  excessive  current  of 
constructive  materials  to  a  spot  where  they  cannot  find  normal  utilization. 
There  sets  in  at  the  same  time,  a  hastened,  new  formation  of  cells,  which 
becomes  evident  in  the  formation  of  the  primordia  of  parenchymatous  ele- 
ments instead  of  prosenchymatous  cells,  as  in  all  other  processes  of  wound 
healing.  Therefore,  the  activity  of  the  new  cell  formation  becomes  excess- 
ively favored  at  a  time  when  the  constructive  enzymes  already  prevail  and 
wall-thickening  as  well  as  a  deposition  of  reserve  substances  should  begin. 
This  prevalence  of  the  enzymes  of  the  youthful  condition  leads  to  the  lique- 
faction of  the  diversely  formed  tissue  groups.  Such  a  displacement  of  the 
enzyme  activity  may  be  considered,  in  its  effect,  to  be  like  a  wave  which 
continues  to  advance  in  the  tree  until  it  is  stopped  by  some  other  constructive 
force.  According  to  practical  experience,  such  a  halt  is  called  by  all  those 
factors  which  condition  a  normal  ripening  of  the  wood  and  a  precipitation, 
at  the  right  time,  of  abundant  quantities  of  reserve  substances;  porous  soils, 
sunny  open  places,  and  a  supply  of  calcium,  avoidance  of  over-abundant 
nitrogen  fertilization. 

In  treating  wounds  v/hich  are  exuding  gum,  the  use  of  vinegar  made 
from  wine  is  warmly  recommended  on  all  sides.  I  have  had  no  personal 
experience  with  it. 

Exudation  of  Gum  in  Other  Plants. 

Exudation  of  Gum  in  the  Acacia. 

Moller^  maintains  that  the  formation  of  Acacia  gum  depends  upon 
changes  similar  to  those  of  the  cherry  gum.  He  says  very  generally  that  the 
gum  of  the  Acacia  is  always  produced  by  a  transformation  of  the  cell  wall, 
advancing  from  the  outside  inward.  The  walls  of  the  parenchyma  cells  and 
the  sieve  tubes  are  the  first  ones  to  fall  victim  to  the  dissolution.  (The 
collapsed  sieve  tubes  form  Wigand's  Horn  prosenchyma.)  MoUer  observed 
the  gum  also  as  a  product  of  the  bark  and  found  that  it  differs  according  to 
the  zone  in  which  it  is  produced.     Gum  arable  is  produced  by  the  dissolving 


1   Moller,   tJber  die  Entstehung-  des  Acacien-Gummi.      SitzungsVjer.   d.   Akad.  d. 
Wissenschaften.  Wein.  1875,  June  issue. 


7oS 

of  the  inner  bark  while  a  less  soluble  form,  similar  to  the  cherry  gum,  occurs 
in  the  middle  bark.     This  may  well  depend  on  the  age  of  the  affected  tissue'. 

As  one  of  the  causes  which  give  rise  to  the  exudation  of  Senegal  gum 
from  Acacia  Vcrek,  Martins'-  mentions  the  action  of  dry  desert  winds  which 
blow  in  the  autumn  and  winter  and  cause  the  rupturing  of  the  outer  bark  of 
the  Acacia,  which  has  become  more  furrowed  because  of  the  August  and 
September  winds.  Other  wounds,  which  result  in  the  exudation  of  gum, 
are  caused  by  a  parasite  which  Martins  calls  Loranthus  scnegalensis. 
Cryptogamic  parasites  are  also  able  to  cause  the  wounds  to  remain  open 
permanently  and  they  thus  exercise  a  stimulus  for  gum  formation. 
Coryneum  gummiparum  Oud.,  which  Oudemans  observed  as  bud  form  of 
Pleospora  gummipara  Oud.,  acts  just  as  Coryneum  Beijerinckii  does  with 
the  Amygdalaceae. 

Gummy  Exudation  of  the  Bitter  Orange^. 

Italian  plantations  of  bitter  oranges  (Citrus  vulgaris),  lemons  (Citrus 
limonum),  and  sweet  orange  trees  (Citrus  Aurantium)  have  suffered  for 
many  years  from  a  disease  which  is  constantly  spreading,  the  ''Mai  dclla 
gamma"  of  the  Italians,  which  causes  such  injuries  that,  according  to 
Novellis*,  the  Italian  Department  of  Agriculture  and  Commerce  has  offered 
for  years  a  premium  of  25,000  lires  for  a  proved  means  of  curing  it. 

The  disease  begins  with  the  appearance  of  black  specks  in  the  bark  of 
the  trunk  and  branches,  especially  near  the  points  of  bifurcation.  These 
spots  increase  rapidly  in  size,  until,  after  a  little  time,  they  become  black 
places  in  the  bark  and  split  open  A  yellowish  white  liquid  exudes  from  the 
surface,  which  gradually  becomes  denser  in  consistency  and  stickier,  and 
finally  hardens  into  yellow  beads,  or  glaze-like  coatings.  The  wood  under 
the  opening  in  the  bark  is  brown  and  in  a  process  of  gummosis.  If  the 
gum  is  washed  by  rain  on  to  other  parts  of  the  tree,  new  centres  of  disease 
are  said  to  be  produced.  We  find  similar  conditions  also  in  regard  to  the 
acacia  gum  and  it  is  not  at  all  impossible  that  such  cases  exist.  Like  the 
mosaic  disease  of  the  tobacco,  this  may  be  explained  as  follows :  The 
enzymatic  bodies  causing  the  formation  of  gum  give  the  impetus  for  similar 
changes  in  predisposed  healthy  specimens  and  spread  further  like  a  wave. 


1  For  the  difCeront  relations  of"  cellulose  and  g-ums  to  each  other  in  different 
mucilaginous  exudations,  compare  ToUens  and  Kirchncr,  Untersuchung:en  liber  den 
rflanzenschleim;  cit.  Bicdcrmann's  Centralbl.  1S75,  II,  p.  28.  In  regard  to  the  forma- 
tion of  the  sugar  known  as  Galactose,  from  mucilaginous  giuns,  soluble  in  water, 
when  treated  with  dilute  acid,  see  Gireaud,  Etude  comparative  des  gommes  et  des 
mucilages.  Compt.  rend.  T.XXX,  p.  477.  Peter  Claessen,  tjber  Arabinose;  cit. 
.lahresber.  f.  Agrikulturchemie,  18S1,  p.  88. 

-  Martins,  Sur  un  mode  particulier  d'  excretion  do  la  gomme  arabique  produite 
par  1'  Acacia  Verek  du  Senegal.  Compt.  rend.  1875,  I,  p.  607.  Killani,  tJber  arabisches 
Gummi.  Berl.  chem.  Ges.  cit.  .lahre.sber.  f.  Agrikulturchemie  1882,  p.  88. 

3  Savastano,  L.  Note  dl  patologia  arboi-ea.  Napoli  1907.  The  work  contains 
various  contributions  on  gummosis  which  we  imfortunately  cannot  make  use  of  at 
present  and  can  only  mention  as  in  the  last  proof  sheets. 

4  Novellis,  Ettore  de,  II  male  della  gomma  degli  agrumi;  cit.  Bot.  Centralblatt 
1880,  p.  469. 


709 

The  gummosis  becomes  fatal  for  the  tree  when  the  gum  centres  make 
up  a  greater  part  of  tlie  trunk  circumference.  According  to  Fliihler^  lemons 
suffer  most  and  sour  oranges  least.  Cuttings  seem  to  retain  the  germs  of 
the  disease,  and  in  the  same  way,  grafted  specimens  seem  to  give  a  higher 
percentage  of  disease  than  seedlings  which  have  remained  ungrafted.  Rich 
fertilization,  heavy  watering,  clayey  soils,  increase  the  evil,  which  is  said  to 
increase  also  if  cover  crops,  like  pumpkins,  beans,  tomatoes,  etc.,  are  grown, 
which  require  heavy  fertilization. 

Judging  by  the  material  to  which  I  have  had  access  thus  far,  I  consider 
the  disease  of  Citrus  fruits  to^  be  exactly  the  same  phenomenon  as  the  exu- 
dation of  gum  in  the  Amgydalaceae.  I  consider  the  excessive  addition  of 
fertilizers  rich  in  nitrogen,  to  be  one  of  the  momentarily  most  frequent 
causes,  which  play  a  brief  role  also  in  Germany  for  the  pitted  fruits  in 
nurseries. 

i\.mong  the  Italian  authors,  Peglion-  shares  the  theory  explained  here. 
He  calls  attention  to  the  fact  that  the  cultivation  of  cover  plants  needing 
rich  fertilization  is  injurious.  Stable  manure  is  not  very  suitable  for  Citrus. 
The  fruit,  to  be  sure,  becomes  large  but  remains  thick-skinned  and  sour. 

Blackleg  of  the  Edible  Chestnut. 

According  to  Gibelli'^  this  disease  is  characterized  by  the  appearance  of 
wilted  yellow  leaves  and  small  fruit,  poor  in  sugar.  In  young  trees  the  base 
of  the  trunk  dries  up,  the  bark  turns  brown,  and  its  tissues  contain  concre- 
tions of  tannin  as  large  as  the  head  of  a  pin.  Analyses  show  all  the  charac- 
teristics of  plants  growing  poorly,  i.  e.  a  large  ash  content  in  proportion  to  the 
dry  substance.  In  the  ash  is  found  a  scarcity  of  potassium  and  phosphoric 
acid  and  a  considerable  increase  of  ferric  oxid. 

Because  of  the  ball-like  concretions,  giving  the  tannin  reaction,  the 
disease  seems  to  me  to  be  related  to  the  disease  "Mai  Nero"  of  the  grape- 
vine (see  page  219).  Comes*  describes  this  form  as  gummosis.  According 
to  Cugini^  this  disease,  because  of  which  bud  development  is  entirely 
retarded  in  the  spring,  or  destroyed,  is  characterized  by  the  appearance  of 
black  stripes  and  spots  on  the  branches,  petioles  and  ribs,  tendrils,  and  stems 
of  the  clusters.  The  spots  extend  into  the  organs  and,  in  fact,  the  trunk 
even  to  the  heartwood.  Besides  this,  the  disease  is  characterized  by  the 
subsequent  appearance  of  yellowish  brown  granules  in  the  parenchymatous 


1  Fliihler.  Die  Krankheit  der  Agrumcn  in  Sicilien.  Biedcrmann's  Centraltalatt 
1S74,  p.  368. 

2  Peglion,  V.  La  concimazione  e  le  malattie  nella  coltura  degli  agrumi.  Boll, 
di  Entomol.  agrar.,  etc.     1901,  in  Bot.  Jaliresber.  1901.  T,  p.  479. 

3  Gibelli,  La  Malattia  del  Castagno;  cit.  Bot.  Jahre.sber.  1879,  II,  p.  37.';.  Gibclli 
ed  G.  Antonielli,  Sopra  una  nuova  malattia  dei  Castagni,  ibid.  Cugini,  Sopra  una 
malattia  che  devasta  i  castagneti  italiani,  ibid. 

4  Comes,  II  Mai  nero  della  vite.  Portici  1882.  Primi  risultati  degli  esperimenti 
t'jitti  per  la  cura  della  Gommosi  o  Mai  nero  della  vite.  Portici  1882.  Sul  pi-eteso 
tannine  scoperto  nelle  viti  affette  da  Mai  nero.     Bot.  Jahresber.  1882. 

5  Cugini,  Ricerche  sul  Mai  nero  della  Vite.  Bot.  Centralbl.  1881,  Vol.  VIII,  p. 
147.  Nuova  indagini  sul  Mai  nero  della  Vite.  Bologna  1882.  II  Mai  nero  della  Vite. 
Firenze  1883. 


elements  of  llic  trunk  and  branches.  These  granules  often  lill  u[)  the  entire 
lumina  of  the  cells  and  consist  either  of  cellulose  or  of  substances  containing 
proteins.  Cugini,  who,  morever,  considers  the  phenomenon  to  be  parasitic, 
also  confirms  the  turning  green  of  the  blossoms  and  connects  it  with  the 
disease.  Differences  of  opinion  prevail  already  among  pathologists  who 
have  found  parasites.  Prillieux^  considers  Rocslcria  hypO(}aca  as  the  cause, 
while  Hartig-  declares  that  this  fungus  is  an  accompanying  phenomenon  and 
that  another,  Demafophora  necatrix  is  the  real  parasite. 

Later  investigations,  especially  those  made  by  Pirotta-',  show  that  tlie 
above  mentioned  granules  in  the  cells  give  the  tannin  reaction  and  arise 
directly  from  the  starch  grains.  He  found  Rhizomorpha  very  frequently 
in  the  diseased  roots,  but  not  always ;  nevertheless,  he  does  not  consider  this 
fact  important  enough  to  place  the  disease  among  fungus  diseases.  Comes 
showed  that  the  granules  in  question  do  not  represent  accumulations  of 
tannin  but  consist  of  a  dififerent  ground  substance  (gum)  which  Is  only 
saturated  with  tannin. 

GUMMOSIS  OF  THE  FiG  TrEE. 

The  disease  of  the  fig  tree  (Marciume  del  Fico"  of  the  Italians),  which 
has  been  well  known  since  the  time  of  Theophrates,  has  been  thoroughly 
studied  by  vSavastano*,  who  recognized  it  as  gummosis. 

This  disease,  to  which  old  plants  are  more  exposed  than  young  ones,  is 
found  most  markedly  in  the  months  of  July,  August  and  September  when 
the  leaves  become  yellow  and  fall,  as  does  the  fruit  also.  Although  numer- 
ous fungi  and  even  insects  are  found  on  the  wilted  and  dead  leaves  (Pujiiofio 
salicina,  Tul,  Urcdo  Ficus,  Cast,  Phyllosticta  Sycophila  Thiim.,  Sporodes- 
mium.  Coccus  caricae  Fab.),  these  parasites  should  not  be  considered  causes 
of  the  disease.  Usually  there  is  no  change  in  the  trunk  and  branches,  but  a 
change  does  occur  in  the  root,  where  the  chief  seat  of  the  disease  should  be 
sought.  In  a  highly  advanced  stage  the  roots  seem  blackish  up  to  the 
crown.    They  sometimes  split  open,  but  oftener  decay. 

It  is  found  in  plants,  raised  from  sprouts,  that  the  seat  of  the  disease 
may  lie  in  the  roots  of  the  mother  plant,  from  whence  the  further  distribu- 
tion takes  place  in  all  directions,  but  especially  upward.  The  outermost  layer 
is  the  most  diseased ;  only  at  times  is  the  innermost  layer  destroyed  to  any 
great  extent.  When  the  destruction  reaches  the  crown,  the  plant  dies 
absolutely. 

When  the  disease  appears,  the  cells  and  ducts  are  found  filled  with  a 
substance  which  at  first  seems  a  lemon  yellow  and  later  a  dark  amber.  At 
first  the  cell  walls  are  covered  with  this  and  then  the  whole  lumen  becomes 


1  Prillipiix,  La  pourridie  dcs  Aisncs  de  la  Haute-Marnc,  pioduit  p.ar  Ic  Rocslcria 
hypogaea.     Pa'ris  1SS2. 

2  Hartig,  R.  Rhizomorpha  (Dematophora)  necatrix.  Der  Wurzelpilz  des 
Weinstocks.  Untersurhiingen  aiis  dem  forstbotanisrlicn  In.stitute  zur  Miinchen. 
1883,  III,  p.  95.     cit.  Bot.  Centralhl.  1883,  No.  46  (Vol.  XVI).  p.  208. 

3  Pirotta,  Primi  studi  sul  Mai  nero  o  Mai  dello  Spaceo  ncolle  viti  1882;  cit.  Bot. 
.lahresber.  1882. 

4  Savastano,  li.  II  Marciume  del  Fico.  Annuario  deUa  R.  Rcuola  Sup.  d'Agri- 
cult.  Portici,  Vol.  Ill,  fasc.  V,  1884,  con  4  tav.  cromot.  (nach  brieflicher  Mitteilung). 


filled  with  it.  The  starch  disappears  with  the  increase  of  these  masses. 
Savastaiio  observed,  even  in  seedlings,  a  production  of  gum  centres  at  the 
point  where  the  young  roots  passed  into  the  trunk  and  branches.  I  found 
similar  conditions  in  the  sweet  cherry,  which  externally  showed  no  trace 
of  disease. 

Savastano  found  gummosis  appearing  also  in  the  trunk  and  branches. 
He  found  a  substance  in  its  gum  which  seems  to  be  similar  to  "Olivile" 
occurring  in  the  gummosis  of  the  olive.  The  gummosis  of  the  trunk  and 
branches  starts  in  the  gum  glands  found  even  in  the  roots  of  saplings.  Only 
after  the  plants  have  become  diseased  with  gummosis  may  the  presence  of 
Rhizomorpha  be  proved  which  other  investigators  have  considered  the 
causes  of  the  disease.  With  the  red  discoloration  of  the  walls,  the  paren- 
chyma cells  of  the  roots  undergo  a  process  of  humi faction  in  which  the 
specific  weight  of  the  tissue  becomes  less  and  less  because  the  organic 
substances  disappear. 

A  later  work  by  Savastano^  gives  the  results  of  comparative  experi- 
ments with  specimens  of  Amygdalus  Persica  and  Amygdalus  communis, 
Pntnus  Cerasiis,  P.  domestica,  P.  inifitia,  P.  Mahaleh,  and  P.  Armeniaca, 
as  well  as  Citrus  Aurantium,  C.  Limonum,  C.  vulgaris  and  C.  nobilis,  and 
also  of  Olca  europaea  afifected  by  gummosis.  The  results  show  that  the 
gummosis  of  the  plants  named  has  much  in  common  with  that  of  Ficus 
Carica.  In  all,  the  formation  of  gum  centres  either  takes  place  as  a  result 
of  injur}',  or  without  any  external  cause.  If  the  wound  is  overgrown 
quickly  and  completely,  the  gum  formed  dries  up,  as  a  rule,  into  brittle 
masses  and  remains  uninjurious  for  the  surrounding  tissue.  If,  on  the 
other  hand,  moisture  is  present  on  the  wounded  places,  the  gum  remains 
soft  and  is  easily  carried  over  the  surfaces  surrounding  the  wounds,  which 
also  succumb  to  gummosis. 

The  Exudation  of  Manna. 

In  many  plants,  instead  of  gum,  a  hard,  clear  substance  containing 
sugar  comes  from  the  bark  of  young  trunks  and  branches,  and  is  called 
Manna  in  trade.  The  liquefaction  product  contains  Mannit  which,  when 
extracted  with  alcohol,  can  be  obtained  in  fine  white  silky  crystals,  tasting 
slightly  sweet,  and  may  also  be  formed  artificially  from  different  sugars. 
Investigations  of  the  Manna  exudation  were  begun  by  Meyen-.  According 
to  him,  the  large  amounts  of  Manna,  which  come  from  Italy,  are  obtained 
artificially  from  a  kind  of  alder,  the  Manna  Alder,  by  making  incisions  in 
the  bark  toward  the  end  of  July.  From  these  incisions  the  Manna  flows 
gradually  as  a  thick, sweetish  juice,  hardening  in  the  air. 

Resinosis. 
The  exudation  of  resin  (resinosis)   is  for  conifers  what  exudation  of 
gum, is  for  the  Amygdalaceae  and  the  Manna  exudation  for  the  Oleaceae. 

1  Gummose  caulinaire  dans  les  Aurantiacees,  Amygdalees,  le  Figuier,  I'Olivier  et 
noircissement  du  Noyer.     Compt.  rend.  I,  Deceln-e,  ISSl.     Reprint. 

2  l^flanzenpatliulogie,  p.  228. 


712 

It  sometimes  occurs  in  the  wood  and  sometimes  attacks  the  parenchyma  and 
bast  cells  of  the  bark.  The  first  stages  of  the  disease  are  found  in  the 
resinosis  of  the  wood;  the  mature  condition  consists  in  the  formation  of 
large  quantities  of  uniform  resin  masses  in  cavities  in  the  trunk  and  branches, 
which  are  usually  called  resin  boils.  It  is  well  known  that  resin  in  the  cell 
contents  normally  occurs  in  the  form  of  drops  or,  as  in  the  glue  mats  of 
many  wood  buds,  in  the  intermediate  lamellae  of  the  cell  wall,  or  finally,  as 
in  our  pines  and  spruces,  in  definitely  distributed,  peculiar  resin  canals.  The 
contents  of  many  parenchyma  cells  near  the  resin  canal  show  resin  drops 
and  starch  grains,  of  which  some  not  infrequently  are  provided  with  a  resin 
coating.  The  immediate  surroundings  must  necessarily  furnish  the  sub- 
stances which  fill  the  large  resin  pockets.  Whether  this  material  is  trans- 
ported in  the  form  of  resin,  as  N.  J.  C.  Miiller^  assumes,  or  in  the  form  of 
some  other  compound  and  is  only  developed  into  resin  where  it  is  found  as 
such,  which  theory  Hanstein-  is  inclined  to  believe,  is  of  little  importance 
for  our  consideration.  In  this  we  have  to  maintain  that  the  formation  of 
considerable  amounts  of  resin  and  gum  is  possible  only  through  the  transfor- 
mation of  a  plastic  substance,  flowing  toward  those  places  where  tine 
liquefaction  takes  place,  i.  e.  a  positive  loss  of  sap.  To  this  it  should  be 
added  for  resinosis,  as  for  gummosis,  that  the  existing  plant  substance,  in 
the  form  of  wood  and  bark  tissue  and  of  starch  grains,  succumbs  to  lique- 
faction and  that,  in  this  way,  considerable  material  is  lost.  According  to 
investigations  made  by  Karsten''  and  \\'igand',  the  wood  at  first  seems 
resiniferous,  i.  e.  saturated  with  resin  and  balsam.  In  most  of  the  cells  of 
this  saturated  tissue,  the  resin  appears  as  a  wall  coating,  or  as  drops  which 
have  spread  together  until  the  cells  seem  completely  filled  with  the  mass. 
The  walls  of  the  cells,  originally  thick,  become  thinner  and  thinner  in  the 
same  degree  as  the  amount  of  resin  increases  within  the  cell,  until,  finally, 
only  a  fine  outline  is  left,  which  is  gradually  lost  in  the  mass  of  resin. 

As  in  gum  exudation,  the  medullary  rays  also  seem  to  be  longer 
resistent,  since  they  are  clearly  seen  to  extend  into  the  uniform  resin  mass 
of  the  dissolved  wood  cells  surrounding  them.  For  complete  analogy  in  the 
two  processes,  there  is  lacking  only  the  proof  that,  in  the  exudation  of 
resin,  an  abnormal  wood  parenchyma  is  formed,  which  undergoes  absolute 
resinosis. 

1  Miiller  (tJber  die  Verteilung  der  Harze  usw.  in  Pring.sheim's  Jahrb.  f.  wiss. 
Bot.  1866 — 67,  p.  387  ff)  says  the  great  amount  of  resin  in  the  resin  ducts  cannot 
have  reached  tliat  place  except  by  penetrating  many  cell  walls.  He  finds  the  ceil 
walls  to  be  permeable  for  resin.  Thin  cross  sections  of  pine  wood  left  lying  for 
some  time  in  water  showed  that  all  the  resin  in  the  cell  walls  has  been  rc^placed 
by  water. 

2  Hanstein  (Uber  die  Organe  der  Harz-  and  Schleimabsonderung  in  dem  Laub- 
knospen.  Bot.  Zeit.,  1868,  No.  33  ff.)  speaks  of  the  occurrence  of  resin  first  in  the 
grooves  of  secretion  cells  as  small  bands  between  the  cuticle  and  the  cellulose  mem- 
brane. This  is  undoubtedly  an  important  reason  for  assuming  that  "the  resin,  which 
occurs  in  the  form  of  intermediate  wall  layers,  first  assumes  its  real  character  after 
it  has  passed  through  the  cell  wall  in  another  form  and  been  deposited  as  an  inter- 
mediate layer." 

3  Karsten,  H.  tJber  die  Entstehung  des  Harzes,  Wachses,  Gummis  und  Schleims 
durch  die  assimilierende  Tatigkeit  der  Zellineml)runen.     Bot.  Zeit.  1857,  p.  310. 

•«  Wigand,  tJber  die  DesoiKanisalion  der  rflanzenzcHc.  I'rin.t;sheiin's  .Jahrb.  f. 
wis.s.  Bot.     Vol.  HI,  p.  165. 


713 


It  has  often  been  observed  that  the  starch  grains  in  resinosis  succumb 
to  Hque faction  just  as  in  gummosis.  Starch  certainly  furnishes  a  large  part 
of  the  resin  in  the  exudation.  Wiesner^  states,  for  example,  that  resin  bodies 
exist  within  the  medullary  ray  cells  of  foliage  trees  and  possess  the  structure 
of  the  starch  grains.  These  rarely  turn  blue  with  the  use  of  pure  iodine  but 
do  so  more  often  with  iodine  and  sulfuric  acid.  With  the  use  of  ammoni- 
acal  cuprous  acid  they  give  the  cellulose  reaction ;  they  react  to  ferric  chlorid 
like  tannin.  Wiesner,  therefore,  concludes  from  his  investigations  that  a 
large  amount  of  the  resin,  occurring  in  nature,  arises  from  starch  grains 
themselves,  or  from  starch  grains  which  have  been  changed  into  tannin.  He 
considers  the  tannin  to  be  a  connecting  link  between  the  cellulose  and  resin. 

We  find  in  Nottberg's"  very  thorough  work  on  resin  pockets  the  proof 
that  even  in  the  exudation  of  resin  an  abnormal  parenchyma  wood  is  formed 
which  succumbs  to  resinosis  and  liquefaction.  Nottberg  proves  that,  as  a 
result  of  any  injury,  whatever,  which  extends  to  the  cambium,  this  responds 
with  the  production  of  a  "tracheidal 
parenchyma"  which  gradually  passes 
over  again  into  the  normal  tracheids. 
The  tracheids  of  the  sap  wood  which, 
as  a  result  of  the  injury,  come  into 
contact  with  the  outer  world,  stop  up 
their  lumina  with  a  mass  resembling 
wound  gum,  which  is  insoluble  in 
alcohol  but  dissolves  after  treatment 
with  Schultz's  mixture.  Usually  res- 
inosis occurs  at  the  same  time  in  the 
wood  body.  The  different  cells  of 
the  diseased  parenchyma  immediately 
after  their  production  begin  to  form 
resin  internally  (resin  cells).  The 
membranes  of  the  new^  cells  of  the  tracheidal  parenchyma  liquefy  very  early. 
The  unthickened  elements,  on  the  other  hand,  as  long  as  they  are  retained, 
constantly  show  only  the  cellulose  reaction.  In  the  resin  cells  a  definite  layer 
may  be  recognized  in  which  the  resin  is  formed  (resinogenous  layer,  Fig. 
157).  Nottberg,  from  whose  book  the  figure  is  taken,  leaves  undecided  what 
this  resinogenous  layer  is;  "a  developmental  product  of  the  membrane,  or  of 
the  cyptoplasm." 

The  pathological  formation  of  resin  may  be  considered  the  most  exten- 
sive process  of  liquefaction  at  present  known  in  the  vegetable  kingdom.  It 
existed  in  the  tertiary  period  as  well  as  now,  for  Conwentz  states  in  his 
monograph  on  the  Baltic  Amber  trees  (Pinus  succinifera,  Conw.),  which 
has  excellent  illustrations,  "there  was  scarcelv  one  healthv  tree  in  the  whole 


Fig-.  157.     Cells  of  the  tracheidal  paren- 
chyma of  Pinus  Strobus  with  the  resin- 
ii'erous  layer  rsg;   ht  resin  drops.    (After 
Nottberg-.) 


1  Sitzung-sbericht  d.  Akad.  D.  Wissensch.  zu  Wien,  Vol.  51. 

2  Nottberg,  P.  Experimentale  Untersuchur.gen  uber  die  Entsteluing  von  Harz- 
gallen  und  verwandter  Gebilde  bei  nnseren  Abietineen.  Zeitsch.  f.  I'flanzenkr.  1S97, 
p.  1.S.3  ff.     TTifM-  nuch  weitere  Literatur. 


7T4 

amber  forest;  the  pathological  condition  was  the  rule;  the  normal  one,  the 
exception."^  We  cannot  better  present  the  processes  of  resinosis  than  by 
showing  copies  of  the  aml^er  sections  wliich  Conwentz  has  reproduced  (Figs. 
158-161). 

Just  as  at  present,  we  find  that  tlie  process  of  resinosis  began  as  follows: 
— resinosis  and  liquefactif)n  of  the  membranes,  and  finally  of  the  whole  n-U 


Pis'.  15S.     Process  of  turning-  to  resin,  beginning-  with  the  formation  ot 
resin  canal  in  the  wood.     205:1.      (After  Conwentz.) 


a  lysigenouF 


Fig.  159.     Horizontal  section.     In  the  summer  wood  of  an  annual  ring  is  a  group  of 

abnormal  wood  parenchyma  cells  (P).     .56:1:     The  holes  in  the  tissue  were  produced 

in  sectioning.     (After  Conwentz.) 


together  with  its  contents,  set  in  in  diiYerent  groups  between  two  medullary 
rays  (Fig.  158).  No  anatomically  different  tissue  is  necessarily  present 
here,  but,  in  the  majority  of  cases,  such  an  one  is  present  and  in. fact  in  the 
form  of  wood  parenchyma  which  develops  in  tangential  strips.     Conwentz 


1     Conwentz,  Monographie  der  baltischen  Bernstoinbiiumc,  Danzig,  1S90,  p.  145. 


715 

describes  these  strips  (Fig.  159)  in  the  summer'  wood.  Up  to  the  present 
I  have  found  them  predominantly  in  the  spring  wood  of  our  trees  so  that 
a  new  annual  ring  begins  at  once  with  the  abnormal  wood,  or  after  only  a 
few  cell  rows.  I  trace  the  production  of  these  strips  back  to  a  transitory 
weakening  of  the  bark  tension  (see  Frost  Phenomena).  This  abnormal 
wood  parenchyma  is  shown  in  a  complete  stage  of  resinosis  in  Fig.  160. 
Masses  of  resin,  or  rather  amber,  already  produced,  can  push  out  the  bark 
away  from  the  oldest  part  of  the  trunk.  Conwentz  found  such  bark  ele- 
ments in  so  good  a  state  of  preservation  that  he  still  could  prove  their 
nuclei,      (Fig.  161.) 

Nottberg  found,  in  the  liquefaction  of  the  solid  tracheid  parenchyma, 
that  the  tertiary  membrane  was  retained  longest ;  this  may  be  observed  also 
in  the  spreading  of  the  gum  centres  of  the  cherry. 


pkmmamimi 


Fig  160.     Horizontal  section  with  abnormal  parenchyma  wood  (P),  which  has  begun 
to  turn  to  sugar.     The  abnormal  tissue  lies  in  the  summer  wood.     J  is  the  edge  of 
the  annual  ring.     210:1.      (After  Conwentz.) 


Nottberg  distinguished  good  and  evil  wounds  according  to  whether  the 
wound  heals  at  once  or  affects  the  surrounding  tissue.  It  should  still  be 
noted  that  the  trees,  of  which  the  wood  normally  has  no  resin  canals  at  all 
(the  white  fir),  are  found  to  abound  in  resin  canals  after  injury,  especially 
in  the  edges  of  the  callus.  These  investigations  have  been  confirmed  by 
v.  Faber\  who  also  emphasizes  the  fact  that  the  pathological  resin  canals 
are  formed  schizogenously.  They  anastomose  in  a  tangential  plane  and 
form  a  connected  network,  while  their  open  ends  extend  into  the  wound. 
Above  these  the  resin  canals  are  more  abundant  and  longer  than  they  are 
below  them. 

In  opposition  to  the  statements  that  the  cause  of  resinosis  may  always 
be  sought  in  wounds,  I  must  maintain,  as  in  gummosis,  that  the  processes 
of  liquefaction  can  also  arise  autogenously,  without  wound  stimulus.  I 
have  observed  this  in  seedlings  of  pines  from  heavily  manured  nurseries. 


1     V.  Faber,  E.  V.     Experimentaluntersuchungen 
flusses  bei  Abietiiipon.     Dissertation.     Hern  1901. 


die  Entstehung  d.  Harz- 


yi6 


and  found  similar  cases  likewise  in  older  plants  of  Pscndotsuga  Dotiglasi, 
Abies  fraseri  and  Abies  concolor,  which  showed  swellings  of  the  bark. 
These  could  be  proved  to  1)C  a  lysigenous  widening  of  schizogenous  resin 
canals.  The  trees  stood  on  moist,  marshy  soil  which  had  been  heavily 
manured  at  intervals  of  two  or  three  years. 

Recently,  I  have  had  opportunity  to  observe  resinosis  as  a  constitutional 
disease,  i.  e.  as  the  manifestation,  even  in  old  trees,  of  a  tendency  throughout 
the  whole  plant  body,  to  form  resin  excessively.  I  have  distinguished  this 
universal  disease,  as  "chronic  resinosis,"  from  the  "acute  resinosis"  pro- 
duced locally  as  a  result  of  wound  stimulus,  and  remaining  localized,  which 
is  connected  with  the  exudation  of  profuse  amounts  of  resin^  Accordingly, 
in  the  future,  a  chronic  and  an  acute  gummosis  would  have  to  be  distin- 
guished from  one  another  and  in 
the  latter,  the  treatment  of  the 
wounds  with  vinegar,  already 
recommended,  might  be  success- 
ful. 

I'oK.MATION      OF      Rf.SIN       IN 
DlCOTYLKDONOUS   PlAXTS. 

The  production  of  resin  and 
gum  resin  in  dicotyledonous 
plants  is  found  to  be  parallel  to 
the  processes  descril)ed  in  the 
]jreceding  section.  Svendsen" 
found  that  the  gum  resins  of 
Sty  rax,  Licjuidamber,  Toluifera, 
etc.,  are  pathological  products, 
produced  as  a  result  of  injury. 
After  every  injury,  which  ex- 
tends as  far  as  the  cambium, 
wound  wood  is  formed  which  is  distinguished  by  its  tracheidal,  parenchy- 
matous character  and  which  gradually  passes  over  again  into  normal  wood. 
The  processes,  therefore,  are  ever}^where  the  same,  just  as  was  described  and 
illustrated  under  injuries  due  to  the  frost.  The  wound  stimulus  makes  itself 
felt  in  the  old  wood  by  a  stoppage  of  the  ducts  with  tyloses,  or  the  closing  of 
them  by  Bassorin.  The  new  wood,  wdiich  is  formed  about  the  wound  and  at 
first  is  parenchymatous,  has  resin  canals  produced  schizogenously ;  and 
widening  lysigenously.  The  resinosis  thus  attacks  the  w^ood  parenchyma, 
with  the  exception  of  considerable  parts  of  the  medullary  rays,  and  con- 
tinues later  in  the  bark,  where  it  becomes  noticeable  within  the  bark  rays ;  a 
fact  which  should  be  emphasized.     In  dicotyledons,  as  in  conifers,  the  patho- 


Fig.  161.  Group  of  parenchyma  cells  from 
the  outer  bark  which  has  been  completely 
separated  from  the  central  wood  cylinder  by 
the  turning  to  resin  of  an  annular,  abnormal 
zone  of  wood  parenchyma.  The  nuclei  may 
still  be  discerned  in  the  bark  cells.  (After 
Conwentz.) 


1  Landwirtschaftliche  Jahrbiicher  1908. 

2  Svendsen,  Carl  Johan.  tJber  den  Hai'zfluss  bei  den  Dicotylen,  speziell  bei 
Styrax.  (\marium,  Shorea,  Tohiilera  und  Lifiuidambar.  Archif  for  Mathematik  og 
Naturvidenskab.    Kristania  1905.  Vol.  XXVI,  No.  13. 


717 

logical  formation  of  resin  is  perfectly  independent  of  the  presence  of  normal 
resin  canals.  The  conditions  seem  to  be  more  complicated  in  Peru  and  Tolu 
Balsam. 

Therefore,  so  far  as  we  can  examine  the  pathological  formation  of  resin, 
it  corresponds  perfectly  to  gummosis  and,  therefore,  the  same  theories,  which 
we  have  expressed  earlier,  hold  good  for  it.  It  is  not  the  wound  stimulus 
in  itself  which  causes  the  liquefaction  of  the  solid  tissues,  but  enzymatic 
actions,  which  we  cannot  determine  at  present,  manifested  in  the  result  that 
scattered  tissue  groups  fail  to  develop  normally  and  dissolve  because  of 
oxydation.  These  processes  can  be  introduced  by  wounds  but  also  arise 
from  a  changed  nutrition.  They  are  dependent  upon  a  definite  develop- 
mental phase,  i.  e.  the  time  of  the  sprouting  of  the  trees.  Centres  of  lique- 
faction, already  existing,  may  be  increased  by  the  transmission  of  their 
enzymes  to  normal,  permanent  tissue. 

Supplementarily,  we  will  cite  a  number  of  phenomena,  some  of  which 
belong  directly  to  degeneration  due  to  gummosis,  and  others  belong  here 
because  we  conceive  them  to  be  the  results  of  enzymatic  disturbances  of 
equilibrium. 

Analogous  to  the  exudation  of  gum  is  the  exudation  of  transparent 
gummy  masses  in  Eleagnus  canadensis,  occurring  especially  about  the  edges 
of  wounds.  Frank  has  described  it  more  exactly.  I  found  the  formation 
of  gum  in  palms,  cucumbers,  cacti,  and  hyacinth  bulbsV 

I  assume  an  enzymatic  disturbance  in  the  heart  rot  and  the  black  ring 
condition  of  the  horse  radish'^,  the  glossiness  of  cacti,  orchids,  carnations, 
etc.  Conditions  of  weakness  are  thus  created  which  render  the  plant  sus- 
ceptible to  parasitic  attacks.  Wood  has  referred  to  this  point  with  especial 
distinctness :  "I  called  special  attention  to  the  fact  that  plants  rich  in 
oxidizing  enzymes  were  morQ  sensitive  to  unfavorable  conditions  of  tem- 
perature, moisture  and  especially  to  insect  enemies  than  plants  poor  in  these 


According:  to  Comes,  the  "Brusca  of  the  Oliw"  is  a  decided  gummosis. 
s.  Zeitschr.  f.  Pflkr.  1S99,  p.  132. 
Loc.  cit.,  p.  22. 


SECTION  IV. 


EFFECTS  OF  INJURIOUS  GASES  AND  LIQUIDS. 


CHAPTER  XVI. 


THE  GASES  IN  SMOKE. 


SuLFUROus  Acids. 

The  injuries  to  vegetation  due  to  tlie  teases  in  smoke  have  become  so 
numerous  and  varied,  with  the  constantly  increasing  spread  of  textile  indus- 
tries, that  the  study  of  them  begins  to  form  a  separate  branch  of  pathology, 
in  which  chemistry  and  botany  are  equally  concerned.  It  is  thus  evident 
that  this  branch  of  science  demands  special  attention.  The  subject  has 
been  most  extensively  treated  in  Haselhofif  and  Lindau's  book^  and  later  in 
that  of  Wieler'-.  Because  of  the  abundance  of  material  on  injuries  from 
smoke  we  can  here  merely  refer  to  these  works  and  treat  more  thoroughly 
only  the  points  less  fully  taken  up  in  them. 

For  a  long  time,  scientists  were  in  doubt  as  to  which  element  in  the 
smoke  was  the  injurious  one,  until  the  investigations  of  Morren^,  Stock- 
hardf*  and  especially  v.  Schroder"'  pro\cd  it  to  be  the  sulfurous  acid.  The 
metallic  poisons,  like  arsenic,  zinc  and  lead,  to  which  especial  attention  was 
formerly  paid  in  studying  the  injuries  due  to  the  smoke  of  smelting  houses, 
have  been  proved  experimentally  to  be  less  injurious  to  our  cultivated  plants, 
while  a  very  small  addition  of  sulfurous  acid  to  the  air  is  able  to  bring  about 
the  death  of  the  plants  under  experimentation.  How  small  this  addition 
need  be  is  shown  by  Morren's**  observations.  He  could  perceive  the  charac- 
teristic indications  of  destruction  in  the  leaves  even  when  the  air  contained 


1  Haselhoff,  E.,  und  Lindau,  G.,  Die  Beschadigung  der  Vegetation  durch  Rauch. 
Berlin  1903,  Borntrag-cr,  412  pages,  with  217  illu.strations. 

-  Wieler,  A.  ITntci-.suchungen  iiber  die  Kinwirkung  schwefliger  Saure  auf  die 
rnanzen.     Berlin  1905,  Gl)r.  Borntrilger. 

3  Rgcherches  experimentales  pour  dMerminer  I'influence  de  certains  gaz  indus- 
triels,  specialement  du  gaz  acide  sulfureux,  sur  la  v6g6tation.  Extracted  from  the 
Report  of  the  International  Horticultural  Exhition,  etc.     London  1S66. 

*  Untersuchungen  iiber  die  schadliche  Einwirkung  des  Hiitten-  u.  Steinkohlen- 
rauches  auf  das  Wachstum  der  Pflanzen.     Tharandter  forstl.    Jahrb.,  Vol.  21,  Part  3. 

•'■  Die  Einwirkung  der  schwefligen  Siiuro  auf  don  I'flanzen,  in  Landw.  Ver- 
suchsstationen  1872. 

u  IjOC.  cit.,  page  224. 


719 

only  1-50,000  of  its  volume  in  sulfurous  acid.  Schroder  states^  that  one 
one-millionth  will  prove  injurious  if  allowed  to  act  for  some  time.  Such 
slight  amounts  are  certainly  present  in  many  kinds  of  smoke,  formed  by  the 
oxidation  of  hard  coal,  which  contains  sulfur.  Moreover,  since  sulfur  in 
the  form  of  iron  sulfid  is  an  abundant  element  in  hard  coal,  it  may  be 
assumed  that,  as  Morren  says,  we  establish  a  poison  centre  for  plants  with 
every  chimney  we  erect. 

Yet,  at  any  rate,  we  should  not  carry  this  anxiety  too  far.  The  experi- 
ments, proving  the  injuriousness  of  such  small  amounts  of  gas,  were  made 
in  a  space  enclosed  by  a  bell  jar  and  the  gas  usually  acted  for  several  hours. 

This  corresponds  in  everyday  life  only  to  the  constitution  of  the  air 
in  the  immediate  proximity  of  an  industrial  establishment,  such  as  smelt- 
ing house,  coke  oven,  etc.,  in  a  narrow  valley  where  the  smoke  lies  day 
and  night  in  great  masses  above  the  vegetation.  In  the  majority  of  cases 
the  motion  of  the  air,  and  especially  wind,  together  with  the  character- 
istic oxidation  of  sulfurous  acid  into  sulfuric  acid  when  in  contact  with 
moisture,  serve  as  a  protection  against  the  most  extreme  action  of  the 
poison,  and  against  immediate  death.  In  any  case,  however,  it  would  be 
well,  in  regions  where  hard  coal  or  peat-  is  burned,  to  choose  for  industries 
producing  a  great  deal  of  smoke,  such  positions  as  are  removed  as  far  as 
possible  from  large  plantations,  especially  from  tracts  of  trees. 

The  gaseous  products,  from  burning  hard  coal  free  from  sulfur  are  not 
injurious  to  vegetation''.  If  the  coal,  however,  contains  some  sulfur  and  gives 
it  off  into  the  air  as  sulfurous  acid,  it  will  be  taken  up  by  the  leaf-organs 
of  the  conifers  and  deciduous  trees.  According  to  v.  .Schroder  the  greater 
part  is  retained  in  these  organs  and  only  a  small  amount  is  carried  into  the 
wood  of  the  plant.  The  experiments  made  by  Freitag'*  directly  in  this  con- 
nection indicate  that  we  shall  have  to  consider  the  leaves  as  the  main  organs 
for  taking  up  the  poison.  Yet  all  leaves  do  not  take  up  equal  amounts  of 
the  poison  offered  them;  in  this,  conifers  differ  markedly  from  deciduous 
trees.  Under  similar  external  conditions,  with  equally  large  leaf  surfaces, 
the  former  take  up  less  sulfurous  acid  than  do  the'  latter.  Yet  it  can  not 
be  said  that  a  plant  suffers  more  when  it  has  taken  up  a  greater  amount  of 
gas.  The  power  of  resistance  depends  rather  upon  the  special  organization 
of  the  plant.  In  this  connection,  the  supposition  is  pertinent  that  the 
anatomy,  especially  the  number  of  stomata,  may  be  determinative  for  the 
sensitiveness  of  a  plant.  This  supposition,  however,  which  has  been  repeat- 
edly expressed  by  Morren,  has  proved  to  be  erroneous,  since  Schroder  has 


1  Schroder,  .J.  v.,  und  Reuss,  C.  Die  Beschadigung  der  Vegetation  durcli  Raucli 
usw.     Berlin  1883,  P.  Parey. 

2  According  to  Stockhardt  the  smoke  from  lignite  and  peat  is  also  injurious,  for 
this  fuel  contains  sulfate  of  silica.  The  smoke  of  lime  kilns  is  less  injurious  because 
the  lime  retains  the  sulfurous  acid  form,  j"ust  as  in  brick  ovens  the  magnesia  content 
frequently  present  in  the  clay  acts  favorably  because  of  the  retention  of  the  sulfurous 
acid.     Chemischer  Ackersmann  1872,  Part  II,  p.  Ill  ff. 

3  Proved  for  plum  and  pear  trees. 

4  Mitteilung  der  landwirtsch.  Akad.  Poppelsdorf.  Vol.  II,  1S69,  p.  34  cit.  bei 
Schroder  loc.  cit.,  p.  321. 


found  that  the  sulfurous  acid  is  taken  up  nf)t  only  by  the  stoniata  but 
uniformly  by  the  entire  uijper  surface  of  the  leaf.  He  found  that  just  as 
much  gas  was  taken  up  by  the  upper  side,  free  from  stomata,  as  by  the 
underside  which  abounds  in  these  respiratory  organs  only  the  action  of  the 
gas  which  had  penetrated  the  underside  was  much  more  rapid  and  energetic. 
This  is  explained  by  the  fact  that  sulfurous  acid  is  greedily  absorbed  by 
water  and  oxidizes  easily  in  contact  with  it.  Now,  since  the  loss  of  water 
from  the  leaf  into  the  air  takes  place  especially  through  the  porous  under- 
side which  abounds  in  stomata,  the  action  of  the  gas  manifests  itself  so  much 
the  more  here.  If  the  water  in  the  niicellar  interstices  of  the  cell-walls  is 
combined  with  the  acid  in  greater  amounts  than  can  be  supplied  to  the 
walls,  they  become  deficient  in  water  and  finally  dry  up,  thereby  losing  their 
capacity  to  conduct  water. 

Thus  only  those  cell  bodies  will  remain  well  supi)lied  with  water  and 
will  retain  their  normal  color,  which  lie  directly  against  the  rapidly  conduct- 
ing tissue  of  the  vascular  bundles  while  the  dry  part,  lying  between  the 
vascular  bundles  (the  leaf  veins)  takes  on  a  faded,  brownish  color.  This 
phenomenon  of  bright  green  venation  in  a  faded  leaf  mass  has  been  taken 
as  a  characteristic  point  for  recognizing  leaf  poisoning  from  sulfurous  acid. 
Hartig^  maintained  that  the  red  coloration  of  the  guard  cells  of  the  stomata 
in  conifers  is  a  positive  characteristic  of  injury  due  to  acid.  This  statement, 
however,  was  immediately  refuted  by  other  observers.  Wieler-  and 
Sorauer^  have  proved  that  slow  death,  under  the  influence  of  light  and  with 
the  action  of  very  different  factors  causes  a  red  coloration.  Directly  in 
connection  with  this  characteristic,  apparent  to  the  naked  eye,  is  the 
decreased  water  evaporation  from  poisoned  leaves,  as  found  by  v.  Schroder 
in  weighing  experiments.  The  amount  of  the  transpiration  may  be  used, 
however,  as  the  expression  of  the  amount  of  production  and  thus  it  may  be 
concluded  here  that  the  leaf-assimilation  is  less.  The  general  effect  of  the 
poisoning  on  the  plant  body  will,  therefore,  resemble  permature  defoliation 
and,  in  fact,  the  action  sets  in  the  more  quickly  the  greater  the  amount  of 
sulfurous  acid  present,  the  drier  the  air,  the  higher  the  temperature  and  the 
stronger  the  illumination,  which  are  the  factors  inciting  the  leaf  to  more 
intensive  activity.  Because^  of  this  fact,  which  has  been  determined  experi- 
mentally, the  supposition  that  the  smoke  from  smelting  works  and  from 
hard  coal  will  act  less  vigorously  at  night  than  during  the  day  is  pertinent, 
and  we  will  find  later  that  it  is  confirmed. 

Caution  is  necessary,  however,  when  forming  one's  judgment  from  the 
characteristic  of  green  venation  and  dried  middle  fields.  Almost  all  injurious 
atmospheric  effects  express  themselves  in  such  a  way  that  the  parts  of  a  leaf 
lying  furthest  from  the  water-conducting  ribs,  namely,  the  fields  between 


1  Hartig-,  Rob.  tJbcr  die  Kinwirkungr  des  Hiitten-  und  Steinkohlenrauches  aiif 
die  Gesundheit  der  Nadelholzbaume.     Miinchcn  1S96,  Rieg-er'sche  Biicbliandl. 

-  Wieler,  tjber  iinsichtl)are  Rauchscluidcn  bei  Nadelbaumen.  Zeitsclirift  I'tir 
Forst.  VI  Jasdwesen  1897,  Sept. 

3  Sorauer,  P.  Ubcr  die  Rotfiirbung:  von  SpaltcJffnungcn  bei  Picca.  Notizbl. 
d.  Bot.  Gart.     Berlin  1S96,  No.  16. 


these  ribs  (intercostal  fields),  suffer  earliest  and  most  extensively  from 
frost,  sunburn,  etc.  With  the  action  of  the  acids  in  smoke,  however,  the 
boundaries  between  the  dead  and  healthy  tissues  are  as  sharp  as  usual,  while 
with  the  action  of  atmospheric  factors  they  are  less  distinct  because  of  the 
many  transitional  stages. 

The  appearance  of  the  injury  in  decidedly  smoky  districts  also  differs 
because,  besides  sulfurous  acid  others/  such  as  sulfuric  acid,  hydrochloric 
acid,  hydrofluoric  acid,  etc.,  become  eff'ective.  The  action  of  these  acids 
strongly  soluble  in  water  (hygrophilous)  is  restricted,  however,  to  the 
immediate  surroundings  of  the  centre  of  production,  where  they  act  at  any 
rate  much  more  intensively  and  kill  the  tissue  rapidly,  while  sulfurous  acid, 
distributed  in  a  gaseous  form  over  wide  districts,  is  usually  breathed  in  by 
the  plant  slowly  but  permanently.  The  former  effect,  appearing  rapidly  and 
eating  into  the  tissue,  is  distinguished  as  "acute"  from  the  phenomenon  of  a 
slow  poisoning  which  is  termed  "chronic  injury  from  smoke."  Of  course,  the 
latter  must  have  made  itself  felt  inside  the  plant  before  the  external  char- 
acteristics appeared.  The  chlorophyll  apparatus  is  changed  (as  has  been 
proved  by  Wislicenus^  with  the  spectroscope  and  by  Sorauer-  with  the 
microscope)  even  if  the  plants  still  appear  perfectly  normal.  In  this  case  an 
"invisible  injury  from  smoke"  is  spoken  of.  Naturally  such  disturbances 
can  be  averted  very  easily  and  the  plant,  as  has  been  found,  is  in  a  position 
to  cure  itself  after  the  cessation  of  a  weaker  action  of  smoke. 

Such  cases  will  also  occur  in  forestry  if  changes  in  local  conditions  take 
place  which  divert  a  stream  of  smoke  or  dilute  it  to  the  point  of  uninjurious- 
ness.  Wislicenus^,  to  whom  we  owe  recent  especially  thorough,  conscien- 
tious investigations,  states  that  the  point  of  uninjuriousness  is  0.0005  P^^ 
cent,  of  the  volume. 

He  emphasizes  the  fact  that,  aside  from  the  extreme  individual  differ- 
ence in  sensitiveness,  the  stage  of  development  of  the  plant  is  of  decisive 
significance.  The  time  when  the  new  leaves  and  needles  tmfold  is  the  most 
critical ;  the  plants  suft'er  most  then,  because  the  cuticular  covering  of  the 
epidermis  is  still  insufficiently  developed.  The  above-mentioned  influence 
of  light,  which  promotes  injury  and  was  observed  by  v.  Schroder  and  Hartig, 
has  been  tested  experimentally  by  Wislicenus*,  who  found  that,  visible 
injuries  did  not  appear  in  young  spruces  in  the  dark  and  in  winter,  although 
an  increase  of  the  sulfur  content  could  be  proved.  Ramann  and  Sorauer^ 
have  also  observed  that  the  amount  of  demonstrable  sulfur  in  an  organ  is 
not  determinative  for  the  degree  of  injury  and  Count  zu  Leiningen''  calls 


1  Wislicenus,  Resistenz  dor  Fichte  g-cg-on  saure  Rauchgase  bei  ruhender  und 
tatiger  Assimilation.     Tharandter  Forstl.    Jahrbiicher  1S9S,  Sept. 

~  Sorauer,  P.,  u  Ramann,  E.  Sogenannte  unsichtbare  Rauchbeschadigungen 
Bot.  Centralbl.  1899,  Vol.  LXXX.  See  also  Brizi  in  Zeitsch.  f.  Pflanzenkrankh.  1901, 
p.  160. 

3  Wislicenus,  H.  Massnahmen  gegen  die  Ausbreitung  von  Hlittenrauchschaden 
im  Walde.     Referat  5  der  Sekton  VIII  d.  Internat.  landw.  Kongresses  in  Wein  1907. 

4  Tharandter  Forstl.  Jahrbucher  1898,  p.  152. 

5  Loc.  cit. 

6  Graf  zu  Leiningen,  W.,  Licht  und  Schattenblatter  der  Buche.  Naturwiss.  Z.  f. 
Landw.  u  Forstw.  III.     Jahrg.     Part  5. 


attention  to  a  factor  which  is  of  decisive  importance  in  niakinj;  tests  as  to  the 
estimate  of  injuries  due  to  acid  viz.,  to  the  very  dift'erent  amounts  of  sulfur 
and  chiorin  in  shade  leaves  as  contrasted  with  sun  leaves.  He  found  in  the 
beech  in  one  square  meter  of  leaf  substances: — 

in  sun  leaves  in  shade  leaves 

SO,    0.2730  g.  0.3004  g. 

CI    0.0190  g.  0.0347  g. 

Therefore,  the  less  abundant  the  i)roduction  of  organic  substances  is 
the  relatively  higher  becomes  the  content  of  sulfuric  acid  and  chiorin.  The 
statements  of  Wislicenus  express  the  same:  "A  poorer  soil  quality,  that  is, 
soil  constitution  of  less  value  physically  and  chemically,  soils  specifically 
unsuitable  for  the  plant  genus  or  primarily  insufficient,  excessive,  or  abnor- 
mally varying  water  content  of  the  soil  create  a  predisposition  to  disease 
from  smoke ;  among  them  the  chief  factor  is  the  lack  of  water." 

The  fact  that  the  conditions  in  a  forest  become  different  because  of  the 
falling  of  the  needles  and  the  dying  of  the  branches,  indeed,  that  the  appear- 
ance of  deciduous  trees  is  changed,  that  the  trunks  become  almost  entirely 
free  from  lichens^  and  that  the  bark  of  the  trunks  of  beeches  takes  on  a 
peculiar  grey  tone,  may  be  mentioned  only  in  passing.  The  statements  of 
V.  Schroder  and  Reuss  point  directly  to  the  change  in  soil  constitution. 
They  still  say  that  an  accumulation  of  undecayed  needles  is  formed  under 
spruces  chronically  injured  by  smoke  and  a  complete  absence  of  all  living 
vegetation  is  noticeable  as  far  as  the  dropping  from  the  tree  extends.  This 
indicates  a  "poisoning  of  the  soil."  This  is  proved  by  Reuss'  experiments, 
in  which  he  carried  soil  from  a  smoke  filled  region  into  a  zone  free  from 
smoke  and  set  out  i)lants  in  it.  After  three  years,  the  loss  in  i  to  2-year-old 
seedlings  of  the  ash  amounted  to  100  per  cent.,  of  the  maple  92  per  cent., 
of  the  beech  y2  per  cent.,  of  the  spruce  and  pine  8  per  cent.,  and  of  the 
oak,  none. 

Wieler-  has  now  taken  in  hand  especially  the  (|Uestion  of  soil  poisoning 
and  has  proved  that  under  certain  circumstances  in  smoky  regions  with  a 
continued  out-pouring  of  smoke,  sulfurous  acid  could  be  proved  to  a  de[)th 
of  30  cm.  and  had,  therefore,  not  been  changed  into  sulfuric  acid.  The 
latter  will  also  remain  uninjurious  only  so  long  as  it  can  combine  with 
bases.  If  these  bases  are  used  up  in  neutralization  and  are  washed  away  by 
rain  the  humic  acid  present  finds  no  possibility  of  combination.  In  fact,  all 
the  soil  tests  made  by  Wider,  from  regions  injured  by  smoke,  showed  great 
amounts  of  humic  acid.  Calcium,  which  could  have  combined  with  the 
humic  acid  produced  is,  therefore,  not  present  in  these  soils.  The  other 
bases,  however,  with  which  the  humic  acid  forms  soluble  compounds  (mag- 
nesium and  iron)  must  have  disappeared  from  the  soil.  Thereby,  naturally, 
the  absorptive  power  of  the  soil  becomes  poorer  for  other  mineral  nutritive 
substances.     This  refers  also  to  the  alkali  forming  soluble  compounds  of 


1     Lindau,  loc.  cit.,  p.  120. 

-  Wieler,  Neuere  Untersuchungen,  etc.,  p.  314. 


723 

humic  acid  which  Hkewise  pass  into  the  subsoil.  The  lack  of  calcium  makes 
more  difficult  the  decomposition  of  the  humus  substances  and  the  nitrogen 
enclosed  in  them  remains  inaccessible  to  the  plants.  At  times  the  bacterial 
flora  is  scanty  in  acid  soils.  The  free  sulfurous  and  sulfuric  acids  may  act 
injuriously  also  on  animal  organisms  such  as  earth  worms.  Soils  in  smoky 
localities  will  become  impoverished  or  poisoned  by  all  these  factors. 

Wieler  ascribes  the  death  of  plants  and  especially  chronic  injuries  to 
the  scantier  absorption  capacity  of  soil,  which  has  been  poisoned  and  weak- 
ened by  sulfuric  acid  or  also  by  hydrochloric  acid,  but  certainly  goes  too 
far  into  this,  since  all  experiments  show  that  the  direct  contact  with  the 
smoke  forms  the  chief  cause  of  death' of  the  aerial  organs:  also  comparative 
chemical  analyses  of  the  foliage  and  of  the  soil  from  which  it  is  produced, 
do  not  always  indicate  an  impoverishment  of  the  supply  of  bases,  but  at 
times,  in  fact,  a  strong  increase  of  calcium  and  magnesium^  Yet,  neverthe- 
less, this  aspect  of  the  effect  of  acid  smoke  remains  of  the  greatest  impor- 
tance and  the  attention  of  practical  workers  should  be  directed  to  period- 
ically repeated  application  of  calcium  to  the  soil. 

We  must  refer  to  special  works  for  the  influence  of  currents  of  air  and 
their  constitution,  especially  their  water  content,  as  well  as  for  proving  acids 
in  the  air  and  the  regulations  for  overcoming  injuries  due  to  smoke.  We 
would  like  to  mention  only  that  Ost'  has  given  a  simple  method  for  deter- 
mining the  amount  of  sulfuric  acid  in  the  air.  He  saturated  small  pieces 
of  cloth  with  corrosive  barite  and  dried  them.  He  then  hung  them  in 
exposed  positions  in  the  places  where  the  experiments  were  being  made  and 
after  a  certain  time  investigated  their  sulfuric  acid  content.  By  this  method 
even  pure  mountain  air  showed  a  certain  amount  of  sulfuric  acid  as  its 
normal  mixture,  which  must  increase  significantly  in  the  neighborhood  of 
\  illages.  We  have  found  recently  in  a  lecture  by  the  chief  forestry  com- 
missioner, Reuss'%  a  summary  of  the  requirements  of  foresters  for  the  pro- 
tection of  the  forest  against  smoke.  He  indicates  the  necessity  of  forming 
indemnification  societies  in  regions  where  many  factories  are  placed  close 
together. 

The  fact  should  not  be  left  unconsidered  that  when  damages  are 
demanded  the  objection  is  raised  not  infrequently  by  the  injuring  smelters 
and  factories  that  eating  by  insects  is  the  chief  cause.  In  this  connection, 
Gerlach*  calls  attention  to  the  fact  that  spruce  plantations,  diseased  by 
smoke,  are  preferred  by  the  resin  weevil.  Not  only  Pissodes  Herciniac  and 
P.  scahricollis,  but  also  other  insects,  like  Grapholithia  pactolana  and  G. 
Chermes  increase  to  a  devastating  degree  in  forests  injured  by  smoke. 


1  Die  landwirtschaftlicliG  Versuchsstation  in  Miinster  1.  W.  Denkschrift  von  J. 
Konig.     Miinster  1S96,  p.  191  ft. 

~  Ost,  H.  Die  Verbreitung-  der  Schwefelsaure  in  der  Atmosphare.  Die  chem. 
Industrie  1900;  cit.  Zeitschr.  f.  Pflanzenkrankh.     1901,  p.  248. 

3  Reuss,  Karl.  Massnahmen  gegen  die  Ausbreitung-  von  Hiittenrauchschaden 
im  Walde.    Internat.  Landw.  Kongress  zu  Wein  1907,  Section  8,  Ref.  5. 

4  Gerlach,  Beobachtungen  und  Erfahrungen  tiber  charakteristische  Beweis- 
mittel  uzw.  Merkmale  von  Rauchschaden.  Osterr.  Forst-  u.  Jagdzeitung;  cit.  Bot, 
Centralbl.  1907,  No.  40,  p.  360, 


724 

Hydrochloric  Acid  and  Chlori.n. 

Besides  sulfur,  hard  coal  also  contains  chlorin  in  the  form  of  sodium 
chloride  The  chlorin  content  varies  between  o.i  to  2.0  per  cent.  Leadbetter 
found  in  hard  coal  0.009  to  0.028  per  cent,  of  chlorin'-.  This,  however,  could 
not  be  proved  in  the  ash  and  must,  therefore,  have  been  forced  out  with  the 
volatile  substances.  Meinecke  has  also  directly  proved  the  presence  of 
chlorin  in  the  j^ases  of  blast  furnaces"  and  Smith*  calls  attention  to  the 
chlorin  content  of  rain  water  in  regions  where  hard  coal  is  burned  in  consid- 
erable amounts.  According  to  these  statements,  therefore,  we  must  not 
consider  any  single  injurious  factor  in  the  smoke  of  hard  coal  but  dilVcrent 
combinations  of  several  factors.  The  difference  will  depend,  on  the  one 
hand,  on  the  composition  of  the  coal  and,  on  the  other  hand,  on  its  use 
industrially. 

Because  of  the  rapid  formation  of  hydrochloric  acid  from  chlorin  in  the 
presence  of  moisture  and  light  both  these  factors  must  be  treated  together. 
In  connection  with  sulfuric  acid,  mention  has  already  been  made  of  the 
impoverishment  taking  jjlace  possibly  from  the  continued  action  of  hydro- 
chloric acid  in  the  soil.  The  action  of  direct  solutions  of  chlorin  alkalies 
will  be  mentioned  in  connection  with  cooking  salt.  The  action  on  the  plant 
varies  according  to  its  species,  the  season  of  the  year,  or  the  place  and 
individual  development.  In  general,  this  results  in  a  bleaching  and  drying 
of  the  leaf  edges,  or  also  of  the  intercostal  fields  in  which  chlorin  vapor  acts 
more  quickly  than  does  hydrochloric  gas.  In  contrast  to  sulfurous  acid, 
however,  dry  leaf  edges  preponderate  here.  It  was  observed  in  the  experi- 
ments made  by  Ramann  and  Sorauer  (see  Sulfurous  Acid)  that  spruces 
sprinkled  with  water  absorbed,  on  an  average,  less  chlorin  than  plants  not 
moistened. 

The  studies  on  the  changes  in  anatomy  have  up  to  the  present  led  to 
contradictory  results.  Thus  Lindau^'  observed  in  Abies  an  alteration  only 
at  and  near  the  stomata,  while  Kinderman*'  confirms  the  investigations  of 
Leitgeb  and  Molisch,  that  the  guard  cells  possess  the  greatest  power  of 
resistance  to  injurious  factors  (among  others,  acids),  which  probably  arises 
from  a  special  constitution  of  the  cytoplasm. 

Because  of  the  uncertainty  of  results  up  to  the  present  time,  I  will 
repeat  here  briefly  the  results  of  my  own  studies  on  grain  and  spruce'.  At 
first  the  heavy  general  falling  ofif  in  reproduction  which  the  plants  undergo, 
because  of  the  hydrochloric  vapors,  and  which  manifests  itself  in  the  quan- 
titative proportions  and  the  formation  of  the  grain,  has  been  found  to  be  very 


1  Hasenclever,  tJbcr  die  Beschadiffung:  der  Vcgretation  durch  saure  Gase.     1879, 
p.  9.     Berlin,  Spring-er. 

2  Chemical  News  1860,  No.  46. 

3  Dingler'.s  Journal  1875,  p.  217. 

4  Bericht  uber  die  Entwicklung  der  chem.  Industrie  von  A.  W.  Hofman,  1875. 

5  I.oc.  cit.,  p.  244. 

6  Kindermann,   V.      Uber   die  auffallende   Widerstandskraft   der   Schliesszellen 
geg-en  schadliche  Einflusse;   cit.  Just.  Bot.  Jahresber.  1902,  II,  p.  6.53. 

7  Sorauer,  P.     Beitrag  zur  anatomischen  Analys^e  rauchbeschadigter  I'flanzen. 
Jjandwirtsch.  Jalirbiicher  1904,  p.  587. 


7^5 

pronounced;  this  confirms  the  investigations  of  Wieler  and  Hartleb^  Such 
an  effect  can  occur  without  an  indication  of  a  disturbance  in  growth  by  any 
striking  external  characteristics.  As  a  rule,  however,  this  disturbance  in 
growth  is  accompanied  by  a  discoloration  of  the  chloroplasts  and  their  subse- 
quent balling.  There  then  follows  a  contraction  of  the  primordial  sack  and 
a  shrivelling  of  the  chlorophyll  grains.  The  leaf  thus  injured  may  still  at 
times  live  out  its  life  normally,  depending  upon  the  intensity  and  length  of 
action  of  the  chlorin.  Usually,  however,  it  dies  prematurely,  in  part  or 
entirely.  In  the  latter  case,  principally  the  leaf  parts  die,  for  which,  because 
of  their  position  and  the  lesser  development  of  mesophyll  and  vascular 
bundles,  the  supply  of  water  is  acquired  less  easily  and  is  smaller;  these  are 
the  tips  and  edges  of  the  leaf.  Therefore,  we  find  dry,  discolored  leaf  tips 
in  grain  and  narrow  dry  outhnes  on  both  sides  of  the  lower  part  of  the  leaf 
surface  which  still  remains  green.  As  a  result  of  rapid  death,  a  compara- 
tively important  condition  is  found  in  the  cell  content  of  the  dead  parts. 
The  drying  with  the  retention  of  air  in  the  tissue  is  connected  with  a  shriv- 
elling of  the  cells ;  yet  in  such  a  way  that  the  walls  of  each  cell  do  not  touch 
one  another.  The  natural  process  of  dr^dng,  on  the  other  hand,  which 
occurs  only  after  complete  impoverishment  of  the  cell  content,  is  character- 
ized by  the  entire  collapse  of  the  mesophyll  cells,  in  which  the  upper  wall 
falls  against  the  lower  wall  and  the  whole  flesh  of  the  leaf,  formerly  green, 
represents  a  pale  straw  colored  strip  of  dense  tissue  with  curving  walls  lying 
upon  one  another  in  layers.  The  collapse  of  the  cells  in  dift"erent  varieties 
of  grain,  with  the  exception  of  barley,  extends  almost  entirely  in  the  meso- 
phyll during  the  natural  process  of  dr}'ing,  while  the  epidermal  cells  retain 
approximately  their  normal  height.  In  barley  (characterized  by  practical 
workers  as  "soft"),  the  epidermal  cells  also  collapse  in  a  natural  death.  But 
in  this,  some  of  the  widest  cells  of  the  upper  surface  form  an  outward  fold. 
In  a  cross-section  through  the  dead  leaf  this  appears  as  a  conical  protuber- 
ance resembling  a  hair  and  gives  the  whole  cross-section  the  appearance  of  a 
thin,  knotty  spiny  cord. 

Because  of  the  importance  of  distinguishing  a  leaf  which  has  died  a 
natural  death  from  one  destroyed  prematurely  by  acid  gases,  we  will  illus- 
trate a  leaf  injured  by  acids  and  one  which  has  died  normally.  Fig  162  / 
is  the  cross-section  through  the  edge  of  an  oat  leaf  dried  by  hydrochloric 
acid,  or  chlorin  vapor.  It  is  seen  that  the  tissue  has  shrivelled  greatly, 
especially  between  the  ribs  (the  intercostal  fields)  zvithout  the  mesophyll 
having  had  time  to  become  empty.  The  cell  contents  appear  a  dirty  green 
to  a  brownish  green  color  and  variously  contracted.  The  walls  of  the  bast 
layers  at  the  angles  of  the  leaf  (B)  and  below  the  vascular  bundles  (b)  like 
the  epidermis  are  colored  a  reddish  yellow  to  a  brownisJi  yellow  and  the 
epidermal  cells  in  places  {s)  are  so  dried  that  the  upper  wall  touches  the 
lower  wall.  Fig.  162,  .?  is  a  magnified  cell  group  from  162,  /,  showing  the 
still  abundant  cell  content. 

1     Wieler,  A.,  and  Hartlel),  R.     tjber  Einwirkung-  dei-  Salzsiiure  auf  die  Assimi- 
lation der  Pflanzen.     Ber.  d.  Deutsch.  Bot.  Ges.  1900,  p.  348. 


Fig.  162.     Difference  between  an  oat  leaf  dried  by  the  fumes  of  chlorin  or  hydro- 
chloric acid  and  one  which  has  died  a  natural  death. 


727 

Fig.  162,  J  illustrates  the  cross-section  through  a  normally  dried  oat 
leaf  from  a  locality  free  from  smoke.  In  the  cross-section  the  leaf  appears 
as  thin  as  a  cord  because  the  mesophyll  (V)  is  approximately  empty  and  the 
cell  walls  have  collapsed.  The  leaf  does  not  shrivel  in  the  same  way  around 
the  larger  vascular  bundles  because  the  strong  layers  of  bast  serve  as  stiffen- 
ing; they  look  like  knots  in  the  cord-like  form.    In  spite  of  the  great  drying 


163.     Leaves  of  a  i-ed  beech,  affected  by  sulfurous  acid, 
and  Reuss.) 


(After  V.   Sclirr.flor 


of  the  leaf,  the  epidermis  retains  its  natural  height  and  at  most  turns  a  pale 
quince  yellow  like  the  bast  cords,  and  is  thus  distinguished  from  that  injured 
by  acids.  Fig.  162,  4  is  a  magnified  group  from  Fig.  162,  5.  E  indicates 
the  epidermis ;  below  this,  the  collapsed  mesophyll  cells  in  which  the  scanty 
cytoplasmatous  remnants  of  the  cell  content  have  been  made  recognizal)le 
by  soaking  tlie  section  in  water.  Also  in  the  oat  leaf  which  has  matured 
slowlv  in  continued  wet  weather  the  part  injured  by  acid  differs  in  color 


728 

from  the  normal  since  it  has  assumed  a  lemon  yellow  color  in  the  walls  of 
the  bast  layers  and  epidermal  cells.  The  intensity  of  the  discoloration  is 
connected  with  the  quality  of  tannin.  In  observing  differences  in  color  one 
must  work  (|uickly,  since  the  coloring  matter  is  soluble  in  water. 

All  tliat  has  been  said  here  of  grain  varieties  may  not  be  applied  .without 
limitation  to  other  plants.  As  a  general  occurrence  may  be  considered  only 
the  fact  that  in  all  kinds  of  sudden  death,  the  cell  contents  are  abundantly 


Fisr.  ]f)6.     Beech  Icavos 
(Aflor  V.  Schii'iflor  and   Rou.ss.) 


retained,  while  they  are  for  the  most  ])art  used  up  in  rcs])irati()n  when  the 
leaf  has  lived  out  its  life  naturally. 

In  order  to  emphasize  the  habitual  differences  in  the  manner  of  attack 
of  the  vapors  of  sulfurous  and  hydrochloric  acids  we  will  give  here  illustra- 
tions of  injured  leaves  co])ied  from  the  repeatedly  cited  works  of  v.  Schroder 
and  Reuss. 

In  Fig.  163  we  see  a  leaf  of  a  red  beech  taken  from  the  vicinity  of  a 
silver  smelter,  which  had  been  injured  by  SD..     Fig.  164  shows  a  birch  leaf 


729 


from  the  neighborhood  of  a  copper  mill  likewise  injured  by  SOo.  The  com- 
mon characteristic  consists  of  more  or  less  sharply  defined  brown  specks  in 
the  intercostal  fields.  The  spots  are  usually  surrounded  by  a  brown  zone 
which  may  vary  in,  tone.  In  many  trees  (for  example,  the  red  beech)  a 
transparent  yellowish  green  band  of  diseased  but  not  dead  tissue  is  found 
around  this  peripheral  zone. 

Figures  165,  166  and  167  illustrate  leaves  from  a  rose  plant,  a  beech 
and  a  birch,  which  have  been  artificially  injured  by  hydrochloric  acid.  They 
have  the  dry  periphery,  which  may  usually  be  observed  after  the  action  of 
pure  chlorin  vapor.  Nevertheless,  it  should  be  emphasized  that  in  testing 
smoke  effect  no  definite  conclusion  may  be  drawn  from  such  structural 
pictures  showing  the  habit  of  growth,  because,  on  the  one  hand,  the  forms 
of  injury  vary  according  to 
the  individual  habitat  and  de- 
velopment of  the  tree  and,  on 
the  other,  dift'erent  factors 
may  produce  similar  injuries. 

Hydrofluoric  Acid. 

More  often  than  was  for- 
merly supposed,  hydrofluoric 
acid  produced  by  the  opera- 
tion of  superphosphate,  glass 
and  chemical  factories  has 
proved  injurious  to  vegeta- 
tion. The  fact,  at  first  so 
puzzling,  that  smoke  from 
kilns  and  terra  cotta  factories 
is  very  injurious  in  many 
cases  and  in  others  non-inju- 
rious has  been  explained  by 
this  action  of  the  acid.  The 
difference    in    effect   depends 

upon  the  presence  and  amount  of  fluorin  compounds  to  be  found  in  the  clay 
and  raw  phosphates.  According  to  Ost,  action  manifests  itself  in  small, 
brown,  corroded  spots  which  in  many  plants  are  surrounded  by  a  yellowish 
zone.  Smoke  experiments  carried  on  by  other  investigators  produced  in  oak 
leaves  narrow,  yellowish  brown,  sharply  defined  peripheral  discolorations. 
The  Norway  maple  showed  similar  tracery  along  the  edges  of  the  leaves  and 
the  leaf  surface  and  later  also  turned  brown.  Lindau^  describes  the  ana- 
tomical condition  in  the  oak.  He  found  both  of  the  epidermal  layers  to  be 
intact  and  the  contents  of  the  mesophyll  cells  slightly  browned.  The  indi- 
vidual chloroplasts  were  still  recognizable,  "but  the  rest  of  the  cell  contents 
had  an  oily  appearance." 


ch    leaves   injured    by   hydrochloric 
n   finne.s.      (After   v.    Schriider   and 
Reuss.) 


1     Loc.  cit.,  p.  250. 


730 

In  regard  to  the  forest  trees,  wliich  come  most  under  consideration,  we 
find  it  stated  that  the  spruce,  even  one  day  after  artificial  smoking,  shows 
some  shoots  with  a  whitish  gray  discoloration ;  in  fact,  they  had  wilted. 
After  a  second  smoking  the  little  trees  were  set  out  of  doors,  where  the  color 
tone,  which  originally  had  been  a  whitish,  yellowish  gray,  passed  through  all 
the  gradations  from  yellow  and  yellowish  red  to  the  "characteristic  red  of 
injury  from  acids." 

Pines,  larches,  and  acacias,  like  the  spruce,  were  found  to  be  discolored 
in  the  vicinity  of  a  phosphate  factory  where  hydrofluoric  vapors  were  devel- 
oped in  the  removal  of  phosphorite  containing  the  calcium-fluorin  by  the 
use  of  sulfuric  acid^  Mayrhofer-  was  able  to  prove  a  strikingly  high 
content  of  fluorin  in  the  needles  and  leaves  at  a  distance  of  500  to  600  m. 
from  the  factory.  The  effect  of  such  an  exhalation  may  be  absolutely 
destructive  to  grain.  Thus  Rhode^  observed  that  in  sortie  plots  rye  devel- 
oped no  kernels  at  all,  or  only  deformed  ones. 

My  own  investigations  were  made  only  on  preserved  material  of  dead 
spruce  needles  which  I  had  received  from  Professor  Ramann,  but,  what  is 
most  important,  the  condition  found  in  them  agreed  with  the  effects  obtained 
with  sulfurous  acid.  Only,  in  the  needles  affected  by  the  hydrofluoric  acid,  I 
found,  however,  a  wrinkling  of  the  tissues  as  a  result  of  the  shrivelling  of 
the  cell  walls.  It  must  be  concluded  from  this  that  the  drying  of  the  needles, 
which  appears  so  quickly  with  the  use  of  sulfurous  acid,  takes  place  only 
after  the  direct  action  of  the  acid  has  already  produced  a  change  in  the  form 
of  the  tissues.  The  contents,  however,  had  not  dried  against  the  walls  as  in 
the  action  of  sulfurous  acid,  and,  on  this  account,  could  not  have  contributed 
to  the  stiffening  of  the  walls  themselves. 

Nitric  Acid. 

We  find  only  one  note  by  Konig*  on  the  influences  of  nitric  acid  (or 
nitrogen  tetroxid).  With  5  grains  nitric  acid  (reckoned  on  nitrogen 
tetroxid)  to  100,000  1.  of  air  or  0.05  g.  of  nitrogen  tetroxid  in  one  cubic  metre 
of  air,  he  found  characteristics  occurring  in  trees  which  resembled  those 
appearing  after  the  action  of  sulfurous  acid  and  hydrochloric  acid.  The  air 
generally  contains  only  0.00003  g.  of  nitric  acid  in  one  cubic  metre. 

Ammonia. 

Ammonia  and  ammonium  carbonate  in  quantities  far  beyond  that  of  the 
usual  content  of  the  air,  which  at  most  may  be  assumed  to  be  0.056  mg.  per 
cubic  metre,  were  found  to  favor  growth.  In  general  manufacturing  pro- 
cesses, however   (ammonium  sodium  processes,  etc.),  such  large  amounts 


1  Allgem.  Forst.  u  Jagdzeitung-  1891,  p.  220. 

2  Mayrhofer,  J.  tJber  Pflanzenbeschadigung,  veranlas-st  durch  den  Betrieb 
einer  Superphosphatfabrik.  Freie  Vereinigung  d.  Bayr.  Vertreter  fiir  angewandte 
Oliemie.     Vol.  X,  p.  127. 

•^     lihode,    A.     Schadigung    von    Roggenfeldoi-n     diirch    dio    pincr    .Siipeiphos- 
phatfabrik  entstromenden  Ga.se.    Zeitschr.  f.  PflanzcMikiankli.  ISlt.''),  p.  I'ir,. 
■»     KiJnig,  Denkschrilt  lSt»6,  p.  202. 


731 

become  free  that  they  produce  injuries,  although  the  plants  in  general  are 
found  to  be  very  resistent.  The  sensitiveness  of  different  species  varies 
greatly,  but  the  kind  of  injury  shows  a  great  uniformity;  namely,  a  black 
coloration  occurring  in  spots  or  surfaces. 

Experiments  made  by  Borner,  Haselhoff  and  Konig^  exhibited  in  the 
oak  the  appearance  of  dark  spots  or  a  complete  blackening  of  the  leaves.  In 
the  cherry  at  first  a  brown  color  was  seen  and  later  black.  After  a  short 
exposure  to  the  action  of  ammonia  the  leaves  and  blades  of  barley  were 
bleached  white  on  the  side  turned  toward  the  sun.  Rye  and  wheat  showed 
rusty  spots  and  edges. 

In  addition  to  the  cases  already  known  in  literature,  I  will  add  here  a 
few  of  my  own  observations.  I  found  the  leaf  tips  of  barley  turning  white. 
The  intercostal  fields  of  young  chestnut  leaves  were  dark  at  first,  but  became 
black  the  next  day  and  later  dried  up.  The  foliage  of  some  of  the  red  blos- 
soming varieties  of  Azalea  indie  a  behaved  similarly,  while  in  a  variety  stand- 
ing nearby  but  bearing  white  blossoms  only  a  browning  of  the  leaf  tips  and 
edges  appeared.  Along  the  edges  of  the  outermost  tips  of  blossoms  of  the 
red  variety,  white,  nearly  round,  or  wedge-shaped  spots  resembling  a  natural 
variegation  were  found,  while  blossoms  of  the  white  variety  within  the  same 
length  of  time  remain  unchanged  with  the  exception  of  scattered  small, 
brown  spots.  No  after  effects  could  be  perceived  after  the  plants  had  been 
removed  from  the  ammonia  atmosphere ;  but  there  was  some  reaction  in  the 
inflorescence  of  a  cineraria.  The  red,  outer  blossoms  which  had  turned  blue 
from  the  ammonia,  became  red  again  some  time  after  their  removal  from 
the  ammoniacal  atmosphere. 

The  spruce  furnishes  an  example  of  the  influence  of  the  developmental 
stage  on  the  amount  of  injury.  The  old  needles  took  on  a  pitch  black  color 
and  were  retained,  while  the  color  tone  of  the  young,  delicate  needles,  at  first 
a  dirty  green,  later  passed  over  into  a  faded,  reddish  yellow.  The  individual 
power  of  resistance  in  the  different  needles  is  shown  especially  clearly  in  an 
experiment  hi  which  some  needles  could  be  observed  on  branches,  among 
the  pitch  black  ones,  which  showed  noi  discoloration  or  at  most  only  a 
darker  green.  The  black  color  was  due  mainly  to  the  pitch  black  color  tone 
which  the  protoplasma  of  the  epidermis  and  mesophyll  cells  had  assumed. 
The  cell  walls  were  only  slightly  brown.  In  the  cells  most  injured  the 
contents  had  become  a  consistent,  granular,  doughy  mass,  which  at  times  had 
drawn  back  from  the  walls.  The  contents  of  the  guard  cells  of  the  stomata 
were  also  pitchy  black,  never  red,  as  in  injuries  due  to  acids.  In  the  transi- 
tional places  between  tissue  which  had  remained  healthy  and  that  which  had 
blackened,  it  was  noticed  that  the  protoplasmic  mass  in  which  the  chloro- 
plasts  were  imbedded  had  already  turned  black,  while  these  granules  ap- 


1  Zeitschr.  f.  Pflanzenki^ankh.  1893,  p.  100.  Lindau  (loc.  cit.,  p.  286)  describes 
the  action  of  the  strongly  concentrated  ammonia  gas  on  the  phmt  cell;  in  the 
interior  of  the  leaf  the  cells  usually  show  very  strong-  plasmolysis;  the  contents 
become  indistinct  and  at  times  drops  of  oil  are  exuded.  In  this  a  brown  to  black 
coloring  matter  is  given  out  which  tinges  the  entire  contracted  conti-nts.  This 
proves  later  to  be  a  ferment. 


732 

pcarcd  unchanged  in  form  and  position.  Only  later  the  green  coloring 
matter  in  the  protoplasm  was  found  to  have  changed  and  become  a  dirty 
brownish  green.  Then  the  ground  substances  of  the  chl()roi)lasts  united 
with  the  other  cell  contents  apparently  leaving  behind  some  granular 
remnants. 

The  ammonia  might  also  exercise  some  special  poisonous  effect  on  the 
cell  contents  besides  combining  with  the  acids  as  has  been  assumed  in  another 
place.  Kny'  has  already  called  attention  to  the  fact  that,  according  to  the 
statements  quoted  in  the  literature  on  this  subject,  the  protoplasm  in  very 
different  parts  of  the  plant  possesses  an  alkaline  reaction  without  having 
influenced  the  chloroplasts.  The  same  author  has  shown  that  a  very  dilute 
ammonia  solution  injures  the  assimilatory  activity. 

In  one  case,  where  the  wall  of  a  stable  was  used  as  the  back  wall  of  a 
greenhouse,  the  way  in  which  ammoniacal  poisoning  may  often  take  ])lace 
was  clearly  demonstrated.  When  the  heat  was  turned  on  in  the  autumn, 
ammonium  carbonate  developed  from  the  wall,  which,  in  a  short  time, 
blackened  the  leaves  of  Aucuba,  Viburnum  Tinus,  Pmuus  Lauroccrasus, 
the  Dracaenae  and  other  plants  in  the  greenhouse.  ( )nly  the  tissue  immedi- 
ately adjoining  the  veins  of  the  leaves  remained  green. 

Tar  and  Asphalt  Fume.s. 

The  discoveries  concerning  the  injuries  of  tar  and  asphalt  fumes  have 
been  explained  only  recently,  since  the  material  for  ol)servation  has  become 
more  abundant.  Aside  from  the  effect  which  the  asphalting  of  streets  can 
])roduce  at  times  in  sensitive  plants,  the  factories  preparing  the  carbons  for 
arc  lights  are  to  be  considered  as  essential  causes  of  disease. 

Roses  rich  in  tannic  acid,  strawberry  leaves,  Ampelopsis  quinquefolia 
and  chestnuts  should  l)e  named  as  the  most  important  plants  showing  injury 
from  asphalt  fumes-'.  Different  varieties  of  roses  suffer  in  very  different 
degrees ;  for  example.  Tea  and  Bengal  Roses  are  less  affected ;  Remontants 
and  their  hybrids,  however,  are  for  the  most  part  very  severely  attacked. 
Parts  of  the  outer  membrane,  or  the  whole  leaf  surfaces  become  a  dull  l)lack. 
Usually  if  the  whole  surface  is  not  discolored  (Fig.  i68  la)  the  blackened 
l)laces  occur  as  interrupted  or  connected  bands  between  the  larger  lateral 
ril)S,  that  is,  in  the  intercostal  fields.  If  the  sepals  have  been  aft'ected  by 
the  funics,  the  l)lossom  buds  unfold  only  poorly.  Soon  after  the  appearance 
of  the  blackening,  the  contents  of  the  epidermal  cells  of  the  upper  side  will 
be  found  deeply  browned,  granular  and  lumpy,  and  usually  deposited  along 
one  of  the  horizontal  walls.  The  cuticle  is  not  browned  and  apparently 
unchanged.  When  the  leaf  is  more  diseased,  the  epidermis  of  the  under 
side  becomes  affected  in  the  same  way  and  later  collapses.  On  the  other 
hand,  the  mesophyll  is  but  little  irritated.  The  fumes  act  only  on  the  exposed 
surfaces  of  the  organs;  all  the  covered  parts    (Fig.    i68  ib)    remain  un- 

1  Bot.  Ccntralbl.  1.S9S,  Vol.  LXXIII,  p.  430. 

2  Sorauer,  P.  Die  Beschadig'un.sren  dcr  Vegetation  durch  Asphaltdampfe 
Zeitschr.  f.  Pflanzenkrankli.  1897,  p.  10. 


733 


734 

changed.  If  the  middle  part  of  the  leaf  is  injured,  the  edges  curl  up  like 
the  sides  of  a  boat. 

Attention  should  be  called  in  passing  to  the  fact  that  in  many  roses 
(for  example,  Rosa  turbinata),  a  similar  discoloration  appears  in  the  late 
autumn.  In  this  rose,  for  example,  I  found  that  the  older  leaves,  still 
hanging  on  the  stems,  had  become  dully  spotted  with  black  without  any 
previous  red  coloration;  this  arose  from  the  contraction  and  browning  of 
the  contents  of  the  epidermal  cells.  These  cells,  however,  retained  their 
natural  turgidity  and  height,  but  began  to  collapse  after  having  been  afifected 
by  asphalt  fumes.  In  this  the  contents  of  the  mesophyll  also  retain  their 
normal  consistency  and  position  for  some  time,  while,  in  the  autumn  colora- 
tion, they  contract  at  once  and  change  into  uniform  masses,  at  first  green, 
but  later  turning  brown.  Under  the  microscope  parasitic  blackening 
(Asteroma  radiosum,  etc.)  can  be  distinguished  easily  from  asphalt  cor- 
rosion. 

Before  I  began  my  experiments,  Alten  and  Jannicke^  had  already 
described  the  blackening  of  roses  and  strawberries  caused  by  the  action  of 
asphalt  fumes.  They  considered  the  iron  which  was  proved  present  in  these 
fumes  to  be  the  actual  injurious  factor  since  it  combined  with  the  tannic 
acid  of  the  cells  and  they  supported  this  theory  by  experiments  in  which 
they  produced  black  spots,  corresponding  to  those  in  asphalt  injuries,  b)' 
sprinkling  the  leaves  with  ferrous  chlorid  and  ferric  sulphate.  Ferric 
chlorid  did  not  have  this  effect. 

I  could  not  obtain  this  result  and  observers  who  have  sprayed  with  iron 
solution  as  a  means  of  overcoming  chlorosis  and  icterus  do  not  report  any 
blackening. 

In  the  strawberry  leaf  illustrated  in  Fig.  i68,  2  (a  cultivated  form  of 
Fragaria  chilcnsis),  only  a  partial  blackening  of  the  upper  side  is  found  at 
g  because  only  this  part  of  the  leaf  had  lain  free ;  otherwise  the  phenomena 
were  similar  to  those  in  roses,  the  curling  of  tlic  leaf  edges,  the  ])artial  dry- 
ing of  the  leaf  serrations,  etc. 

In  Fig.  168  5  we  see  a  leaf  of  Ampelopsis  quinquefolia  a  few  weeks  after 
it  had  been  acted  upon  by  tar  fumes  from  a  factory  making  electric  light 
carbons.  The  less  diseased  leaves  were  found  to  be  still  green  but  not  out- 
spread; the  edges  were  curled  up  like  bowls  and  the  inside  of  the  blade 
wrinkled  by  the  outpushing  of  some  of  the  tissue  lying  between  the  finer 
ramifications  of  the  veins.  At  times  small  places  with  a  cork  colored  upper 
surface  were  found  near  the  midrib.  With  more  extensive  injury,  these 
places  were  always  present  and  passed  over  partially  into  blight  spots  which 
became  dry  and  ultimately  united.  Finally,  each  leaf  may  show  very  regular 
markings  due  to  the, drying  of  the  intercostal  fields.  (Fig.  168  jj.)  These 
dry  places  often  break  away,  due  to  the  rubbing  of  the  leaves  against  one 
another,  thus  producing  a  lattice-like  perforation  (Fig.  168  3/). 


1     Alien,   H.,    und   Jannicke,   W.     Eine    Schadig-ung   von   Rosenblattern    durch 
Asphaltdampfe.    Rel".  Zeitschr.  f.  Pflanzenkrankh.  1891,  p.  156  und  1892,  p.  33. 


735 

Young  branches  become  corky  on  the  side  affected  and  show  fine  cracks. 
Any  existhig  air  roots  dry  up. 

When  the  action  of  the  asphalt  fumes  ceases,  the  leaf's  attempt  to  heal 
itself  at  once  become  apparent.  In  case  the  palisade  parenchyma  has  been 
only  a  little,  if  any,  affected,  it  may  elongate  somewhat  and  slightly  push  out 
the  epidermis,  which  has  collapsed  to  a  state  of  irrecognisability.  If,  how- 
ever, the  palisade  layer  has  also  died  the  healthy  underlying  mesophyll 
develops  a  perfectly  regular  layer  of  flat  cork  cells.  The  same  process  may 
be  noticed  on  the  leaf  stems :  the  brown,  dead,  ruptured,  outer  cork  and 
parenchyma  layers,  together  with  the  hard  bast  bundles  which  at  times  have 
also  succumbed  to  the  necrosis,  are  separated  from  the  healthy  tissue  by  a 
broad  cork  band  which  in  extreme  cases  extends  as  far  as  the  cambium. 

Vitis  vinifera  suffers  sooner  and  more  than  does  Ampelopsis,  so  that  its 
leaves,  at  times,  are  curled  entirely  out  of  shape  and  perforated.  In  this  it 
was  observed  that  in  places  lightly  affected  the  guard  cells  of  the  stomata 
had  suffered  first.  Other  plants  behaved  differently ;  in  regard  to  these, 
reference  must  be  made  to  my  original  work  on  the  subject.  The  corrosion 
of  the  epidermal  cells,  however,  may  be  cited  as  the  universal  characteristic. 

As  in  all  injuries  due  to  gaseous  bodies,  the  fact  that  the  injury  is 
chronic,  or  acute,  determines  the  results ;  in  the  former  case,  with  slower 
action,  the  organ  affected  can  remain  alive  for  some  time  by  its  counter 
action  and  may  slowly  live  out  its  life.  In  this  the  characteristics  differ 
frOm  those  found  when  the  action  is  that  of  more  highly  concentrated  gas 
waves,  which  result  in  a  rapid  death.  Thus,  for  example,  in  the  slow  death 
of  spruce  needles,  a  strong,  red  discoloration  of  the  cytoplasm  of  the  guard 
cells  and  later,  in  fact,  of  their  walls  was  perceived  in  the  still  green  parts, 
but  not  if  the  injury  was  acute.  The  walls  of  the  vascular  bundles  element 
also  discolored ;  as  always  happens  from  asphalt  fumes,  the  cell  walls  suffer 
especially  quickly.  This  is  seen  very  well  in  the  older  fir  needles  which 
acquire  a  metallic  lustre. 

Bromine. 

In  the  ordinary  industries  in  which  bromine  is  produced  injuries  due 
to  bromine  alone  may  scarcely  be  spoken  of  because,  as  a  rule,  sulfurous 
acid  works  with  it.  At  considerable  distances  from  the  factories  the 
bromine  may  still  be  perceived  by  its  odor,  but  no  decided  injuries  from 
the  acid.  Therefore,  any  description  of  natural  occurrences  in  the  neigh- 
borhood of  bromine  factories  may  be  omitted  here  and  only  the  behavior  of 
plants  under  the  artificial  action  of  intense  bromine  fumes  be  described. 
I  carried  out  experiments  as  follows  for  4  days : — 

Small,  well-rooted  spruce  saplings  in  pots  were  exposed  several  hours 
each  day  to  gaseous  bromine,  being  left  out  of  doors  between  times.  The 
branches  nearest  the  bromine  sources  naturally  suffered  most  and  all  their 
needles  turned  brown.  On  the  less  injured  branches  many  needles  were 
found  to  be  partially  brown  from  the  tip  back,  while  on  the  branches  furthest 
away  from  the  course  of  the  bromine  only  a  few  brown  needles  were  found 


736 

anKjiig  the  healthy  ones.  The  red  hrowii.  which  in  the  bei^inning  was  very 
bright,  soon  turned  into  a  gray  l)r()wn.  The  needles  kept  this  cohjr  until 
they  fell,  about  two  weeks  later,  but  this  took  place  only  on  greatly  injured 
branches.  It  was  found  in  the  discolored  places  of  the  slightly  injured 
needles,  remaining  on  the  branches,  that  the  walls  of  some  groups  of  meso- 
phyll  cells  near  the  epidermis  had  turned  a  faded  \o  reddish  yellow,  while 
the  contents  had  lost  their  color  and  finally  with  a  complete  disorganization 
of  the  walls  had  dried  up.  In  this  they  not  infrequently  passed  through  a 
stage  of  foamy  consistency.  For  some  time  after  the  action  of  the  gas  the 
guard  cells  of  the  stomata  seemed  to  have  become  discolored  up  to  the 
healthy  tissues  only  in  the  zones  of  transition  whereby  their  walls  had  turned 
a  brownish  yellow.  The  epidemiis  was  slightly  browned ;  the  sub-epidermal 
prosenchymatous  fibres  were  found  to  be  colorless.  The  mesophyll  near 
the  brown  places  remained  green  and  had  either  a  tlocculent  green  content 
or  the  chloroplasts  were  united  into  lumi)s.  Healthy  tissue  adjoined  this 
immediately. 

At  places  more  strongly  injured  the  vascular  bundles  were  also  affected 
and  discolored  just  as  from  sulfurous  acid,  but  the  color  tone  of  the  injured 
needles  was  only  rarely  a  reddish  brown.  They  were  generally  a  yellowish 
brown  and  less  hard,  a  fact  distinguishing  them  from  needles  affected  by 
SO^.  The  slight  amount  of  difference  is  of  less  moment  here  because,  as 
said  above,  in  general  injuries  from  bromine  occur  as  a  rule  in  connection 
with  those  caused  by  sulfurous  acid. 


CHAPTER  XVII. 


SOLID    SUBSTANCES    GIVEN    OFF   BY    CHIMNEYS   AND   THE 
DISTILLATES  THEY  CONTAIN. 

The  best  survey  of  the  material  from  the  streams  of  smoke  affecting 
vegetation  is  found  in  a  table  by  Wislicenus^  which  we  may  repeat  here  un- 
changed because  it  is  so  very  clear. 

No  general  decision  can  be  reached  as  to  the  substances  given  in  this 
table.  Under  certain  circumstances  they  may  become  injurious  and,  indeed, 
very  injurious  but,  in  other  cases,  they  do  not  cause  any  loss  of  crops  worth 
mentioning.  This  depends  not  only  upon  the  greater  or  less  exposure  of 
the  plants  but  also  on  locally  different,  secondary  conditions.  Aside  from  the 
individual  sensitiveness  of  different  species  of  plants,  the  constitution  of  the 
soil  and  the  weather  at  times  become  decisive,  especially  with  fine  fi3ang 
ashes. 

It  should  be  mentioned  in  connection  with  the  injuriousness  of  tar 
vapor  that  tar  vapors  from  lime  kilns  also  cause  injuries.  In  burning  lime- 
stone, when  the  calcination  begins,  that  is,  the  breaking  down  of  the  carbon- 
dioxid,  the  smoke  becomes  laden  with  great  cjuantities  of  the  distillates  given 
in  the  table,  which  produce  corrosions  similar  to  those  described  under 
asphalt  fumes.     These  vary  with  the  plant. 

The  injuriousness  of  soot  was  previously  universally  overestimated 
and  is  still,  to  some  extent.  The  more  recent  investigations  of  v.  Schmitz- 
Dumont  and  Wislicenus^  confirm  Stockhardt's  older  discoveries,  that  soot 
is  usually  non-injurious.  More  delicate  plants  may  show  corrosion  because 
of  phenol,  etc.,  carried  in  the  soot. 

The  theory  of  the  stoppage  of  the  stomata  must  be  left  undiscussed. 
According  to  my  investigations  of  plants  covered  with  soot  the  cases  are 
very  rare  in  which  the  soot  particles  have  succeeded  in  getting  into  the 
cavities  of  the  stomata,  or  actually  have  stopped  them  up,  and  even  in  these 
rare  cases,  I  have  not  been  able  to  perceive  any  change  in  the  surrounding 
cells.  Considerable  quantities  of  extractive  substances  (sulfates  and 
phenols)  must  first  be  leached  out  from  the  soot  before  any  injury  may  be 


1     Wislicenus,    H.      Zur    Bcuiteiluna:   und    Abvvehr    von    Rauchschaden,    Vortragr 
in  Dresden  am  31  Mai  1901.     Zeitschr.  f.  angewandte  Chemie  1901,  Part  28,  Taf.  V. 


738 


(Til Mimical  cokstitutioiv  op 


(THK    nCilJKlO.S     INDICATE 


Distillates 
and  Solid  .Matter- 
Contained 


TyiMcally 


(  on>titii('iit.~ 

in  (ia.-vs 
l'i<ini  SnioUe 


Oniiiiar.v 
Smoke  from 

Ilard-n.al 

Furnaces 
(Double  Chemical 

Air  Content) 


Steam 

Boilers 


Heaters 


Tai:   Kimks  ( Injurious) 

Aromatic  Carhuretted  Hydro 

«en 
I'licnol  ("Creosote") 
Auilin 
i'yridin 
I'Vrrol 


Ordinary 

Coke 
and  Brick 

Ovens, 
Occasion- 
ally in 
Charcoal 

Kilns 


So(yr  ( Practically  Non-injurious) 
Carbon  Avilli  Compounds: 
Tardike,  Nil:, 
I'otiissium,Soi|iuni,Calcituu 
Sull'uric  Acid 
Chlorin 
Kliodan,  etc. 


Ft.viNc  AsiiEs  (Conditionally 
Injurious) 

Oxids  1  Various  Rases  as 

Carbonates  [     Nrm-injurious 
I'liospliates  f         Insoluble 
SilicMles  I        Sul)stanccs 

As..(>,  Soluble  with    Dillicully 
Siillales    I   ofF(>.    )      Soluble" 
Clilori.ls  fZii.Cu  I    lujurions 
Alkalies  and  Am-  (        Sub- 
monia  Salts  )      stances 


rnsuital)iy 

Csed. 
Ordinary 
Hard-coal 
IIeatiu<:. 

Iron 

lietineries. 

Steel 

Smellers 

(Ke.lucini: 

Heat) 


Metal  Keliueries 


(  hiiKi;  .SpKcii-K    Soi.iDs: 
Zn  and  ZnO 
Ca(\^,  (\i(()H),.  CaCO. 
("ement  Dust 


/ilie  Keliue 
Carbid  I'ac 
PurtlaiKlCe 


:t  Works 


( '(  L 
(CO) 


ll,( 


8(L  with 

(.<<).,  and) 

1 1. .SO, 


ICI 


11  F 


Si  !•', 
ILSiF 


Nitric  and 

NiirosAcid.- 


II,S 

(CS.,) 


NH.. 

(Arain  Base^s. 
Ammonia  Salts ) 


Cvanids 
Khodani.l^ 


Ktlier  and 

Hen/.in 
Imumcs,  etc. 


(  — ) 
1.7 


(-) 


(Manufacture  of 


(Manufacture  of/ 
(IManufacture  /       I 


739 


ARIOUS  KINDS   OF  SMOKE 


lUME    PERCKNTAGE) 


7 

8 

9 

10 

11 

12 

13 

14 

15 

16 

17 

18 

.-r^ 

-f.S 

i 

s 

i; 

'^ 

=  ■3 

^ 

73     ^ 

II 

II 

II 

'2. 

> 

s 

1 

1 

"^ 

i=^'u: 

=^ 

?s 

Kj 

"P 

'^2 

> 

(18.44 

49.;;!) 

S.!»() 

<;.3 

15.7 

5.41 

(-) 
40.  St; 

Mncii! 

In 

Annealing 

Ultra- 

0.2() 

0.OS9 

In 
Fusing 
0.44;] 

O.U74 

0.02;] 

manne 

Ovens 

3.0..0.5 

0.039 

0.004 

1 

Chiefly 

I 

Wasle 

t  1 

Gases 

Containing 

Boric 

riuonn 

Acid 

UNO:, 

lluniinatiiig  Gas,  .Suda  Eesidue  in  Refuse  P 

leaps. ) 

lluniinating  Gas,  Prussic  Acid,  Ferrocyani< 

,  etc.) 

holographic  Papers,  etc. ) 

740 

manifested.  This  is  shown  in  Wislicenus'  experiments  with  the  soot  from 
hard  coal,  Ugnite  and  benzine,  as  well  as  extracts  from  soot,  by  means  of 
which  the  leaves  of  the  hornbean  and  linden  and  later  also  spruce  needles 
were  slightly  etched.  Probably,  as  they  dry  up,  the  salts  effect  an  osmotic 
removal  of  w^ater  and  a  drying  of  the  cells.  The  same  experiments  also  dis- 
pelled the  fear  that  a  thick  coating  of  soot  absorbs  the  light,  changing  it  into 
heat  and,  therefore,  acting  disadvantageously. 

It  is  theoretically  possible  that  the  carbon  dio.vid  carried  in  the  smoke 
can  act  injuriously  for  even  experiments  with  an  extreme  increase  of  this 
gas  above  the  normal  0.04  to  0.06  per  cent,  have  proved  the  retardation  of 
assimilation  but  this  can  scarcely  be  spoken  of  in  practical  industry.  The 
same  holds  good  for  carbonic  oxid. 

The  metallic  elements  of  the  smoke  from  smelters  (see  table)  also  enter 
into  the  question  of  the  effect  of  fllying  ashes.  According  to  Freytag's  inves- 
tigations\  pure  metallic  oxids  are  usually  non-injurious.  Naturally,  foliage 
bearing  such  oxids  cannot  be  used  as  food  for  animals,  since  they  may  easily 
cause  inflammator}-  diseases. 

Also,  these  metallic  elements  such  as  insoluble  oxids  or  carbonates  and 
silicates  scarcely  injure  the  aerial  parts  of  the  plants  more  than  does  the 
street  dust.  Soluble  compounds,  on  the  other  hand,  such  as  arsenous  acids, 
sulfates,  and  chlorides  {copper,  zinc,  and  lead)  are  principally  concerned 
here  and  produce  brown  spots  through  the  corrosion  of  the  tissue,  as  soon  as 
they  are  deposited  on  moist  leaves.  They  are  said  not  to  injure  dry  foliage 
and  a  subsequent  wetting  from  rain  easily  washes  away  the  coating.  Mer- 
cury fumes  in  the  air  always  act  very  injuriously.  The  compounds  washed 
into  the  soil  by  rain  are  absorbed  by  it  and  are  usually  non-injurious.  A 
large  accumulation  of  arsenic  (more  than  o.i  per  cent.)  is  disadvantageous. 
Experiments  made  by  Phillips-  prove  that  healthy  plants  undergo  no  dis- 
turbances in  growth  from  the  taking  up  of  lead  and  zinc,  while  copper  acts 
as  poisonously  as  arsenic  and  disturbs  the  root  development.  Klein-'  and 
numerous,  more  recent  observers  furnish  proof  of  the  presence  of  arsenous 
acids  in  plants.  Such  poisoning  of  the  soil  may  occur,  for  example,  near 
copper  smelters  and  in  the  litigation  against  the  Manns feld-Hettstadter 
copper  smelters  Grouven  refers  especially  to  this  point*.  My  own  experi- 
ence in  the  same  region  shows  that,  at  present,  large  surfaces  of  the  fields 
have  become  poisoned  and,  despite  very  abundant  fertilization,  yield  very 
meager  harvests.  The  experiments  in  which  soil  which  had  become  unfer- 
tile was  carried  from  the  vicinity  of  copper  works  to  a  region  free  from 
smoke  prove  that  the  gases  in  the  smoke  are  not  alone  the  injurious  factors. 


1  Freytag,  in  .Tahrb.  fiir  da.s  BeiK-  und  Huttenwesen  im  Kclnigieich  Sachsen 
1S73,  pp.  24  and  36,  cit.  in  Hasenclever. — Landwirtsch.  Jahrb.  1S82,  p.  315-375.  In 
regard  to  the  action  of  smoke,  the  author  differs  from  Schroder  inasmuch  as  he  does 
not  consider  the  sulfurous  acid  as  such  to  be  the  injurious  agent,  but  only  the  sul- 
furic acid  which  is  being  formed  from  it. 

-  Phillips.  The  absorption  of  Metallic  Oxides  by  plants;  cit.  Bot.  Centralbl. 
1883,  Vol.  XIII,  No.  11,  p.  364. 

3  Chemischer  Ackersmann,  1875,  Pai't  4. 

4  Fuhling's  neue  landwirtsch.  Z.  1871,  Part  7,  p.  534. 


741 

but  also  the  soil  which  has  been  rich  in  copper  salts.  Even  in  the  latter 
place,  which  is  free  from  smoke,  the  plants.  {Phase olus  vulgaris)  became 
diseased  while  those  sown  in  the  same  region  in  soil  which  had  always  been 
there  remained  healthy  and  developed  vigorously. 

An  analysis  of  potatoes,  of  which  the  plants  themselves  were  covered 
by  the  metallic  dust  from  a  nickel  factory,  shows  how  much  of  the  metal 
may  be  taken  up  by  the  plants  during  one  period  of  growth.  The  healthy 
foliage  contained  (in  percentages  of  substances  free  from  water  and  from 
sand)  : 

Copper  oxid    0.19S 

Zinc  oxid   0.169 

Nickel  oxid   

The  diseased  foliage  contained  (in  percentages  of  substances  free  from 
water  and  sand)  : 

Copper  oxid    0.0713 

Zinc  oxid    0.1712 

Nickel  oxid    0.0251 

Analyses  of  the  tubers  from  these  plants,  however,  did  not  give  any 
zinc  and  nickel  oxid,  and  only  0.0043  P^r  cent,  of  copper  oxid  as  contrasted 
with  healthy  tubers  which  contained  0.0041  per  cent^ 

Besides  copper  as  a  poison  the  arsenic  compounds  are  important  because 
of  their  injuriousness.  According  to  v.  Schroder  these  impair  vegetation 
even  if  present  in  the  soil  in  amounts  of  less  than  o.i  per  cent. 

Nevertheless,  the  improved  technique  of  manufacture  takes  care  that 
more  and  more  of  the  arsenic,  as  well  as  the  soluble  metal  salts,  is  kept  back 
from  the  smoke  in  the  flying  dust  flues,  so  that  at  present  a  fresh  metallic 
poisoning  of  the  soil  is  less  to  be  feared. 

And  yet  the  throwing  off  of  flying  ashes  requires  increased  attention.  A 
number  of  my  own  experiments  have  shown  that  with  many  flying  ashes 
which  become  mixed  with  the  soil  a  visible  increase  of  growth  may  be 
obtained,  while  those  from  other  industries  have  caused  poisoning.  This  is 
less  often  a  direct  injury  to  the  aerial  parts  of  the  plants,  but  more  fre- 
quently an  indirect  one,  manifesting  itself  by  its  effects  on  certain  heavy 
kinds  of  soil,  rich  in  water.  In  aerial  injuries,  sodium  sulfid  and  calcium 
sulfid  can  produce  corrosion  in  some,  more  tender  plants.  The  course  of 
the  action  in  the  indirect  injuries  has  not  yet  been  sufficiently  explained. 
In  my  opinion,  reduction  phenomena  in  the  soil  are  partially  concerned  in  it 
by  which  hydrogen  sulfid  is  developed. 

In  heavy  soils  deeply  covered  by  flying  ashes,  especially  if  they  have 
been  heavily  fertilized  with  lime,  a  phenomenon  of  disease  appears  to  such 
an  extent  in  barley  (I  have  called  it  "spotted  necrosis")  that  the  harvest  is 
greatly  reduced.  All  parts  of  the  plants,  even  the  beards  of  the  glumes, 
appear  closely  stippled  with  brown.     The  brown  points  represent  centers  of 

1  Konig-,  J.  Denkschrift  der  Landwirtschat'tl.  Versuchsstation  Munster  i.  W. 
1S96,  p.  204. 


742 

dead  tissue  of  which  parasites  certainly  are  not  the  cause.  Black  fungi 
may  later  infest  these  spots  and  then  this  complication  is  described  as  the 
" H ormondendron"  disease.  The  spotted  necrosis  is,  however,  not  a  disease 
peculiar  to  regions  of  flying  ashes  but  it  undoubtedly  occurs  most  inten- 
sively there.     I  found  it  could  be  lessened  by  a  heavy  application  of  lime. 

The  opinions  handed  down  by  Steffeck^  give  the  best  references  to  the 
injurious  action  of  hydrogen  sulfid.  In  them  the  repeated  decrease  in  the 
value  of  the  harvest  by  a  mechanical  coating  of  the  soil  is  also  considered. 
I  also  know  of  cases  in  which  a  deposition  of  ashes  on  vegetable  plants, 
especially  varieties  of  cabbage,  was  so  heavy  and  could  be  removed  to  such 
a  slight  extent  that  the  quality  of  the  plants  became  poor,  or  they  were  abso- 
lutely unsalable.  If  fodder  carrots  and  sugar  beets  had  been  heavily  covered 
and  their  leaf  heads  used  later  as  fodder  some  of  the  animals  died.  Incred- 
ibly large  amounts  of  ashes  were  found  in  the  stomachs  of  these  animals. 

Hydrogen  Sulfid. 

In  consideration  of  our  theory  that  hydrogen  sulfid  may  be  formed  in 
certain  heavy  kinds  of  soil  after  flying  ashes  have  been  deposited  on  them, 
I  made  some  experiments  with  barley.  In  some  pots,  pieces  of  potassium 
(poly  sulfids)  from  sulphur  liver  were  laid  between  the  young  barley  plants  ; 
in  other  they  were  put  in  the  water  in  saucers  in  which  the  pots  of  barley 
stood.  A  piece  of  lead  paper,  laid  between  the  plants,  slowly  turned  brown. 
After  six  days  the  leaves  began  to  turn  yellow  usually,  in  fact,  beginning  at 
the  center,  more  rarely  at  the  tip.  The  discolored  areas  appeared  to  be 
more  watery  and  transparent  than  when  the  yellow  discoloration  was  pro- 
duced by  other  causes-.  A  wilting  of  the  tissue  followed  the  yellow  discol- 
oration and  a  drying  of  the  green  leaf  surface  lying  above  it,  together  with 
the  assumption  of  a  grayish  yellow  color. 

The  first  symptom  of  the  disease  is  always  the  bleaching  of  the  chloro- 
phyll coloring  matter,  which  at  once  begins  to  spread  into  the  cytoplasm. 
This  is  not  preceded,  nor  accompanied,  as  in  other  cases  of  poisoning,  by  a 
contraction  of  the  primordial  pouch  (or  a  shrivelling  of  the  chloroplasts). 
Instead  of  this,  in  places,  the  passing  over  of  the  cell  water  into-  the  inter- 
cellular spaces  becomes  noticeable,  thereby  explaining  the  transparent 
appearance  of  the  yellowish  areas.  The  outlines  of  the  individual  chloro- 
plasts then  disappear  up  to  the  appearance  of  a  granular  mass  which  is 
contracted  in  the  centre  of  the  whole  cloudy,  pale  yellowish,  green  cypto- 
plasm.  The  impression  given  is  that  here  the  cell  contents  as  a  whole  swell 
up  into  an  uniform,  doughy  mass,  while  in  the  action  of  the  hydrochlorin 
and  hydrochloric  acid  shrivelling  phenomena  are  perceived  and,  with  sul- 
furous  acid,. a  process  of  drying  of  the  contents  which  remain  differentiated. 


1  Steffeck,  Die  durch  g-ewerbliche  Einwirkung-en  hervorg-erufenen  Flurschaden 
iind  Verunieinigung-en  von  Wasserlaufen  und  Teichen.  Magdeburg-er  Zeitung  1907. 
Nos.  329  and  331. 

2  Sorauer,  P.  Beitrag'  zur  anatomischen  Analyse  rauchbeschadigter  Pflanzen. 
Landwirtsch.  Jahrb.  1904,  p.  643. 


743 

In  oats  the  bleaching  of  the  chlorophyll  coloring  matter  was  slower  and  less 
intensive.  As  a  result  of  the  subsequent  diseased  condition  of  the  roots, 
the  walls  of  the  vascular  bundle  elements  became  a  deep  brown. 

Soda  Dust. 

Ebermayer^  has  reported  on  the  injuriousness  of  sodium  fumes.  In 
the  manufacture  of  cellulose,  sodium  lye,  under  high  pressure,  is  permitted 
to  act  on  pulverized  pine  wood.  To  get  back  the  sodium,  the  lye  used  is 
vaporized  and  the  residue  burned  to  destroy  the  organic  substances.  In 
this  way  a  considerable  amount  of  sodium  carbonate  is  freed  in  the  air.  The 
leaves  of  fruit  trees  near  such  factories  appear  brown  or  black  and  die  after 
a  short  time. 

Leaves  which  had  been  dipped  into  a  dilute  sodium  solution  (i.oi 
specific  gravity)  took  on  the  same  color;  apple  leaves  appeared  to  be  some- 
what less  resistant  than  pears  and  plums. 

In  regard  to  soda  dust,  as  yet  only  those  cases  have  been  known  in 
which  soda  from  ammonium  soda  factories  was  turned  to  dust  by  an 
improper  method  of  ventilating  the  factory  rooms.  The  soda  dissolved  by 
dew,  or  rain,  easily  produced  in  many  trees  an  appearance  of  the  injury  from 
acid  vapor,  such  as  the  dying  of  the  edges  of  the  leaves,  or  scattered  cor- 
roded areas. 

In  doubtful  cases  the  expert  is  helped  by  the  condition  in  wild  grasses 
and  especially  grain  stalks  which  assume  a  lemon  yellow  color.  Grain  can 
become  sterile  according  to  the  time  and  intensity  of  the  giving  ofif  of  the 
soda  dust  and  trees  may  gradually  be  killed  by  the  repeated  annual  injury 
to.  their  leaves.  Besides  this,  dififerent  plant  species  vary  greatly  in  sensi- 
tiveness and  often  are  resistant  to  soda  but  sensitive  to  acid  smoke,  or 
conversely.  My  experiments  on  grain  and  wild  grasses  (Agropyrum 
re  pens,  Agrostis  vulgaris,  Lolium,  etc.),  in  which  I  covered  them  with  dust 
while  wet  with  dew,  gave  the  same  yellow  discoloration,  even  in  the  glumes, 
just  as  in  natural  injuries-  which  were  demonstrable  at  a  distance  of  2  kilo- 
meters from  the  factory.  Konig^  observed  that  the  edges  of  barley  leaves 
became  white.  Red  clover  is  said  at  first  to  show  small  black  spots  on  the 
leaves,  some  of  which  later  become  entirely  black  and  drop  ofif.  The  same 
is  true  of  potatoes.  Konig  found  perforations  near  the  brown  edges  of  the 
leaves  in  oaks  as  in  cherries.  The  needles  of  the  white  fir  are  said  to 
become  yellow  at  the  tip  and  fall  oil.  As  a  result  of  his  analyses,  Konig 
considers  the  action  of  the  soda  to  lie  not  only  in  a  humification  of  the  leaf 
substances,  but  also  in  the  taking  up  of  soda  by  the  leaves,  from  which  it 
wanders  down  to  the  roots.  An  increase  in  acids,  especially  silicic  and 
sulfuric  acids,  takes  place  at  the  same  time  with  the  increase  of  the  amounts 


1  Ein  Beitrag  zur  Patholog-ie  der  Obstbaume.  Tag-ebl.  d.  Naturf. — Vers,  zu 
Hamburg,  cit.  Biedermann's  Centralbl.  1S77,  II,  p.  318. 

2  Zeitsch.  f.  Pflanzenkrankh.  1892,  p.  154,  note. 

3  Borner,  Haselhoff  and  Konig.  tJber  die  Schadlichlteit  von  Sodastaub  und 
Ammoniakgarf  auf  die  Vegetation.  Mitgeteilt  von  Konig,  Landwirtscli.  .Jahrb.  XXI, 
cit.  Zeitscli.  f.  Pflanzenkrankh.  1893,  p.  98. 


744 

of  sodium'.  Often  the  phosphoric  acid  and  chlorin  also  increase.  In  the 
injuries  due  to  acid  gases  this  reaction  of  the  plant  body  is  shown  also 
.further  by  the  fact  that  the  leaves,  not  yet  injured  beyond  a  certain  extent, 
contain  more  bases  than  do  healthy  ones. 

Control  Plants. 

Reference  must  be  made  to  technical  handbooks  for  technical  regula- 
tions regarding  the  avoidance  or  decrease  of  injuries  due  to  smoke  and 
flying  ashes.  However,  I  would  like  to  give  here  one  method  in  clearing 
up  the  question  whether  the  injuries  already  perceived  are  connected  with 
the  poisoning  of  the  soil,  or  are  due  to  the  purely  aerial  action  of  gas  waves 
containing  acid.  This  method  is  that  of  control  plant  cultivation  and  is 
carried  out  as  follows :  Wooden  cases,  containing  at  least  one  cubic  meter, 
are  sunk  in  the  fields  in  question  and  are  filled  with  soil  which,  before 
witnesses,  has  been  taken  from  a  region  free  from  smoke.  On  the  other 
hand,  soil  taken  from  the  fields  in  question  is  put  in  similar  cases  which  are 
sunk  in  a  field  in  a  region  free  from  smoke.  Both  series  of  cases  are  then 
sown  in  the  same  way  with  beans  {Phase olus  vulgaris  nanus)  and  harvested 
simultaneously  after  a  number  of  weeks.  The  harvest  is  examined  micro- 
scopically and  chemically. 

The  poisoning  of  the  soil  is  proved  by  the  fact  that  the  plants  grown 
in  the  soil  taken  from  the  fields  in  question  but  kept  in  cases  in  regions  free 
from  smoke  become  diseased  with  the  same  characteristics  as  those  near  the 
source  of  smoke.  If,  on  the  other  hand,  the  beans  from  the  cases  filled 
with  soil  from  a  region  free  from  smoke  which  had  been  sunk  in  the  fields 
in  question,  near  the  injurious  industrial  establishment,  show  the  charac- 
teristics of  smoke  poisoning,  this  then  proves  that  the  dangerous  streams  of 
smoke  alone  are  sufficient  to  injure  vegetation. 

These  comparative  cultures  have  the  advantage  of  giving  the  contesting 
parties  an  insight  into  the  kind  of  injury  which  is  recognizable  to  the  layman 
and  thereby  furnish  the  means  of  an  unification,  of  opinion,  thus  avoiding 
lengthy  lawsuits.  It  is  well  in  regard  to  these  to  strive  for  the  formation  of 
federal  smoke  commissions.  We  mean  by  this  the  appointed  persons  from 
among  botanists,  chemists,  agriculturalists  and  foresters,  who  would  meet 
together  as  a  commission  of  specialists  and  would  always  be  the  same  for 
the  different  districts.  By  retaining  the  same  persons  they  would  have  a 
more  exact  insight  into  the  special  conditions  of  their  districts  and  a  more 
assured  judgment  in  these  difficult  cjuestions. 

Illuminating  Gas  and  Acetylene. 
The  injurious  efifect  which  illuminating  gas  exerts  on  plants  has  been 
ascribed  to  the  hydrogen  sulfid  abundantly  present   in  it.     This  is,  how^- 
ever,  not  the  only  cause,  for  Kny-  has  shown  that  gas,  carefully  purified 

1  Konig  (Denkschrift  1896,  P.  207),  found  only  in  rye,  despite  a  higher  sodium 
content,  a  smaller  ash,  and  especially  less  silicic  acid.  It  seemed  to  him  that  the 
silicic  acid  was  dissolved  by  the  soda  in  the  g-lume  and  then  washed  away. 

-     Sitzungsber.  d.  Ges.  naturforsch.  Freunde  zu  Boilin  in  Bot.  Zeit.  1871,  p.  869. 


745 

from  hydrogen,  is  still  injurious  to  roots.  I  conclude  from  the  violet  gray 
color  in  many  roots  of  trees  injured  by  illuminating  gas  that  some  of  the 
tars,  or  the  ammonia,  carried  over  in  the  gas  are  the  injurious  factors.  For 
the  present,  this  violet  discoloration  of  the  roots  may  be  considered  the  best 
indication  of  the  injury  even  if  it  is  not  an  absolutely  certain  one.  We  must 
agree  with  Wehmer^  that  such  root  discolorations  occur  also  in  death  due  to 
other  causes  and  that  often  in  trees  killed  by  illuminating  gas  in  the  soil 
this  characteristic  is  found  only  sparingly.  The  later  case  is  easily  explained 
since  only  those  roots  discolor  w^hich  come  in  direct  contact  with  the  injuri- 
ous agent  and  thus  cause  the  death  of  the  tree.  The  root  dying  subsequently 
remains  uncolored. 

The  different  trees  and  shrubs  show  a  great  diversity  in  their  power  of 
resistance  to  the  affect  of  gases.  While  in  Kny's  experiments,  for  example, 
the  elm  died  very  soon,  Cornus  sanguinea  withstood  the  poisoning  of  illum- 
inating gas  without  any  perceptible  injury.  An  analysis  made  by  Girardin- 
shows  how  far  the  effect  of  a  gas  pipe  may  extend.  According  to  it,  the 
soil  at  the  distance  of  one  meter  showed  empyreumatic  oils  and  sulfur  and 
ammonium  compounds. 

A  further  example  of  the  different  behavior  of  plants  toward  illumin- 
ating gas  is  given  by  Lackner^.  His  observations,  however,  relate  to  the 
effect  which  the  gas  is  said  to  exert  when  burned  in  the  room.  Retention  in 
a  room  where  much  gas  is  burned  is  very  injurious  to  camilleas  and  azaleas 
and  ivy  is  said  to  die  at  once.  On  the  other  hand,  palms.  Dracaenae, 
Aucuba  japonica  and  other  plants  are  found  to  be  not  at  all  sensitive  to  it. 

Richter's  experiments*  prove  that  illuminating  gas  acts  arrestingly  on 
the  growth  in  length  of  bean  seedlings  and  other  plants  and  favors  the 
growth  in  thickness.  It  is  not  true  that  the  amount  of  carbon  dioxid,  rapidly 
increasing  by  combustion,  acts  as  injuriously  on  the  plant  body  as  on  the 
animal  body,  as  people  were  inclined  to  assume^ ;  it  is  rather  to  be  supposed 
that  different  products  of  incomplete  combustion  of  the  illuminating  sub- 
stances should  be  to  blame  for  this. 


1  "Wehmer,  C.  tjber  einen  Fall  intensiver  Schadigrung  einer  Allee  durch  aus- 
stromendes  Leuchtgas.    Zeitschr.  f.  Pflanzenkrankh.  1900,  p.  267. 

2  Jahresber.  iiber  Agrikulturchemie  Jahrg-.  VII,  1866,  p.  199. 

3  Monatsschrift  d.  Ver.  z.  Beford.  d.  Gartenbaues  in  d.  Kgl.  Preuss.  Staaten. 
January,  1873,  p.  22. 

4  Richter,  O.  Pflanzenwachstum  und  Laboratoriumsluft.  Ber.  d.  D.  Bot.  Ges, 
1903,  Part.  3. 

5  We  repeat  that  with  otherwise  favorable  conditions  for  growth,  the  presence 
of  carbon  dioxid  up  to  a  high  percentage  is  useful,  since  it  advances  the  production 
of  plant  substance  as  shown  by  the  increased  elimination  of  oxygen.  According  to 
the  investigations  of  Godlewski  ("Abhangigkeit  der  Sauerstoffausscheidung  der 
Blatter  von  dem  Kohlensauregehalt  der  Luft"  in  Sachs'  Arbeitfen  des  bot.  Inst,  of 
Wiirzburg,  1873,  III,  p.  343-70)  the  optimum  for  the  carbon  dioxid  content  lies 
tremendously  high  (5  to  10%)  in  comparison  with  the  content  of  the  air.  In  this 
way  is  explained  the  favorable  action  of  hot  beds  and  of  the  low  sunken  glass  houses 
of  the  gardener  warmed  with  horse  manure.  Here  the  high  carbon  dioxid  produc- 
tion of  the  organic  substances,  which  are  being  decomposed,  is  united  with  the 
abundant  development  of  heat,  weakened  light  and  moist  air;  i.  e.  the  factors 
essential  for  a  luxiu-iant  leaf  growth.  But  blossom  development  is  promoted,  how- 
ever, since  with  the  increased  carbon  dioxid  content  of  the  air,  the  blossoms  are 
formed  earlier  and  more  abundantly.  (Demoussy,  tJber  die  Vegetation  in  kohlen- 
saurereichen  Atmospharen.     Compt.  rend.  1904,  Vol.  139,  p.  883). 


746 

According  to  my  experience  with  house  plants,  the  dryness  of  the  air 
is  primarily  the  chief  cause  of  death,  and  manifests  itself  in  the  drying  of 
the  leaf  tips  and  edges. 

In  regard  to  the  effect  of  illuminating  gas  on  roots,  Bohm's  experi- 
ments', with  willow  cuttings  in  bottles  of  water  through  which  illuminating 
gas  was  passed,  showed  that  the  action  was  slowly  fatal.  The  cuttings 
which  died  after  3  months  had  formed  new  short  roots  at  the  expense  of 
the  stored  starch.  The  action  was  thus  less  intensive  than  it  was  when  carbon 
dioxid  was  passed  through  the  water.  In  this  case  all  formation  of  new 
structures  by  the  submerged  stem  was  suppressed  while  the  upper  part, 
which  formed  tyloses  in  its  ducts,  developed  sickly  shoots.  Death  occurred 
after  2  months.  In  other  experiments  in  which  hydrogen  was  passed 
through  the  water,  development  was  practically  normal.  (Compare  the 
section  on  Excess  of  Carbon  Dioxid.) 

The  plants  also  died  when  illuminating  gas  was  introduced  into  the 
earth  in  their  pots.  Seeds,  set  in  earth  through  which  illuminating  gas  had 
passed  for  almost  2^  years,  developed  more  poorly.  If  a  stream  of  atmos- 
pheric air  was  drawn  through  such  soils  for  a  considerable  time,  the  soil  did 
not  lose  its  injurious  effect  entirely  so  that,  as  already  stated,  this  effect  may 
indeed  be  ascribed  chiefly  to  the  tarry  products  which  are  deposited  in  the 
soil  in  a  fluid  or  solid  form. 

Spath  and  Meyer^  found  that  even  a  comparatively  small  amount  of  gas 
(25  cu.  ft.  distributed  daily  on  14.19  sq.  m.  at  a  depth  of  1.25  m.)  killed  the 
roots  which  came  in  contact  with  it.  Even  a  greater  quantity  of  gas  was 
found  to  be  less  injurious  if  it  reached  the  trees  during  their  winter  dormant 
period.  Here  too  different  varieties  of  trees  display  a  different  power  of 
resistance. 

Most  expedient  at  present  seems  to  be  Juergens'  method,  as  recom- 
mended by  Bohm,  of  laying  the  gas  pipes  through  the  streets,  etc.,  in  glazed 
terra  cotta  pipes  which  have  openings  leading  to  the  light  standards  so  that 
constant  ventilation  can  take  place  within  the  terra  cotta  pipes. 

Brizi"  has  made  experiments  in  regard  to  Acetylene  poisoning.  He 
found  in  one  Italian  city  that  Quercus  Ilex  died  when  growing  alongside  a 
pipe  carrying  this  gas.  Herbaceous  plants  died  in  pots  and  dried  up  if 
acetylene  was  introduced  into  the  soil.  The  nuclei  disappeared  in  the  pali- 
sade cells  of  Coleus,  the  roots  lost  their  hairs,  the  lateral  roots  seemed  wilted, 
crushed  and  brown,  the  bark  cells  lacked  all  fluids.  In  Evonymous  Japonica 
the  plants  in  dry  soil  seemed  perfectly  normal  after  7  days,  while,  in  moist 
earth  they  had  all  dropped  their  leaves  after  the  6th  day  and  most  of  the 
young  roots  had  died.     The  laurel  and  the  grapevine  behaved  similarly. 


1  Uber  den  Einfluss  des  Leuchtg-ases  auf  die  Veg-etation.  Sitzungsber  d.  k. 
Akad.  d.  Wissench.  zu  Wein,  Vol.  LXVIII  B. 

2  Spath  and  Meyer,  Beobachtung-en  iiber  den  Einfluss  des  Leuchtgases  auf  die 
Vegetation  von  Baumen.     Landwirtsch.  Versuchsstat.  1873,  p.  336. 

3  Biizi,  U.  Sulle  alterazioni  prodotte  alle  piante  coltivate  dalle  principnli 
emanazioni  g-asose  degii  stabilimente  industriali.  Staz.  sporim.  agrar.  ital.  XXXVF; 
cit.  Zeitschr.  f.  Pflanzenkrankh.  1904,  p.  160. 


747 

Brizi  considers  the  action  of  the  gases  contained  in  the  acetylene  and  the 
admixtures  to  be  a  displacement  of  the  normal  air,  containing  oxygen,  so 
that  the  roots  suffocated  and  he  thinks  that  illuminating  gas  will  act  similarly 
but  more  powerfully.  The  moisture  in  the  soil,  therefore,  favors  the  injury 
because  it  reduces  the  imperviousness  of  the  soil  to  the  gas.  This  theory  of 
Brizi's  of  the  suffocating  effect  on  the  roots  exercised  by  illuminating  gas, 
together  with  the  products  its  contains,  finds  support  in  so  far  that  I  have 
perceived  clearly  the  odor  of  butyric  acid  when  cutting  the  roots  of  lindens 
in  Berlin  after  poisoning  from  gas  and  I  could  determine  a  violet  brown 
discoloration  of  the  membrane  of  roots  of  trees  which  had  died  because  of 
stagnant  water. 


CHAPTER  XVIIT. 


WASTE  WATER. 


Water  Containing  Sodium  Chlorid. 

Of  all  the  injuries  caused  by  waste  water,  the  most  common  are  those 
produced  by  sodium  chlorid.  These  are  found  especially  in  regions  where 
extensive  hard  coal  mining  takes  place.  From  the  experiments  published 
by  Konig^  in  association  with  Storp-,  Bohmer,"'  Stood**  and  Haselhoff"',  we 
will  quote  a  few  figures  about  the  composition  of  mine  water  which  will 
suffice  to  show  what  quantities  of  sodium  chlorid  and  other  salts  are  con- 
tained in  it  at  times.     It  contains  per  litre 

Name  of  Mining    Sodium  Calcium  Magnesium  Potassium  Magnesium 

Company           chlorid  chlorid  chlorid           sulfate        sulfate 

Levin 65.949  g  1 1.056  g  3.736  g           0.659  g             — 

Matthias  Stinnes..   33.244  g  3-631?  1-735  g              —              0.042  g 

Saline  Konigsborn.  45.413  g  4-o6i  g  0.189  g               —               1-256  g 

From  these  examples  it  is  easy  to  reckon  the  effect  of  irrigating,  or 
flooding  land  with  such  solutions.  The  action  will  be  direct,  as  well  as 
indirect,  according  to  the  changes  which  the  soil  undergoes.  In  the  latter 
connection,  the  fact  that  nutrient  substances  in  the  soil  (Potassium,  calcium, 
magnesium,  and,  under  certain  circumstances,  also  phosphoric  acid)  are 
dissolved  in  increased  amounts  and  washed  away  should  receive  first  consid- 
eration. This  leaching  process  begins  with  the  percentage  of  0.5  g.  sodium 
chlorid  per  litre.  Nevertheless,  all  water  containing  any  considerable 
amount  is  dangerous  for  irrigation.  Pot  experiments  with  meadow  grass 
show  a  considerable  reduction  in  harvested  substances  corresponding  to  the 
loss  in  nutrition  of  the  soil. 

A  second  disadvantage  of  irrigation  with  water  containing  sodium 
chlorid  is  the  increased  density  of  the  soil.     Even  0.41   per  cent,  sodium 


Die  landwirtsch  Versuchsstat.  Miinster  i.  W.     Denkschrift  1.S96,  p.  I!i3. 

Landwirtsch.  Jahrblicher  1883,  XII,  p.  Ttif). 

Ibid,  p.  897. 

Landwirtsch,  Versuchsstat.  1S99,  P.  113. 

Landwirtsch.  .lahrbiicher  1893,  p.  845. 


749 

chlorid  in  the  soil  is  enough  to  make  it  sterile  because  of  the  density.  Sanna^ 
found  near  salt  works  a  preponderance  of  fine  earth  over  coarse  particles  and 
calls  attention  to  the  fact  that  the  work  of  the  soil  bacteria  is  stopped  by 
the  decreased  supply  of  air.  Such  soils  must  unquestionably  be  laid  open  in 
furrows  before  winter  so  that  they  may  again  undergo  a  breaking  up  by 
frost.  Finally,  one  more  point  must  be  cited  to  which  Preglion-  has  called 
attention.  He  studied  the  peculiar  deforming  of  the  ears  which  is  called 
"Garbin",  and  ascribed  to  the  action  of  sea  winds.  According  to  him,  how- 
ever, physiological  drought  is  to  blame  for  this.  The  salty  soil  holds  the 
water  so  fast  that  the  roots  are  not  able  to  take  it  up  in  sufficient  amounts. 

In  regard  to  the  direct  effect,  consideration  must  be  given  to  the  fact 
that  a  plant  can  particularly  adjust  itself  to  water  containing  salt,  according 
to  its  own  peculiarity,  and  change  its  habit  of  growth  accordingly.  Hoster- 
mann^  has  proved  that  meadow  grasses  take  on  a  xerophyte  structure ;  they 
become  smaller  and  squattier ;  the  internodes  shorter  and  the  leaves  smaller  ; 
the  plant  growth  is  meagre  and  the  root  system  develops  weakly.  Transpi- 
ration retrogresses  and  the  energy  of  assimilation  is  arrested  with  0.05  per 
cent.  In  regard  to  the  germinating  power  of  seeds,  it  has  been  observed 
that  weak  concentrations  (0.5  to  0.75  per  cent.)  act  favorably,  but  above 
that  amount  injury  sets  in. 

Areschoug*  mentions  other  phenomena  of  adjustment,  since  he  considers 
the  retention  of  water  in  tissues  not  directly  connected  with  assimilation 
(storage  tracheids,  slime  cells)  to  be  a  protection  against  the  accumulation  of 
chlorids.  Also,  the  hydathodes  appear  to  eliminate  water  containing  sodium 
chlorid.  Diels''  found  that  structural  adjustment  for  arresting  transpiration 
increases  with  the  saltiness  of  the  habitat.  It  might  be  concluded  from  this 
that  vegetation  from  the  coast  would  also  behave  differently  in  basins  of 
water  containing  different  amounts  of  salts.  Rostrup^  also  actually  calls  atten- 
tion to  this  point.  Pines  suffer  the  most  and  birches  the  least.  It  is  evident 
from  the  notes  made  by  the  Economic  Society  of  the  Province  of  Maribo 
after  the  floods  of  1858,  '63,  '65  that  the  effect  of  salt  water  is  greater  the 
more  loam  the  soil  contains.  Of  winter  plants  thus  flooded,  rye  suffered  more 
than  wheat.  In  early  spring  seeding  on  land  saturated  with  salt,  barley  and 
peas  were  injured  most  of  all.  Mangelwurzels,  potatoes,  white  clover  and 
ray  grass  did  not  seem  to  suffer  very  much  from  the  effect  of  salty  soil.  On 
the  other  hand,   red  clover  was  very  sensitive.     In  Wohltmann's  experi- 


1  Sanna,  A.,  Einfluss  des  Seesalzes  auf  die  Pflanzen.  Staz.  sperim  XXXVII-  cit 
Centralbl.  f.  Agrikulturchemie  1904,  p.  826. 

2  Peg-lion,  V,  Der  Salzgehalt  des  Bodens  und  seine  Wirkung-  auf  die  Veg-etation 
des  Getreides.  Staz.  speriment  agrar.  ital.  1903;  cit.  Centralbl.  f.  vVgrikulturchemie 
1904,  p.  507.  Ricome,  Influence  du  chlorure  de  Sodium,  etc.;  cit.  Zeitschrift  fiir 
Pflanzenkrankh.  1904,  p.  222. 

3  Hostermann,  Einfluss  des  Kochsalzes  auf  die  Veg-etation  von  Wiesengrasern. 
Landwirtsch.  Jahrb.  Suppl.  1901;  cit.  Centralbl.  f.  Ag-rikulturchemie  1903,  p.  211. 

*  Areschoug-,  P.  W.  Untersuchungren  iiber  den  Blattbau  der  Mangrovepflanzen. 
Bibl.  bot.  1902;  cit.  Bot.  Jahresber.  1902,  II,  p.  295. 

5  Diels,  L.  Stoffwechsel  und  Struktur  der  Halophvten;  cit.  Bot.  .Tahresber. 
1898,  I,  p.  606. 

G     Rostrup,  Plantepatolog-i,  p.  74,  75. 


750 

mcnts^  with  artificial  sodium  chloric!  fertilization,  barley  and  wheat  (among 
summer  grains)  showed  great  sensitiveness,  while  winter  wheat  throve  fairly 
well  even  with  heavy  additions  of  salt.  Peas  failed  entirely  with  a  strong 
fertilization;  oats  were  more  resistent.  Winter  rye  was  found  to  be  the 
least  sensitive.  In  potatoes,  the  starch  content  was  much  decreased;  the 
protein  content  not  affected;  the  amount  of  ash  increased.  In  sugar  and 
fodder  beets  the  quantity  harvested  was  increased  without  a  decrease  of  the 
sugar  content.     Their  descent  from  coast  plants  may  be  noticed  in  this. 

The  effect  of  salty  soil  manifests  itself  in  trees  only  after  they  have 
stored  up  the  salt  for  some  time.  Weber-  is  an  advocate  of  the  theory  that, 
in  many  cases,  it  is  not  the  excess  of  salt  but  the  marshiness  of  the  soil  which 
causes  death.  He  found  in  the  yellowed  branches  of  Salix  viminalis  in  the 
valley  of  the  Lahn  near  Bersenbruck,  where  the  mine  water  flows  in  from 
Eversburg,  that  the  leaves  had  a  chlorid  content  of  1.309  per  cent.,  while 
those  of  healthy  plants  contained  only  0.877  per  cent.  We  find  abundant 
statements  concerning  the  behavior  of  decorative  plants  in  Otto's  book^  He 
gives,  as  a  universal  characteristic,  the  reddening  of  the  tips  of  plants  before 
they  die. 

Aside  from  mine  water,  a  high  content  of  sodium  chlorid  manifests  itself 
in  the  sewage  fields.  In  summer  the  concentration  of  the  liquid  sewage 
becomes  relatively  large  and  many  plants  are  found  "to  scorch"  as  the 
gardener  on  such  fields  says.  Tobacco  has  proved  to  be  very  sensitive  so 
that  up  to  the  present  there  has  been  a  complete  failure  of  the  tobacco  crops, 
as  emphasized  by  Ehrenberg*,  who  has  considered  very  thoroughly  all  the 
injuries  due  to  liquid  sewage. 

Besides  the  sodium'  chlorid  the  amount  of  magnesium  chlorid  also  comes 
under  consideration.  The  effects  of  the  leaching  action  are  changed,  as  the 
experiments  of  Fricke,  Haselhoff,  and  Konig^  have  proved.  While  irriga- 
tion with  water  containing  sodium  chlorid  results  in  an  increased  removal 
of  calcium,  magnesium,  and  potassium,  yet  from  water  containing  mag- 
nesium chlorid,  the  calcium,  potassium  and  sodium  are  lost  and  the  mag- 
nesium is  retained.  In  irrigation  with  water  containing  calcium  chlorid,  the 
calcium  will  be  retained  by  the  soil  and  plants,  while  considerable  amounts  of 
magnesium,  potassium  and  sodium  are  lost. 

In  large  cities,  however,  the  cfuestion  of  injury  from  sodium  chlorid  has 
still  a  different  side,  that  is,  in  its  use  in  thawing  street  railways.  Besides 
this,  coarse  salt  is  strewn  on  the  pavements  by  many  householders.  In 
Berlin,  this  is  forbidden,  to  be  sure,  l)ut  the  police  is  often  deceived  by  the 


1  Wohltniann,  F.     Die  Wirkung-  der  Kochsalzdiing-ung'  auf  unsere  FcldfrucMe. 
I^andw.  Zeit.  f.  d.  Rhoinprovinz  1904,  p.  46. 

2  Weber,  C.     Kritische  Bemerkungren  usw.;   cit.  Bot.  .Tahresber.  1898,  II,  p.  301. 

3  Otto,   R.     tJber  durch   kochsalzhaltig-es   Wasscr  verursachte    Pflanzenschadi- 
gungen.     Zeitsch.  f.  Pfl.anzcnkrankh.  1904,  p.  136. 

4  Ehrenberg,    Paul,    Einig-e    Bcobachtungen    ijber   Pflanzenschadig-ungen    durch 
Spiiljauchenberieselung.     Zeitschr.  f.  Pflanzenkrankh.  1906,  p.  193. 

''     Fi'icke,  Haselhoff,  E.,  u.  Konig-,  J.,  tJber  die  Verandcrung-en  und   Wirknngon 
des  Rieselwassers.     Landwirtsch.  Jahrbucher  1893,  p.  801. 


EDGAR  TULLIS 


751 


mixing  of  salt  with  sand\  The  salt  used  to  remove  the  snow  melts  and 
passes  into  the  soil  where  the  street  is  not  asphalted.  In  the  spring  the  trees 
start  to  grow  but  die  during  the  course  of  the  summer.  Here,  too,  the 
different  varieties  display  dift'erent  degrees  of  resistance-.  Besides  this,  the 
action  of  a  solution  of  sodium  chlorid  varies  according  to  whether  it  is  con- 
stantly sprinkled  on  the  roots  or  whether  the  soil  dries  out  between  times. 
The  latter  case  is  the  more  dangerous  one. 

Extensive  injuries  have  also  been  found  near  volcanoes  due  to  the  effect 
of  the  vapors.  The  sulfurous  acid  occurring  in  varying  amounts  in  the 
vapor  mixture,  and  also  the  hydrochloric  acid  and  hydrogen  sulfid,  may  well 
be  the  chief  causes  of  the  poisoning.  They  might  also  give  rise  to  the 
destructive  effect  of  the  showers  of  ashes;  yet  this  has  been  ascribed  also  by 
some  observers  to  the  extensively  deposited  sodium  chlorid.  According  to 
Pasquale's  reports^,  some  of  the  red  and  violet  colors  of  blossoms  change  to 
blue  (Papaver,  Rosa  and  Gladiolus),  some  remain  unchanged  {Viola  tri- 
color, Convolvulus,  Digitalis).  The  green  parts  of  the  plants  become  brown, 
during  a  fall  of  ashes  occurring  at  the  time  the  trees  begin  to  grow,  just  as 
after  burning  or  drying  but  not  scalding.  .Succulent  and  leathery  leaves  did 
not  suffer.  Mechanical  effects  from  the  showers  of  ashes,  such  as  a  possible 
stoppage  of  the  stomata,  could  not  be  confirmed  immediately.  They  seemed, 
however,  to 'make  themselves  felt  after  some  days. 

Sprenger*,  who  describes  the  results  of  the  Vesuvius  eruption  in  April, 
1906,  advocates  the  same  theory  as  does  Pasquale. 

Waste  Water  Containing  Calcium  Chlorid  and  Magnesium  Chlorid. 

These  are  found  abundantly  in  mine  water  from  hard  coal  mines,  in  the 
mother  liquor  flowing  away  from  salt  works  and  baths,  in  factories  preparing 
calcium  chlorid,  and  potassium  salts,  in  the  waste  waters  of  ammonium 
sodium  factories,  etc.  The  analysis  of  the  neutral  fluid,  which  flows  from 
the  kettles  to  which  the  ammonium  chlorid  obtained  in  the  manufacture  of 
ammonium  sodium  is  decomposed,  shows,  for  example,  what  amounts  come 
under  consideration  in  these  cases.  Konig^  found  in  i  liter,  80.06  g.  of 
sodium  chlorid,  56.00  g.  calcium  chlorid,  1.02  g.  sodium  sulfate.  In  other 
tests,  which  were  strongly  alkaline,  less  of  the  substances  named  were  found, 
but,  in  place  of  these,  sodium  sulfate  and  3  to  5  g.  of  free  calcium.  The 
changes  in  composition  in  the  soil  have  already  been  considered  in  the  pre- 
vious section,  but  it  should  still  be  emphasized  here  that  favorable  effects 
have  been  observed  if  weak  amounts  are  given  temporarily  (up  to  2.0  g.  per 
liter).     The  germination  of  seeds  was  increased.     Raspberries  and  straw- 


1  Weiss,  A.     Zeitsch.  f.  Gartenbau  und  Gai^tenkunst.  1S94,  No.  37. 

2  Ritzema  Bos,  Schadlichkeit  des  Auftauens  der  Trambahnlinien  mit  Salz- 
wasser  fiir  die  In  der  Nahe  stehenden  Baume.  Tijdschrift  over  Plantenziekten 
189S,  p.  1. 

3  Pasquale,  Di  alcuni  effetti  della  caduta  di  eenere,  etc.     Bot.  Zeit.  1872,  p.  729. 
•1     Spreng-er,  C,  Vegetation  und  vulkanische  Asche.     Osterreich.  Gartenzeitung- 

1906,  Vol.  VII. 

5     Denkschrift,  p.  161. 


752 

Ijcrrics  were  found  to  be  very  large  and  brightly  colored  on  the  soil  saturated 
with  calcium  chlorid.  The  fruit,  liowever,  tasted  of  calcium  chlorid  and 
did  not  keep  vvelP. 

Barium  Chlorid. 

This  is  a  comparatively  less  important  element,  which  is  found  only  at 
times  in  the  waste  waters  of  hard  coal  mines.  Its  [joisonous  action  has  been 
proved  by  Haselhofif-  in  water  cultures  of  niaisc  and  horsebeans.  (irowth  in 
height  was  arrested;  the  leaves  wilted  and  fell.  In  nature,  however,  direct 
injury  will  occur  only  rarely,  because  the  sulfurous  salts  rapidly  transform 
it  into  insoluble  and  non-injurious  barium  sulfate. 

Waste  Watkr  Containing  Zinc  Sulfate. 

Konig''  has  paid  especial  attention  to  the  investigations  of  such  waters 
from  Zinc  Blend  Mines.  It  was  proved  that  the  brooks  which  take  up  the 
waste  water  contained  sulfurous  zinc  oxide  in  solution.  An  evident  retro- 
gression in  the  yield  and  in  places  a  \Qvy  poor  growth  was  noticed  on 
meadows  thus  watered.  The  grasses  grown  on  such  sterile  places,  as  well 
as  the  deformed,  bushy  beech  and  maple  trees,  contained  up  to  2.78  per  cent, 
of  their  ash  in  zinc,  while  the  ash  of  normal  meadow  plants  did  not  contain 
this  metal.  Vegetation  dies  in  places  where  zinc  ore  happens  to  be  deposited 
accidentally.  Only  one  specific  zinc  plant  (the  "white  mineral  blossom") 
was  still  visible.  This  "mineral  copper  blossom"  contained  not  less  than  1 1 
to  15  per  cent,  zinc  oxid  in  its  ash.  It  is  thus  seen  how  differently  the 
various  plants  behave  and  what  high  concentrations  may  often  be  endured. 
The  injuries  appear  only  after  a  considerable  number  of  years,  after  the 
zinc  oxid  present  in  very  small  amounts  in  the  water  of  the  brook  has  accu- 
mulated to  considerable  quantities.  Konig  is  justified  in  concluding  from 
this  that  the  requirement  made  upon  mines  by  the  Concession  Department 
that  only  clear  water  be  allowed  to  flow  away  into  the  streams  is  not  enough 
protection  to  the  owners  of  meadows. 

The  books  supplement  the  discoveries  mentioned,  one  of  w'hich  by 
A.  Baumann"*  treats  exclusively  of  the  effects  of  zinc  salts  on  plants  and  soil ; 
while  another,  by  Nobbe,  Bassler  and  Will"'  takes  up  injuries  due  to  arsenic 
and  lead  as  well  as  zinc. 

It  must  be  emphasized,  from  the  results  of  Baumann's  experiments,  that 
the  zinc  sulfate  in  solution  is  much  more  injurious  to  plants  than  had  been 
supposed  up  to  that  time.  Small  amounts  (possibly  .1%  zinc,  that  is,  4.4  mg. 
zinc  vitriol  in  a  litre)  have  been  proved  absolutely  non-injurious  in  all  the 
plants  under  experimentation  (13  species  from  7  families)  with  the  excep- 

1  Denkschrift,  p.  161. 

2  Landwirtsch  Jahrbiicher  1895,  p.  962. 

3  Konigr,  Untersuchung-en  iiber  Beschadiffungen  von  Boden  u.  Pflanzen  durch 
industrielle  Abflusswasser  und  Case;  cit.  in  Biedermann's  Centralbl.  1S79,  p.  564. 

4  Baumann,  A.,  Das  Verhalten  von  Zinksalzcn  ffofren  Pflanzen  und  im  Boden. 
I'reisschrift  1S84.    Landwirtsch.  Versuchsstat.  Vol.  XXXI,  Part  1,  p.  1. 

5  Nobbe,  Bassler  und  Will,  Untersuchung-en  iiber  die  Giftwirkung-  des  Arsen, 
Blei  und  Zink  im  pflanzlichen  Organismus.  Landwirtsch.  Versuchsstat.  Vol.  XXX, 
Parts  5  and  6. 


753 

tion  of  the  radish.  Conifers  are  very  resistent.  They  withstood  a  solution 
containing  i  per  cent,  zinc  while  the  Angiosperms  died  with  even  5  mg.  zinc 
per  litre  and,  indeed,  older  plants  died  in  general  more  quickly  than  did 
young  ones. 

The  effect  of  the  poison  manifests  itself  by  a  striking  change  in  color  of 
the  diseased  plants.  Scattered  small  areas  of  a  metallic  lustre  on  a  rusty 
yellow  color  appear  on  the  leaves  and  finally  spread  over  the  whole  surface. 
The  fact  that  the  zinc  attacks  the  chlorophyll  apparatus  especially,  thereby 
hindering  the  work  of  assimilation,  is  proved  by  the  observation  that  seed- 
lings in  which  the  chlorophyll  grains  are  not  yet  matured  as  well  as  plants 
grown  in  the  dark  and  fungi  behave  indifferently  to  relatively  highly  con- 
centrated zinc  solutions. 

Zinc  carbonate  and  zinc  sulfate  placed  in  the  soil  exercise  an  injurious 
effect.  In  themselves,  to  be  sure,  they  are  not  injurious  although  they  are 
soluble  in  pretty  considerable  amounts  in  water  containing  carbon  dioxid, 
whereby  the  zinc  sulfid  is  first  changed  to  zinc  carbonate.  But  their  dan- 
gerous action  lies  in  the  transformation  which  the  zinc  undergoes  in  the 
form  of  vitriol  with  the  potassium,  calcium,  and  magnesium  salts.  In  this 
these  nutrient  substances  become  soluble  and  may  be  wasted  away.  In  poor 
sandy  soils  sterility  may,  indeed,  be  produced  and  the  injuriousness  of  irri- 
gation with  waste  water  from  zinc  smelters  lies  especially  in  this  removal  of 
the  nutrient  substances. 

The  injurious  solubility  of  zinc  in  the  soil  depends  essentially  on  the 
amount  of  calcium  carbonate  contained  in  it.  In  the  presence  of  this  min- 
eral to  possibly  four  times  the  amount  of  the  zinc  sulfid  no  more  zinc  will 
be  dissolved.  A  soil  ruined  by  zinc  sulfate  can  be  improved  by  the  addition 
of  substances  which  render  the  soluble  zinc  salts  insoluble.  Humus  has 
been  proved  to  be  splendid  and,  on  this  account,  fertilization  with  moor  soil 
can  be  recommended.  In  the  absence  of  this,  abundant  stable  manure,  clay, 
or  marl  may  be  used.     Marl,  or  calcium,  must  be  given  under  all  conditions. 

Tschirch  mentions,  in  regard  to  injuries  due  to  lead  salts,  that  a  peculiar 
kind  of  dwarfing  is  produced.  The  plants  which  have  received  i  kg.  mennig 
(red  oxid  of  lead)  to  2  sqm.  of  surface  remain  small  and  do  not  bloom  (lead- 
nanism)  \  Devaux-  found  that  lead  solutions  in  a  dilution  of  1-10,000,000 
acted  injuriously.     This  metal  was  fixed  by  the  cell  wall  and  contents. 

To  purify  waters  containing  zinc  sulfate,  the  use  of  filtering  layers  of 
limestone  dust  and  moor  earth  could  be  recommended;  insoluble  carbonic 
and  humic  zinc  oxid  is  formed  in  them. 

Water  Containing  Iron  Sulfate. 

The  waste  water  from  mines  and  washeries  of  sulfur  silicate  and  from 
hard  coal  mines,  the  water  which  drains  from  piles  of  hard  coal  culm  and 


1  Tschirch,   A.,   Das   Kupfer   voni    Standpunkt   der   gerichtlichen   Cheniie    usw. 
Stuttg-art  1893,  F.  Enke. 

2  Devaux,  De  I'absorption  des  poisons  metalliques  tres  dilues  par  les  cellules 
vegetaux.     Conipt.  rend.  1901,  cit  Just's  Jahresber.  1902,  II,  p.  353. 


754 

the  waste  water  from  wire  factories  usually  eontains  iron  sulfate.  Besides 
this,  the  use  of  ferrous  sulfate  as  a  disinfectant  in  cesspools  should  also  be 
taken  into  consideration.  Large  amounts  of  iron  sulfid  are  thus  produced 
which,  through  oxidation  in  the  air,  are  transformed  into  iron  sulfate  and 
sulfurous  iron  oxid. 

The  ferrous  oxid,  like  zinc  from  zinc  sulfate,  is  retained  by  the  soil  and 
changed  to  ferric  oxid^  while  a  corresponding  quantity  of  other  bases,  such 
as  calcium,  magnesium,  and  potassium,  combine  with  the  sulfuric  acid  and 
arc  easily  washed  away.  This  impoverishment  of  the  soil  is  accompanied  by 
an  increase  of  magnetic  oxid  which  initiates  a  souring  and  choking  of  the 
ground.  As  soon  as  the  bases  for  the  transformation  of  the  iron  sulfate  are 
exhausted,  the  ferrous  sulfate  remains  untransposcd,  or  appears  also  as  free 
sulfuric  acid. 

However  useful  small  amounts  may  be  on  rich  soils  (up  to  150  kg.  per 
hectare,  according  to  Konig^),  since  the  sulfuric  acid,  thus  set  free,  must  act 
as  a  loosening  medium,  just  as  injurious  will  be  a  continued  addition  of  iron 
sulfate  with  constant  irrigation  of  pastures.  Experiments  show  that  if  acid 
compounds  are  given  the  plants  instead  of  the  basic  salts  which  alone  favor 
their  growth  (iron  sulfate  is  strongly  acid)  a  deterioration  of  the  hay  results 
and  a  decrease  in  the  yield  of  milk.  The  different  clovers  and  sweet  grasses 
(possibly  with  the  exception  of  Glyceria  flidtans)  disappear  gradually  from 
such  pastures  and  sour  grasses,  the  horsetails  (Equisetum)  and  mosses  take 
possession  of  the  soil.  An  addition  of  lime  water  causes  the  elimination  of 
ferrous  hydroxid  with  the  formation  of  gypsum  and  it  will  thus  be  possible 
to  purify  waste  water  containing  iron  sulfate  by  the  use  of  calcium. 

Waste  Water  Containing  Copper  Sulfate  and  Copper  Nitrate. 

Waste  water  from  silver  factories  and  brass  foundries  is  concerned 
here.  An  insight  into  the  composition  of  such  water  is  given  by  an  analysis 
of  solutions  flowing  from  a  brass  foundry  published  by  Haselhoff-.  He 
found  in  one  liter : 

Copper  sulfate,  51.619  g ;  Copper  nitrate,  5.298  g ;  Zinc  sulfate,  14.045  g ; 
Ferrous  sulfate,  2.422  g;  Calcium  sulfate,  1.943  g;  Magnesum  sulfate, 
0.459  g;  and  free  Sulfuric  acid  (SO;;),  30,376  g.  This  is,  at  any  rate,  a- 
very  extreme  case,  for  it  is  one  hundred  times  greater  in  the  individual 
elements  than  is  the  content  of  the  water  which  flows  from  copper  works 
and  silver  factories.  For  the  nature  of  the  injury,  however,  the  amount  of 
the  elements  is  unimportant,  since  small  quantities  produce  the  same  effect 
when  used  in  continual  irrigation.  The  way  in  which  the  sulfate  and  nitrate 
of  the  copper  salts  act  on  the  soil  is  the  same  as  with  zinc  and  iron  salts. 
Copper  oxid  is  retained  in  the  soil  and  remains  chiefly  in  the  upper  surface 
of  the  pasture  land.  The  sulfuric  acid,  which  is  set  free,  combines  with  the 
calcium,  magnesium,  and  potassium,  and  these  salts,  with  irrigation,  pass 


1     Denkschriit,  p.  175. 

-     Haselhoff,  Landwirtsch.  Juhrb.  1892,  p.  263  and  1893,  p.  848.     Denksch.,  p.  176. 


into  the  subsoil.  Aside  from  the  impoverishment  in  basic  nutritive  sub- 
stances the  copper  sulfate  (such  plants  as  grasses,  for  instance,  take  up 
rather  considerable  amounts  of  copper  and  zinc  salts)  acts  finally  also  as  a 
direct  poison  so  far  as  cultural  experiments  in  nutrient  solutions^  have 
demonstrated. 

Masayasu  Kanda-  found  that,  in  water  cultures  of  peas,  injuries 
appeared  even  with  0.000000249  per  cent,  of  copper  sulfate.  On  the  other 
hand,  if  added  to  soil  in  a  concentration  a  million  times  greater,  it  acted  as 
a  stimulant.  The  conditions  are  even  more  favorable  for  plants  in  natural 
soil.  According  to  Tschirch^  almost  all  plants  possess  some  copper  since, 
indeed,  all  field  soils  may  contain  traces  of  it.  The  vegetation,  on  soils  to 
which  copper  is  added  abundantly,  takes  up  usually  but  very  little  copper, 
50  that  the  danger  of  poisoning  is  not  imminent.  This  theory  finds  sub- 
stantiation also  in  the  fact  that  in  the  very  frequent  use  of  copper  sulfate  as  a 
spraying  substance  against  parasitic  diseases  a  constant  enrichment  of  the 
soil  takes  place  without  any  injuries  being  demonstrable  with  certainty.  We 
personally  believe,  at  any  rate,  that  a  time  will  come  in  which  a  constant 
addition  of  copper  will  make  itself  felt  as  a  retardation  to  vegetation. 

The  waste  water  containing  nickel  and  cobalt  found  near  nickel-rolling 
factories  will  act  in  the  same  way  as  described  above.  It  may  be  mentioned 
here  supplementarily  that  John^  in  1819,  in  his  book  "The  Feeding  of 
Plants,"  had  studied  sand  and  water  cultures  to  which  solutions  of  different 
metallic  salts  had  been  added.  He  proved  thereby  that  sunflowers  did  not 
take  up  copper  given  them  in  the  form  of  insoluble  copper  carbonate,  while 
peas  and  barley  stored  up  great  masses  from  a  soil  to  which  a  solution  of 
copper  nitrate  had  been  added  drop  by  drop. 

The  fact  that  local  conditions  sometimes  make  possible  a  beneficial  use 
of  the  waste  water  but  at  other  times  cause  injurious  factors  to  be  felt, 
prevents  our  consideration  in  more  detail  of  the  different  industries.  In 
this  connection  the  poisonous  peculiarity  of  the  soil,  due  to  its  power  of 
absorption,  plays  a  principal  part.  Hattori'  calls  especial  attention  to  this 
in  regard  to  copper  salts. 

The  injuries  due  to  municipal  irrigation  with  liquid  sewage  have  been 
mentioned  already  in  the  section  "Sewage  Disposal  Fields"  (page  364). 


1  otto,    R.,    Untersuchungen    liber   das   Verhalten    der    Pflanzenwurzeln    gegen 
Kupfersalzlosungen.     Zeitsclir.  f.  Pflanzenkrankh.  1S93,  p.  322. 

2  Masayasu  Kanda,  Journ.  College  of  Science.     Tokyo,  "Vol.  XIX,  Art.  13. 

3  Tsehirch,  A.,  Das  Kupfer  voni  Standpunkt  der  gerichtlichen  Cheniie,   Toxi- 
kologie  und  Hyg-iene.  Stuttgart  1893,  Fr.  Enke,  8°.     138  p. 

•1     Miiller,  Carl,  Zur  Geschichte  der  Physiologic  und  der  Kupferfrage.  Zeitschrift 
flir  Pflanzenkrankh.     1894,  p.  142. 

5     Just's  bot.  Jahresber.  1902,  Absch.  Krankh.    Ref.  277. 


CHAPTER  XIX. 


INJURIOUS  EFFECTS  OF  CULTURAL  METHODS. 


A.     Coating  Substances. 

1.  Tar.  The  inside  of  the  framework  of  conservatories  is  often 
coated  with  tar  in  order  to  increase  its  resistance  to  great  dampness.  We 
are  confronted  with  a  long  list  of  complaints  that,  after  setting  out  the 
plants  in  the  tarred  greenhouses,  a  blackening  and  falling  of  the  leaves 
takes  place.  I  noticed  the  same  phenomena  near  freshly  tarred  fences.  The 
conditions  found  agree  in  all  essentials  with  those  described  for  asphalt 
fumes  and  are  explained  by  the  exhalations  from  the  fresh  tar  coating.  The 
injurious  results  do  not  appear  if  the  tarring  has  taken  place  a  few  months 
before  the  plants  are  brought  into  the  greenhouses.  I  found  a  method  used 
in  the  vicinity  of  Berlin  which  acted  as  well.  The  boards  and  framework 
v/ere  treated  with  hard  coal  tar  and  after  this  had  dried  were  coated  with 
cement. 

An  attempt  has  been  made  recently  to  keep  the  paths  in  gardens  and 
public  parks  free  from  dust  by  means  of  a  thin  layer  of  tar.  The  process 
is  much  recommended^  and  the  experiments  made  in  France  and  Italy  have 
shown  that  even  paved  streets  can  be  treated  advantageously  in  this  way. 
This  process  necessitates,  however,  the  edging  of  the  path  with  a  strip  of 
galvanized  tin  8  to  lo  cm.  high,  since  the  injurious  elements  of  the  tar  would 
otherwise  attack  the  vegetation.  This  process,  which  despite  its  necessary 
annual  renewal  is  said  to  be  still  cheaper  than  asphalting  and  less  trouble- 
some than  oiling,  or  the  treatment  of  the  streets  with  "W'estrumit,"  must 
still  be  tested  by  further  experiments. 

2.  Refuse  from  Gas  Works.  According  to  a  report  from  Mr. 
Klitzing,  at  Ludwigslust,  where  roads  on  sandy  soil  have  been  hardened  by 
the  use  of  such  refuse,  a  dying  back  of  the  street  trees  was  caused. 

3.  White  Lead.  In  a  case  of  which  I  have  heard,  it  was  necessary  to 
put  potted  plants  in  greenhouses  a  short  time  after  these  had  been  coated 
with  white  lead,  and  then  the  unpleasant  discovery  was  made  that  the  plants 
dropped  their  leaves. 


1     Das  Teeren  von  Fuss-  und  Fahrwegen  in  Garten  und  Parks.     Der  Handels- 
gartner,  herausgegr.  von  Thalacker,  Leipzig--Gohlis  1906.     No.  50. 


757 

4-  Oil  Fumes.  Korff^  used  lead  oxid  as  an  addition  to  boiling  linseed 
oil  in  order  to  test  experimentally  the  influence  of  oil  fumes.  He  was  led 
to  make  these  experiments  by  the  injuries  which  had  occurred  near  a 
linseed  oil  and  varnish  factory.  Just  as  in  the  decomposition  of  fats  by 
alkali,  a  mixture  of  fatty  acid  alkahes,  soap,  is  produced,  a  mixture  of  cor- 
responding lead  salts,  lead  plaster,  is  formed  similarly  by  the  decomposing 
of  fat  with  lead  oxid.  In  both  cases  glycerine  occurs  as  a  by-product. 
When  the  glycerine,  or  fat,  is  heated  to  a  high  temperature  fumes  of  akrolein 
are  formed  which  smell  like  scorched  fat  and  quickly  pass  over,  through 
oxidation,  into  an  akroyl  acid  which  is  recognized  by  its  suffocating  odor. 
Yellow  red  to  brown  spots  are  produced  in  the  intercostal  fields,  or  along 
the  edges  of  the  leaves  according  to  the  nature  of  the  plant.  These  increase 
in  size  with  longer  action,  spread  and  actually  unite.  Most  of  the  cells  of 
the  leaf  mesophyll,  especially  of  the  spongy  parenchyma,  collapse  because 
of  the  loss  of  turgidity.  The  cell  contents  contract  from  the  walls  and 
the  chloroplasts.  form  greenish  yellow  to  brown  masses.  Finally  the  struc- 
tureless cell  contents  and  walls  become  brown.  The  elimination  of  tannin 
is  especially  noticeable  in  the  epidermal  cells,  the  contents  of  which  take  on 
a  bluish  black  color  with  ferric  chlorid.  The  flesh  of  apples  and  pears 
which  have  been  exposed  for  4  hours  to  the  oil  fumes  has  an  oily  rancid 
taste. 

Since  akrolein,  obtained  by  boiling  glycerin,  produced  the  same  phe- 
nomena the  injuries  from  oil  fumes  may  in  all  essentials  be  ascribed  to  this 
substance. 

5.  Turpentine  Fumes.  Molz-  made  experiments  on  the  effect  of 
turpentine  fumes,  because  a  case  was  brought  him  for  observation  in  which 
the  leaves  of  grapevines  were  said  to  have  been  injured  by  the  fresh  coating 
of  oil  in  the  grape  house.  The  action  of  turpentine  fumes  on  the  grape 
leaves  became  noticeable  after  a  half  hour  in  the  slight  discoloration  of  the 
edges  and  the  increased  curling;  after  an  hour,  apple  leaves  showed  a 
weakly  reddish  browning;  after  three  hours,  an  intense  dark  red  brown 
discoloration  of  the  upper  side.  The  grape  leaves  became  an  olive  brown. 
At  times  some  green  areas  were  found  within  the  brown  surface,  so  that 
the  leaves  looked  dappled.  Rose  leaves  turned  an  olive  brown ;  pear  leaves, 
a  shiny,  blackish  gray.  Molz  suspects  the  cause  to  be  a  process  of  oxy- 
dation  produced  by  "the  existence  of  'terpentinozone'  and  its  action  on  the 
'bradoxydable'  substances  of  the  cell." 

6.  Carbolineum.  Like  tar,  Carbolineum  is  used,  on  the  one  hand,  as 
a  coating  substance  for  the  framework  of  greenhouses,  hot  beds,  stakes,  etc., 
in  order  to  increase  the  resistance  of  the  wood  to  moisture;  on  the  other 
hand,  as  a  remedy  for  injuries  to  trees  and  a  means  of  destroying  injurious 
insects.     The  great  difference  in  opinion  as  to  its  effectiveness  is  due  in  part 

1  Korff,  G.,  ijber  Einwirkung-  von  Oldiimpfen  auf  die  Pflanzen.     Pi^akt.   Bl.  f. 
Pflanzenbau  u.  Pflanzenschutz  1906,  Part  6. 

2  Bericht  der  Kg-1.  Lehranstalt  fur  Wein-  Obst-  und  Gartenbau  zu  Geisenheim 
a.  Rh.     1905. 


758 

to  unsuitable  manipulation  and  also  because  "carbolineum"  is  a  general 
term ;  the  different  kinds  have  different  compositions  and  effects  according 
to  the  factories  producing  them. 

In  general,  all  that  has  been  said  of  tar  holds  good  for  the  use  of  car- 
bolineum as  a  coating  substance.  If  plants  are  brought  into  rooms  where 
the  carbolineum  coating  has  not  dried  sufficiently,  they  suffer  and,  at  times, 
show  symptoms  resembling  those  produced  by  asphalt  fumes.  Thus,  for 
example,  Zorn  in  Hofheim  (Taunus)  reports^  that  the  leaves  of  strawberry 
plants  set  out  in  hot  beds  of  which  only  the  outer  side  had  been  painted  with 
carbolineum,  became  a  peculiar  brown,  very  shiny  and  curled.  Under  the 
subject  of  coating  the  tips  of  grapevine  stakes,  a  "Chronique  agricole"-  calls 
attention  to  the  fact  that  even  when  such  stakes  have  been  painted  in  the 
winter  and  the  young  shoots  of  the  grapevine  have  already  overgrown  the 
painted  part  in  spring,  unpleasant  phenomena  can  still  occur.  Some  berries 
on  the  bunches  which  touched  the  saturated  spots  were  found  with  blackish 
lirown  spots  and  had  a  slightly  tarry  taste.  Also  the  saturated  parts  of  the 
stake  were  found  less  resistant  to  fungi  than  those  treated  with  copper 
vitriol.  It  was  noticed  in  a  peach  trellis  which  was  painted  in  the  autumn 
and  exposed  to  the  weather  for  the  whole  winter  that,  nevertheless,  in  the 
spring  after  every  rain  the  youngest  tips  of  the  shoots  looked  as  if  they  had 
been  burned.  Such  occurrences  are  by  no  means  uncommon.  It  is  the 
vaporizing  phenol  and  similar  bodies  which  cause  the  injury. 

Since  1899  carbolineum  has  been  used  extensively  as  a  remedy  applied 
directly  to  fruit  trees^.  As  to  the  results,  we  find  some  unusually  laudatory 
opinions,  some  very  harsh  ones.  The  reason  for  this  lies,  on  the  one  hand, 
in  the  difference  in  carrying  out  the  experiments ;  on  the  other,  in  the  vary- 
ing composition  of  the  substance  which  is  a  mixture  procured  in  the  produc- 
tion of  tar  from  hard  coal  and  charcoal.  If  the  tar  which  is  produced  in 
the  manufacture  of  gas  from  hard  coal  together  with  the  illuminating 
gas,  coke  and  ammonia  water,  is  reheated  in  a  distilling  apparatus  up  to  a 
temperature  of  150  degrees  C,  so-called  light  oil  is  obtained;  between  150 
degrees  and  210  degrees  C.  middle  oil ;  between  210  degrees  and  270  degrees 
C.  heavy  oil,  and  between  270  degrees  and  450  degrees  C.  anthracene-. 

The  pitch  remains  in  the  oven.  Wood  tar  behaves  in  much  the  same 
way.  In  preparing  carbolineum  the  oils  above  named  are  used  since  they 
are  mixed  in  definite  percentages  and  decomposed  with  kolophonium, 
asphalt,  boiled  linseed  oil,  etc.  Aderhold*  states  that,  at  the  present  time, 
possibly  80  carbolineum  factories  furnish  the  trade  with  200  to  300  varieties. 
The  distillation  experiments  made  by  Scherpe  in  the  Biological  Institution 
of  Agriculture  and  Forestry  with  25  varieties  proved  that  often  the  (espe- 
cially  injurious)    light   and   middle   oils   were   absent   and   the   heavy   and 


1  Praktischer  Ratg-eber  im  Obst-  and  Gartcnbau  1905,  No.  51. 

2  Chroniqiic  agricole  du  canton  de  Vaud  1S92,  No.  10. 

3  Mende,  O.,  Zur  Ob.stbaumpfleg-e.     Gartenflora,  1906.  No.  1. 

4  Aderhold,  R.,  Karbolineum  als  Baumschutzmittel.     Deutsche  Obstbauzeitung 
(Ulmer- Stuttgart)  1906,  Part  22. 


759 

anthracene  oils  alone  were  present,  while  in  other  varieties  the  opposite  was 
found  to  be  true.  Accordingly,  the  results  in  treating  wounds  were  very 
different.  While  normal  overgrowth  occurred  with  some,  with  others  there 
was  a  very  visible  increase  in  the  size  of  the  wounds  due  to  the  dying  back 
of  their  edges. 

But,  aside  from  this,  the  carbolineum  as  a  means  of  closing  wounds, 
even  in  the  viscid  varieties  abounding  in  pitch  and  asphalt,  does  not  stand 
comparison  with  plain  hard  coal  tar,  for  Aderhold  has  observed  that  a  few 
weeks  after  the  painting,  fungus  species  had  already  appeared  on  the  car- 
bolineum surfaces.  Since  the  painted  surface  may  also  crack,  under  the 
influence  of  the  atmospharilia,  such  fungi  have  a  good  opportunity  of  pene- 
trating into  the  wood. 

In  regard  to  the  very  fluid  kinds  of  carbolineum,  that  is,  those  rich  in 
light  and  middle  oils,  which  are  warmly  recommended  for  coating  trees 
attacked  by  red  aphis  and  scale^,  the  promptness  of  their  action  in  killing 
insects  is  unmistakable,  but  its  protection  is  not  permanent.  The  recoloni- 
zation  of  the  painted  wounds  by  red  aphis  has  been  repeatedly  confirmed. 
To  this  should  be  added,  however,  the  often  observed  injury  to  the  buds 
which  cannot  be  avoided  in  painting  or  spraying  the  trees  and  which  is  to 
be  ascribed  especially  to  the  vaporization  and  direct  action  of  the  light  oils. 
Therefore,  the  substances  should  be  diluted.  It  is  advisable  to  use  the 
commercial  carbolineum  varieties  which  are  soluble  in  water  and  to  add 
them  to  Hme  water  up  to  about  20  per  cent." ;  even  an  addition  of  10  per 
cent,  acts  favorably^. 

An  action  directly  favoring  growth  is  said  to  have  been  observed  in 
trunks  thus  coated*,  and  also  the  increase  of  the  chlorophyll  content  of  the 
painted  bark  has  been  microscopically  determined  in  Brunswick  with  the 
use  of  a  definite  brands  We  believe  that  this  result  is  due  to  the  fact  that 
in  coating  smooth  barked  trunks  tears  are  frequently  produced  in  the  bark 
which  must  be  overgrown  subsequently.  An  increased  bark  activity  in  the 
overgrowth  walls  has  also  been  proved  in  common  scarification. 

The  use  of  this  substance  as  a  coating  for  trees  is  advisable  only  during 
the  dormant  period  and  in  fact  with  some  tested  brand.  "Schacht's  fruit 
tree  Carbolineum"  (containing  20  to  30  per  cent.)  has  been  repeatedly 
recommended*'.  We  would  never  advise  spraying  in  summer.  As  a  means 
of  closing  wounds  we  would  prefer  coal  tar  because  not  only  Aderhold's 
discoveries,  but  also  experiments  made  by  Schweinbez'^  in  Hohenheim,  and 
our  own  have  shown  no  advantage  in  the  use  of  carbolineum.     Its  recom- 


1  Baumann,  R.     Geisenheim.  Prakt.  Ratg-eber  1905,  p.  459. 

2  Praktischer  Ratg-eber  im  Obst-  und  Gartenbau  1906,  No.  49. 

3  Praktische  Blatter  fiir  Pflanzenbau  und  Pflanzenschutz,  herausg-.  v.  Hiltner. 
1906,  November. 

4  Gartenflora  1906,  No.  3. 

5  Graef,  tjber  Karbolineumversucbe  im  Jahre  1906,  Prakt.  Blatter  f.  Pflanzen- 
bau und  I'flanzenschutz,  1907,  Part  3. 

6  Steffen  in  Prakt.  Ratg-eber  1906,  p.  23. 

7  Vom  Karbolineum.     Gartenflora  1906,  p.  22. 


y6o 

mendation  as  a  remedy  for  chronic  gummy  exudations  is  based  at  least  upon 
self-delusion  if  not  the  exigencies  of  advertising. 

Schweinbez  holds  the  same  opinion  of  the  related  substances  "Tuv", 
"Dendrin",  "Baumschutz",  "Neptun". 

7.  Lyzol.  Formerly  lysol  had  its  enthusiastic  adherents  and  doubters 
just  as  carbolineum  has  them  now.  The  Lysolum  puriim  of  Scholke  and 
Mayr  in  Hamburg,  introduced  into  trade  about  the  end  of  the  8o's  of  the 
last  centur)',  is  a  transparent,  brown,  syrup-like  fluid  which  remains  dissolved 
and  perfectly  clear  in  pure  water,  and  has  been  extensively  used  as  a  means 
of  disinfection.  In  introducing  it,  it  was  said  that,  according  to  experi- 
ments, 3g.  of  lysol  to  a  litre  of  liquid  was  enough  "to  destroy,  in  15  to  20 
minutes,  bacteria  in  all  their  developmental  forms,  if  suspended  in  liciuids." 
We  are  concerned  here  witli  a  solution  of  tar  oils  in  neutral  soap  and, 
indeed,  with  the  light  tar  oils  (cresol),  for  they  volatilize  almost  entirely 
between  187  and  200  degrees^  In  contrast  to  other  commercial  products, 
like  creoline,  cresoline,  Little's  Soluble  Phenyle.  which,  as  solutions  of  resin 
or  fatty  soap  in  tar  oil  only  form  emulsions  with  water  and  usually  give  off 
carburetted  hydrogen  oil  (Ethylene),  when  diluted,  lysol  has  the  advantage, 
at  any  rate,  of  complete  solubility  in  water,  but  shares  with  the  above 
preparations  an  injurious  effect  on  the  tissues  of  plants.  It  was  used  in 
horticulture  mostly  as  a  spraying  substance  for  leaf  lice,  thrip.  black  fly,  and 
other  injurious  insects.  Otto's-  cultural  experiments,  made  soon  after  the 
introduction  of  the  substance,  showed  that  0.5  i)er  cent,  lysol  solution,  the 
one  commonly  used  for  disinfection,  proves  to  be  a  severe  poison  for  plants 
if  added  to  the  soil,  even  if  it  does  not  come  directly  in  contact  with  the 
seeds  or  seedlings.  With  direct  action,  even  in  a  much  more  diluted  form, 
it  attacks  uncommonly  sharply  the  roots  of  water  cultures.  It  was  used  in 
a  0.25  to  0.5  per  cent,  solution  as  a  protection  against  leaf  lice.  In  this, 
however,  it  kills  only  some  of  the  leaf  lice,  the  majority  of  which  die  onlv 
with  a  2  per  cent,  solution;  the  plants  were  then  so  blackened  and  injured 
that  they  could  not  be  considered  capable  of  further  life. 

8.  Carbolic  Acid,  Amylocarhol,  and  Sapocarhol.  The  amylocarbol  is 
a  mixture  of  soft  soap,  fusel  oil,  and  pure  carljolic  acid.  Sapocarbol  is 
saponified  carbolic  acid. 

All  substances  containing  carbolic  acid  are  dangerous  and  usually 
directly  fatal  for  plants.  In  Fleischer's  experiments'*  with  the  above  prepa- 
rations, the  sapocarbol  in  one  per  cent,  solution  was  effective  for  leaf  lice 
without  any  injur}-  to  the  leaves  from  the  spraying,  with  a  few  exceptions. 
In  dilutions  which  completely  kill  the  leaf  lice,  Pinosol  and  Creolin  act  injuri- 
ously since  both   can  only  be  emulsified   in  water.     The  Antinonnin,  the 


1     Zpitschr.  f.  Pflanzenkrankh.  1S91,  p.  185. 

-  Otto,  R.,  tJber  den  schadlichen  Einflu.ss  A'on  wasserlgen,  im  Boden  befind- 
lUhen  T-,ysoll()sungen  usw.     Vorl.  Mitt.     Zeitschr.  f.  Pflanzenkrankh.  1892,  p.  70ff. 

•■!  Fleischer,  E.,  Die  Wasch.-  und  Spritzmittel  zur  Bekampfung  der  Blattlause, 
Blutlause  u.  ahnlicher  Schadlings  usw.    Zeitsch.  f.  Pflanzenkrankh.  1S91,  p.  325. 


7^1 

potassium  salt  of  Orthodinitro-Cresol  is  more  injurious  to  plants,  according 
to  Frank's  experiments^  than  to  leaf  lice  and  other  animal  parasites. 

9.  Refuse  from  Lactic  Acid  Factories.  To  those  injuries  we  will  add 
a  case  which  we  owe  to  a  report  from  Mr.  Klitzing  of  Ludwigslust.  He 
noticed  that  the  refuse  from  a  factory  which  produced  lactic  acid  from  maize 
and  potatoes,  for  the  treatment  of  leather,  caused  the  death  of  plants. 

10.  Calcium  arscnitc.  The  arsenic  solutions  which  are  being  accepted 
more  and  more  as  a  means  for  combating  insects  are  used  as  a  rule  in  the 
form  of  Schweinfurter  green,  or  calcium  arsenite.  Injuries  to  the  leaves 
have  been  observed  in  aqueous  solutions  as  also  in  lime  water  or  Bordeaux 
mixtures,  or  sodium  arsenite  calcium  solutions.  In  general  we  would  refer 
to  the  special  books  on  the  subject". 

11.  Hydrocyanic  acid.  Fumigation  with  hydrocyanic  acid  has  recently 
been  accepted  as  a  modem  method  of  combating  animal  parasites  in  plants 
and  has  been  developed  especially  in  America.  It  may  be  said  in  general,  in 
opposition  to  individual  complaints  of  injuries  to  plants,  that  these  should 
not  prevent  the  use  of  this  substance''.  Townsend  confirmed,  for  dry  seeds, 
that  the  germinating  capacity  does  not  suffer  if  the  action  of  the  hydrocyanic 
gas  is  not  continued  longer  than  is  necessary  for  killing  animal  life.  A 
longer  treatment,  however,  causes  considerable  injury.  Moist  seeds  suffer 
more  quickly  and  lose  their  power  to  germinate. 

12.  Copper  solutions.  These  come  under  consideration  here  only  in 
so  far  as  their  injuriousness  is  concerned.  Their  usefulness  as  fungicides, 
which  will  be  considered  in  the  second  volume  of  this  book,  depends,  in  our 
opinion,  chiefly  upon  the  fact  that  the  fungi  give  out  ferments  which  dissolve 
the  copper  salts  dried  on  the  plant  parts  and  thus  poison  themselves. 
Bordeaux  mixture  which,  without  doubt,  is  of  great  importance  as  a  means 
for  fighting  fungi,  may  primarily  favor  growth,  as  its  enthusiastic  advocates 
would  like  to  prove,  but  it  cannot  be  acknowledged  as  a  promotor  of  growth. 

Opinions  as  to  whether  the  copper  can  penetrate  through  a  normal 
cuticle  in  all  plants  are  not  unanimous.  According  to  Bouygues*  this  is  not 
the  case.  Rumm'''  also  could  not  prove  the  existence  of  copper  in  the  tissue 
of  sprayed  leaves  and  believes  that  the  favorable  action  can  be  traced  only 
to  the  chemico-tactic  stimulus.  The  electric  currents,  resulting  from  it,  are 
said  to  cause  the  favorable  effect  in  the  leaf  tissue.  The  question  whether 
copper  can  react  on  the  interior  of  any  part  of  a  plant  and  how,  cannot  be 
decided  universally  but  must  be  taken  into  consideration  case  by  case.  Old 
cuticule,  provided  with  a  thick  wax  coating,  will  possibly  not  be  attacked 


1  Krankheiten  der  Pflanzen  1S95,  Vol.  I,  p.  329. 

2  Hollrung-,  M.,  Jahresbericht  auf  dem  Gebiete  der  Pflanzenkrankh.  Berlin,  Paul 
Parey.  Published  since  189S.  Hollrung',  M.,  Handbuch  der  chemisclien  Mittel  gegen 
Pflanzenkrankheiten.     Berlin  1898.     Paul  Parey. 

3  Townsend,  W.  O.,  tJber  die  Wirkung-  gasformiger  Blausaure  usw.  Bot.  Gaz. 
XXXI;  cit.  Bot.  Jahresber.  1902,  I,  p.  354. 

4  Bouygaies,  H.,  La  cuticule  et  les  sels  de  cuivre  I;  cit.  Centralbl.  f.  Bakt.  nsw. 
1905,  N.  24. 

5  Rumm,  C,  Zur  Frage  nach  der  Wirkung  der  Kupferkalksalze  usw.  Ber.  d. 
Deutsch.  Bot.  Ges.  1893,  p.  445. 


7(^2 

while  a  young  leaf  can  suffer.  In  older  leaves,  however,  injuries  may  also 
occur  in  one  case  and  not  in  another;  the  cuticle  covering  may  be  broken  by 
atmospheric  action  (late  frost)  and  the  copper  solution  may  remain  for  some 
time  in  these  tears.  Finally,  the  specific  sensitiveness  of  the  plant  variety  is 
decisive,  as  will  be  shown  in  later  examples. 

The  first  doubt  as  to  the  peculiarity  of  copper  mixtures  for  favoring 
growth  arose  from  the  results  of  some  spraying  experiments  made  in  i89i\ 
An  arrestment  in  the  development  of  potato  plants  could  be  proved  as  com- 
pared with  unspraycd  plants  which  remained  healthy.  The  considerable 
amounts  of  starch  and  chlorophyll  contained  in  leaves  treated  with  copper 
which  are  considered  as  an  indication  of  favoring  growth  were  traced  by 
Schander  to  the  effect  of  the  shade  caused  by  the  calcium  copper  coating'-. 
Ewert  confirms  the  effect  of  shading  but  calls  attention  to  the  fact  that  this 
may  not  be  the  only  arresting  factor-'.  Through  the  effect  of  the  copper  sub- 
stances, especially  Bordeaux  mixture,  stoppages  occur  in  the  transference  of 
the  ass'unilates.  The  considerable  amounts  of  starch  and  protein,  here 
observed,  are  not  the  results  of  increased  assimilation  which,  as  has  been 
proved,  is  repressed  together  with  transpiration  and  respiration,  but  is  the 
action  of  arrested  transpiration.  This  point  of  view  which  we  represent 
presupposes,  at  any  rate,  that  copper  actually  enters  the  plant  and  this  theory 
is  substantiated  by  the  fact  that  scientists  who  do  not  assume  a  penetration 
of  the  copper  still  find  copper  reactions  in  a  number  of  their  experiments 
(Frank  and  Kriiger).  Besides  this,  Ewert  has  also  proved  the  presence  of 
copper  in  plants  sprayed  with  Bordeaux  mixture.  Later  we  will  quote  notes 
from  Schander's  work  as  to  the  way  in  which  the  copper  is  taken  up. 

In  my  opinion,  the  copper,  entering  through  wounds,  or  through  the 
epidermis  of  plants  treated  with  copper  mixtures,  is  combined  at  once  with 
the  proteins  of  the  protoplasm  and  thereby  reduces  cell-life.  Since  spraying 
does  not  represent  a  complete  wetting  of  all  the  leaf  surface,  certain  areas 
remain  healthy,  between  injured  ones,  and  these  must  show  an  increased 
growth  activity.  This  makes  itself  evident  at  times  with  an  abundant 
supply  of  light  and  moisture,  in  the  formation  of  intumescences.  I  described 
the  first  case  of  this  kind  in  potatoes^.  Later  v.  Schrenk''  observed  intu- 
mescences on  cabbage  plants  as  a  result  of  their  treatment  with  copper- 
ammonium-carbonate,  copper  chlorid,  copper  acetate,  copper  nitrate  and 
copper  sulfate.  Very  recently  Muth"  has  observed  a  very  strong  formation 
of  intumescences  in  grape  leaves  after  a  treatment  with  copper. 


1  Soruuer,  P.,  Einige  Beobachtungen  bei  der  Anwendung  von  Kupfermitteln 
gegen  die.  Kartoffelkrankheit.     Zeit.schr.  I.  I'flanzenkrankh.  1893,  p.  32. 

-  Schander*  K.,  tjber  die  physiologisclic  Wirkung  der  Kupfei-vitriolkalkbriihe. 
Inaug'.-  Diss.  Berlin  1904  und  Ijaindwirtsch.  Jalirbiiclier  1904,  Parts  4  and  .^). 

3  Ewert,  Der  wecliselseitige  Einfluss  des  Lichtes  und  der  Kupferkalkbriihen 
auT  den  Stoffwechsel  der  Pflanze.     Landwirtsch.  Jahrbiiclier  1905,  p.  233. 

4  Zeitschr.  f.  Pflanzenkranldi.  1893,  p.  122. 

5  Schrenk,  H.  v.,  Intumescences  formed  as  a  result  of  chemical  stimulation. 
Sixteentli  annual  report  Missouri  Botanical  Garden.     Rlay,  190."}.     Special  reprint. 

6  Muth,  Franz,  Uber  d.  Beschadigung  d.  Rebenblilltorn  durch  Kupfeisprilzmittel. 
Mittel.  d.  Deutsch.  Weinbauvereins  I.  Jahrg.  No.  1,  p.  9. 


7'^3 


Such  effects  may  be  produced  if  the  tissue  is  partially  poisoned  but  does 
not  actually  die.  They  may  also  occur,  however,  when  death  actually  takes 
place  in  which  case  the  dead  tissue  areas  in  many  plants  fall  out  of  the  leaf, 
causing  perforation.  Such  cases  have  recently  been  described  by  Schander^ . 
In  connection  with  this,  it  is  mentioned  that  Fuschia  and  Oenothera  secrete 
acids  which  dissolve  small  amounts  of  copper  hydroxid.  Alkaline  secretions 
have  also  been  found  (Phaseolus  multiflorus) ,  or  the  copper  is  dissolved  not 
by  secretions  of  the  leaf  but  simply  by  the  atmospharillia,  especially  with 
continued  wet  weather. 

Ruhland-  declares,  on  the  other  hand,  that  the  assumption  of  a  dissolv- 
ing of  the  copper  by  leaf  secretions  has  no  justification,  and  that  this  can  be 
ascribed  only  to  the  atmospharillia. 

Reports  as  to  the  injury  to  foliage  from  spraying  with  copper  have 
appeared  as  the  process  has  been  more  generally  used.  In  1891  it  was 
observed  in  fighting  Peach  rot  that, 
after  using  Bordeaux  mixture,  not 
only  the  leaves  and  blossoms  fell, 
but  the  young  wood  also  was  in- 
jured''. The  Amygdalaceae  and 
especially  peaches  have  been  found 
to  lie  especially  sensitive.  Bain* 
showed  in  his  experiments  with 
apple,  grape  and  peach  leaves  that 
this  is  connected  with  the  specific 
sensitiveness  of  the  protoplasm.  He 
says  that  the  peach  leaf  is  able  to 
dissolve  copper  oxid  by  a  substance 
secreted  on  its  upper  surface. 
Young  leaves  suffer  most.  The  in- 
jured part  of  the  leaf  is  then  cut  off 
by    a    cork    layer   and   thrown    off 

(Shot  disease,  which  Aderhold^  has  also  described  for  the  cherry).  Severely 
diseased  peach  leaves  fall  but  the  apple  leaf,  as  well  as  the  grape,  possesses 
the  ability  to  continue  assimilation  by  means  of  the  remaining  lamina. 

According  to  Hedrick's"  more  recent  studies,  peaches,  apricots,  and 
Japanese  plums  are  the  most  sensitive  fruit  trees,  while  the  common  plum  is 
not  affected  more  severely  than  the  pear,  apple  or  quince.  The  different 
varieties  behave  differently.    The  most  highly  cultivated  examples,  with  the 


An  apple  with  brown  spots  and 
•acks.      (After  Hedrick.) 


1     Loc.  cit. 

~  Ruhland,  W.,  Zur  Kenntnis  der  Wirkung-  des  unloslichen  basischen  Kupfers 
auf  Pflanzen  usw.  Arbelten  d.  Biol.  Abt.  f.  Forst.-  u.  Landwirtsch.  beim  Kaiser. 
Gesundheitsamt  Vol.  IV,  1904,  Part  2. 

3  Report  of  the  Secretary  of  Agric.  for  1891,  "Washington  1892,  p.  364. 

4  Bain,  S.  M.,  The  action  of  copper  on  leaves,  etc.  Ag-ric.  Exp.  Stat,  of  the 
University  of  Tennessee,  1902,  Vol.  XV. 

n  Aderhold,  R.,  tjber  Clasterosporium  carpophilum  usw.  Arh.  d.  Biolog-.  Abt.  d. 
Kais.  Gesundheitsamtes,  1902,  Part  5. 

6  Hedrick,  U.  P.,  Bordeaux  injury.  New  York,  Agric.  Exp.  Stat.  Geneva.  Bull. 
No.  287,  1907. 


764 

most  watery  leaves,  suffer  most.  Atmospheric  conditions  have  great  influ- 
ence, and  on  them  depends  the  more  dehcate,  or  coarser  development  of  the 
leaves  and  .especially  of  their  cuticule.  The  year  1905  furnished  the  best 
proof  in  New  York  State.  Its  warm,  misty,  spring  weather  left  the  foliage 
very  tender.  Many  apple  growers  declared  that  there  was  greater  injury  in 
that  year  than  benefit  from  spraying  with  Bordeaux  mixture.  Hedrick 
cites  examples  in  which  spraying  was  unusually  injurious  when  the  following 
weather  continued  moist,  while  8  days  later  after  dry  weather  had  set  in  the 
s])raying  did  not  have  any  bad  effects. 


Fis-.  170.     Young-  apples  with  one-sided  malformation,  after  spraying-  with  Bordeaux 
mixture.      (Aftei'  Mediick.) 


^       J 


FiPT.  171.     Cross-section  through  the  bark  of  a   IJaldwin  apple  injured  by  spraying? 
with  Bordeaux  mixture.     (After  Hedrick.) 


Wc  have  borrowed  from  the  above  mentioned  author  some  illustrations 
of  fruit  and  leaves  which  have  been  injured  by  spraying.  The  injury  at 
first  appears  on  the  fruit  in  the  form  of  small  brown  specks  which  spread  to 
extensive  rust  markings  (Fig.  169).  If  these  injuries  to  the  upper  surface 
occur  during  the  period  of  swelling,  the  growth  of  the  fruit  may  liecome 
irregular  (Fig.  170),  or  gapping  cracks  may  be  produced  in  young  apples. 
Fruit  thus  injured  becomes  mealy  and  easily  decays. 

Microscopic  investigation  of  the  brown  spots  shows  that  the  cuticle 
covering  with  its  wax  coating  is  destroyed  (Fig.  171).  The  walls  of  the 
adjacent  epidermal  cells  and  the  exposed  flesh  become  greatly  thickened  and 


765 


give  a  cork-like  appearance.  They  cannot  respond  any  longer  to  the  swelling 
of  the  fruit,  which,  therefore,  cracks.  The  w^oiind  cork  formed  in  the 
cracks,  together  with  the  tissue  killed  by  the  Bordeaux  mixture,  then  causes 
the  peculiar  "rust  figures"  shown  in  Fig.  169.  The  amount  of  injury 
increases  with  the  tenderness  of  the  skin,  which  shows  the  initial  stages  of 
browning,  as  a  rule,  around  a  hair  or  a  stoma.  With  the  increasing  age  of 
the  fruit,  the  hairs  are  thrown  ofif  normally  and  lenticels  are  produced  instead 
of  stomata.  In  this  the  wax 
coating  is  thickened  and  the 
fruit  becomes  immune  to  the 
poisonous  copper.  Brown  spots 
may  be  produced  also  on  the 
leaves  which  at  times  repture 
(Fig.  172).  Naturally  the 
blossoms  suffer  most  severely. 
It  can  be  assumed  with  cer- 
tainty that  in  these  blossoms 
the  copper  unites  with  the  cell 
contents.  Hedrick's  remark 
that  a  considerable  addition  of 
lime  scarcely  decreases  the 
injury  is  worthy  of  consider- 
ation in  regard  to  the  prepa- 
ration of  the  Bordeaux  mix- 
ture. This  is  treated  more 
thoroughly  in  the  second  vol- 
ume of  this  book  (page  521). 
All  that  is  true  of  calcium 
copper  mixtures  holds  good  to 
a  higher  degree  in  the  Asur'me 
in  which  ammonia  is  used  to 
neutralize  the  copper  vitriol. 
Pure  deep  blue  solutions  are 
produced,  according  to  the 
amounts  of  ammonia  used, 
such  as  "Bouille  Celeste"  and 
the    "Azurine    Siegwart,"    or 

especially  with  greater  dilution  basic  copper  compounds  remain  as  a  precipi- 
tate, as  is  found  in  the  " Crystal- Asurine  Mylius."  The  more  ammonia  used, 
the  greater  is  the  danger  of  burning  the  leaves\ 

Anaesthetica. 

In  considering  the  so-called  "forcing  zv'ith  ether,"  that  is  to  say  the 

process,  of  exposing  the  plants  to  ether  vapor  in  order  to  hasten  their  growth, 

1     Kulisch,    p.,    tJber    die    Verwendung-    der    "Azuiine"    zur    Bekampfung'    der 
Peronospora.     Landwirtsch.  Z.  f.  ELsass-  Lothringen  1907,  No.  26. 


P"ig-.  172.    Apple  leaf  with  dead  spots  and  holes 

in   the   tissue,   after   spraying-   with   Bordeaux 

mixtiu-e.      (After  Hedrick.) 


766 

we  must  take  up  also  the  subject  of  anaesthetica.  The  favorable  results 
which  can  be  obtained,  especially  in  the  early  forcing  of  lilacs,  by  a  proper 
use  of  this  method  are  certain  beyond  doubt ;  but  with  an  incorrect  use  dis- 
advantageous results  become  noticeable.  The  action  of  ether,  chrom-ether 
chloroform,  nitrous  oxid,  morphine,  cocaine,  etc.,  as  proved  by  repeated 
experiments,  consists  in  retarding  the  complete  development  of  protoplasmic 
activity.  If,  in  this,  the  protoplasm  undergoes  a  continued  injury  to  its 
physical  or  chemical  structure,  death  follows ;  otherwise,  the  plant  gradually 
returns  to  the  normal  activity.^  Naturally  the  effect  depends  upon  the  con- 
dition of  the  protoplasm.  Thus,  Coupin-  has  proved  that  even  an  atmos- 
phere saturated  with  chloroform  and  ether  can  exert  no  influence  on  the 
protoplasm  of  seeds  in  a  dormant  stage.  If,  however,  their  life  activity  has 
been  aroused  by  moistening  very  small  amounts  (.00037)  are  enough  to 
cause  injury.  Yet  the  figures  given  here  should  not  be  considered  as  a 
standard,  for  aside  from  the  individuality  of  the  species  even  plants  of  the 
same  species  can  develop  a  different  power  of  resistance  by  self  adjustment. 
Thus,  for  example,  Townsend^  states  that  spores  of  Mucor  and  Pcnicillium 
ripened  under  a  strong  ether  atmosphere  germinated  and  produced  spores 
just  as  quickly  as  when  they  had  germinated  in  an  atmosphere  free  from 
ether.  The  same  observer  mentioned  that  here  and  in  other  poisons  very 
weak  doses  act  as  a  stimulus  and  shorten  the  period  of  germination,  while 
stronger  doses  are  injurious. 

The  observations  of  Markowine"*  give  an  insight  into  the  kind  of  action. 
He  draws  the  conclusion  from  his  experiments  that,  in  the  long  continued 
action  of  anaesthetizing  vapors,  respiration  becomes  considerably  increased. 
He  found  that,  under  the  influence  of  alcohol  vapor,  the  respiration  of 
etiolated  plants  was  increased  more  than  one  and  a  half  times ;  ether  acted 
still  more  strongly. 

We  may  assume  here  a  specific  response  to  stimulation.  Behrens"'  also 
holds  this  theor}\  He  would  like  also  to  consider  as  a  response  to  stimula- 
tion the  hastened  germination  of  seeds  after  mechanical  injury  which  Hiltner 
ascribes  to  the  facilitated  absorption  of  water.  Behrens  bases  his  theory  on  ex- 
periments with  injured  seeds  in  which  the  wounded  places  were  covered  at 
once  with  colophoneum  wax.  Although  the  absorption  of  water  by  these  grains 
did  not  seem  increased  as  compared  with  normal  grains,  there  appeared,  never- 
theless, an  appreciable  increase  of  growth.  Experiments  with  filing  and 
other  intentional  injuries  to  hard  shelled  seeds  proved,  however,  that  even 
the  mechanical  facilitation  of  the  entrance  of  water  favors  germination. 

1  Kaufmann,  C,  tJber  die  Einwirkung-  der  Anaesthetica  auf  das  Protoplasma 
und  dessen  biologisch-physiologrische  Eigenschaften;  cit.  Just's  Jahresber.  1900,  II, 
p.  301. 

2  Coupin,  H.,  Action  dos  vapeurs  anesthesiques  sur  la  vitalite  des  graines 
seches  et  des  g-raines  humides;  cit.  Just's  Jahresber.  1900,  II,  p.  301. 

3  Townsend,  C.  O.,  Tlie  effect  of  ether  upon  tlie  germination  of  seeds  and 
spores;  cit.  Just's  Jahresber.  1899,  II,  p.  142. 

4  Markowine,  N.,  Rccherches  sur  I'influence  des  anesthesiques  sur  la  respiration 
des  plantes;  cit.  Just's  Jahresber.  1899,  II,  p.  143. 

5  Behrens,  Bericht  d.  Grosshorzogl.  Badischen  Landwirtsch.  Versuchsanstalt 
Augiistenberg-  f.  d.  Jahr.  1906. 


76/ 

Injuries  Due  to  Fertilizers. 

I :  Chili  saltpetre.  Unfavorable  secondary  and  subsequent  effects 
have  often  been  observed  with  the  use  of  Chili  saltpetre.  The  cause  lies  in 
part  in  the  presence  of  potassium-hyperchlorate.  Numerous  cultural  experi- 
ments have  proved  that  grain  is  especially  sensitive  and  shows  striking 
injuries  with  2  per  cent,  hyperchlorate,  while  alfalfa,  peas  and  mustard 
could  endure  this  concentration.  In  rye,  a  deformation  of  the  plant  was 
observed  when  grown  as  a  late  crop^.  Vegetables,  requiring  hoeing,  and 
sugar  beets  were  not  injured  by  2  per  cent,  hyperchlorate  to  200  to  500  kg. 
saltpetre  per  hectar-.  Jungner  and  Gerlach^  describe  the  formal  changes  in 
wheat  and  lye  seedlings  as  follows :  The  primordial  leaf  remains  for  some 
time  partially  rolled  and  encloses  the  secondary  leaf  so  firmly  that  it  loosens 
its  tip  only  with  difficulty  and  consequently  forms  a  loop,  or  knot,  in  which 
it  is  folded  crosswise  and  rolled  about  its  own  axis ;  it  finally  may  even  tear. 
At  the  same  time  a  yellowing  of  the  leaf  tip  takes  place  and  a  considerable 
reduction  in  the  elongation  of  the  whole  plant.  Retardation  of  germination 
\vill  occur,  in  fact,  according  to  the  amount  of  hyperchlorate  present.  This 
has  not  been  observed  with  weak  doses.  The  forming  of  loops  by  leaves 
because  of  the  retention  of  their  tips  in^  the  sheath  of  the  next  older  leaf 
seems  to  be  a  marked  characterization  of  grain  when  poisoned  with  hyper- 
chlorate. It  is,  however,  not  limited  to  grain,  since  similar  phenomena  occur 
in  Tylenchus  devastatrix*. 

Dafert  and  Halla^  describe  a  case  of  the  appearance  of  free  iodine  in 
Chili  saltpetre  which  thus  gave  the  odor  of  iodoform.  The  saltpetre  con- 
tained 0.31  per  cent.  KCLO4  and  0.04  per  cent.  KIO3.  In  such  cases,  how- 
ever, the  danger  is  slight  in  general  agriculture,  since  it  is  only  necessary  to 
expose  the  sacks  of  Chili  saltpetre  to  the  air  in  order  to  evaporate  the  iodine. 
Voelker*^,  among  others,  has  showed  that  the  iodids  of  manganese,  potassium, 
sodium  and  lithium  act  injuriously  while  the  oxids  are  proved  to  be  favorable. 
In  connection  with  his  earlier  experiments  by  which  he  proved  the  injurious- 
ness  of  larger  amounts  of  sodium  iodid  and  bromid  and  of  lithium  chlorid, 
while,  on  the  other  hand,  an  advance  in  germination  w^as  found  when  the 
seeds  were  moistened  with  more  dilute  solutions,  Maze'^  concludes  that  the 


1  Ullmann,  Martin,  In  welchem  Grade  ist  Kaliumperchlorat  ein  Pflanzens:ii't? 
Die  Regelung-  des  Verkehrs  mit  Chilisalpeter.  Meffe  1901.  Cit.  Centralbl.  f.  Agrikul- 
turcliemie  1903,  Part  7. 

2  Stcklasa,  Beitrag-e  zur  Kenntnis  des  schadlichen  Einflusses  des  Chilisalpeters 
auf  die  Vegetation.     Z.  f.  d.  landwirtsch.  Versuchswesen  in  Osterreich  1900,  p.  35. 

3  Jungner  nnd  Gerlach,  Versuclie  niit  Kaliumperchlorat.  Jahresber.  d.  landw. 
Versuehsstation  in  Jersitz  bei  Posen  1S97-9S,  p.  29. 

*  Krijger,  Fr.  u.  Berju,  G.  Ein  Beitrag'  zur  Giftwirkung-  des  Chilisalpeters. 
Centralbl.  f.  Bakt.  II,  1898,  Vol.  IV.  p.  674. 

5  Dafert,  F.  W.,  u.  Halla,  Ad.,  tJber  das  Auftreten  von  freiem  Jod  im  Chilisal- 
peter.   Z.  f.  d.  landw.  Versuchswesen  in  Osterreich  1901. 

6  Voelker,  A.,  iiber  den  Einfluss  von  Mangansalzen  sowie  von  Jodiden  und 
Oxyden  von  Mangan,  Kali,  Natrium  und  Lithium  auf  Gerste  und  Weizen.  Journ. 
Royal.  Agric.  Soc.  of  England,  Vol.  64  and  65;  cit.  Centralbl.  f.  Agrikulturchemie 
1905,  p.  715. 

7  Maze,  Einfluss  der  in  den  Pfianzen  in  geringer  Menge  enthaltenen  Mineral- 
stoffe  auf  das  Pflanzenwachstum.  Biedermann's  Centralbl.  f.  Agrikulturchemie 
1902,  p.  686. 


768 

cell  needs  stimulation  by  such  salts  for  the  complete  develo[)ment  of  its 
functioning.  Aso'  has  made  similar  discoveries  as  to  the  injuries  due  to 
stronger  concentrations  of  sodium  fluorid  and  the  favoring  of  growth  by 
very  weak  concentrations.  Suzuki-  has  also  found  this  to  be  true  of 
potassium  iodid.  Similar  discoveries  have  often  been  observed  by  others. 
Miani-'  also  reports  the  favorable  action  of  copper  solutions. 

2 :  Superphosphate.  We  should  briefly  consider  the  brcakimj  dou.m  of 
phosphoric  acid  in  superphosphate  and  Thomas  meal  in  many  soils  which  are 
rich  in  calcium  and  ferric  oxid.  In  sour,  marsh  soil  and  sour  meadow  soil, 
rich  in  humus,  retention  of  the  phosphoric  acid  in  a  soluble  form  predomi- 
nates since  w'ater,  carbon  dioxid,  humic  acid  and  some  salts  act  as  solvents. 
In  sandy  soil  containing  humus  but  not  acid  the  process  of  soluticjn  is  approx- 
imately held  in  equilibruim  with  the  process  of  transforming  the  dissolved 
phosphoric  acid  into  less  soluble  forms  but  in  loamy  soils,  containing  calcium 
and  iron,  the  process  of  decomposition  preponderates,  that  is,  the  process  of 
transforming  the  soluble  phosphoric  acid  into  phosphates  which  are  dissolved 
with  difficulty.  Under  such  circumstances  the  use  of  Thomas  meal  in  the 
s[)ring  would  not  be  advisable. 

3:  Gas  phosphate.  Rhodanammonium  is  found  in  different  amounts 
in  the  refuse  of  gas  factories.  This  has  attained  a  heightened  agricultural 
significance  since  a  fertilizer,  containing  nitrogen,  has  been  produced  by  the 
purification  of  illuminating  gas  with  superphosphate,  and  has  been  introduced 
in  trade  as  "(jas  phosphate."  The  acid  phosphate  has  taken  up  the  ammonia 
from  the  stream  of  illuminating  gas  but  at  the  same  time  has  retained  the 
Rhodanammonium.  Because  of  the  repeatedly  proven  poisonous  quality  of 
this  compound  the  purification  of  the  fertilizer  has  been  attempted  by  wash- 
ing the  gas  phosphate  with  a  concentrated  solution  of  ammonium  sulfate 
in  which  the  Rhodanammonium  compounds  are  easily  soluble.  The  amount 
of  Rhodan  compounds  contained  could  be  reduced  thereby  to  0.9  per  cent, 
and,  consequently,  the  direct  use  of  this  fertilizer  has  been  recommended. 
It  is,  in  fact,  distinguished  by  its  large  content  of  phosphoric  acid  and 
nitrogen. 

The  experimental  results  are  contradictory  in  that  favorable  effects  have 
been  observed  on  sandy  soil  and  unfavorable  effects  on  loamy  soils.  This 
brought  about  the  supposition  that,  in  sandy  soils,  a  more  rapid  decompo- 
sition of  the  Rhodanammonium  into  ammonia,  nitric  acid  and  sulfuric  acid 
occurs  whereby  the  poisonous  effect  is  repressed.  This  hypothesis  is  con- 
firmed by  other  experiments  which  demonstrate  that  in  using  the  fertilizer 
some  weeks  before  seeding,  no  injuries  appear,  while  severe  losses  take  place 
when  it  is  used  simultaneously  with  seeding.  The  same  result  was  found 
in  using  dust  from  a  blast  furnace  containing  i  per  cent.  Rhodanammonium. 


1     Aso,  Bull.  Coll.  Ag-ric.  Tokyo;   cit.  Bot.  Jahresber.  1902,  p.  353. 
-     Suzuki,  S.  ibid. 

a     Miana,  D.,  t)ber  Einwirkung  von  Kupfersulfat  auf  das  Wachstum  lebender 
Pflanzenzellen.    Ber.  d.  Deutsch.  Bot.  Ges.  1901,  Part  7. 


769 

The  recent  experiments  of  Haselhoff  and  GosseP  leave  no  doubt  as  to 
the  poisonous  effect  of  Rhodanammonium,  the  decomposition  of  which  even 
in  sandy  soil  does  not  take  place  so  easily  as  earlier  examples  seemed  to 
prove.  Even  a  very  small  amount,  such  as  0.0025  per  cent.,  produces  a  con- 
siderable delay  in  germination  and  since  the  purified  gas  phosphate  still 
contains  0.76  per  cent.  Rhodanammonium  the  above  named  scientists  could 
not  recommend  it  at  all  as  a  fertilizer,  even  with  the  difficult  solubility  of 
phosphoric  acid. 

4:  Ammonium  sulfate.  In  connection  with  this,  a  case  of  injury 
due  to  ammonium  sulfate  should  be  mentioned  here,  which  was  previously 
unknown.  A  car  full  of  plants  (Azaleas),  when  opened,  showed  that  the 
leaves  had  been  partly  blackened  as  if  from  ammonia  fumes.  Subsequent 
investigations  showed  that  the  car  had  been  used  previously  for  the  trans- 
portation of  ammonia  sulfate.  Experiments  made  immediately  proved  that 
free  ammonia  developed  in  the  presence  of  calcium.  In  the  same  way,  fresh 
ammonium  sulfate  which  has  not  been  sufficiently  dried  and  neutralized 
can  develop  ammonia  and  as  in  the  case  described  in  the  section  on  am- 
monium fumes  this  can  adhere  to  the  walls  and  subsequently  act  injuriously. 

5  :  Calcium  nitrid.  This  recent  product  of  our  fertilizer  industry  still 
gives  rise  to  repeated  complaints.  Calcium  carbid  used  primarily  in  the  pro- 
duction of  the  very  bright  illuminating  gas,  acetylene,  and  obtained  from  the 
interaction  of  lime  and  carbon  in  an  electric  oven  is  exposed  in  hermetically 
sealed  iron  mufflers  to  the  action  of  nitrogen  with  intense  heat  and  then 
furnishes  the  calcium  nitrid  as  an  unpurified  calcium  cyanamid  with  possibly 
20  to  24  per  cent,  nitrogen.  This  calcium  nitrogen,  or  calcium  cyanamid,  has 
the  peculiarity  of  giving  off  all  its  nitrogen  in  the  form  of  ammonia  when 
heated  with  water  under  pressure.  By  passing  the  ammonia  through  sulfuric 
acid  it  is  possible  to  produce  the  valuable  fertilizer,  ammonium  sulfate. 
The  "calcium  nitrid"  (CaCN^)  contains  about  20  to  21  per  cent,  nitrogen; 
40  to  42  per  cent,  calcium  and  17  to  18  per  cent,  carbon,  besides  impurities  of 
silicic  acid,  clay,  traces  of  phosphoric  acid,  etc.  By  removing  the  calcium, 
there  are  produced  Cyanamid  (CN.NH.)  and  the  homologous  Dicyandiamid 
[CN,(NH,)2]- 

The  calcium,  present  in  the  calcium  nitrogen,  which  acts  as  a  strong 
alkali,  is  partly  free  and  partly  combined  in  the  form  of  calcium  cyanamid. 
For  this  reason  it  should  not  be  brought  into  contact  with  supersulfat 
because  the  phosphoric  acid  would  then  be  made  insoluble.  The  rules  for  its 
use  are  approximately  as  follows  :- — The  quantity  used  per  hektar  according 
to  the  constitution  of  the  field,  is  150  to  300  kg.  corresponding  to  30  to  60  kg. 
nitrogen.  To  avoid  the  loss  in  dust  the  calcium  nitrid  is  mixed  with  twice 
the  amount  of  dry  earth.     This  should  be  spread  i  to  2  weeks  before  the 


1  Haselfhoff,  E.,  u.  Gossel,  F.  Versuche  tiber  die  Schadlichkeit  des  Rhodanam- 
iiioniums  fur  das  Pflanzenwachstum.  Zeitschr.  f.  Pflanzenkrankh.  1904,  p.  1.  Bibli- 
ography here  g-iven. 

2  Brahm,  Der  Kalkstickstoff  und  seine  Verwendung-  in  Gartenbau  und  Land- 
wirtschaft.     Gartenflora,  Berlin,  1906,  Part  10. 


770 

sowing  of  the  seed  and  i!ie  fertilizer  must  be  covered  at  least  3  to  5  inches 
so  that  the  soil  can  take  up  the  ammonia  freed  by  the  action  of  the  soil 
moisture  and  thus  be  nitrified. 

The  production  of  the  ammonia  from  the  calcium  nitrate  takes  place  by 
means  of  bacterial 

The  fertilizing  experiment,  carried  out  in  vegetating  vats,  has  shown 
the  possibility  of  obtaining  the  same  fertilizing  action  with  calcium  nitrid  as 
with  saltpetre  nitrid  and  ammonia  nitrid.  In  all  field  experiments,  made  as 
yet,  the  calcium  nitrid  has  developed  about  74  per  cent,  of  the  action  of  the 
saltpetre  nitrid". 

The  agriculturalist  will  cause  great  injury  if  he  sows  his  seed  soon  after 
scattering  the  calcium  nitrid.  Usually  only  those  grain  seeds  will  then 
sprout  which  lay  on  the  ridges  of  the  furrows.  If  the  first  shock  is  over- 
come, the  abundant  supply  of  ammonia  manifests  itself  in  the  especially  dark 
green  of  the  plants.  The  injury  consists  of  a  drying  of  the  leaf  parenchyma 
and  a  poor  root  development".  The  calcium  nitrid  may  not  be  used  as  a 
top  dressing  any  more  than  as  a  direct  fertilization  before  seeding.  This 
substance  acts  unfavorably  on  certain  soils  even  if  it  is  hoed  under  according 
to  rule.  Remy*  found  the  most  favorable  action  on  clayey  soils.  On  sandy 
soil,  however,  action  was  considerably  slower  and  the  directly  injurious  effect 
on  germination  much  more  persistent.  Only  three  months  after  fertilization 
did  he  find  that  the  injurious  effect  in  the  sandy  soils  had  disappeared.  All 
soils,  tending  to  the  formation  of  acids,  retard  the  normal  formation  of 
ammonia.  Tacke  has  proved  that,  on  acid  soils,  the  transformation  into 
ammonia  is  so  hindered  that  fertilization  of  marshes  with  calcium  nitrid 
must  be  omitted  there.  On  the  other  hand,  when  a  great  deal  of  calcium  is 
I)resent  in  the  soil,  the  ammonia  formation  can  take  place  so  rapidly  that 
extensive  losses  arise  from  the  vaporization  of  the  ammonia.  On  high  moor 
soils  poisonous  action  is  found  which,  according  to  Gerlach,  may  be  traced 
back  to  the  fact  that,  with  the  decomposition  of  the  calcium  cyanamid  and 
the  deposition  of  the  calcium,  considerable  amounts  of  the  poisonous  dicyana- 
mid  are  produced  within  a  few  days. 

The  conversion  of  the  ammonia  into  ammonium  sulfate,  which  thus 
overcomes  these  disadvantages,  is  useless  for  agriculture,  since  the  cost  of 
the  nitrogen  would  thus  become  too  great. 

A  still  newer  fertilizer  is  associated  with  this  "calcium  nitrid,"  "the 
nitrogen  calcium"  which  is  free  from  cyanamid  compounds  and  contains  22 
per  cent,  nitrogen ;  19  per  cent,  carbon ;  6  per  cent,  combined  chlorin  ;  and  .15 
per  cent,  calcium..     Bottcher's'"'  experiments  have  shown  that  with  this,  how- 

1  Lohnis,  P.,  Vsher  die  Zersetzung  des  Kalkstickstoffs.  Centralbl.  f.  Bakt.  1905, 
II,  Vol.  XIV,  p.  87.  Behrens,  J.,  Vcrsuche  mlt  Kalkstick.stoff.  Beiicht  der  Gross- 
herzog-1.  Bad.  landw.  Vei-suchsanstalt  Angu.stenbci-s'  1904,  Karlsruhe  1905,  p.  36. 

-  Gerlach  u.  Wagner,  P.,  Gewinnung-  u.  Landwirtschaltliche  Verwendung  des 
Salpcterstickstoffs.  Verhandl.  d.  Winterversammlung-  1904  d.  Deutsch.  Landwirtsch. 
Ges.  Jahrh.  d.  D.  L.  G.  Vol.  19,  p.  33-39. 

3  Perotti,  R.,  tJber  die  Verwendung'  des  Calciumcyanamids  zur  Dungrung.  Staz. 
sper.  agrar.  Ital.  1904,  Vol.  XXXVII;  cit.  Centralbl.  f.  Ag-rikulturchemie  1905,  p.  814. 

4  Blatter  f.  Zuckerrubenbau,  31  May,  1906. 

5  Deutsche  landw.  Presse  1906,  No.  34. 


771 

ever,  the  same  precautionary  measures  are  necessary  as  with  calcium  nitrid. 
It  may  not  be  used  immediately  before  seeding,  nor  as  a  top  dressing,  because 
it  is  then  injurious \ 

In  regard  to  the  Ammonia  nitrid,  we  should  not  forget  to  call  atten- 
tion to  the  fact  that  it  may  also  become  injurious  under  conditions  in  which 
the  nitrifying  bacteria  do  not  act  sufficiently.  For  heavy  soils,  which  contain 
more  water  and,  therefore,  dissolve  the  ammonia  more  abundantly  there  is 
no  danger,  but  in  sandy  soils  the  retarded  solubility  may  lead  to  direct 
phenomena  of  corrosion-. 


1  Blatter,  f.  Zuckerrubenbau  1906,  No.  10. 

2  Maze,  Untersuchungen  iiber  die  Einwirkungen  des  Salpeterstickstoffs  und 
des  Ammoniakstickstoffs  auf  die  Entwicklung-  des  Mais.  Annal.  agron.  t.  26;  cit. 
Centralbl.  f.  Agrikulturchemie  1901,  p.  5SS. 


SI'XTION  V. 

WOUNDS. 

CHAPTER  XX. 


WOUNDS  TO  THE  AXIAL  ORGANS. 


General  Discussion. 

However  much  accidental  or  intentional  injuries  to  the  tree  trunk  may 
differ,  nevertheless,  the  process  of  healing  alv^^ays  agrees  in  the  essential 
I)oints. 

We  find,  in  all  cases  in  which  the  injury  to  the  trunk  and  branches  is  so 
extensive,  that  the  wood  body  composes  part  of  the  wound  surface  and  that 
both  the  cambium  lying  between  wood  and  bark  which  with  undisturbed 
development  makes  possible  the  growth  in  thickness  of  the  trunk  as  well  as 
the  young  tissue  elements  directly  formed  from  the  cambium  (which  in  the 
following  will  be  included  under  the  term  "Cambium"),  take  over  the  heal- 
ing of  the  wound  surface  of  the  mature  part  of  the  trunk.  In  herbaceous 
stems,  or  the  still  herbaceous  developmental  stages  of  w^oody  trunks  and 
branches  other  tissue  forms  can  participate  in  healing  the  wounds  as  will  be 
shown  later  in  discussing  individual  cases  under  this  head. 

The  structures  of  the  forms  developed  from  the  cambium  in  the  healing 
of  wounds  may,  however,  vary  greatly  from  that  of  the  normal  wood  ring. 
The  reason  for  this  difference  in  structure  of  wound  ivood  should  be  sought 
in  the  fact  that  pressure  conditions  under  which  the  tissue,  serving  for 
healing  the  wound,  is  produced,  are  very  different  from  those  existing  during 
the  formation  of  the  normal  wood  body. 

Supported  by  the  investigations  of  G.  Kraus,  it  should  be  recalled  first 
of  all  that  each  trunk  and  branch  has  considerable  internal  tension,  due  to 
the  difference  in  growth  of  its  individual  tissue  forms  which  are  connected 
with  one  another.  The  experiments  on  tissue  tension  begun  by  Hofmeister^, 
extended  by  Sachs",  and  especially  fully  carried  out  by  Kraus",  have  proved 

1  Hofmeister,  tjber  die  Beugnng-  saftreicher  Pflanzenteile  durch  Erschiitterung. 
Ber.  d.  Kg-1.  Sachs.  Ges.  d.  Wissensch.  18.59,  p.  194. 

2  Sachs,  Expei'imentalphysiologie,  p.  465-514. 

3  Kraus,  Gregor,  Die  Gewebespannung  des  Stammes  und  ihre  Folgen.  Botan. 
Zeit,  1867,  No,  14.  ff. 


773 

that  the  growth  in  length  of  each  branch  of  our  trees  is  regulated  by  two 
factors. 

The  central  tissue  of  the  shoots,  especially  the  pith,  is  tke  elongating 
factor^  the  tissue  which  forces  the  shoot  into  the  air.  Its  very  considerable 
striving  to  grow  longer  and  to  carry  the  surrounding  tissue  with  it  into  the 
air  which  becomes  evident  in  an  isolation  from  other  tissues  is  modified  and 
retarded  by  the  strain  exercised  by  the  very  elastic  peripheral  tissue  parts  of 
the  bark  body.  These  contract  and  become  shorter  if  isolated.  They 
uniformly  grow  shorter  even  in  their  natural  position  on  the  tree  in  the  night 
because  of  a  radial  swelling  resulting  from  the  taking  up  of  water-. 

Therefore,  as  the  shoot  grows,  there  develops  a  considerable  longitudinal 
tension  due  to  the  struggle  of  the  elongating  force  of  the  surrounding  tissues, 
at  times  of  the  bark  body,  to  contract  both  themselves  and  those  surrounding 
them.  The  result  of  this  struggle  is  evidenced  in  the  length  of  the  pith  cells 
within  one  internode.  Cell  measurements  have  shown  that  the  pith  cells  are 
longer  at  first  than  they  are  later  and  that  a  very  strong  growth  in  breadth 
is  associated  with  their  subsequent  shortening. 

This  increase  in  breadth  is  the  result  of  the  ultimate  preponderance  of 
the  peripheral  strain.  When  the  increase  in  length  of  the  internode  is 
complete,  the  cross  tension  becomes  great. 

It  is  easy  to  understand  that  other  strains  must  occur  after  the  length- 
ening of  a  plant  part  is  ended  when  one  considers  that  the  part  of  the  trunk 
which  has  already  elongated  now  thickens  permanently  and  that  this  thick- 
ening depends  upon  the  differentiation  of  the  cambial  cells,  lying  between 
the  bark  and  wood,  into  new  wood  and  bark  elements  of  the  following  year  ; 
the  year  old  shoot  forms  new  wood  layers  above  those  of  the  previous  year ; 
these  new  wood  layers  must  make  room  for  themselves  under  the  girdle 
formed  by  the  bark  and  its  outermost  cork  layers.  This  can  be  done  only 
by  a  distension  of  the  bark  mantle  which,  however,  does  not  give  way  without 
resistance.  This  resistance  makes  itself  felt  in  pressure  and  thus,  during 
the  period  of  the  growth  in  thickness  of  a  shoot,  we  find  the  tender  tissue  of 
the  cambium  pressed  on  one  side  by  the  mature  but  still  distending  young 
wood  and  on  the  other  side  by  the  constricting  influence  of  the  bark  mantle, 
which  gives  way  only  to  very  strong  pressure. 

Under  this  double  pressure,  the  elements  of  the  wood  are  formed  from 
the  cambium,  that  is,  the  elongated,  thick-walled  wood  cells,  poor  in  contents, 
or  finally  entirely  empty,  as  well  as  the  ducts  and  duct-like  cells. 

De  Vries^  has  now  determined  experimentally  that  the  cells  of  the  wood 
become  narrower  (and  the  ducts  fewer)  the  greater  the  bark  pressure.  He 
increased  the  constricting  effect  of  the  bark  mantle  by  putting  on  a  firm 


1  According  to  Kraus  (loc.  cit.,  p.  141),  Hales  had  already  adopted  the  theory 
expressed  by  Borelli  in  his  book  "de  motu  animalium"  that  "The  young  shoot  grows 
and  elongates  by  the  spread  of  the  moisture  in  the  spongy  pith." 

2  Kraus,  G.,  Uber  die  Vei'teilung  und  Bedeutung  des  Wassers  bei  Wachstums- 
und  Spannungsvorgangen  in  der  Pflanze.     Bot.  Zeit.  1S77,  p.  595. 

•■i  Hugo  de  Vries,  tJber  den  Einfluss  des  Rindendinickes  auf  den  anatomischen 
Bau  de  Holzes.     Flora  1S75,  No.  7,  Sanio,  Bot.  Zeit.  1863,  p.  393. 


774  • 

band  and  in  other  specimens  weakened  artificialUy  the  pressure  of  the  bark 
by  cutting  it  longitudinally.  He  thus  succeeded  in  explaining  what  Sachs^ 
had  already  suspected,  that  the  difference  in  the  production  of  the  annual 
ring  is  due  to  bark  pressure,  which  changes  regularly  in  the  course  of  the 
year-. 

In  the  spring,  at  the  time  when  the  wood  is  most  swollen  because  of 
its  absorption  of  water,  the  bark  pressure  is  very  great,  as  may  be  noticed 
in  the  production  at  this  time  of  new  bark  tears  and  the  widening  of  those 
already  present.  During  the  unfolding  of  the  foliage,  the  wood  loses  a 
great  part  of  this  water  by  evaporation.  It  then  contracts,  reducing  the 
pressure  of  the  distended  bark.  This  explains  the  recognized  formation  of 
larger  wood  cells  at  this  time.  However,  the  more  new  wood  is  formed 
under  the  bark  in  the  course  of  the  summer,  the  greater  will  be  its  internal 
pressure  against  the  underside  of  the  bark ;  at  the  same  time  the  bark  layers 
lose  a  part  of  their  elasticity  because  of  drought  and  thus  their  resistance  to 
the  internal  pressure  of  the  wood  becomes  much  greater.  Under  such 
increased  pressure  conditions,  we  find  a  production  of  narrow  and  broad 
celled,  thick-walled  autumn  wood. 

Another  point,  which  I  had  an  opportunity  to  observe  in  artificially 
constricted  places,  is  the  increase  of  spiral  twisting  in  zvood  elements  due  to 
the  increased  bark  pressure.  Finally,  in  the  overgrowing  of  constrictions 
made  by  wires,  this  twisting  is  found  to  be  so  increased  that,  in  a  certain 
zone  of  the  overgrowth  callus,  the  wood  cells  which  otherwise  have  a  longi- 
tudinal course  lie  almost  horizontal.  A  radial  section,  made  directly  above 
the  overgrown  wire  ring,  shows  a  zone  of  wood  cells  cut  across  instead  of 
lengthwise.  These  fibres,  running  horizontally,  gradually  reassume  their 
vertical,  normal  course  when  the  swelling  becomes  less  and  passes  over  into 
the  normal  trunk. 

The  increased  twisting  of  the  wood  elements  due  to  increased  bark 
pressure  explains  also  the  well-known  phenomenon  of  the  non-parasitic, 
twisted  growth,  which  occurs  especially  in  dry,  poor  soils  (with  Syringa  and 
Craetaegus)  and  has  been  observed  in  very  different  kinds  of  trees.  The 
causes  of  the  increase  in  bark  pressure  differ  in  the  different  cases. 

The  regular  stratification  in  the  wood  body  of  the  wide  spring  zvood  and 
narrow  autumn  wood  thus  caused  is  only  a  special  case  of  the  law  proved  by 
De  Vries,  that  an  increase  of  the  bark  pressure  produces  narrow  celled  wood 
but  a  loosening  of  the  bark,  on  the  contrary,  a  wide  celled  wood. 

It  is  easy  to  convince  oneself,  however,  by  counting  the  cells  after  an 
artificial  loosening  of  the  l)ark,  that  this  acts  not  only  on  the  development  Imt 


1  Sachs,  Lehrb.  d.  Bot.  1st  Edition,  p.  409. 

2  Investigations  by  Krabbe,  published  later  (Sitzung-sbericht  d.  Akad.  d. 
Wissensch,  z.  Beiiin,  14.  Dez.  1882;  cit.  Bot.  Zeit.  1883,  p.  399)  on  the  relations  of 
bark  tension  to  the  formation  of  the  annual  rings  and  displacement  of  the  medullary 
rays  led  to  the  conclusion  that  no  effect  on  the  annual  ring  formation  could  be 
ascribed  to  the  radial  bark  pressiu-e,  on  account  of  its  insignificance.  To  me,  the 
method  used  does  not  seem  free  from  criticism,  so  that  some  douiit  of  the  correct- 
ness of  the  result  is  justifiable. 


775 

also  on  the  number  of  the  cambial  cells.  The  less  the  hark  pressure,  the 
greater  is  the  number  of  cell  divisions  in  the  direction  of  the  radius  of  the 
trunk;  the  greater  also  the  elongation  of  the  individual  cells  and  ducts  in  a 
radial  and  tangential  direction,  the  lesser,  however,  in  a  longitudinal  direc- 
tion. This  change  in  the  dimensions  increases  to  such  an  extent  that  in 
those  places  where  the  bark  pressure  is  almost  entirely  removed  the  thick- 
walled,  elongated  wood  cells  are  found  to  pass  over  into  short  parenchy- 
matous cells.  In  this,  the  differentiation  of  the  tissue  into  cells  and  ducts  is 
lost.     Only  a  uniform  parenchyma  zvood  develops. 

A  work  by  Gehmacher^  takes  up  the  influence  of  bark  pressure  on  the 
structure  of  the  bark  itself.  His  investigations  lead  to  the  conclusion  that 
the  greater  the  pressure,  the  fewer  the  cork  cells  formed  and,  conversely  in 
the  same  way,  the  radial  diameters  of  the  individual  cells  differ.  The  cells 
of  the  primary  bark  parenchyma  seem  contracted  not  only  radially  but  also 
laterally.  Their  form  is,  therefore,  angular  while  in  those  produced  under 
less  pressure  it  is  spherical  with .  considerably  larger  intercellular  spaces 
(which  can  disappear  entirely  under  strong  pressure).  The  number  of  bast 
fibres  is  said  to  increase  considerably  with  a  reduction  of  pressure  (which  I 
have  not  observed  myself)  and  to  decrease  almost  to  disappearance  with  an 
increase  of  the  bark  pressure. 

Nordlinger-  also  considers  the  production  of  a  wavy  periphery  of  the 
wood  body,  instead  of  the  regular  spherical  one,  to  result  from  bark  pressure. 
Where  the  wood  seems  indented  the  bark  frequently  appears  thicker.  The 
strongly  developed  groups  of  stone  cells  are  said  to  be  the  ones  which  are 
pressed  by  the  bark  into  the  cambium  and  arrest  the  growth  of  the  opposite 
part  of  the  wood. 

If  we  now  give  credence  to  the  circumstance  to  which  Kraus'"'  calls 
attention,  that  part  of  the  cell  content  is  more  quickly  pressed  out  from  the 
cell  tissue  under  increased  bark  pressure,  possibly  toward  those  places  in 
which  the  bark  pressure  is  less,  it  can  be  no  surprise  that  a  large  amount  of 
reserve  substances  are  found  stored  in  the  porous  parenchyma  wood,  formed 
from  the  cambium  as  a  result  of  the  reduced  bark  pressure.  The  wide- 
lumined,  thin-walled  parenchyma  wood  is  the  most  accessible  center  of 
deposition  for  the  constructive  material  flowing  toward  it.  For  this  reason, 
we  see  that  where  the  wood  cylinder  forms  parenchyma  tissue  instead  of 
prosenchymatous  elements,  this  usually  (with  the  exception  of  the  young 
callus  rolls)  is  richly  filled  with  reserve  substances  for  a  large  part  of  the 
year  and,  in  fact,  in  our  trees  also  containing  starch. 

All  the  wounds  to  the  tree  trunk  bring  about  a  loosening  of  the  bark. 
Nevertheless,  the  wood,  formed  in  healing  the  wound,  must  vary  in  structure 
so  much  the  more  from  normal  wood  and  take  on  and  retain  so  much  the 


1  Aus  Sitzungsl)er.  d.  Wiener  Akad.  d.  Wissen.sch.  Vol.  'LXXXVIir,  pt.  T;  cit.  in 
Botan.  Centralbl.  1S83,  No.  47,  P.  228. 

-  Nordlins"ei",  Wiikiing-  des  Rindendriickc.s.  Centralbl.  1".  d.  gesamte  Forstwesen. 
^Vien.    October  issue,  ISSO,  p.  407. 

3     Loc.  cit.,  p.  l.SS. 


77^ 

more  the  characteristics  of  parenchyma  wood,  the  less  the  pressure  of  the 
bark  girdle  on  the  cambium  at  the  time  of  ringing  and  the  longer  this  loosen- 
ing lasts. 

We  have  seen  in  canker  wounds  how  this  porous  structure  at  the  edge 
of  the  wound  causes  more  and  more  a  new  loosening  of  the  bark,  a  new 
excrescent  production  of  porous  tissue  and  the  final  exhaustion  of  the 
branch,  due  to  this  production. 

Every  overgrowth  edge  formed  about  open  wounds  on  the  trunk,  there- 
fore, begins  with  the  formation  of  short-celled,  wide-lumined  wood  elements 
which,  sharply  bounded,  lie  against  the  normally  exposed  wood.  The  wood 
elements  also  pass  gradually  over  into  a  normal  structure,  according  to  the 
increase  of  the  overgrowth  edges  and,  therefore,  the  stronger  bark  pressure. 
Tf,  finally,  the  overgrowth  edges  coalesce  and  the  bark  again  becomes  a 
uniformly  connected  girdle  around  the  trunk,  or  branch,  the  normal  amount 
of  hark  pressure  again  sets  in  and  with  it  the  normal  direction  of  wood 
cells  and  ducts.  Every  year  normal  wood  is  deposited  above  .the  closed 
wound. 

Scarification  Wounds. 

The  best  example  of  the  changes  in  tissues  during  the  process  of  wound 
healing  is  found  in  the  cicatrization  of  scarification  wounds.  By  the  term 
"scarification,"  as  is  well  known,  is  understood  the  cutting  through  the  bark, 
lengthwise  of  the  stem,  down  to  the  wood  body,  without  the  removal  of  any 
substance.  If  the  tree  is  slit  in  this  way,  the  edges  of  the  wounds  pull  apart 
(Fig.  173).  Naturally,  the  two  edges  of  the  wound  are  nearer  at  the  end 
of  the  incision  (Fig.  173  a).  The  process  of  healing  is  completed  most 
rapidly  there.  Fig.  174  shows  the  cross  section  of  a  healed  incision  on  a 
sweet  cherry  tree,  from  the  end  of  the  wound,  i.  e.  from  the  region  marked 
a.  We  see  at  h  the  old  wood,  which  was  cut  at  w,  and  shows  that  part  of 
its  ducts  and  wood  cells  died  because  of  the  effect  of  the  air.  The  cambial 
zone  (c)  which  at  the  time  the  incision  was  made  lay  above  h  has  formed, 
during  the  process  of  healing,  new  bark  {nr)  and  new  wood  {nh).  The 
newly  formed  wood  zone,  however,  does  not  resemble  the  normal  wood 
jjroduced  beneath  the  uninjured  bark  either  in  position,  or  in  structure. 

It  forms  one  part  which,  projecting  outwardly,  is  three-cornered  in 
shape,  its  highest  point  coming  nearest  the  groove  {s)  formed  by  the  previ- 
ous incision.  This  three-cornered  convexity  is  caused  by  the  development 
of  parenchyma  wood  {hp)  which  exceeds  that  of  the  tissue  lying  farther  at 
the  side.  This  production  of  wood  was  the  first  activity  of  the  two  edges  of 
the  cambium  which  were  separated  by  the  incision  {s).  Here  the  bark 
pressure  was  the  weakest,  the  cell  increase  the  greatest,  but  the  elongation 
the  least.  Only  after  the  new  bark,  formed  from  the  young,  inner  bark  and 
the  cambial  zone,  has  attained  at  j  a  greater  power  and  greater  resistance 
because  of  the  newly  produced  cork  layer  {k')  does  the  bark  pressure 
gradually  increase.  Its  influence  on  the  cambial  zone  producing  the  wood  is 
stronger  and  the  form  of  the  wood  elements  gradually  becomes  more  like  the 


717 


normal.  The  part  hp.  passes  over  gradually  into  the  regular  wood  much 
more  distinctly  divided  by  medullary  rays  (m).  The  transformation  of  the 
bark  elements,  taking  place  parallel  to  the  change  of  the  wood  elements,  will 
be  described  more  in  detail  in  the  callus  rolls  due  to  girdling. 

When  the  trunk  grows  further,  the  cambial  zone  (c)  always  deposits 
new  normal  wood  and  new  bark  with  hard  bast  {hh')  above  the  wound  sur- 
face and  when  finally  the  old  parts  of  the  bark  {ar) ,  separated  by  the  pre- 
vious incision,  with  their  cork  zone  (^)  and  the  dead  wound  edges  of  the 
bark  formation  {t)  which  have  been  separated  by  the  cork  zone  of  living 
tissue,  die  and  scale  off,  the  wounded  place  externally  becomes  smooth  and 
even. 

We  will  have  to  consider  Fig.  175,  if  we  wish  to  go  somewhat  more  in 
detail  into  the  beginnings  of  the  process  of  healing.  This  represents  a  cross- 
section  through  a  single  wound  edge  of  a  place  of  scarification  (Fig.  173  6) 

^  7c 


Fig:.  173.     Scarification  wound. 


Fig-.  174.     Healed  scarification  wound. 


in  the  sweet  cherry  at  a  time  when  this  edge  had  not  yet  united  with  the 
opposite  one,  growing  from  the  other  side  of  the  wound.  The  wound  sur- 
face (Fig.  175  w)  has  not  yet  been  covered,  h  indicates  here  also  the  old 
wood  which  at  w  has  been  exposed  by  the  incision.  At  the  time  the  incision 
was  made,  the  knife  passed  from  j  to  zv.  The  old  bark  {ar)  was  drawn 
back  towards  the  sides  from  this  plane  of  incision.  This  part  corresponds 
to  that  similarly  indicated  in  Fig.  174.  The  upper  part  of  this  old  piece  of 
the  bark,  as  well  as  the  edge,  which  has  dried  out  because  of  the  incision 
(Fig.  174  t),  is  indicated  in  Fig.  175  by  the  contours  marked  t  and  only  one 
hard  bast  bundle  {hh)  has  been  sketched  in  the  bark  parenchyma  {ar).  At 
the  time  the  incision  was  made,  the  cambial  zones  {c)  and  the  young  inner 
bark  (fr)  lay  close  to  the  old  wood  {h).  The  cells  which  bounded  the  plane 
of  the  wound  incision  {s  to  w)  reacted  differently  to  the  wound  stimulus. 
The  parenchyma  of  the  older  bark  dried  backward,  for  a  certain  distance, 


77^ 

and  formed  the  hnnvn,  dry  edge  of  tlie  wound,  recognizable  to  the  naked 
eye,  and  thus  enclosed  each  slit  (Fig.  173  c).  The  parenchyma  of  the  inner 
bark  (ir),  still  capable  of  increasing,  its  growth  not  yet  having  ended,  takes 
advantage  at  the  edge  of  the  wound  of  the  opportunity  of  spreading  toward 
each  side  where  the  pressure  has  decreased,  that  is,  over  the  plane  ^  to  zv. 
These  cells,  therefore,  curve  outward.  Those  from  the  cambial  zone  shove 
the  first  bark  cells  further  out  and  mature,  in  the  subsequently  growing  zone, 
to  bark  cells  (r)  containing  chlorophyll;  and  in  this  way  the  tender  paren- 
chymatous edge  of  the  wound  (r,  ir)  is  primarily  produced.  The  peripheral 
cells   (r)   of  the  convex  edge  of  the  wound  turn  brown  later  and  dry  ui*. 


Fig:.  17.').     Overgrowth  edg:e  produced  in  a   scariHcation  wound. 


Cork  (k)  is  produced  in  the  cells  lying  directly  underneath  this.  This  cork 
zone  {k  to  k),  covering  the  whole  wall  of  the  wound,  now  attaches  itself  to 
the  outer  cork  covering  of  the  old  bark  so  that  the  new  structure  is  sur- 
rounded by  a  ver)^  inelastic  cork  layer  which  conseciuently  presses  on  the 
swelling  tissue  lying  beneath  it. 

On  this  account,  the  bark  pressure  is  also  produced  at  intervals.  The 
influence  of  this  bark  pressure  on  the  immediately  succeeding  products  of 
the  cambial  zone  (c),  which  is  bent  forward  like  a  snail  but  does  not  reach 
to  the  old  w^ood  (A),  manifests  itself  by  the  formation  of  thicker  walled  ele- 
ments.    New  wood    (n/i)is  produced   which  toward  the  wounded  side  is 


PART  X. 


MANUAL 


OF 


Plant  Diseases 

BY 

PROF.  DR.  PAUL  SORAUER 


Third  Edition --Prof.  Dr.  Sorauer 

In  Collaboration  with 

Prof.  Dr.  G.  Lindau       And       Dr.  L.  Reh 

Private  Doceat  at  the  UoiTersity  ActitUat  io  the  Museum  of  Natural  Hietorr 

of  Berlin  in  Hamburg 


TRANSLATED  BY  FRANCES  DORRANCE 


Volume  I 
NON-PARASITIC  DISEASES 

BY 

PROF.  DR.  PAUL  SORAUER 

BERLIN 


WITH  208  ILLUSTRATIONS  IN  THE  TEXT 


PART  X. 


MANUAL 


OF 


Plant  Diseases 


BY 


PROF.  DR.  PAUL  SORAUER 


Third  Edition—Prof.  Dr.  Sorauer 

In  Collaboration  with 

Prof.  Dr.  G.  Lindau       And       Dr.  L.  Reh 

Private  Docent  at  the  University  Assistant  in  the  Museum  of  Natural  History 

of  Berlin  in  Hamburg 


TRANSLATED  BY  FRANCES  DORRANGE 


Volume  I 
NON-PARASITIC  DISEASES 

BY 

PROF.  DR.  PAUL  SORAUER 

BERLIN 


WITH  208  ILLUSTRATIONS  IN  THE  TEXT 


Copyrighted,   1920 

By 

FRANCES  DORRANCE 


THE  RECORD   PRESS 
Wilkes-Barre.    Pa. 


779 

parenchymatous,  short,  with  wide  lumina  (x)  and  perforated  by  isolated, 
short,  wide  ducts  (g).  The  further  the  new  wood  lies  from  the  edge  of  the 
wound,  the  more  regular,  narrow,  dense  and  longer  celled  it  is,  the  sharper 
appear  the  medullary  rays  (m)  and  their  continuation  (m)  in  the  bark.  The 
more  gradual  the  formation  of  the  new  wood,  the  more  taut  is  the  tension 
in  the  outer  cork  zone  (^  to  ^)  of  the  overgrowth  edge.  This  frequently 
tears  apart  in  places  as  a  result  of  the  inner  pressure,  so  that  the  bark 
parenchyma  is  exposed  and  pushes  out  into  the  torn  place.  On  these  out- 
pushing  cells,  new  cork  cells  are  formed  in  the  shortest  possible  time,  which 
lie  against  the  surrounding  ones  and  thus  close  the  cork  girdle. 


-  -^'^  - . 

,/' 

•'t 

i 

'■%.,: 

v._^ 

Fig-.    176.     Cross-section   through   a  hollow  pine   trunk  in  which   only  the   circum- 
vallation  edges,  several  years  old,  carry  on  the  nutrition  of  the  trunk. 

In  case  a  scarifying  incision  is  so  broad  that  the  overgrowth  edge  of  the 
first  year  cannot  cover  it,  the  new  wood  of  the  following  year  will  overgrow 
the  wound  surface  like  a  lip.  In  this  lip-like,  convex  overgrowth,  which  is 
recognized  best  by  the  course  of  the  new  covering  cork  zone  {k  to  k,  Fig. 
175)  the  cambial  zone  (c)  assumes  a  special  curvature,  which  becomes  more 
marked  the  deeper  the  wound  surface  lies.  If  it  now  happens  that,  in  old 
trunks,  a  broad  longitudinal  wound  is  made,  instead  of  a  scarifying  one,  and 
the  wound  body  is  destroyed  by  atmospheric  influences,  together  with  para- 
sitic action,  so  that  the  trunk  becomes  hollow,  ultimately  only  the  overgrowth 
edges  will  remain.  Fig.  176  represents  such  a  case.  It  is  a  cross-section 
from   a   hollow   pine   trunks     Because   of   the  slow   rotting  away   of   the 

1  The  orig-inal  may  be  found  in  the  Botanical  Museum  in  Berlini, 


78o 

younger  annual  rings,  the  overgrowth  edges  have  assumed  a  beautiful, 
spiral  form,  rarely  to  be  observed,  and  the  nutrition  of  the  trunk  depends 
on  the  comparatively  slender  wood  layers  of  the  last  few  years.  The 
process  is  shown  in  less  striking  form  in  all  hollow  trees,  for  example,  often 
in  willows  and  poplars.  In  conifers,  the  rotting  away  of  the  trunk,  as  a 
result  of  longitudinal  wounds,  is  a  less  frequent  case,  because  the  wound 
surface  usually  coats  over  with  resin,  or  at  least  the  parts  of  the  wood 
exposed  become  resinous.  This  self  protection,  after  a  longitudinal  injury, 
becomes  most  apparent  in  the  gathering  of  resin,  as  Fig.  177  shows. 


Fig-.   177.     Section   of  a  tiunk   of   Picea   vulgaris   with   the  overgrowth   of  the   resin 
channels.     The  entire  age  of  the  tree  is  70  years.     The  first  resin  tapping   (a)   took 
place  at  the  age  of  50  years,  the  second  (b)  at  51,  the  third  (c)  at  62,  and  the  fourth 
(d)  at  65  years.     (After  Dobner-Notabe.) 


The  wounds  resulting  from  the  gathering  of  resin,  in  the  form  of  strips 
some  centimeters  broad  and  about  2  m.  long,  from  which  the  bark  has  been 
removed,  do  not  die  for  some  time.  In  spruce  trees,  R.  Hartig  found  that 
the  turpentine  flowed  in  drops  from  the  resin  canals,  lying  in  the  medullary 
rays,  soon  after  injury.  Although  a  large  amount  of  resin  is  accessible  to 
the  wound,  since  the  resin  canals  running  vertically  in  the  trunk  are  in  open 
connection  with  those  of  the  medullary  rays,  yet  the  very  fluid  turpentine, 
as  a  rule,  ceases  to  flow  after  the  first  year.  The  turpentine  becomes  thicker 
by  the  volatilization  of  the  turpentine  oil  and  the  turning  to  resin   (oxida- 


78i 

tion).  After  the  resin  has  been  scraped  off  from  both  sides  of  the  tapped 
place,  the  overgrowth  roll  is  cut  away  in  order  to  open  new  resin  canals,  or 
new  strips  of  bark  are  removed  from  other  sides  of  the  tree. 

Inscriptions. 

Inscriptions  and  numerals  cut  into  the  trunks  of  trees,  as  also  the 
irregularly  gnawed  and  bitten  places  produced  by  the  gnawing  of  wild 
animals  in  winter,  should  be  mentioned  as  special  cases  of  a  common  form 
of  longitudinal  wound  extending  into  the  old  wood  and  connected  with  a 
loss  of  substance. 

In  inscriptions,  the  knife  has  removed  considerable  amounts  of  old 
wood  and,  therefore,  has  penetrated  deeper  into  the  trunk;  on  the  other 
hand,  however,  the  wound  is  not  so  broad.  The  healing  of  deep  incisions 
begins  at  the  longitudinal  edges  of  the  wound ;  the  upper  and  lower  edges 
share  only  to  a  very  insignificant  amount  in  this.  The  edges  of  the  wound, 
produced  by  the  cambial  zone  and  provided  with  their  own  bark,  extend 
further  every  year,  forming  overlapping  layers,  and  thus  gradually  grow 
over  the  wound  surface  without  becoming  re-united  with  the  old  wood,  of 
which  the  outermost  cell  layers,  bounding  the  wound,  turn  brown  and  die. 
These  healing  layers  form  only  a  mass  lying  close  against  this  wood,  like 
the  metal  in  a  mould.  At  the  moment  when  the  two  opposite  edges  of  the 
wound  of  each  letter  coalesce,  i.  e.  their  cambial  zones  unite,  these  zones 
again  form  nonnally  arranged  wood  elements,  which  become  increasingly 
thicker  because  of  the  annual  zone  of  increased  growth,  and  thereby  leave 
the  original  incision  deeper  and  deeper  in  the  trunk.  In  splitting  the  wood, 
a  lucky  blow  will  separate  the  intermediate  layers,  which  had  not  been 
injured,  between  the  individual  letters  or  numerals,  and  the  original  brown 
mould  falls  away  from  the  in-grown  w^ood  mass. 

Injury  Due  to  Wild  Animals. 

In  injury  due  to  wild  animals,  the  wounds  are  broader,  more  irregular 
but,  as  a  rule,  extend  only  into  the  sap  wood. 

If  the  bark  and  sapwood  are  torn  off  from  the  entire  circumference  of 
the  trunk,  it  dries  up  after  a  number  of  years,  if  the  injury  did  not  occur 
early  in  spring  or  in  summer.  As  a  rule,  however,  the  gnawing  and  barking, 
due  to  wild  animals,  takes  place  only  on  scattered  parts  of  the  trunk  and 
then  there  follows  gradually  a  formation  of  overgrowths  from  the  edges  of 
the  remaining  bark.  If  such  overgrowth  edges  are  injured  again  in  some 
subsequent  year,  before  the  first  wound  is  closed,  the  wood  body  apparently 
takes  on  a  very  complicated  formation  of  annual  rings. 

The  injuries  differ  with  the  kind  of  animal.  According  to  Ratzeburg^ 
red  deer  and  elk,  but  not  the  roebuck,  "peel"  the  tree,  since  usually  in  the 
spring,  in  feeding,  they  loosen  strips  of  bark  at  the  bottom  by  means  of  their 
incisors  and  then  tear  them  off  upward.     The  healing  then  takes  place  either 


Walclverderbnis,  I,  p.  50  ff. 


782 

by  overgrowth  or,  in  some  cases,  by  a  new  formation  of  bark  (cf.  Barking 
of  Fruit  Trees).  The  bark  may  also  be  worn  off  by  rubbing  and  blows, 
but  in  this  the  half-loosened  remnants  remain  on  the  edges  of  the  uninjured 
bark  in  the  form  of  tatters,  or  small  rapidly  drying  and,  therefore,  curling 
strips.  Usually  the  traces  of  hair  on  the  bark  remain.  Since  deer  and 
roebuck  rub  their  horns  up  and  down  against  the  tree,  to  free  them  from 
the  velvet,  these  rubbing  wounds  are  longer  than  the  peeling  wounds  and 
more  frequently  extend  around  the  trunk.  Now,  the  roebuck  sheds  its 
velvet  in  February  and  March ;  the  deer  about  the  first  of  May,  and  others 
four  weeks  later.  The  wounds,  due  to  the  latter,  therefore,  fall  in  a  time 
when  the  tree  has  the  greatest  amount  of  plastic  material  at  its  disposal. 
They  will,  therefore,  heal  much  more  quickly  than  wounds  made  in  the 
winter  and  spring.  It  thus  happens  that  the  wound  does  not  once  reach 
the  cambium,  but  only  removes  the  outermost  bark  layers.  If  the  inner 
bark  remains  in  place  the  annual  ring  develops  almost  normally  beneath  it 
from  the  cambium,  at  least,  so  far  as  the  arrangement  of  wood  and  vascular 
elements  is  concerned.  The  wood  cells,  however,  are  usually  thinner 
walled,  with  broader  lumina,  the  ducts  much  more  numerous,  the  whole 
annual  ring  broader.  If  the  weather  is  wet,  or  the  habitat  of  the  trees 
shady  and  damp,  a  callus  tissue  frequently  develops  on  the  outerside,  from 
the  cells  of  the  youngest  bark  which  has  been  left  in  place.  This  callus 
tissue  leads  to  the  formation  of  new  bark ;  in  rarer  cases,  with  luxuriantly 
growing  trees,  to  the  formation  of  isolated  wood  bodies. 

Wounds  from  blows  and  splitting  of  the  bark  also  arise  at  the  time  of 
"rubbing"  and  in  the  period  of  "heat"  in  the  late  summer.  A  different 
method  of  healing  the  wounds  now  often  sets  in,  since  a  callus  tissue  is 
formed  from  the  youngest  sapwood  layers  on  the  wood  body,  which  has 
been  freed  from  the  bark;  it  fills  out  the  hole,  as  in  budded  trunks  (cf. 
Budding). 

We  have  still  to  consider  gnawed  wounds,  as  produced  by  mice  and 
rabbits,  beavers  and  hares.  The  latter,  with  their  teeth,  cut  young  branches 
or  weak  plants.  Real  gnawing,  which  is  so  disastrous  for  our  fruit  trees,  is 
found  usually  only  after  deep  snows.  The  wounds  extend  to  the  older 
wood  on  which  may  be  recognized  the  tooth  marks.  If  these  reach  around 
the  trunk  in  connected  surfaces,  the  tree  is  lost.  If,  on  the  other  hand, 
isolated  particles  of  bark  are  left  in  place,  an  overgrowth  takes  place  from 
these. 

According  to  v.  Berg,  it  is  advisable  to  fell  Aspens  and  Sallows  {Salix 
caprca),  which  game  peels,  at  once,  in  order  to  protect  the  other  trees  from 
similar  injury.  Finally,  the  scattering  of  food,  during  the  winter,  might  be 
cited  as  the  best  means  of  protection.  We  insert  this  chapter  on  the  injury 
due  to  game  only  in  its  relation  to  the  anatomical  processes  of  healing 
wounds.  This  subject  is  treated  very  thoroughly  in  a  recent  work  by 
Eckstein^. 


Eckstein,  Die  Technik  des  Forstschutzes  ffegen  Tiere.    Berlin  1904,  Paul  Parey. 


783 

In  places  where  grazing  cattle  are  driven  into  the  forest  they  frequently 
cause  greater  injury  than  do  game.  Roots  will  be  exposed  to  such  an  extent 
that  whole  trees  die  along  the  paths.  Sheep  and  goats  bark  larches,  firs  and 
balsams,  etc.  As  v.  Mohl  indicates,  and  Ratzeburg  confirms,  deciduous 
trees  endure  injuries  to  their  trunks,  extending  to  the  cambium,  much  better 
than  do  conifers. 

Klein,  in  his  latest  forest-botanical  note  book^  gives  numerous  and 
good  reproductions  of  trees  that  have  been  gnawed  by  grazing  animals. 

Overgrowth  of  Cross  Wounds  in  Many-year  Old  Trees. 
If  branches,  or  trunks,  are  cut  across  the  same  processes  of  breaking 
the  bark  and  the  new  formation  of  overgrowth  edges  must  set  in  as  were 


Fig.  178.     Remains  of  a  sawed  off  branch  whicli  had  died  back  from  the  cut  surface 
and  which  had  been  covered  over  as  witha  cap,  by  the  overgrowth  edges  of  following 

years. 

described  above  in  scarification.     The  injury,  however,  in  itself  is  much 

more  dangerous  because  in  this  all  the  annual  rings   of  the  branch  are 

exposed  and  the  effect  of  the  atmosphere  and  wood  destroying  fungi  is 

uncommonly  facilitated. 

We  see  in  the  adjoining  cut  (Fig.  178)   the  product  of  several  years' 

overgrowth  of  the  old  stump  of  a  branch.     The  darker,  central  part  is  the 

cut  end  of  the  branch,  which,  under  the  influence  of  the  atmosphere,  has 

died  far  back  into  the  trunk.     In  five  years,  the  wood  cap  of  the  overgrowths 

1  Klein,  Ludwig,  Bemerkenswerte  Baume  im  Grossherzogtum  Baden.     214  Illus. 
Heidelberg  190S,  Winters  Universitatsbuchhandhing. 


784 

which  have  extended  farther  each  year,  has  been  formed  over  the  surface 
of  the  wound  and  has  finally  closed  it.  The  overgrowth  in  this  case  has 
taken  place  principally  from  above,  since  most  of  the  plastic  material  has 
come  from  that  direction.  In  a  slender,  longitudinal  wound  the  overgrowth 
takes  place  principally  from  the  sides. 

The  process  of  overgrowth,  which  sets  in  in  the  branches  of  trees,  also 
causes  the  closing  of  wounds  on  cut  or  chopped  surfaces  of  stumps  left 
when  trees  are  felled.  The  process  extends  only  comparatively  slowly, 
since  the  cambial  ring  producing  the  overgrowth  edges  has  to  cover  a  very 
large  wound  surface.  The  result  is  that,  long  before  the  overgrowth  edge 
has  reached  the  central  part  of  the  cut  surface,  this  has  decayed  and  the 
center  of  the  branch  in  consequence  has  become  hollow.  The  overgrowth 
masses  now  sink  down  into  the  cavity  in  very  different  forms  and,  at  times, 
in  twisted  cords  covering  projecting  si)lintcrs  or  stones.  Thus  they  can 
attain  a  considerable  size\ 

The  question  is  now  pertinent,  whence  comes  the  material  necessary  for 
such  an  extensive  new  formation.  The  opinion  usually  expressed  is  that 
the  reserve  substances,  formed  before  the  felling  of  the  tree  and  present  in 
the  stump,  can  be  the  only  source  of  all  the  new  structures.  In  other  cases, 
root  union,  which  occurs  not  infrequently,  is  used  to  explain  this,  for  it  is 
assumed  that  the  stump  is  nourished  by  the  uniting  of  its  root  branches  with 
the  stronger  roots  of  adjacent  trees,  which  still  retain  their  crowns. 

Certainly,  cases  of  this  kind  are  not  rare  in  larger  tracts  of  trees-  and 
such  a  nourishing  trunk  can  actually  give  considerable  assistance  to  the 
stump.  Nevertheless,  there  also  exist  instances  in  which  absolutely  isolated 
trees  have  formed  such  large  overgrowth  masses  on  the  stump  that  the 
supposition  of  a  production  of  such  massive  new  structures  from  the  reserve 
substances  alone  does  not  seem  sufficient  explanation. 

In  my  opinion,  however,  there  exists  universally  in  such  cases  an  acces- 
sory apparatus,  which  is  capable  of  conveying  newly  assimilated  material. 
If  the  young  overgrowth  edges  are  investigated  more  or  less  chlorophyll 
will  be  found  in  their  bark,  according  to  the  amount  of  light  the  trees  receive, 
and  it  is  by  no  means  clear,  why  this  chlorophyll  apparatus  should  not 
assimilate  just  as  well  as  the  green  bark  of  the  trunk.  The  fact  that 
branches  are  found  growing  out  of  older  overgrowth  edges  shows  how 
abundant  is  the  life  prevailing  in  them^. 

The  formation  of  branches  from  the  cambial  ring  of  tree  stumps  is  a 
very  common  occurrence,  which  comes  to  view  on  all  sides  with  felled 
poplars  and  arises  from  the  production  of  adventitious  buds  in  the  paren- 
chymatous overgrowth  tissues. 


1  Good  illustrations  of  such  cases  in  Goppert,  Nachtrage  zur  der  Schrift  tiber 
Inschriften  und  Zeichen  in  lebenden  Baumen.     Breslau,  Morgenstern  1870. 

2  Goppert,  Beobachtungen  iiber  das  sogen.  tjberwallen  der  Tannenstocke.  Bonn, 
Henry  &  Cohen,  1842. 

3  V.  Thielau,  in  Lampersdorff  near  Frankenstein  in  his  advertisements  of  the 
Goppert  Treatise  (tJber  die  Folgen  aussersr  Verletzungen  der  Bilume,  etc.)  in  May, 
1874. 


785 

Even  in  the  poplars  a  complete  circle  of  strong  green  branches  grows 
up  around  the  edge  of  the  cut  wood  body.  Such  an  "eruption  of  shoots" 
degenerates,  as  a  rule,  after  a  few  years  because  it  is  not  able  in  its  place  of 
production  between  bark  and  wood  to  form  new  roots  which  can  reach  the 
soil.  If  soil  reaches  the  base  of  these  shoots  by  being  covered  or  by  prema- 
ture decay  of  parts  of  the  bark,  the  shoots  can  free  themselves  from 
the  nutritive  trunk  by  growing  roots  and  form  long  lived,  independent 
individuals. 

The  ability  to  produce  new  shoots  from  the  tree  stump,  very  differently 
developed  in  different  tree  genera  and  very  rarely  in  conifers,  does  not 
always  depend  on  the  formation  of  adventitious  buds  but  also  on  the  awak- 
ening of  dormant  eyes  as  in  conifers.  In  this,  however,  the  hard  cortex  of 
the  stump  often  hinders  further  development. 

If  such  a  subsequent  development  of  shoots  is  expected  and  desired,  as 
in  forestration  or  in  parks,  the  trees  must  be  cut  down  as  deep  as  possible 
in  order  to  give  the  new  shoots  a  good  chance  to  root. 

The  custom,  not  infrequently  found,  of  renewing  tree  plantations  by 
leaving  stumps  one  meter  high,  should  be  given  up  absolutely.  The  new 
shoots  developing  on  such  stumps  are,  on  an  average,  much  weaker  and  are 
often  surpassed  by  shoots  at  the  surface  of  the  soil. 

Overgrowth  Processes  in  Year  Old  Branches. 

In  our  cultivated  trees,  the  necessity  arises  of  cutting  back  the  tops  in 
order  to  prune  the  foliage  shoots  and  thus  favor  the  fruit  buds,  or  in  trans- 
planting to  bring  the  top  into  balance  with  the  injured  root  system.  The 
pruning  affects  principally  the  year  old  growth,  and  is  done  either  in  the  fall 
or  early  spring.  Consequently,  a  considerable  time  passes  before  the 
processes  of  closing  the  wounds  begin  through  new  formation  of  tissue.  In 
this  it  is  found  not  infrequently  that  such  young  growth  dies  back  for  a 
short  distance  from  the  cut  surface. 

In  Fig.  179  is  shown  the  tip  of  a  year  old  cherry  branch  which  has 
dried  back  some  distance  from  the  cut  surface.  Fig.  180  shows  the  same 
branch  cut  through  longitudinally ;  .y  to  /  is  the  original  cut  surface ;  t  is  the 
boundary  layer,  back  to  which  the  twig  has  died ;  a,  a  swelling  frequently 
found  in  such  cases.  Fig.  181  shows  the  anatomical  structure.  In  it,  s  to  / 
is  the  plane  of  the  cut,  a  h,  the  last  peripheral  particle  of  the  old  wood  of  the 
cut  surface;  a  r,  the  old  bark  with  its  outer  normal  cork  layers  (k).  Of 
this  bark,  the  tissue  indicated  by  T  has  dried  back  and,  in  fact,  the  tissue 
near  the  hard  bast  cords  (b)  dies  the  furthest  downward;  the  bast  cord  is 
also  dead  and  together  with  the  outer  cork  layers  of  the  bark,  which  also  are 
but  little  shriveled,  projects  from  the  discolored  parenchyma.  The  cut 
surface  is,  therefore,  uneven  and  rough. 

The  next  process  which  sets  in,  after  injury  and  after  the  upper  bark 
tissue  has  died,  consists  in  the  cutting  off  of  the  dead  from  the  healthy  tissue, 
by  means  of  the  formation  of  a  cork  zone  (k',  k").     The  cork  zone  is  devel- 


786 


oped  more  extensively  about  the  base  of  the  bast  bundle  and  represents  a 
radiating  overgrowth  (k").  The  increase  in  cell  numbers  begins  at  once  in 
the  layers  of  the  cambial  zone  (c)  lying  next  to  the  cut  surface,  and  of  the 
bounding,  inner  bark  which,  at  the  time  the  pruning  was  done,  lay  close  to 
the  wood  body  (a  h). 

Exactly  as  in  the  protuberance  of  the  roll  in  the  scar  wound  shown  in 
Fig.  173,  the  protruding  bark  zone  (n  r)  is  formed  from  the  products  of  the 


Fie;.  179. 


Fig.  isi. 


A  one  year  old  branch  of  the  sweet  cherry  cut  through  in  cross-section,   the  cut 

surface  of  which  has  dried  baclt. 

Fijr.  179.     From  without  the  cut  surface  of  the  branch  appears  somewhat  dried  back  and  has  a  swelling  (a) 

below  the  dried  tissue.     Fig.  180.   The  same  branch  cut  throuKh  in  tlie  median  line.     Fig.  181.  Anatomical 

sketch  of  the  region  a  to  s'  of  Fig.  180. 


cambial  zone  and  the  young  bark,  and  this  protuberance  is  closed  in  the  same 
way  by  a  cork  girdle  {k'  k"').  The  wood  products  of  the  cambial  zone,  the 
maturing  of  which  changes  gradually  because  of  the  pressure  of  the  newly 
produced  wound  bark,  are  produced  at  first  as  parenchyma  wood  {hp)  in 
which  cord-like,  short,  porous  duct  cells  {g)  occur.  The  further  the  for- 
mation of  the  new  wood,  produced  after  injury,  is  traced  back  from  the  cut 


787 

surface,  the  more  the  elements  of  this  wood  are  found  to  resemble  the 
normally  elongated,  thick-walled  elements  (g,  h').  In  the  drawing,  the 
transition  from  the  short  vascular  elements  to  the  long  ones  is  interrupted 
by  the  continuation  of  an  old  medullary  ray  (w)  into  the  medullary  ray 
(m')  of  the  new  wood. 

Besides  this  formation  of  new  wood  and  independent  of  it  still  another 
cell  increase  manifests  itself  in  the  bark  near  the  hard  bast  bundle.  The 
parenchyma  cells  divide  and  increase,  thereby,  the  thickening  of  the  original 
bark,  which  is  forced  out  by  these  new  growths  and  causes  the  externally 
visible  swelling  (Figs.  179  a,  180  a,  181  a).  Under  certain  circumstances, 
the  new  growth  within  the  bark  is  so  intensive  that  a  meristematic  zone  is 
produced,  which  remains  active  for  some  time,  producing  in  turn  wood  and 
vascular  elements,  and  gives  rise  to  the  formation  of  wood  fibres  in  the 
bark,  said  to  have  been  found  in  the  production  of  gnarl  tubers. 

The  drawing  of  a  cut  branch,  reproduced  in  Fig.  181,  does  not  agree 
entirely  with  the  structure  found  in  the  overgrowing  cross-wound  of  the 
stump  of  a  branch.  The  reason  for  ^this  is  that  we  usually  think  of  such 
cuts  as  having  been  made  late  in  the  spring  or  summer  on  older  branches. 
In  these  cases  the  drying  back  of  the  tissue  from  the  surface  of  the  wound  is 
not  extensive  until  the  time  when  the  wound  begins  to  heal,  i.  e.  until  the 
formation  of  the  overgrowth  edge  {nr,  nh).  This  overgrowth  edge  soon 
appears  above  the  cut  surface  and  lies  in  a  curve  over  the  old  wood,  which 
had  been  formed  before  the  time  of  pruning  and  is  indicated  by  ah.  The 
arrangement  of  the  elements  then  corresponds  to  the  formation  of  the  callus 
roll  in  the  cuttings  illustrated  in  a  later  figure ;  the  nature  of  the  cell  elements 
remains  that  shown  in  Fig.  181. 

As  the  branch  becomes  older  and  the  wood  layers,  formed  from  cambial 
zones,  become  increasingly  thicker,  the  overgrowth  edge,  projecting  on  all 
sides  above  the  cut  surface  of  the  branch,  also  becomes  thicker  and  thicker 
until  the  opposite  sides  touch  one  another  and  unite  in  a  cap  which  entirely 
encloses  the  cut  surface. 

Each  overgrowth  edge  begins  in  the  way  shown  in  cross  section  in  Fig. 
175.  It  can,  therefore,  be  said,  figuratively,  that  the  new  wood  layers, 
formed  after  injury,  spread  over  the  old  wood  body,  laid  bare  by  pruning, 
and  finally  shut  it  in  by  a  cap. 

Girdling  Callus. 

By  "girdling"  is  understood  the  removal  of  a  small  circular  strip  of 
bark  around  the  whole  axis,  usually  at  the  time  of  the  greatest  cambial 
activity,  since  only  at  this  time  can  the  bark  body  be  loosened  easily  and 
completely  from  the  wood. 

In  girdling,  only  the  part  of  the  branch  lying  above  the  wound  receives 
the  plastic  material  prepared  by  its  leaf  apparatus.  This  cannot,  as  des- 
tined, be  used  to  strengthen  the  wood  ring  for  the  whole  length  of  the 
branch,  but  is  held  back  above  the  place  of  girdling,  thus  conditioning  a 


more  abundant  cell  increase  in  the  cambial  ring  at  that  place.  We  find  that 
the  diameter  of  the  upper  part  of  the  branch  has  strikingly  increased  in  pro- 
portion to  that  lying  below  the  girdling  cut.  The  supply  of  water  carried 
up  from  the  roots  to  this  place  is  at  first,  however,  considerably  decreased. 
In  the  first  place,  the  amount  of  water  ascending  in  the  bark  is  prevented 
from  rising  further  by  the  girdling  cut,  and  then  the  main  stream,  ascending 
in  the  wood,  loses  no  inconsiderable  amount  of  water  at  first  by  evaporation 
at  the  place  laid  bare  by  the  girdling.  Therefore,  in  the  upper  part  of  the 
branch  the  main  factor  of  cell  elongation,  turgor,  is  decreased  by  the  lessen- 
ing supply  of  water  from  below.  The  cell  increase  is  indeed  greater  but 
the  cell  elongation  is  less  than  in  the  normal  branch.  While  the  growth  in 
thickness  of  the  part  of  the  axis,  which  lies  above  the  girdle,  is  increased, 
the  apical  growth  of  the  branch  remains  moderate;  the  intemodes  are  not 
as  much  lengthened.  Shortening  of  the  intemodes  with  abundant  supply 
of  plastic  material  is  the  first  step  toward  the  formation  of  fruiting  wood; 
thus  fertility  of  the  branch  is  more  rapidly  brought  about  by  tjirdling.  The 
part  of  the  branch  above  the  girdling  is  demonstrably  poorer  in  water ;  its 
leaves,  likewise  poorer  in  water,  take  on  an  autumnal  coloration  earlier, 
and  the  ripening  of  its  fruit  is  hastened. 

The  assertion  that  larger  fruit  can  also  be  obtained  by  girdling  has 
been  confirmed  only  in  certain  cases.  Grapevines,  for  example,  and  the 
American  varieties  especially,  after  girdling  seem  still  to  get  such  a  consid- 
erable amount  of  water  in  the  upper  part  of  the  vine  that  no  retarding  of 
the  apical  growth  is  noticeable.  In  this  case,  therefore,  the  development  of 
the  fruit  depends  essentially  on  the  amount  of  plastic  material  and  this 
varies  in  different  years,  according  to  the  prevailing  atmospheric  conditions. 
In  the  same  way,  the  character  of  the  variety  is  of  influence.  For  example, 
Paddock^  observed  that  the  variety  of  grape,  "Empire  State,"  ripened  its 
fruit  three  weeks  earher  than  usual  because  of  girdling,  the  "Delaware,"  on 
the  other  hand,  showed  scarcely  any  reaction  and,  in  fact,  its  quality  was 
poorer. 

Girdling  is  used  on  grapevines  as  a  means  for  curing  the  dropping  of 
the  young  berries-,  but  as  a  constant  regular  treatment  in  cultural  pruning 
girdling  will  never  find  an  opening;  it  may  always  be  used  only  as  a  drastic, 
exceptional  method,  in  special  cases,  the  injuriousness  of  which  frequently 
exceeds  its  usefulness. 

Even  in  the  grapevine,  in  which  girdling  is  used  most  frequently,  its 
use  must  remain  limited.  In  the  "Annalen  der  Oenologie"^  Gothe  judges 
that  the  hope  of  a  general  application  of  the  process  in  grape  culture  will 
not  be  realized.  The  advantage  of  hastened  ripening,  he  thinks,  is  unmis- 
takable. In  this  way,  late  varieties  may  still  be  brought  to  ripening,  but 
the  grapes  of  girdled  vines  give  a  worthless  wine.     The  part  of  the  vine 

1  Paddock,  W.,  Experiments  in  Ringing-  Grape  Vines.     New  York  Agric.   Exp. 
Sta.  Bull.  No.  151,  1898. 

-  Jilger,  Obstbau  1856,  p.  125. 
3  Vol.  VI,  1877,  Part  1.  p.  126, 


789 


above  the  girdled  place  dies  (at  least  in  European  varieties),  the  part  below 
it  is  poorly  nourished,  so  that  the  eyes  remain  sterile  and  should  not  be  taken 
into  account  in  pruning.     Besides  this,  girdled  shoots  break  off  very  easily. 

In  many  trees  also  there  is  found  frequently  a  hastening  of  the  develop- 
ment of  the  leaf  buds  below  the  place  girdled,  which  can  increase  to  the 
formation  of  water  sprouts.  This  case  is  more  frequent  in  apple  trees 
than  in  pears. 

Recently,  girdling  has  also  been  made  use  of  in  herbaceous  plants  with 
edible  fruits.  Thus,  for  example,  DanieF  obtained  larger  fruit  with  the 
Solaneae  by  this  treatment.  Other  observers  could  not 
confirm  this,  but  found  a  retrogression  in  the  develop- 
ment of  the  whole  plant". 

If  we  now  pass  over  to  the  study  of  the  anatomical 
conditions  produced  by  the  girdling  cut,  or  "pomological 
magic  ring,"  by  means  of  the  adjoining  illustrations,  we 
shall,  we  believe,  best  further  thereby  an  understanding 
of  the  matter  by  giving  first  of  all  a  general  description 
of 'Figs.  182  and  183. 

Fig.  182  represents  a  girdled  grapevine;  ii  is  the 
lower  overgrowth  edge,  it  the  upper  edge ;  bl,  the  bared 
surface  of  the  wood  body. 

Fig.  183  is  a  longitudinal  section  through  the  lower, 
smaller  overgrowth  edge  (Fig.  182,  u).  S,S'  is  the  plane 
of  the  lower  knife  cut  in  girdling;  S,S'C'  is  the  protrud- 
ing tissue  of  the  overgrowth  edge.  H  represents  the 
outermost  layer  of  the  exposed  wood  body;  in  this,  g,g' 
indicates  the  ducts  and  h,h'  the  porous  wood  cells.  R, 
as  in  Fig.  182,  is  the  bark  cut  through  in  girdling, 
which  appears  pushed  back  from  the  wood  by  the  out- 
swelling  overgrowth  tissue  {r,C,C').  This  tissue  at  s' 
lies  close  against  the  wood  and  is  protected  externally 
by  a  cork  layer  {k,k').  This  protruding  overgrowth 
edge  of  parenchymatous  tissue  is  differentiated  by  the 
arched  cambial  zone  c,c,c',  into  the  parenchymatous 
wound  wood  (wh)  and  the  wound  bark  (wr).  Both 
are  traversed  by  radiating  medullary  rays  (m). 

Figs.  184  and  185  show  how  such  an  overgrowth  edge  appears  in  cross 
section.  The  first  was  taken  from  the  upper  wound  wall,  close  to  the  place 
where  it  leaves  the  bark ;  the  second  figure  originates  from  a  broader,  most 
distant  region. 

In  considering  Fig.  183,  we  see  that  a  mass  of  tissue  has  protruded 
from  the  edge  of  the  wound  produced  by  a  3  to  4  fold  division  of  the 

1  Daniel,  Lucien,  Effets  de  la  decortication  annulaire  chez  quelques  plantes 
herbacees.     Conipt.  rend.  Paris  1900,  p.  1253. 

2  Hedrick,  Taylor  and  Welling-ton,  Ringing  herbaceous  plants.  New  York  State 
Agric.  Exp.  Sta.,  Geneva,  Bull.  No.  2SS.  1906. 


Fig.  182.  A  ring- 
ing wound  on  a 
grapevine  witli  the 
upper,  more 
strongly  developed 
overgrowth  edge 
(u')  and  the  more 
weakly  formed 
lower  one  (u). 


790 

cambium  and  having  at  first  the  character  of  callus\  This  holds  good  for 
the  products  of  division  of  the  youngest  bark,  which  united  with  the  cambial 
callus  from  the  later  overgrowth  roll. 

At  the  time  of  girdling  (in  July)  the  old  wood  body  of  the  vine  (Fig. 
183,//)  was  already  strongly  developed.  We  can  recognize  elongated, 
thick-walled  wood  cells  in  the  immediate  proximity  of  the  ducts  (g),  chiefly 


yr  _.- 


S...-' 


Fig.    183. 


Long-itudinal   section   through   an   overgrowth   roll   which   has   developed 
from  the  lower  edge  of  the  ringing  wound  (Fig.  182,  u). 


provided  with  horizontal  cross  walls  (h),  otherwise  usually  pointed  like -a 
wedge  and  having  fine  pore  canals  (h').  The  narrower  vessels  are  spiral  or 
ring  ducts  (g)  ;  the  wider  ones  show  circular  or  slit-like  pits  (g).  The 
broadest  of  all  have  a  ladder-like,  or  reticulated,  porous  wall.     The  ladder- 


1  All  juvenile  cicatrization  membrane  with  apical  growth  of  its  cell  rows,  no 
matter  whether  produced  on  a  cut  surface  above  or  beneath  the  surface  of  the  soil, 
may  be  called  "callus."  "We  will  call  the  callus  which  has  a  bark,  is  lignified,  and 
continues  its  growth  by  an  inner  meristem  zone  the  "overgrowth  edge." 


791 

like  arrangements  of  pits  corresponds  to  the  pores  of  the  cells  surrounding 
the  ducts  in  rows,  the  walls  of  which  cells  are  pressed  against  those  of  the 
ducts. 

The  lower  cut,  by  which  the  ringed  place  was  laid  bare  (Fig.  182  bl)  is 
indicated  in  Fig.  183  by  the  plane  S,S'.  In  this  longitudinal  cut,  therefore, 
the  girdled  exposed  surface  extends  from  vS  upward  along  the  exposed  wood 
cells.  At  S',  we  see  how  the  knife  has  smoothly  cut  the  bark  (R)  perpen- 
dicular to  the  longitudinal  diameter  of  the  vine.  At  the  time  the  cut  was 
made,  the  bark  (R)  lay  close  against  the  wood  (H).  The  tissue  lying 
between  them  and  projecting  far  out  (r,C,C')  has  been  produced  after  the 
girdling.  And,  indeed,  the  extreme  lessening  of  the  bark  pressure  con- 
nected with  the  removal  of  the  bark  in  the  sectional  plane  SS'  and  the  parts 
adjoining  it  in  the  cells  of  the  cambium,  as  well  as  in  those  of  the  youngest 
wood,  likewise  in  those  of  the  younger  and  youngest  bark,  causes  a  forma- 
tion of  callus  with  a  surprisingly  great  cell  increase,  since  the  end  cells  of 
the  tissues  named  and  those  directly  adjoining  them  push  outward,  divide, 
elongate  and  cut  off  their  anterior  ends  by  cross  walls.  In  these  anterior 
ends,  the  elongation  and  construction  is  repeated  many  times.  In  this  way, 
a  callus  wall  (C,C')  projects  in  a  circle,  around  the  cut  edge  of  which  the 
inner  side  at  s'  lies  close  against  the  wood,  without  uniting  with  it. 

At  any  rate,  this  callus  wall  at  first  has  neither  the  extent  nor  the 
structure  given  it  in  the  drawing;  this  represents  rather  a  wound  wall  devel- 
oping from  the  callus  which,  by  the  increase  of  the  new  cambial  zone  (c), 
has  already  formed  secondary  elements  of  thickening.  Originally  this  callus 
wall  consisted  only  of  thin-walled  parenchymatous  cells  (s,s')  appearing 
immediately  and  radially  arranged,  their  diameter  in  all  directions  being 
almost  equally  long. 

In  such  a  juvenile  callus  wall,  which  is  early  differentiated,  a  cork  zone 
is  formed  (k,k"')  first  of  all  on  the  outer  circumference.  It  gradually 
increases  in  thickness  and  serves  as  a  layer  protecting  the  thin-walled, 
newly  formed  tissue  mass.  The  cut  surface  of  the  old  bark  tissue  (R) 
which  has  been  separated  widely  from  the  wood  by  the  new  wound  tissue, 
is  cut  off  in  the  same  way  by  the  cork  layer  (k").  The  old,  hard  bast  cells 
(b),  which  have  been  cut,  have  turned  brown  from  the  cut  surface  deep 
down  into  the  healthy  tissue  and  died.  The  original  bark  tissue  (r)  lying 
inside  and  back  of  these  bast  cells  has  participated  in  the  cell  increase  and 
callus  formation;  only  the  cells  lying  next  to  the  hard  bast  of  the  original 
bark  have  formed  a  cork  zone  (k"  '),  cutting  off  the  dead  part.  Near  this 
cork  zone  run  the  hard  bast  cells  (&'),  which  were  already  formed  at  the 
time  of  girdling,  but  under  the  influence  of  the  cut  do  not  extend  normally 
as  at  b.  The  elements  of  these  cells  arranged  in  rows  may  be  traced  back- 
ward into  the  healthy  tissue  and  gradually  pass  over  into  the  old  bast;' this 
row  of  cells  is  continued  in  the  wound  wall  in  the  elongated,  but  very  thin- 
walled  groups  of  cells  (b"),  which  lie  at  equal  distances  from  the  cambial 
zone. 


792 

The  cambial  zone,  which  runs  close  to  the  prosenchymatous  wood 
elements  in  that  part  of  the  normally  developed  vine  which  lies  below  the 
place  of  the  cut,  describes  a  wide  circle  c,c,c'  at  its  entrance  into  the  wound, 
or  overgrowth  wall ;  it  divides  the  apparently  uniform  ground  tissue  into  one 
part  lying  against  the  old  wood  body  of  parenchyma  cells  with  strong,  porous 
walls,  the  ivound  wood  (zvh),  and  an  outer  part,  the  wound  bark  (wr).  In 
the  clearly  marked,  radiating  arrangement  of  the  individual  cell  rows,  this 
row  is  recognized  as  a  secondary  growth  of  the  cambial  zone,  appearing 
very  early  in  the  callus  roll.  The  elements  formed  from  the  cambial  zone 
have  approximately  the  same  parenchymatous  form  in  the  same  horizontal 
surface,  only,  as  already  said,  the  parenchymatous  wood  (wh)  differs  from 
the  bark  tissue  by  its  porous  walls,  which  are  more  greatly  thickened  and 
more  dense  and,  therefore,  lie  against  one  another  with  sharper  angles;  a 
stronger  pressure  has  already  made  itself  felt  here. 

But  an  evident  differentiation  is  noticeable  in  the  bark  tissue  itself. 
Between  the  somewhat  oval  cells,  forming  the  ground  mass  of  the  bark,  we 
find  more  elongated,  more  slender,  somewhat  prismatic  cells  arranged  in  a 
curve  (b")  approximately  parallel  to  the  cambial  zones.  These  represent 
the  very  beginnings  of  the  hard  bast  cells.  They  are  richer  in  content  and 
accompanied  by  pouch-like  cells,  which,  in  their  longer  axis,  usually  run 
parallel  to  the  young  bast  bundles  and  contain  raphides  of  calcium  oxalate 
(o).  The  bark  tissue  produced  from  the  youngest  bark  already  formed  at 
the  time  of  cutting  and  containing  thick-walled,  but  short  and  broad  hard 
bast  contains  its  calcium  oxalate  in  the  form  of  stellate  druses,  or  separate 
crystals,  similar  to  those  which  occur  chiefly  in  the  normal  bark  (o').  At  the 
place  of  the  transition,  raphides  and  stellate  druses  are  often  separated  from 
each  other  only  by  two  cells.  Here  also  only  the  loosely  constructed  tissue 
contains  raphides. 

The  parallel  arrangement  of  the  crystal-containing  cells,  with  the  bast 
fibers,  is  seen  best  in  tangential  section  in  the  cherry ;  here  the  base  bundles, 
lying  in  a  net  work  upon  one  another,  are  found  to  be  accompanied  by 
parenchymatous  cells  lying  close  against  one  another  and  elongated.  Almost 
every  one  of  these  contains  a  crystal  of  calcium  oxalate.  In  the  grape  this 
is  less  sharply  marked  and  becomes  relatively  indistinct  as  the  tissue,  as  a 
whole,  loses  its  differentiation  in  the  overgrowth  walls.  In  this  less  differ- 
entiated part  may  already  be  recognized  thicker  walled  elements  lacking  the 
deposition  of  calcium  oxalate  in  the  surrounding  tissues.  The  calcium 
appears  in  the  cells  formerly  filled  with  starch,  a  fact  which  indicates  that 
the  calcium  oxalate  is  one  of  the  end  products  in  the  solution  of  the  carbo- 
hydrates. 

Therefore,  no  calcium  oxalate  is  found  in  the  outermost  peripheral 
zones  of  the  overgrowth  edge  because  these  zones  consist  of  the  first  formed 
tissue  of  the  quickly  growing  undifferentiated  callus  projecting  beyond  the 
cut  surface.  In  these  the  material  has  been  utilized  entirely  for  cell  increase 
and  is  not  deposited  in  the  end  as  reserve  starch.     On  the  whole,  however, 


793 

only  a  few  peripheral  cell  rows  always  remain  free  from  starch  and  free 
from  subsequently  formed  calcium  oxalate,  for  the  tissue  which  extends 
beyond  the  cut  surface,  and  which  warrants  the  name  "callus"  only  so  long 
as  it  is  absolutely  undifferentiated,  soon  shows  a  difference  in  its  structure 
and  passes  very  rapidly  from  the  callus  stage  into  that  of  the  overgrowth 
edge.  Soon  after  the  formation  of  the  peripheral  cork  covering,  a  meristem 
zone  appears  also  in  the  interior  of  the  callus  tissue  and  represents  the 
continuation  of  the  cambial  ring  of  the  normal  piece  of  the  vine  within  the 
overgrowth  edge.  Besides  this  meristematic  zone,  the  first  traces  of  a  bast 
body  may  also  be  recognized  in  the  separated  parenchymatous  cells  lying 
scattered  close  under  the  cork  zone.  These  cells  appear  to  have  somewhat 
more  strongly  refractive,  easily  swelling  walls  (&"').  In  some  of  these  I 
think  I  have  recognized  indications  of  sieve  pores  similar  to  those  found  in 
the  tangential  walls  of  normal  bark  sieve  cells  (ss),  so  that  the  conclusion 
may  be  drawn  that  the  first  differentiation  of  the  callus  tissue,  appearing 
almost  simultaneously  with  the  formation  of  the  new  cambial  zone,  consists 
in  the  formation  of  sieve  cells  within  the  bark. 

The  tissue  formed  in  the  cambial  zone  appears,  in  Fig.  183,  to  be  divided 
longitudinally  by  the  medullary  ray  cells  (w).  These  are  elongated  radially, 
have  clearer  contents  and  like  the  rest  of  the  tissue  are  small  celled  at  the 
periphery  of  the  overgrowth  edge.  Their  approximately  perpendicular 
direction  changes  gradually  into  the  normal  horizontal  one  as  the  rays 
extend  into  the  normal  tissue  of  the  uninjured  piece  of  the  vine. 

In  the  youngest  portion  of  the  callus  edges,  where  the  tissue  lying  next 
the  cork  border  first  arose,  one  finds  the  wood  lying  between  the  clearer 
medullary  rays  to  be  short,  thin-walled  and  parenchymatous.  The  further 
the  wood  is  examined  back  toward  the  normal  tissue,  the  longer  and  thicker 
walled  it  appears  and  it  passes  from  its  radial  direction  more  and  more  into 
the  longitudinal  elongation  of  the  normal  wood  elements.  The  earlier  in 
the  year  the  girdling  is  undertaken,  i.  e.  the  longer  the  newly  produced 
cambial  zone  of  the  overgrowth  wall  produces  wood,  so  much  the  more  do 
the  later  formed  elements  approach  normal  wood  in  length  and  form. 

Scalariform  vessels  (g,s)  appear  in  this  thin-walled  parenchymatous 
wood  as  the  first  thick-walled  elements ;  they  have  at  first  the  size  and 
arrangement  of  the  wood  parenchyma  cells  of  the  surrounding  tissue  but 
assume  gradually  the  form  and  arrangement  of  normal  vessels  the  nearer 
they  approach  the  uninjured  parts  of  the  wood.  In  opposition  to  de  Vries,  I 
must  maintain  that  the  short  duct  cells  are  not  always  the  first  formed  thick- 
walled  elements.  When  the  callus  at  the  lower  margin  of  a  girdle  is  very 
weakly  developed,  the  wood  parenchyma  often  passes  over  directly  into 
normally  arranged,  slightly  thickened  xylem,  elements,  without  the  previous 
appearance  of  short  duct  cells. 

In  the  callus  at  the  upper  margin  of  a  girdle  which  in  the  same  length 
of  time  has  developed  more  than  twice  as  extensively  as  the  lower  callus, 
the  cambial  zone  is  broader,  all  the  elements  are  more  numerous  and  the 


794 


beginnings  of  the  vascular  bundles  in  the  callus  always  start  with  duct  cells. 
The  formation  of  these  cells  takes  place  the  earlier  the  nearer  to  the  old 

wood  they  are  formed.  Their  form, 
size,  thickness  of  wall  and  arrange- 
ment will  be  more  nearly  normal  the 
further  back  the  tissue  lies  from  the 
cut  surface.  The  vascular  strand  {g,2) 
of  this  tissue  grades  gradually  into  the 
normal  wood  formed  before  girdling, 
thereby  forming  a  pseudo-secondary 
growth  in  that  area. 

According  to  the  anatomical  condi- 
tions shown  in  Fig.  183,  we  may  say 
that  the  girdling  has  produced  an  un- 
usual loosening  of  the  wood  in  the 
uninjured  part  of  the  vine  adjacent  to 
the  wound.  In  this  way  the  vascular 
bundles,  which  are  formed  of  vessels 
and  thick-walled  tracheids  on  one  side 
of  the  cambium  and  of  the  thick-walled 
phloem  fibres  and  sieve  tubes  on  the 
other,  and  which,  in  normal  wood,  are 
arranged  close  against  one  another  in 
concentric  circles,  are  separated  and 
broken  up  into  single  strands  by  masses 
of  parenchyma.  These  strands,  g,3 
(vascular  strands),  and  b'  (phloem 
strands),  the  elements  of  which  con- 
stantly become  fewer  in  number,  change 
constantly  and  continue  into  the  callus, 
which  is  gradually  covering  the  girdle. 

We  may  best  see  by  means  of  cross 
sections  taken  at  different  heights 
through  the  callus,  what  happens  to  the 
vascular  cylinder  which  in  the  unin- 
jured portion  of  the  vine  consists  of 
the  wood  and  the  phloem  rings,  only. 
slightly  broken  by  few-celled  medullary 
rays.  This  cylinder  finally  is  separated 
into  single  strands  by  the  growth  of 
parenchyma  induced  by  the  girdling. 
The  strands  gradually  become  narrower 
as  they  pass  outward  radially  and  tan- 
gentially  in  wavy  lines,  they  are  at  first  distinct,  but  later  anastamose  forming 
a  net  and  finally  split  up  into  isolated  strands  arranged  in  fans. 


Fig.  184.  Cross-section  tlirough  a  ring- 
ing roll  close  to  the  point  where  it 
appears  on  the  plane  S  to  S'  in  Fig.  183. 


795 


For  the  sake  of  greater  clearness,  the  cross  sections  shown  in  Figs.  184 
and  185  have  been  taken   from  the  upper  similarly  constructed  but  more 


Fig.  185. 
place  of 


strongly 
section, 


Cross-section  through  the  ringing  roll  at  a  considerable  distance  from  the 
its  appearance,  i.  e.  where  it  is  more  luxuriously  developed,  as  would  be 
found  in  Fig.  183,  possibly  in  the  plane  k  to  wh. 

developed  callus  of  the  same  vine,  which  furnished  the  longitudinal 
Fig.  183. 


796 

Fig.  184  shows  the  callus  in  cross  section  at  the  place  where  it  leaves 
the  old  bark,  i.  e.  about  at  6*  to  S'  in  Fig.  183.  Fig.  185  is  a  cross  section 
through  the  middle  of  the  projecting  part  of  the  callus,  i.  e.  about  in  the 
place  k  to  wh  in  Fig.  183.  In  Fig.  184,  H  represents  a  part  of  the  old  wood 
formed  before  girdling,  g'  indicates  the  wide,  scalariform  vessels  of  which 
those  lying  nearest  the  cut  surface  vS  to  S'  have  filled  with  tyloses  (t)  as  a 
result  of  the  injury,  and  consequently  have  become  impervious  to  air;  h 
shows  the  tracheids  in  cross  section.  S'  to  C  (in  Fig.  185,  C  to  C)  is  the 
new  wood  formation  of  the  callus.  We  find  that  the  medullary  rays  (w), 
from  the  normal  tissue  (H),  are  continued,  after  a  short  interruption,  into 
the  callus.  The  medullary  rays  become  constantly  broader;  the  vascular 
bundles,  the  xylem  elements  of  which  in  normal  wood  are  closely  packed, 
are  separated  further  and  further  by  the  constantly  widening  medullary 
rays.  The  bundles  thus  have  fewer  elements  and  normal  tracheids  are  no 
longer  present.  The  strand  (st')  consists  only  of  short,  wide  vessels,  and 
narrow  ones  with  transverse  walls,  together  with  wide,  thinner  walled  wood 
cells,  abutting  on  each  other  transversely. 

The  single  strand  in  Fig.  184  (st)  in  the  normal  wood  has  divided  in 
the  tissue  of  the  callus  into  two  strands  (st'),  and  these  again  into  four 
strands  in  the  part  still  further  from  the  cut  surface  (Fig.  185  st'),  at  the 
same  time  the  new  bundles  are  pushed  out  of  their  original  position  by 
the  formation  of  new  medullary  rays  (Fig.  185  ni).  They  advance  as 
separate  groups  toward  the  periphery  of  the  constantly  thickening  callus. 
With  the  broadening  of  the  tertiary  medullary  rays  these  thin  vascular 
strands  (Fig.  185  st'),  which  (in  longitudinal  section)  seem  to  branch  as 
they  growth  in  length,  separate  farther  and  farther  from  each  other  until 
they  finally  disappear  entirely  near  the  outer  edge  of  the  callus.  The 
terminals  of  these  strands  are  short,  broad,  porous  cells  of  wood  parenchyma. 

It  is  well  known  that  each  vascular  strand  is  made  up  of  both  phloem 
and  xylem.  The  wood  and  phloem  are  sister  elements*  In  Fig.  184  b,  we 
see  a  group  of  wood  fibres,  which  belongs  to  the  xylem  strand  st ;  b'  and  bb' 
represent  the  phloem,  belonging  to  st',  the  cells  of  which,  analogous  to  w^ood 
elements,  have  become  broader.  The  radial  thickening  of  the  phloem  cells 
is  not  very  well  shown  in  the  drawing. 

In  the  fall,  when  the  grapevine  has  cut  off  the  cortex  by  a  cork  zone, 
the  sinuous  cork  layer  (k),  in  the  callus,  has  divided  the  phloem  bundles 
into  two  parts  (Fig.  184,  b'  to  bb')  ;  cV  represents  in  Figs.  184  and  185,  the 
cambial  zone.  In  Fig.  185,  0  is  a  pouch  cell  with  calcium  oxalate  in  the 
form  of  raphides.  In  some  pouch  cells  sharp,  jagged  very  small  protuber- 
ances project  from  the  inner  cell  wall. 

The  first  differentiation  in  the  callus  may  still  be  recognized  after  it  has 
passed  over  into  the  finished  overgrowth  of  the  callus,  beginning  at  the  outer- 
most cork  layer;  i.  e.  if,  in  Fig.  185,  the  section  begins  at  the  part  curling 
farthest  downward  and  then  advances  upward.     If  we  designate  the  part 

1   Ratzebui-g:,  Waldverderbnis  I,  70. 


797 

adjoining  the  old  wood  (Fig.  183,5:'  to  S),  as  its  innerside,  in  contrast  to 
the  spherically  convex  outer  side,  the  parenchymatous  tissue  of  the  inner 
edge,  lying  directly  under  the  cork  zone,  is  seen  even  in  the  second  sections 
to  color  more  deeply  when  treated  with  iodine  than  does  the  corresponding 
part  of  the  opposite  outer  side.  In  the  same  way,  by  using  iodine,  a  radial 
division  of  the  tissue  may  also  be  recognized,  for  certain  bands  at  first  only 
one  to  three  cells  broad  take  on  a  deeper  color  than  the  broader  parts  lying 
between  them.  A  difference  may  be  seen  also  in  the  form  of  the  cells  in  the 
first  cross  sections,  for  those  lying  nearer  the  outer  edges  appear  rounder 
than  the  more  densely  crowded  ones  nearer  the  inner  edge ;  also  all  the  cells, 
lying  directly  tmder  the  corky  outer  layer,  are  smaller  than  those  at  the 
centre.  The  lighter  colored  bands  contain  cells  with  a  greater  radial  elon- 
gation, the  first  indication  of  the  medullary  rays.  The  zone  of  the  renewed 
cell  division,  which  will  form  the  beginnings  of  the  later  cambial  rings, 
lies  close  to  the  inner  side  of  the  callus  roll  adjoining  the  region  of  cells 
which  were  the  last  to  divide  to  strengthen  the  peripheral  cork  zone.  From 
there,  in  the  subsequent  cross  sections,  the  division  zone  moves  farther  and 
farther  from  the  old  wood  (compare  the  curved  course  in  the  longitudinal 
section,  Fig.  183,  c  to  c'),  reaching  its  greatest  distance  from  the  old  wood 
outside  the  plane  in  which  the  girdling  occurred  and  again  within  the  old 
bark,  approaching  the  normal  wood  until  it  takes  up  the  usual  position  of 
normal  cambium. 

The  principles  that  have  been  discussed  here  in  detail  with  reference 
to  the  grape  are  expressed  in  any  kind  of  girdling,  the  special  structure 
naturally  varying  with  the  kind  of  plant. 

Czapek^  has  shown  that,  of  the  conducting  elements,  only  sieve  tubes  and 
cambiform  cells  come  under  consideration  for  all  assimilating  products, 
indeed,  the  paths  which  convey  substances  are  straight,  even  in  the  phloem. 
The  phloem  parenchyma,  like  the  medullary  rays,  serves  as  storage  tissue. 
The  deposition  of  reserve  substances  is  influenced  by  girdling,  inasmuch  as 
(according  to  Leclerc  du  Sablon-)  the  roots  of  trees  girdled  near  the  base 
of  the  trunk  in  the  spring  at  the  time  of  sprouting  are  richer,  and  the  trunks 
poorer,  in  reserve  materials,  than  those  of  trees  which  have  not  been  girdled. 
The  leaves  of  the  former  to  be  sure  are  not  so  green,  but  contain  much 
more  reserve  materials  than  ungirdled  specimens  and  according  to  my  obser- 
vations color  much  earlier  in  the  autumn. 

Injuries  to  the  Bark. 

A.     Historical  Survey. 

The  processes  of  healing  a  wound  which  has  exposed  the  wood  all  the 
way  around  the  trunk  often  a  meter  in  width,  produced  by  the  removal  of 

1  Czapek,  Fr.,  tJber  die  Leitungsweg-e  der  org-anischen  Baustoffe  im  Planzen- 
korper.    Bot.  Centralbl.  1897,  Vol.  69,  p.  318. 

2  Leclerc  du  Sablon,  Recherches  physiologiques  sur  les  matigres  de  reserves  des 
arbres.  Revue  generale  de  Bot.,  Vol.  XVIII;  cit.  Bot.  Centralbl.  v.  Lotsy,  1906,  No, 
43,  p.  447. 


798 

all  tissue  down  to  the  cambium,  have  been  the  subject  of  observation  for 
more  than  lOO  years. 

Thus  Treviranus^  quotes  that  L.  Firsch  found  some  apple  and  pear 
trees  on  an  estate  in  the  Province  of  Brandenburg,  from  which  all  the  bark 
had  been  removed  from  the  points  of  insertion  of  the  lowest  branches  down 
to  the  roots,  completely  around  the  trunk,  so  that  the  white  wood  could  be 
seen  everywhere.  The  trees  were  covered  again  with  new  bark.  Frisch 
assures  us  that  this  experiment  will  always  succeed  if  made  at  the  time  of 
the  solstice  and  if  the  exposed  outer  surface,  over  which  the  sap  is  spread 
uniformly  with  a  feather,  is  protected  by  linen  or  split  cane  against  the  sun 
and  wind*. 

The  celebrated  experimenter,  DuhameP,  removed  a  ring  of  bark  from 
several  young  trees,  elms,  plums,  etc.,  7  to  10  cm.  wide  down  to  the  wood,  at 
the  time  when  the  sap  was  flowing  and  surrounded  the  wounds  with  glass 
cylinders,  which  were  closed  at  the  top  and  bottom  against  the  uninjured 
part  of  the  trunk  with  cement  and  tissue.  He  found  delicate,  jelly-like 
warts  forming  on  the  exposed  wood  surface,  and  pushing  out  between  the 
wood  fibres  of  the  sap  wood  (des  mamelons  gelatineux  qui  sortaient  d'entre 
les  fibres  longitudinales  de  I'aubier).  These  little  warts,  which  push  out 
under  very  tender,  probably  left  over,  phloem  lamellae,  were  at  first  white, 
and  half  translucent,  later  gray,  and  after  10  days  (on  April  i8th)  green. 
These  new  structures,  broadened  in  the  course  of  the  summer  and  finally 
uniting,  produced  a  rough  bark  beneath  which  delicate  wood  lamellae  were 
recognizable.  "Ainsi  il  est  bien  prouve  que  le  bois  pent  produire  de  I'ccorce 
et  que  cette  ecorce  est  des  lors  en  etat  de  produire  feuillets  ligneux    ..." 

Knight  made  similar  experiments  and  obtained  similar  results.  He 
found  once''  on  Ulmus  montana,  a  regeneration  of  the  bark  when  the  wound 
had  not  been  covered.  The  tree  grew  in  a  shady  place.  Knight  found  in 
old  topped  oaks,  with  an  incompletely  formed  new  bark  growth,  that  the 
jelly-like  w^arts  had  pushed  out  from  the  parenchymatous  cell  tissue  and  "in 
many  cases  new  bark  was  formed  in  small  and  isolated  portions  only  on  the 
upper  surface." 

Meyen*  cjuotes  W^erneck's  observations,  according  to  which  the  regen- 
eration of  the  bark  will  take  place  only  if  the  barking  happens  about  the 
25th  of  June,  when  the  trunks  are  still  young  and  the  wounded  place  is 
"very  carefully  protected  against  drying  by  a  hollow  and  closely  adjusted 
bandage." 

We  find  Meyen's  own  theory-''  in  the  description  of  his  experiments 
given  in  his  Phytopathology.     On  April  30th,  1839,  in  warm  sunshine  he 


1  Treviraniis,  Physiolog-ie  der  Gewachse,  Vol.  TI,  1S3S,  p.  222. 

2  Duhamel,  Physique  des  arbres  1758,  Vol.  IT,  p.  42.    Vol.  VII,  p.  63,  and  loc.  cit., 
p.  44.     Vol.  VIII,  p.  66,  67. 

3  Treviranus,  loc.  cit,  p.  223  (Beytr.  223). 

4  Meyen,  Neues  System  d.  Pflanzenpliys.  1837,  p.  394. 

5  Meyen,  Pflanzenpatliologie,  published  by  Nees.  v.  Esenbeck.    Berlin  1841,  p.  14. 


Miscell.  Berolin.  Contin,  II  (1727),  26. 


799 

removed  the  bark  from  the  little  trunks  and  larger  branches  of  the  hazlenut, 
the  snowball,  Syringa  and  willow  and,  like  Duhamel,  enclosed  the  barked 
places  with  cemented  glass  tubes,  which  in  addition  were  wrapped  with 
paper,  although  he  made  the  experiments  in  thickly  shaded  places.  Jelly- 
like drops  were  "sweated  out"  here  also,  "which  always  occurred  on  the 
places  where  the  medullary  rays  appeared  on  the  upper  surface  of  the 
wood." 

Microscopic  investigation  of  this  "sweating"  showed  the  warts  to  be 
composed  of  tender  cell  tissue,  "which  enlarged  constantly  because  of  the 
gum  in  the  sap,  exuded  by  the  medullary  ray  cells." 

The  greenish  color,  which  these  new  structures  assume,  arises  from  the 
chlorophyll  grains.  In  the  course  of  the  experimental  year  these  structures 
reached  a  thickness  of  ii  mm.  but  shrivelled  greatly  when  dried. 

Meyen  cannot  ascribe  the  significance  of  bark  to  these  new  structures, 
which  are  also  produced  naturally  in  shady  places^.  For  "no  separation  into 
different  layers,  of  which  the  normal  bark  of  the  same  tree  is  composed,  can 
be  seen  and  moreover  there  is  no  trace  of  sieve  tubes  in  it,  which  are,  of 
course,  very  important     ..." 

This  physiologist,  very  distinguished  in  his  time,  who  according  to  the 
Mirbelian  theory  considered  the  cambium  to  be  a  structureless  sap,  which 
brought  forth  such  cell  structures  as  those  from  which  it  had  appeared,  has 
indeed  the  merit  of  having  made  use  of  the  microscope  to  investigate  the 
new  structures  which  appeared  with  the  healing  of  bark  wounds.  He  was 
not  fortunate  enough,  however,  to  observe  the  production  of  wood  among 
these  new  structures  and  to  prove  the  analogy  between  these  forms  and 
normal  bark. 

Probably  the  moist  air  and  heavy  shading  from  his  cylinder  were  to 
blame,  since  as  we  shall  see  these  factors  influence  considerably  the  charac- 
ter of  the  new  structure. 

Dalbret^  experimented  earlier  than  Meyen,  for  on  the  21st  of  June  he 
barked  an  ash  and  a  walnut,  enclosed  the  barked  places  in  a  cylinder  and 
obtained  the  same  results  as  Duhamel. 

Th.  Hartig^  in  the  spring  of  1852  at  the  time  the  new  annual  rings  had 
begun  to  develop  removed  the  bark  from  30  to  40  somewhat  older  oaks  for 
6  to  8  meters  above  the  ground  and  in  August  found  the  majority  of  the 
mutilated  trees  bore  as  dense  foliage  as  the  adjacent  ones  from  which  the 
bark  had  not  been  removed.  On  5  or  6  young  trunks  a  scabby  eruption, 
pressed  out  from  the  medullary  rays  of  the  wood,  had  formed  "curiously" 
only  on  the  sunny  side.  Anatomical  investigations  showed  that  the  erup- 
tion, quite  independent  of  the  phloem  and  cambium,  had  come  from  the 
wood  alone  and  was  a  product  of  the  medullary  rays. 

1  Pflanzenphysiologie,  Vol.  1,  p.  390. 

-  Journal  de  la  societe  d'agronomie  pratique  1830;  quoted  by  Trecul  in 
"Accroissement  des  vegetaux  dicotyledones  ligneux."  Annales  des  sciences  natur. 
Ill,  Serie,  Vol.  XIX,  Paris  1853. 

3  Th.  Hartig.  Vollst.  Naturgesch.  d.  forstl.  Kulturpfl.  Deutschlands.  Berlin  1852. 
Explanation  of  the  figures  (plate  70,  Pigs.  1-3). 


8oo 

The  new  structure  begins  with  the  appearance  of  a  layer  of  cork  cells 
at  the  periphery  of  the  healthy  medullary  ray  tissue,  cutting  off  an  outer, 
dead  part.  The  living  part  of  the  medullary  ray  now  develops  several 
layers  of  parenchymatous  cells  about  its  circumference,  which  cells  turn 
green  like  the  medullary  tissue  already  present.  By  the  increase  of  the 
parenchymatous  tissue  around  the  medullary  rays,  a  callus  roll  is  produced, 
which  rapidly  becomes  larger  and  constantly  presses  farther  outward  the 
cork  layer  which  begins  with  the  formation  of  lenticels.  "The  new  cell 
tissue  does  not  develop  on  any  one  place  from  the  living  medullary  ray,  but 
as  everywhere  new  cells  are  formed  in  all  places  inside  the  cells  already 
formed ;  these  reabsorb  the  mother  cell,  grow  out  to  its  size  and  widen  the 
mass  on  all  sides.  In  spite  of  the  widening  of  the  callus,  due  to  the  growing 
cell  tissue,  the  living  part  of  the  medullary  ray,  nevertheless,  always  retains 
the  same  circumference,  the  same  size,  number,  form  and  position  of  the  cell 
tissue  constituting  it." 

"When  the  callus  reaches  a  certain  size,  different  parts  become  unusu- 
ally thick  walled,  as  is  also  the  case  in  the  normal  course  of  the  life  of 
the  bark  (stone  cell  aggregations).  Further,  on  each  side  of  the  living 
medullary  ray  not  far  from  its  tip,  a  vascular  bundle  develops  in  the  cell 
tissue,  which  consists  of  pitted  tracheids  and  vessels  between  the  medullary 
ray  and  the  cork  layer."  By  the  fusion  of  the  individual  coordinate  tissue 
zones  of  the  new  structures,  which  up  to  that  time  had  been  completely 
isolated  and  wart-like,  a  continuous  bark  layer  covered  with  a  cork  layer  is 
produced,  differing  only  by  the  radial  arrangement  of  its  cell  elements  in 
cross  section  from  the  structure  of  the  normal  bark.  "Along  the  sides  of 
the  tip  of  the  medullary  ray,  the  development  of  the  wood  advances  up  to 
the  formation  of  a  connected  wood  layer,  traversed  by  the  cell  tissue  of  the 
old  medullary  rays  just  as  by  newly  formed,  smaller  ones.  The  various 
wood  bundles  consist  of  tracheids  and  fibres.  True  spiral  elements  are 
lacking.  A  line  of  division  between  the  wood  and  the  bark  (Meristem  zone 
Ref.)  is  formed  more  and  more  sharply  with  the  advancing  development  of 
the  wood,  although  no  trace  can  be  discovered  either  of  phloem  fibres  or 
of  sieve  tubes." 

Th.  Hartig's  observations,  which  represent  an  important  advance, 
show,  therefore,  that  the  development  of  the  new  bark  on  a  bark  injury, 
takes  place  at  the  expense  of  the  nutritive  substances  present  in  the  wood 
and  begins  with  the  formation  of  a  callus  tissue  around  the  tips  of  the 
medullary  rays. 

It  cannot  be  learned  either  from  the  description,  or  from  the  drawings, 
which  cells  initiate  the  callus  formation. 

TrecuP  fills  this  gap  with  his  thorough  anatomical  investigations,  which 
prove  at  the  same  time  the  participation  of  the  zvhole  young  tissue  left  on 


1  Trecul,    Accroissement    des    vegetaux    dicotyledones    ligneux.      Annales    des 
science,  nat.  XIX,  p.  165. 


8oi 

the  harked  wood  stem  and  not  merely  that  of  the  medullary  rays  in  the 
formation  of  callus.  Nevertheless,  under  special  conditions  the  medullary 
ray  cells  can  alone  cause  the  formation  of  callus  and  yet  the  case  often 
occurs  where  the  callus  formation  is  initiated  by  the  young  wood  cells  alone. 

The  young  wood  cells,  the  medullary  ray  cells  and  the  narrow  elements 
participate  in  the  callus  formation  by  a  transformation  into  parenchyma 
cells  which  now  increase  in  number \ 

The  youngest  cells,  left  on  the  wood  cylinder,  widen,  elongate  and 
divide.  The  end  cell  of  the  last  row  of  callus  cells  becomes  largest.  It  is 
often  spherical,  or  club  shaped,  and  the  new  cross  wall  is  produced  generally 
in  this  stage.  The  new  end  cell  now  formed  by  the  cross  wall  repeats  the 
process.     The  older  cells,  lying  back  of  it,  elongate  and  divide. 

Besides  this  kind  of  callus  formation,  Trecul  observed  still  another 
case.  While  the  outermost  remaining  cells  develop  into  callus  tissue,  by 
distention  and  division,  it  also  happens  that  they  show  only  a  slight  develop- 
ment, while  the  innermost  young  wood  cells,  lying  beneath  them,  take  over 
the  role  of  the  actual  callus  former,  Trecul  sketches  (pi.  7,  Fig.  11)  a 
longitudinal  section  of  the  elm,  the  callus  on  the  edge  of  which  consists  of 
short,  isodiametric  cells.  This  gradually  drying  layer  has  been  pushed  up 
from  the  wood  by  means  of  a  thick  callus  layer,  of  which  older  cells  now 
adjoin  the  wood.  The  youngest  cells  most  distant  from  the  old  wood, 
lying  directly  under  the  outpushed  dying  layer,  have  stretched  radially  and 
formed  radially  parallel  rows. 

Both  cases  of  callus  formation  can  occur  at  the  same  time  in  the  same 
specimen.  Probably  the  innermost  layers  of  the  exposed  cambial  body  are 
incited  to  increase  by  the  drying  of  the  outermost  layers. 

As  my  experiments  show,  all  the  cells  of  the  cambial  region  can  partici- 
pate in  the  callus  formation,  not  only  the  young  wood  cells,  as  de  Vries 
thinks,  but  also  the  young  bark  cells.  It  depends  alone  upon  which  cell 
layers  are  left  when  the  bark  is  removed.  If  it  is  loosened  in  such  a  way 
that  only  a  few  of  this  year's  sapwood  cells  still  capable  of  increase  remain 
on  the  old  wood,  the  callus  must  be  formed  from  them;  if,  on  the  other 
hand,  the  very  youngest  cambium  cells  remain  in  place,  they  take  over  this 
formation  of  callus,  while  the  underlying  young  sapwood  develops,  accord- 
ing to  its  position,  into  differentiated  wood  with  vessels  and  is  changed  only 
in  so  far  as  all  its  elements  become  shorter,  broader  in  the  radial  dimension 
and  thinner  walled. 

Trecul-,  in  his  Fig.  5,  pi.  3,  of  a  linden,  gives  the  best  example  of  this 
case.  We  will  use  this  (see  Fig.  186)  to  confirm  our  theory.  B  indicates 
the  young  wood  of  the  current  year  formed  before  the  removal  of  the  bark, 


1  "Les  fibres  ligneuses,  les  rayons  medullaires  et  les  vaisseaux  d'un  petit 
diametre  eux-memes  sont  metamorphoses  en  tissu  cellulaire  proprement  dit;  car  il 
y  a  une  metamorphose  reelle  de  ces  organes  elementaires  en  tissu  utriculaire 
ordinaire,  et  ensuite  multiplication  de  ces  utricules  nouvelles. 

2  Trecul  loc.  cit.,  p.  167. 


802 

with  its  vessels  (v).  A  to  A',  according  to  Trecul,  is  the  old  bark  of  the 
previous  year^  The  split,  which  pushed  up  the  bark,  extends  horizontally 
above  the  highest  vessel  {v)  to  the  point  marked  x' ;  from  there  it  runs 
downward  toward  the  right  almost  to  the  thin-walled,  last-formed  cells  of 
the  previous  year,  so  that  the  whole  group  {g)  should  be  considered  as  a 
new  structure.  At  x,  the  loosened  bark  has  removed  only  the  outermost 
layers  of  the  youngest  wood,  or  has  possibly  extended  only  to  the  central 
cambial  zone,  so  that  the  whole  sapwood  has  remained  in  place.  The 
outermost  cells  elongate  (/)  and  divide  (/').  The  upper  cell  (r)  of  each 
row,  cut  ofif  by  the  new  wall,  repeats  the  process. 


Fig.  186.     Callus  formaton  from  young  bark  cells  in  a  barked  trunk.     (After  Trecul.) 


The  young  wood  (sapwood)  has  been  stretched  radially  by  the  injury, 
i.  e.  by  the  removal  of  the  bark  pressure.  It  forms  shorter  cells  with  wider 
lumens  but  has  remained  thin-walled,  while  the  vessels  already  started  have 
matured. 

From  x'  out,  the  young  sapwood  has  been  removed  with  the  loosened 
bark  and  on  the  wood  of  the  previous  year  only  a  few  young  wood  cells  of 
the  current  year  were  left.     These  cells  have  now  taken  over  the  formation 


1  It  might  seem  strange  that  the  annual  ring  at  A'  ends  with  a  very  thin- 
walled  spring  wood,  but  such  cases  actually  occur.  I  obtained  from  the  Eifel  in 
January  larches  diseased  with  canker,  the  annual  ring  of  which  had  formed  over 
the  summer  wood  a  layer  six  cells  thick  of  thin-walled  spring  wood. 


8o3 

of  callus,  which  naturally  lacks  vessels,  though  it  reaches  the  thickness  of 
the  adjoining  parts  by  a  more  rapid  increase  in  the  lumen  of  the  cells^ 

Opinions  differ  greatly  as  to  the  life  period  of  barked  trunks. 

The  best  example  of  an  unusually  long  life  period  in  trees  which  have 
lost  their  bark  extensively,  and  have  not  replaced  it,  the  exposed  wood  con- 
sequently falling  victim  each  year  to  decay,  is  furnished  by  Trecul  in  his 
description  of  the  linden  at  Fontainebleau".  Yet  we  have  still  earlier 
observations. 

In  1709,  Parent  reported  the  following  observation  to  the  Academy: 
An  elm  in  the  Tuileries,  which  at  the  beginning  of  spring,  1708,  had  lost  all 
its  bark  nevertheless  developed  its  leaves,  even  if  somewhat  less  vigorously, 
and  kept  them  all  summer. 

DuhameP  expresses  himself  as  follows  in  this  connection:  Trees  with 
bark  wounds,  which  remain  uncovered,  gradually  go  to  pieces  (sometimes 
not  until  four  years  later). 

At  the  sitting  of  the  Academy  on  May  nth,  1852,  Richard  related  a 
case,  similar  to  the  one  described  by  Parent  as  something  very  extraordi- 
nary, since,  in  the  majority  of  cases,  the  trees  die  soon  after  such  injuries. 

Gaudichaud*  disputes  this  latter  statement  by  referring  to  trees  in  St. 
Cloud,  in  the  Luxembourg,  and  at  Fontainebleau,  which  after  such  injuries 
lived  a  great  many  years,  although  the  outside  of  the  exposed  trunk  was 
partially  destroyed. 

At  the  sitting  of  the  Academy  of  March  7th,  1853,  the  same  botanist 
returns  to  this  point  and  now  cites  the  linden  at  Fontainebleau.  According 
to  Trecul,  this  tree  was  planted  about  1780  and  in  1810  was  very  irregularly 
barked  by  some  dump  carts.  On  the  north  side,  the  barked  place  was  32 
cm.  long,  and  began  57  cm.  above  the  ground,  while  on  the  south  side  it 
was  4.05  m.  long  and  began  immediately  at  the  surface  of  the  soil.  The 
barking  extended  completely  around  the  tree  and  yet,  despite  this,  the  tree 
lived  for  44  years  (it  did  not  die  until  1854).  The  diameter  at  the  place 
of  injury  was  20  cm.,  below  it,  18  cm.  The  surface  of  the  injured  trunk, 
the  centre  of  which  was  so  cut  by  the  carts  that  the  diameters  of  the 
remainder  were  10  and  5^  cm.,  was  entirely  worm-eaten  and  dry.  After 
the  dead  wood  had  been  removed,  the  remaining  living  central  portion  was 


1  To  characterize  Trecul's  theory,  we  will  g-ive  his  explanation  of  the  figure,  loc. 
cit.,  p.  191:  A,  A'  bois  de  I'annee  precedente,  V,  vaisseaux  de  ce  bois;  R  rayons 
medullaires — B  jeune  bois  fonne  au  printemps  avant  la  decortication.  Tons  les 
elements  de  ce  jeune  bois,  et  la  partie  la  plus  externe  A'  de  celui  de  I'annee  prece- 
dente, ont  subi  un  amincissement  dans  leur  membrane.  Les  cellules  externes  des 
rayons  medullaires  R  ont  donne  lieu  a  une  multiplication  utriculaire,  quelquefois 
abondante  en  r.  La  multiplication  commence  aussi  en  I,  I',  dans  les  elements  du 
tissue  lig-neux.  En  g,  cette  multiplication  s'etend  a  toute  la  couche  I'annee  et  meme 
aux  rtbres  ligneuses  les  plus  externes  A'  de  I'annee  precedente.  Les  vaisseaux  qui 
existaient  primitivement  dans  la  couche  de  cette  annee,  comme  en  B,  v,  sont 
disparu  en  g. 

2  Trecul,  M.  A.,  L'influence  des  cortications  annulaires  sur  la  yegStation  des 
arbres  dicotyledon6s.  Annales  di.  scienc.  nat.,  IV  Serie,  Vol.  Ill,  Botanique  1S55, 
p.  341. 

3  Physique  des  arbres.  Vol.  II,  p.  46. 

4  Compt.  rend,   (from  31st  of  May,  1852). 


8o4 

found  to  be  only  2>^  cm.  thick;  it  was  very  juicy  and  looked  like  young 
wood.  Almost  all  the  root  nourishment  for  the  top  of  the  old  tree  had  to 
ascend  this  slender  cylinder,  and  yet  in  the  year  observed,  viz :  March  29, 
1853,  the  top  developed  just  as  early  and  had  as  many  leaves  and  blossoms 
as  the  other  lindens.  But  this  tree,  which  at  its  base  had  sent  out  a  number 
of  branches  and  leaved  sprouts  5  to  6  cm.  thick  lost  its  foliage  in  August. 

Trecul  ascribes  to  these  shoots  the  maintenance  of  the  basal  part  of  the 
trunk,  below  the  barked  place;  they  prepared  for  it  the  plastic  material 
which  a  normal  trunk  receives  from  the  top  through  the  bark. 

Lindley^  describes  an  analogous  process  in  a  birch  branch  wliich  had 
been  completely  robbed  of  bark  and  sapwood  near  the  place  where  it  joined 
the  tree  and  yet  had  continued  to  grow  for  several  years. 

Th.  Hartig-  found  that  a  linden,  from  which  a  ring  of  bark  had  been 
removed,  was  still  alive  9  years  after  the  operation ;  in  fact,  its  fertility 
was  increased. 

The  court  gardener,  Reinecken,  in  Greiz,  reports  a  grafted  elm  10  cm. 
in  thickness,  which  for  6  years  was  connected  with  its  stock  only  through 
the  wood  and  not  through  the  bark.  The  Inspector  of  the  Gardens,  Roth, 
in  Moscow,  also  found  a  red  beech  75  cm.  thick  and  25  feet  high,  which  for 
45  years  had  never  been  connected  with  the  parent  trunk  by  the  bark  (as 
Goppert  states)  but  was  connected  only  by  the  wood  layers.  Nevertheless, 
it  grew  vigorously  and  was  finally  broken  off  by  the  wind.  In  the  botanical 
garden  at  Breslau,  a  linden  14  m.  high  and  one-third  meter  thick  blossomed 
every  year.  Its  bark  had  been  removed  completely  and  carefully  in  1870 
for  a  distance  of  one-third  meter,  and  above  the  barked  place,  an  overgrowth 
layer  scarcely  2  cm.  long  had  grown  in  the  first  2  years'*. 

The  result  of  the  barking  cannot  be  determined  in  advance.  The  life 
duration  in  the  barked  trunk  depends  considerably  on  the  variety  of  tree. 
Rapid  growing,  deciduous  trees  best  endure  such  extensive  injuries.  Satis- 
factory results  have  not  as  yet  been  reported  for  conifers.  Hartig*  did  not 
find  any  new  formation  of  bark  but  discovered  that'the  piece  of  the  branch 
below  this  barked  place  down  to  the  next  lower  branch  had  developed  into 
very  resinous  wood.  StolF  also  could  find  no  regeneration  of  bark.  He 
states,  however,  that  Nordlinger  had  observed  a  new  formation  of  bark  but 
had  expressed  the  opinion  that  the  newly  formed  bark  was  not  capable  of 
conducting  the  descending  sap  current. 

StoU  states  of  monocotyledons  that  he  found  a  cicatrization  of  wounded 
surfaces  in  a  Dracaena,  from  which  he  had  removed  the  bark.  It  was  kept 
in  a  greenhouse. 

The  resulting  phenomena  depend  not  only  on  the  plant  variety  but  also 
on  the  time  of  the  manipulation  and  the  ease  with  which  the  individual  can 

1  Gardener's  Chronicle  of  Nov.  13,  1852,  p.  726. 

2  Hartig,  Th.,  Folgen  der  Rinselung  an  einer  Linde.     Bot.  Zeit.  1863,  p.  286. 

3  Goppert,  Uber  das  Saftsteigen  in  unseren  Baumen.  57.  Jahresber.  d.  Schles. 
Ges.  f.  vaterl.     Kultur  1880,  p.  293. 

4  Folgen  der  Ringelung-  an  Nadelhnlzasten.     Bot.  Zeit.  1863.  p.  282. 

5  tJber  Ringelung.     Wiener  Obst-  und  Gartenzeitung  1876,  p.  167. 


8o5 


produce  accessory  organs  in  the  form  of  adventitious  buds  and  roots.  In 
fruit  culture,  the  girdhng  process  is  used  only  as  the  most  extreme  means 
of  obtaining  the  setting  of  fruit  in  trees  exhausted  by  a  too  vigorous  forma-' 
tion  of  wood. 


Personal  Observations. 

To  test  the  processes  described 
by  earlier  observers,  the  bark  was 
peeled  from  a  considerable  number  of 
strong,  about  5  year  old,  sweet  cherry 
tree  trunks  in  July.  The  upper  and 
lower  parts  of  the  barked  places  were 
scraped  for  a  length  of  2  to  4cm.  with 
a  knife  to  destroy  the  sap  wood ;  the 
remaining  part  of  the  exposed  surface 
was  left  untouched  (see  Fig.  187). 
Some  of  the  experimental  saplings 
grown  on  open  ground  were  bent  from 
their  natural,  vertical  position  to  one 
inclined  toward  the  ground. 

The  formation  of  new  bark  did 
not  take  place  in  all  specimens,  but  in 
a  few  it  occurred  to  a  considerable 
extent.  Among  the  latter  were  found 
some  small  specimens  which  had 
formed  new  bark  on  all  sides  with 
the  exception  of  the  perfectly  dry, 
scraped  places  near  the  upper  and 
lower  edges  of  the  cut.  The  new  bark, 
therefore,  had  no  connection  whatever 
with  the  old  bark.  The  initial  stages 
had  appeared  simultaneously  on  all 
sides.  The  thickness  of  the  new  bark, 
however,  was  more  than  twice  as 
great  on  the  lower  part  of  the  exposed 
surface  as  on  the  upper  part ;  in  fact, 
at  the  lower  edge,  it  had  spread  in 
short  bands  with  wartlike  thickenings 
in  places  on  the  scattered  scraped 
areas.  In  an  inclined  trunk  the  con- 
tinuation of  the  bark  had  turned  away  from  the  scraped  place  and  started  to 
grow  down  toward  the  ground,  as  Fig.  187  e'  shows. 

In  Fig.  187,  u  is  the  lower  and  u  the  upper  overgrowth  edge  of  the 
peeled  surface.  This  overgrowth  edge,  which  in  structure  resembles  the 
callus  of  the  grapevine,  has  not  been  developed  all  around  the  trunk,  since 


Pig.   liiT.     A   ijuiked  trunk  of  a  sweet 

cherry.      All    young-    tissue    has    been 

removed    from    the    upper    and    lower 

edges  of  the  place  barked. 


8o6 


a  part  of  the  bark  has  been  left  standing  in  the  loose  strips  /  and  / .  New 
wood  with  bark  (nh)  has  been  formed  in  places  on  these  strips  at  a  little 
distance  from  the  place  of  their  attachment.  The  real  exposed  surface  of 
the  trunk  has  been  cut  off  from  all  connection  with  the  overgrowth  edges 
u,u',  because  at  i  and  i'  the  young  wood,  as  already  mentioned,  had  been 
scraped  off  all  around  the  trunk,  in  this  manner  forming  an  isolating  band. 
The  new  formation  of  bark  "elements  with  the  beginnings  of  wood  had 
started  on  the  exposed  surface,  cut  off  from  all  connection  with  the  bark 
and  sapwood  layers.  These  new  structures  do  not  form  a  connected  mantle 
but  consist  of  isolated  groups.     On  other,  more  carefully  barked  trunks. 


Fig.  15 


Cross-section  through  a  newly  produced  tissue  outgrowth  on  the  exposed 
wood  of  the  barked  sweet  cheriy  trunk. 


the  new  bark  extends  perfectly  uniformly  over  the  bared  surface.  In  the 
middle  of  this  surface  an  irregular  zone  of  exposed  wood  has  remained 
without  any  new  formation.  Therefore,  the  new  product  (b)  is  not  con- 
nected with  the  upper  one  (a),  which  is  considerably  thicker.  Common  to 
both  and  just  as  clearly  recognizable  in  all  new  structures  on  other  trunks 
is  the  thickening  which  increases  from  above  downward  in  each  individual 
tissue  strip  and  in  its  appearance  resembles  perfectly  the  phenomenon 
produced  by  the  drippings  of  a  badly  burning  candle.  In  fact,  the  lower 
end  of  the  new  structure,  resembling  the  callus,  is  poured  in  the  form  of 
drops  over  the  parts  of  the  wood  which  have  remained  naked   (ee).     On 


8o7 

the  trunks  which  had  been  kept  inclined  intentionally  the  new  structure 
hangs  free  from  the  axis,  like  the  drippings  of  a  slanted  burning  candle  and, 
in  response  to  the  force  of  gravity,  grows  downward  like  an  isolated  pendent 
braid,  perpendicular  to  the  earth's  surface. 

In  order  to  show  that  the  various  small  spots,  as  has  been  observed  by 
Meyen,  Th.  Hartig  and  others,  possibly  are  not  merely  productions  of  the 
medullary  rays,  one  such  structure  is  shown  in  cross  section  in  Fig.  i88,  aftd 
in  longitudinal  section  in  Fig.  189.  Fig.  188  H  indicates  the  old  wood,  the 
barked  surface  of  which  {t  to  t)  is  partially  dead;  only  the  middle  portion 
has  started  new  production  {N-N). 

The  production  began  with  a  raising  of  the  outermost  cell  layer  by  the 
rapidly  forming  products  of  division  of  the  immediately  underlying  sap- 
wood  layer  and,  in  fact,  also  of  the  young  wood  cells  together  with  the 
vessels  and  the  medullary  ray  cells. 

After  the  cork  zone  {k),  which  is  becoming  thicker,  has  surrounded 
the  comparatively  scanty  new  parenchymatous  tissue  (r  to  p) ,  an  inner 
meristem  zone  appears  very-  early  at  first  in  bands  and  then  connected. 
This  meristematic  zone  is  new  cambium  {c  to  c),  which  now  takes  over  the 
secondary  growth  of  cork. 

In  this  way  the  two  processes  of  growth,  which  can  take  place  in  the 
formation  of  bark  on  barked  surfaces,  differ  considerably.  If,  as  is  the 
case  in  enclosed  wounds,  which  have  been  kept  moist,  the  new  bark  begins 
with  a  great  production  of  callus,  together  with  a  long  continued  division 
of  the  peripheral  cells,  as  Fig.  186  shows,  the  formation  of  the  outer  cork 
zone  and  especially  the  production  of  the  inner  meristem  zone  takes  place 
very  late.  In  contrast  to  this,  as  in  the  present  case,  the  wounded  places 
which  have  been  exposed  unprotected  to  the  hot  summer  sun  show  the 
second  process,  since  the  outermost  remaining  cells  quickly  thicken  their 
outer  walls,  collapse  and  in  this  way  furnish  for  the  immediately  underlying 
layers  the  necessary  protection  against  drying.  In  this  only  a  slight  forma- 
tion of  parenchyma,  but  a  very  rapid  appearance  of  the  cambial  zone,  takes 
place.  It  seems  that  the  inner  meristem  zone  has  developed  the  more 
quickly  into  a  callus  the  more  rapidly  a  sufficient  bark  pressure  is  produced 
by  suberization. 

The  next  production  of  the  new  cambial  regions  (Fig.  188,  c-c)  con- 
sists in  the  formation  of  isolated  new  vascular  bundle  strands,  which, 
beginning  with  scattered  short  vessels  {g),  rapidly  increase  with  age  the 
number  and  size  of  thgir  elements  and  thus  assume  a  wedge-like  form  which 
constantly  narrows  toward  the  medullary  ray  regions  (m)  and  at  the  begin- 
ning is  very  broad,  until  structure  and  arrangement  of  the  elements  have 
reached  the  normal  stage  of  the  unbarked  trunk.  To  each  xylem  part 
belongs  a  phloem  part  {ph),  near  which  appear  numerous  cells  containing 
calcium  oxalate  (o). 

We  see  that  the  appearance  of  the  vascular  bundles  in  the  parenchy- 
matous ground  tissue  is  the  same  as  in  the  callus.     This  is  true  wherever 


8o8 


a  parenchymatous  ground  tissue  of  considerable  extent  has  been  formed. 
By  cross-division  of  a  number  of  cells  which  at  first  do  not  differ  in  form 
from  the  ground  mass  and  are  but  slightly  elongated  radially  and  longi- 
tudinally, a  number  of  meristematic  centres  are  formed  from  which  the 
beginnings  of  thick-walled  tissue  elements  start.  By  a  very  luxuriant 
callus-like  cell  increase  from  the  beginning,  two  parallel  zones  of  meriste- 
matic strands  can  be  produced  simultaneously,  with  the  tissues  as  they 
grow  older.  These  parallel  zones  mature  into  two  wood  areas,  which 
remain   distinct   until   they  have   become   very   thick.     The    formation   of 


Fig.  189. 


I^ongitudinal  section  through  the  basal  part  of  Fig 
to  be  found  from  g  to  p. 


188,  about  in  the  zone 


isolated  vascular  bundles  in  the  bark  of  our  trees  is  not  rare  as  is  said  to  be 
shown  in  tuber-gnarls. 

The  first  processes  of  change  in  the  sapwood  of  the  barked  cherry  tree 
may  be  recognized  in  Fig.  189,  which  gives  a  longitudinal  section  from  the 
base  of  the  barked  portion  in  Fig.  188.  H  is  the  old  wood,  which  because 
of  the  cut  has  not  changed  any  further,  with  its  loosely  reticulated  vessels 
{g).  In  the  sapwood,  lying  just  outside  it,  the  cut  has  so  affected  the 
nearly  mature  vessel  {g)  that  its  inner  cavity  has  become  filled  with  tyloses; 
these  have  been  used  to  form  new  cells  and  been  changed  into  wood  paren- 
chyma.    The  new  layer  of  wood  parenchyma  consists  of  only  a  few  cells 


8o9 

and  exhibits  immediately  the  first  stages  of  thicker  walled  elements  in  the 
form  of  shorter,  porous  vessels  (gs)  as  the  first  production  of  the  newly 
formed  cambial  layer  c-c.  Each  successive  tissue  layer,  formed  from  the 
cambium,  has  longer  vessels ;  at  h,  we  find  thin-walled  elements,  shortened, 
to  be  sure,  but  unmistakably  resembling  the  normal  wood  cells ;  correspond- 
ing to  these  thin-walled  elements,  the  phloem  elements  appear  at  j  in  the 
bark  (r)  :  ;ir  is  the  xylem  ray,  ph  the  phloem  ray. 

If  in  the  early  spring,  when  the  bark  is  easily  loosened,  homologous 
cells  are  torn  around  the  whole  circumference  of  the  trunk  in  the  process  of 
removing  the  bark,  thereby  causing  a  reproduction  of  similar  bark,  arising 
from  similar  elements,  we  find  that  the  bark  wounds  become  more  irregular 
from  the  time  of  the  leaf  development  until  late  in  June.  More  cell  groups 
remain  attached  to  one  place  on  the  wood  cylinder  than  to  another  and  the 
new  structures  differ  accordingly.  It  thus  happens  that  pieces  of  sapwood 
of  the  current  year,  which  contain  vessels,  are  forced  up  by  a  callus  tissue 
produced  beneath  them. 

If  the  bark  wounds  are  left  uncovered,  the  new  formation  of  bark  will 
in  many  cases  be  more  doubtful.  According  to  my  experience,  the  bark 
regeneration  succeeds  better  in  July,  for  some  trees  in  August,  than  in  April, 
May  or  June.  The  maple  and  alder  must  be  barked  earlier;  numerous 
experiments  made  on  these  trees  in  August  gave  no  results  at  all. 

If  the  bark  wound,  made  in  the  heat  of  the  day  and  left  without  any 
protection  whatever,  is  investigated  after  some  hours  (sweet  cherry  trees 
were  used  for  the  experiment)  it  was  found  that  the  color  of  the  originally 
white  wood  cylinder  had  changed  to  yellow.  The  wound  surface  owed  this 
color  especially  to  the  browning  of  the  medullary  ray  cells. 

The  browning  is  more  intense  on  the  southwest  side  than  on  the  north 
side. 

The  medullary  rays  are  easily  recognized  by  the  fact  that  immediately 
after  the  removal  of  the  bark  they  project  somewhat  above  the  barked 
surface. 

This  fact  indicates  that  the  medullary  ray  cells  at  the  same  radial  dis- 
tance from  the  median  line  of  the  trunk  have  firmer  walls  than  the  young 
wood  cells,  i.  e.  their  development  is  further  advanced  than  that  of  the 
equally  old  cells  of  the  vascular  bundle. 

Such  an  advance  of  the  medullary  rays  over  the  other  tissue  will  stamp 
them  as  a  tissue  of  increase,  which  creates  space  for  the  newly  produced 
ivood  tissue  in  the  direction  of  the  radius  of  the  trunk. 

This  prominence  of  the  medullary  ray  groups  takes  place  also  in  part 
because  of  the  more  rapid  outcurving  of  their  outer  walls,  resulting,  as  a 
rule,  from  the  barking.  These  outer  walls  (unprotected)  grow  thick  very 
rapidly  and  turn  brown. 

The  cell  contents  increase  in  the  medullary  ray  and  young  wood  cells 
lying  immediately  beneath  the  wound  surface;  masses  of  cyptoplasm  and 
later  of  starch  appear,  the  former,  when  treated  with  glycerin,  rounds  up 


8io 

into  scattered  yellow  globules.  Beneath  the  outermost  cell  layer,  which  at 
once  collapses  and  forms  a  protective  mantle  for  the  underlying  young 
tissue,  the  new  cell  formation  begins  by  means  of  cross  walls.  The 
medullary  ray,  the  cells  of  which  as  a  rule  are  in  advance  of  the  others,  is 
frequently  broadened  by  this  new  formation  since  the  later  ray  cells  push 
out  in  a  fan  over  the  adjoining  wood  cells. 

It  has  already  been  stated  that  often  the  medullary  ray  cells  can  remain 
partially  or  entirely  undeveloped.  Then  the  parenchymatous  callus  cells, 
which  are  never  round  but  always  polygonal,  and  are  produced  from  the 
young  wood  fibres,  spread  over  the  medullary  ray  groups.  As  a  rule,  how- 
ever, the  whole  tissue  participates  equally  in  the  formation  of  a  thin  callus 
layer  which  pushes  out  the  outermost  cells  of  the  old  wood.  By  drying 
these  old  cells  produce  a  protecting  layer. 

While  the  callus  formation  through  the  excrescent  apical  growth  of 
the  various  cell  rows  is  very  considerable  in  the  barked  places,  which  are 
kept  protected  and  moist,  it  is  very  small  in  unprotected  places.  Cork  is 
formed  at  once  beneath  the  dried,  outer  cell  layer  and  becomes  a  constrict- 
ing, firmly  protecting  girdle  for  the  underlying  young  tissue,  which  is 
turning  green. 

The  new  formation  of  bark  on  barked  places  may  occur  in  still  another 
way.  If  the  bark  wound  is  made  in  such  a  way  that  young  bark  cells  form 
the  outermost  layers  of  the  exposed  surface,  they  initiate  the  callus  forma- 
tion and  the  real  cambial  layer  is  only  slightly  disturbed. 

The  transition  of  the  callus  into  normal  tissue  takes  places  in  general 
in  such  a  way  that  isolated,  short  celled,  vascular  strands  occur  deeper 
inside  the  callus  after  the  cork  cells  have  begun  to  form  about  its  edge. 
About  this  time  thick-walled,  slightly  porous,  irregular,  or  polygonal  cells 
are  found,  possibly  in  the  same  radial  direction  but  more  in  the  vicinity  of 
the  peripheral  zone  of  the  callus.  These  cells  are  the  first  traces  of  a  phloem 
formation.  In  many  trees,  the  first  phloem  elements  in  the  form  of  aggre- 
gations of  stone  cells  are  found  isolated  or  soon  united  into  groups.  In  one 
zone,  cells  with  a  cloudier,  denser  content  are  found  between  the  phloem 
and  the  vessel  elements.  In  them  occur  a  great  many  rectangular  walled 
cells,  somewhat  stretched  in  the  direction  of  thd  long  axis  of  the  trunk, 
which  might  be  the  very  first  stages  of  the  newly  forming  camhimn.  From 
this  cambium  are  produced  gradually  the  elongated  elements  which  finally 
develop  into  normal  wood  and  fibres  but  no  more  long,  spiral  elements  seem 
to  be  formed. 

With  the  development  of  these  normal  fibres,  the  last  to  appear,  the 
new  bark  may  take  on  the  function  of  the  uninjured  bark. 

The  Bending  of  the  Branches. 

Branches  are  often  bent  as  a  special  aid  in  fruit  culture.  Experience 
shows  that  shoots  which  grow  upright  develop  most  quickly  and  strongly 
and  that  their  growth  in  length  will  be  the  more  retarded,  the  further  the 


8ii 

branch  inclines  from  the  vertical  toward  the  horizontal.  The  same  retarda- 
tion of  the  apical  growth  is  found,  however,  if  branches  are  bent  artificially 
from   a  natural  horizontal  position  toward  the  downward  perpendicular, 


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^, 

..^" 

/•■  - 

r 

r/- 

Figs.  190  and  191.     Artificially  bent  apple  twig-  in  longitudinal  and  in  cross-section. 

from  which  it   is   evident  that  the  bending  itself   exercises  the  arresting 
influence. 

No  externally  perceptible  wound  is  produced  if  the  manipulation  is 
carefully  carried  out,  though  a  somewhat  greater  tension  may  be  seen  on 
the  upper  side  and  a  folding  of  the  bark  on  the  under  side. 


Fig.  192.     Fold  in  the  bark  on  the  under  side  of  the  bend. 

The  development  of  the  buds  is  affected  by  the  bending,  since  the  buds 
below  the  place  of  bending  swell  up  more  and,  not  infrequently  burst  pre- 
maturely.    The  success  depends  upon  the  time  and  place  where  the  branch 


8l2 

is  bent.  The  nearer  the  tip  of  the  twig  the  bent  place  lies,  the  less  the 
internal  injury  is,  but  also  the  less  the  desired  result.  The  buds  beneath 
the  place  bent  will  then  develop  into  slender  leaf  shoots.  But  when  the 
branch  is  bent  near  its  base  the  buds  stimulated  to  growth  will  develop  only 
short  shoots ;  these,  however,  show  a  tendency  to  change  to  fruiting  w^ood. 


•^c-^PP 


91. 


ITr 


Fig.  193.     Longitudinal  section  through  the  wood  within  the  bend. 

We  have  spoken  above  of  an  internal  injury  to  the  axis  even  when 
carefully  bent.  This  is  best  seen  in  a  definite  example  as  shown  in  Figs. 
190-194  of  an  apple  branch. 

The  folding  of  the  bark  is  indicated  in  Fig.  190  (rf)  and  Fig.  191  (rf). 
Upon  examination  with  the  naked  eye,  one  sees  first  of  all  a  swelling  of  the 
wood  on  the  under  side,  below  a  pale,  brownish  zone,  widened  at  the  place 
of  bending  (Figs.  190  and  191,  hp),  in  the  longitudinal  section  (Fig.  190  h) 


8i3 


and  in  the  cross  section  (Fig.  191  u).     Except  for  the  folding  of  the  bark 
body  no  perceptible  uniformly  increased  thickening  is  seen  in  the  wood. 

In  the  apple  branch  here  drawn  the  proportion  of  thickness  between 
the  bark  on  the  under  side  and  the  upper  side  is  50  to  42,  while  that  on  the 
under  side  of  the  wood  is  2  to  i.-  The  pith  (w)  seems  in  the  longitudinal 
section  slightly  brown  in  stripes,  especially  in  the  lower  half.  Under  the 
microscope  many  of  the  cells  of  the  pith  and  the  pith  crown,  often  arranged 
in  wavy  lines,  are  found  to  have  a  brownish  content  and  browned  walls 
which,  in  various  cells  belonging  to  the  under  side  of  the  pith,  are  sharply 
bent  here  and  there  and  at  these  places  separated  from  one  another  by 
newly  produced  intercellular  spaces  (Fig.  194).  The  cells  show  the  same 
separation  even  in  the  cross  section. 

The  disturbances  to  the  bark  may  be  recognized  most  easily  in  the 
projecting  folds  of  the  under  side  (Figs.  190  and  191,  rf).  In  such  folds, 
split  off  from  the  wood  by  the  bending,  the  phloem  bundles  (Fig.  192,  hb), 
as  a  rule,  show  a  marked  outward  curving,  corresponding  to  the  peripheral 
cork  layers  (k)  produced  in  considerable  thickness  by  the  squeezing  of  the 
epidermal  cells  and  corresponding  also 
to  the  bark  parenchyma  (r),  which 
has  been  broken  up  by  numerous  holes 
(/)  into  irregular  particles.  Some 
time  after  bending  some  bridges  of 
radially  elongated  cell  rows  are  found 
in  these  holes,  produced  by  the  elon- 
gation of  the  still  elastic  cells  of  the 
young,  inner  bark. 

The  apple  branch  in  question  was 
bent  at  the  beginning  of  summer  as  is  generally  done  in  practice.  The  bark 
has  been  pushed  up  from  the  wood  at  the  above  described  folds  in  the  cam- 
bial  region.  The  relief  from  bark  pressure  at  these  places  has  resulted  in 
the  formation  of  an  abundant  wood  parenchyma,  filled  with  starch,  as  shown 
in  the  longitudinal  section  through  the  wood  (Fig.  193  hp).  After  the  holes 
have  been  filled  in  and  the  bark  pressure  re-established,  the  wood  paren- 
chyma has  gradually  changed  into  normal  wood  (Fig.  193  hh'). 

The  filling  of  the  holes  takes  place  here  after  the  coalescence  of  both 
parenchyma  parts  growing  toward  one  another  and  uniting  in  the  medial 
zone  (2).  This  yellow  colored  zone,  under  strong  magnification,  resolves 
itself  into  a  stripe  of  closely  compressed  cells.  In  other  cases,  the  filling  of 
the  holes  is  produced  also  by  new  parenchymatous  structures  from  the  raised 
bark  zone  as  well  as  from  the  remaining  young  sapwood  tissue  (as  in  bark 
wounds).  In  all  cases  vessels  first  begin  to  appear  in  the  wood  parenchyma 
after  the  holes  are  filled  out;  they  gradually  reach  their  normal  length  and 
development,  are  accompanied  at  first  by  shorter,  thinner-walled  wood  cells, 
later  by  normally  long  and  thicker-walled  ones,  and  thus  the  normal  wood 
formation  begins. 


Fig-.  194.     a  pith  cells  which  have  been 

broken   apart  in   the  bending-;    b   those 

which  have  remained  uninjured. 


8i4 

After  these  wounds  are  closed,  the  influence  of  the  bending  is  still 
always  noticeable  in  a  production  of  wood  which  takes  place  more  vigorously 
on  the  under  side  than  on  the  upper  side.  The  arrangement  of  the  newly 
formed  wood  (Fig.  193  h)  follows,  on  the  under  side,  the  wavy  line  caused 
by  the  cone  of  parenchyma  wood  (/?/').  In  contrast  to  the  scantier,  simul- 
taneously produced  elements  of  the  upper  side  of  the  bent  place,  the  prosen- 
chyma  cells  of  the  under  side  are  at  first  shorter  and  arranged  bluntly  against 
one  another,  with  broad  w^alls.  Further,  more  abundantly  divided  wood 
cells  and  rows  of  wood  parenchyma  (hp'),  filled  with  starch,  are  found  on 
the  under  side  between  the  thick-walled  parenchymatous  elements. 

On  account  of  the  limited  space  considerable  parts  of  the  tissue  have 
been  omitted  in  the  drawing;  also  part  of  the  normal  wood,  formed  before 
the  bending,  as  well  ias  a  part  of  the  transitional  tissue  produced  after  the 
formation  of  the  wood  parenchyma  and  equalizing  the  bending.  In  Fig. 
193,  fh  indicates  the  spring  wood  of  the  current  year,  g  the  spiral  elements 
bordering  the  pith  (mk).  In  Fig.  194,  a  indicates  the  pith  cells,  which  have 
been  loosened  by  the  bending;  b,  those  which  have  remained  uninjured  and 
originate  from  the  upper  half  of  the  pith  body. 

If  the  bent  twig  is  investigated  above  and  below  the  bend,  it  is  found 
that  in  the  present  case  the  influence  of  the  bending  extends  on  an  average 
over  6  to  8  cm. 

The  measurements  of  the  branch,  chosen  for  the  drawings,  are  as 
follows : 

Its  thickness  amounted  to  4.65  mm.  beneath  the  bend,  5.50  mm.  at  the 
bend  and  5.06  mm.  above  it.  The  bark  showed  toward  the  tip  a  considerable 
increase  in  thickness. 

The  thickness  of  the  wood,  before  the  treatment,  amounted  to 

-f,  ,         ,     ,       ,    (  upper  side  62.0  per  cent.  "1 

below  the  bend   |  ^^-^^^^  ^.^^  ^^^        .<  I    ^^  ^j^^  ^^,^^^^  cylinder  existing 

.      I     1       ,  (  upper  side  50.6        "  1    at  the  time  of  the  measure- 

I  under  side  35.2        "  (  ment,    and    strengthened    by 

Above  the  bend  I  ''^Y'  '■'I''  ^'^"^        '^  1    ^"^^^"^"^"^  ^''''''^^'- 

(  under  side  51.4  J 

The  increase  in  growth   from  the  time  of  bending  up  to  the  time  of 

investigation  amounted  to 

Autumn  \\'ood 

Below  the  bend   j  "PP^^  ^}f  3i-0  per  cent. 
(  under  side  31.9 

At  the  bend         I  "Pg^''  ^\'\^  39-o        " 
(  under  side  si -8 

Above  the  bend  j  "PPer  side  28.1        " 
(  under  side  27.2 

Therefore,  the  increased  wood  growth  is  comparatively  greater  on  the 
upper  side  of  the  bend  than  above  and  below  the  bent  place  in  spite  of  the 
great  tension  which  may  prevail  on  the  convex  side  within  the  bend  due  to 


Spring 

W^ood 

8.0  per 
6.1 

cent. 

10.4 

134 

5-9 

21.9 

8i5 


the  bending  of  the  branch^  The  loosening  of  the  tissue,  manifested  at  the 
bend,  can  no  longer  be  recognized  on  the  upper  side.  On  the  other  hand, 
on  the  under  side  it  may  be  traced  for  6  cm.  toward  the  tip. 

The  wood  cells  are  the  widest  at  the  bend  but  are  wider  above  it  than 
below  it;  they  seem  to  be  wider  on  the  under  side  of  the  branch  than  on  the 
upper  side. 

The  anatomical  changes  vary  in  c^uantity  according  to  the  size  of  the 
curve,  which  the  twig  describes  when  bent,  as  well  as  the  time  of  bending, 
the  species  and,  indeed,  the  individuality  of  the  branch. 

Therefore,  one  has  in  the  bending  of  branches  a  simple  means  for  mod- 
erating the  grozvth  in  length  and  for  directing  the  supply  of  water  tozvard 
the  buds  which,  because  of  their  position  and  nature,  are  capable  of  little 
further  development. 

The  Twisting 
OF  Branches 

The  effect  of  twisting 
the  branches  is  much  more 
pronounced  and  persistent 
than  that  of  bending,  but 
follows  the  same  general 
principles.  It  represents  a 
further  cultural  method  for 
the  fruit  grower,  wdien  he 
wishes  to  change  the  growth 
of  branches.  During  the 
period  of  growth,  a  too  lux- 
uriantly growing  branch  is 
first  loosened  in  a  short 
woody  region  by  a  half  turn 

of  the  tissues  about  their  long  axis ;  hereby  the  tissue  is  usually  crushed  and 
split  longitudinally  and  then  bent  at  this  broken  place,  with  the  tip  of  the 
branch  downward,  so  that  the  tip  is  permanently  bent  toward  the  base.  Thus 
at  the  place  of  twisting  the  under  side  of  the  branch  lies  on  top ;  the  former 
upper  side  forms  the  inner  side  of  the  sharp  bend,  in  which  the  wood  is 
broken  down  to  the  pith. 

The  most  comprehensive  view  possible  of  the  changes  produced  by 
twisting  is  given  in  the  longitudinal  section  through  the  knotty,  deformed 
place  of  twisting,  which  is  a  year  old  (Fig.  195).  In  this  figure,  m  indicates 
the  pith  which  has  been  destroyed  by  the  breaking  of  the  wood  when 
twisted ;  h  is  the  wood  of  the  present  upper  side  on  which  a  bud  is  seen  at  a. 
Because  of  the  turning  of  the  under  side  to  the  present  upper  side,  the  wood 

1  On  the  production  of  tension  due  to  pressure,  compare  Ursprung:,  H.,  Beitrag- 
zur  Erklarung  des  exzentrischen  Dickenwachstums  an  Krautpflanzen.  Ber.  d. 
Deutsch.  Bot.  Ges.  1906,  Part  9,  p.  499.  Further:  Blicher,  H.,  Anatomische  Veran- 
derungen  bei  gewaltsamer  Krummung-  und  g-eotropischer  Induktion.  Jahrb  f. 
Wiss.  Bot.  1906,  Vol.  43,  p.  271. 


a 

d 

n 

'  '.^>^, 

m 

M 

\ 

m 
a 

I 

•^:k 

/.  r; 

w 

\ 

r'    k^' 

~h      • 

r 

Fig.   195.     A  branch  bent  with  its  tip  downward 

and    twisted    at   the   point   of   bending   about    its 

longitudinal    axis,    after    the    coalescence    of    the 

inner  injuries. 


8i6 

has  been  repeatedly  split  longitudinally,  and  the  "lamellae"  produced  by  the 
tears  have  a  spiral  twist  which  is  indicated  by  dd.  The  tears  are  first  filled 
by  parenchyma  and  then  the  cambial  zone,  which  gradually  closes  together, 
deposits  wavy  layers  of  new  wood  («)  over  the  wounds  below  the  unusually 
strained  bark  (r),  which  not  infrequently  splits  here  and  there  in  spiral, 
longitudinal  cracks. 

The  original  upper  side,  which  has  become  the  under  side  from  twisting, 
shows  still  greater  disturbances.  The  wood  {h'),  broken  at  w  and  partially 
split  off  from  the  pith,  ends  in  a  large  knot  (m)  due  to  very  irregularly 
curved  particles  of  wood  parenchyma.  This  knot  constantly  increases  in 
size  with  continued  growth  by  the  formation  of  new  wood  (n'). 

It  is  easy  to  perceive  that  the  nourishment  of  the  tip  of  the  branch  must 
be  disturbed  by  such  an  injury  to  the  tissues  and  that  the  reserve  substances, 
visible  as  starch  in  the  parenchymatous  overgrowth  parts  of  the  edges  of  the 
wound,  must  be  enough  for  the  use  of  the  immediately  adjacent  buds.  From 
what  has  already  been  said,  it  is  evident,  likewise,  that  besides  this  increase 
in  nourishment  the  buds  found  directly  beneath  the  place  of  twisting  wall 
also  profit  from  the  increased  water  pressure. 

The  treatment  of  twisting,  as  already  remarked,  is  an  effective  means 
of  retarding  the  apical  growth  of  a  branch  to  the  advantage  of  the  basal  buds 
7,  it.'. out,  however,  causing  the  uppermost  lateral  buds,  lying  below  the  injury, 
to  sprout  at  once.  The  lateral  bud  immediately  below  the  place  of  twisting, 
grows  out  to  a  new,  vigorous  leafy  shoot  only  when  the  injury  to  the  tissues 
in  the  twisting  has  been  so  great  that  the  leader  can  no  longer  receive  the 
amount  of  water  most  necessary  to  replace  that  lost  by  evaporation.  It, 
therefore,  dries  quickly  especially  if  the  maniplation  is  carried  out  too  early 
in  the  year.  This  result  is  naturally  not  desired  by  the  grower.  A  twisting, 
carried  out  too  late  in  the  year,  would  not  produce  an  effect  sufficient  to 
prepare  the  basal  buds  for  fruiting  buds,  but  still  would  arrest  the  growth  of 
the  branch  in  length  and  cause  a  better  ripening  of  the  wood  so  that  it  will 
better  withstand  the  winter. 

In  the  propagation  of  quinces  by  layering,  the  branch,  which  is  to  be 
layered,  is  twisted  once  about  its  long  axis  at  the  place  where  it  is  to  form 
roots  in  the  soil.  This  kind  of  disturbance  is  similar  to  that  in  the  above- 
mentioned  case;  the  result  different  inasmuch  as  the  retarded,  descending 
plastic  material  is  used  chiefly  for  the  formation  of  adventitious  roots. 

German  grape  growers  in  the  vicinity  of  Tiflis  are  said  to  twist  the 
stems  of  the  ripe  clusters  and,  thereby,  obtain  a  better  wine.  The  changes, 
initiated  by  this  treatment,  dovetail  into  one  another  as  follows :  the  supply 
of  water,  from  the  vine  to  the  cluster,  is  lessened  by  the  twisting  of  the 
stem.  Consequently,  the  evaporation  greatly  exceeds  the  supply  and  the 
juice  of  the  berries  becomes  more  concentrated.  Whatever  starch  happens 
to  be  in  the  stem  is  carried  as  sugar  to  the  berries.  They  break  up  and  utilize, 
thereby,  a  part  of  the  organic  acids.  The  same  processes  occur  in  the 
ripening  of  cut  grapes. 


8i7 

The  Effect  of  Constricting  the  Axis. 

The  "Constriction"  consists  in  the  close  binding  of  an  inelastic  band 
(i.  e.  string,  wire,  etc.)  about  a  trunk  or  branch.  The  results  of  this  treat- 
ment show,  to  the  casual  observer,  that  this  constriction  of  the  axis  is 
nothing  but  a  local,  artificial  increase  of  the  sap  pressure.  But  here  the 
most  extreme  case  of  sap  pressure  takes  effect  at  once,  since  the  formation 
of  new  structures  below  the  constricting  place  are  gradually  reduced  to  a 
minimum  and  finally  disappear  entirely.  The  xylem  elements,  near  the  con- 
stricting band,  thus  deviate  from  their  perpendicular  course,  even  increasing 
their  inclination  to  the  horizontal,  so  that  I  think  in  the  different  normal 
trees  themselves  the  more  or  less  spiral  twisting  of  the  wood  fibres  is  con- 
nected with  the  greater  or  lesser  pressure  exerted  by  the  sap. 

Finally,  the  tree  becomes  so  thick  above  the  constricted  place  that  the 
bark  splits  above  the  band  and  later  also  below  it.  This  removes  the  sap 
pressure  almost  entirely.  The  result  is  a  luxuriant  formation  of  wood 
parenchyma  which,  with  the  aging  of  the  plant  part,  passes  over  gradually 
in  the  later  annual  layers  into  normal  wood  and  overgrows  completely  the 
band  or  the  wire.  Such  an  overgrown  constriction  bears  great  outward 
resemblance  to  a  grafted  place  but  has  naturally  no  internal  structural  resem- 
blance to  it. 

In  Fig.  196  (see  page  819)  two  dift'erent  stages  of  the  constriction  are 
shown.  Fig.  196,  /  is  a  year  old  maple  branch,  with  a  constricted  place 
only  a  few  months  old.  Fig.  196,  2  is  an  older  branch,  which  shows  the 
overgrowth  of  a  wire  ring,  several  years  old.  Fig.  196,  J  is  a  longitudinal 
section  of  Fig.  196,  2,  where  d  and  d'  represent  the  cross  sections  of  the  wire 
ring;  u  represents  the  overgrowth  edge,  which  is  more  greatly  developed  on 
one  side  {u)  by  the  increased  supply  of  nutritive  substances  from  the  branch 
{2)  above  it.  Here  it  has  overgrown  the  wire  earlier  than  on  the  opposite 
side. 

An  anatomical  investigation  of  the  stage  represented  in  Fig.  196,  i 
shows  that  the  constriction  at  first  cannot  produce  very  extensive  changes. 
The  bark  has  suffered  the  greatest  disadvantage  and  it  is  chiefly  the  cell 
layers,  lying  on  the  outer  side  of  the  primary  bark,  between  the  phloem 
fibres,  or  between  the  stone  cell  aggregations  and  the  epidermal  cells,  which 
have  been  especially  compressed.  The  cell  layers  next  the  phloem  fibres 
seem  to  be  the  most  pressed  together ;  the  effect  is  less  marked  on  the  next 
layers  toward  the  outside,  which  are  often  thickened  like  collenchyma. 
Their  cells  are  compressed  to  j^  or  %  their  normal  diameter  and  it  would 
seem  as  if  they  hereby  become  somewhat  longer  than  the  corresponding 
cells  in  an  unconstricted  place.  The  sub-epidermal,  almost  square  cells,  are 
compressed  to  half  their  diameter.     The  epidermis  suffers  least  of  all. 

If,  as  in  Fig.  196,  i,  the  constricting  band  is  wound  several  times  about 
the  branch,  apparently  very  prominent  callus  rolls  become  noticeable 
between  every  two  turns.     In  them  the  aforesaid  parts  of  the  bark  are  devel- 


8i8 

oped  in  a  way  exactly  the  reverse  of  that  at  the  constricted  place.  The  cells, 
bounding  the  phloem  fibres,  which  in  the  normal  branch  are  elongated, 
become  considerably  broader  radially;  in  fact,  they  appear  Hke  long 
cylinders,  lying  perpendicular  to  the  phloem  fibres;  thereby,  the  overlying 
bark  tissue,  which  participates  less  in  the  radial  elongation,  is  pushed  out- 
ward. Moreover,  the  rolls,  lying  between  the  two  constricted  places,  are 
not  absolutely  large ;  they  are  relatively  conspicuous  only  in  contrast  to  the 
depressions.  The  secondary  bark  and  the  wood  follow  the  convexities  and 
concavities  of  the  primary  bark  even  if  with  far  smaller  variations.  The 
pressure,  which  makes  itself  felt  in  the  tissues,  acts  not  only  where  the  band 
lies  on  the  bark  but  also  somewhat  above  and  below  the  actual  place  of 
constriction ;  this  is  seen  especially  in  the  cross  section  of  the  cells.  The 
mutual  proportion  in  the  mean  of  measurements  is : 

In  the  I-.ark 

Normal                                                Roll  Constricted 

Fig.  196,  /  n                                 Fig.  196,  /  w  Fig.  196,  /  g 

11,2                                                   11,8  9,4 

In  the  Wood 

7>3                                                  6,9  4,<3 

Therefore,  according  to  these  mean  figures  which,  moreover,  show  con- 
siderable fluctuation,  an  increase  manifests  itself  only  in  the  round  and 
apparently  broader  cortical  cells ;  the  wood  cells,  on  the  contrary,  seem  some- 
what narrower  than  those  of  the  normal  wood  but  it  should  be  emphasized 
that  the  same  maximum  diameter  of  the  wood  cells  has  been  found  in  the 
roll  as  in  the  normal  part  of  the  branch  at  some  distance  from  the  constricted 
place  and  only  the  frequency  of  the  occurrence  gives  the  decision. 

If  the  constriction  becomes  older,  without  the  band  being  broken  or 
loosened,  as  was  the  case  with  the  wire  band  shown  in  Fig.  196,  2  and  5, 
then  the  pressure  of  the  wire  on  the  layers  of  the  bark  finally  increases 
because  of  the  growth  in  thickness  of  the  underlying  wood  in  such  a  way 
that  the  bark  layers  are  killed  and  changed  into  a  brown  crumbling  mass. 
Finally,  the  healthy  bark  splits  above  and  below  the  wire  and  inclosure  of 
the  wire  begins.  Because  the  overgrowing  layers  of  the  annual  ring  are 
considerably  thicker  in  wood  and  bark  than  at  places  at  some  distance  from 
the  wire,  the  former  constricted  place  finally  projects  in  a  considerable  roll. 

Fig.  196,  4  shows  the  section,  indicated  in  Fig.  196,  5  at  a,  considerably 
magnified.  We  see  here  in  longitudinal  section  a  little  of  the  old  wood  of  a 
branch  (//)  before  the  wire  (d)  was  bound  about  it  and  perceive  the  new 
structures  of  the  overgrowth  edge  at  first  in  the  immediate  vicinity  (U)  of 
the  wire  and  then  a  continuation  of  these  tissues  from  the  older  annual  layer 
(U').  The  transitional  stages  have  been  omitted  for  lack  of  space,  likewise 
the  representation  of  the  coalescence,  extending  about  U',  of  the  very 
uppermost  overgrowth  edge  with  the  under  one  and  the  representation  of 
the  transition  from  the  irregularly  running  wood  elements  of  the  overgrowth 


U' 


I  r: 


n^.4. 


hn 


\ 


ff 


# 


•jjc 


■*. 


^ 


Fig-.  196.     I  Is  a  consti-icted  one  year  old  branch;  2,  a  branch  several  years  old  which 

has  overgrown  the  wire  ring;   3,  longitudinal  section  through  Fig.  2;   4,  anatomical 

sketch  of  a  longitudinal  section  fi'om  a  zone  originating  at  a  in  Fig.  3. 


820 

edge  to  the  normal  wood  structure,  as  it  gradually  forms  in  the  later  annual 
layers  above  the  place  where  the  wire  is. 

If  the  wood  had  grown  normally,  without  the  arrestment  of  the  wire, 
its  structure  would  have  necessarily  remained  the  same  as  before  it  was 
constricted,  as  represented  at  //;  wood  cells  (h)  with  vessels  (g)  would 
have  been  formed  in  regular  succession  and  this  broad  wood  would  have 
been  uniformly  divided  by  radially  extending  medullary  rays  (w).  Instead 
of  this,  we  find  the  constricted  place  and  above  it  (h',h)  a  kind  of  wood 
produced  by  the  effect  of  the  wire  composed  almost  entirely  of  wood  cells 
without  vessels.  Only  in  the  beginning  are  these  wood  fibres  deposited  at  h' 
exactly  parallel  with  the  long  axis  of  the  branch;  the  more  they  are  found 
in  tlie  direction  {h',h"  ')  the  more  diagonally  they  run  and  the  more  twisted 
they  seem.  The  wood  formed  after  the  wire  has  been  bound  on  has,  there- 
fore, become  denser,  poorer  in  vessels  and  more  twisted.  The  medullary 
rays,  which  otherwise  run  as  straight  radial  bands  from  the  pith  toward  the 
I  ilk.  are  as  twisted  and  outspread  toward  the  top  as  the  wood  cells,  so  that  a 
section  made  exactly  in  the  direction  of  the  radius  intersects  several  of  the 
curved  rays  (w"). 

The  difference  between  the  wood  cells  and  medullary  ray  cells  is  not 
noticed  until  at  some  distance  from  the  wire.  In  the  immediate  vicinity  of 
this  we  find  an  almost  uniform  parenchymatous  wood  (hp),  of  which  the 
edge  is  dead  and  black  and  represents  the  dark  line  which  may  be  seen  in 
Fig.  196,  s,  extending  upward  a  little  distance  from  the  wire  {d').  The 
t)lack  furrow  no  longer  extends  entirely  to  the  outside,  since  the  later 
annual  layers  (Fig,  196,  5,w')  have  already  united  with  one  another.  These 
overgrowth  edges,  united  with  one  another  to  form  a  common,  connected 
wood  layer,  are  indicated  in  Fig.  196,  4,  by  the  tissue  H.'  Here  we  find  the 
ducts  (g)  and  the  wood  cells  {nh')  formed  as  in  normal  wood  (only 
shorter)  but  their  course  is  horizontal  instead  of  vertical  in  the  plane  lying 
at  the  same  height  as  the  wire.  Only  at  some  distance  from  the  actual  place 
of  constriction  upward  or  downward  do  these  elements  begin  to  pass  over 
gradually  into  their  normal  perpendicular  course  (Fig.  196,  4  g'h').  The 
browned,  or  blackened,  zone  {hp)  is  not  continued  to  U'. 

The  term  "browned"  or  "blackened"  has  not  been  chosen  without  good 
reason,  for  the  color  from  t  to  t'  is  as  black  as  ink,  from  there  toward  t"  a 
brownish  black.  In  fact,  it  is  ink  which  colors  the  clotted  cell  contents  near 
the  wire.  The  tannic  acid  of  the  tissue  has  combined  with  the  iron  of  the 
wire  and,  therefore,  killed  the  cell  contents  in  the  immediate  vicinity. 

This  compound  is  diffused  for  considerable  distances  and,  in  fact, 
farther  into  the  old  wood  through  the  medullary  ray  tissue  than  transversely 
through  the  wood  cells.  The  fact  that  the  wire  lies  directly  against  the  old 
wood  and  has  killed  a  zone  of  it  should  not  be  surprising,  when  we  think 
that  the  constantly  increasing  pressure  of  the  distending  branch  against  the 
inHexible  wire,  leads  to  the  compression  of  the  soft  bark  and  the  cambium 


.821 

and  kills  them.     The  dead  tissue  can  be  recognized  only  in  small  fragments 
along  the  wire. 

We  have  already  explained  above  how  these  different  tissue  forms  are 
produced  by  the  sap  pressure,  at  first  greatly  increased  and  then  nearly 
removed  by  the  splitting  of  the  bark  around  the  wire.  The  almost  complete 
breaking  up  of  the  split  bark  makes  possible  the  appearance  of  wood  paren- 
chyma from  the  cambial  zone ;  later,  if  sap  pressure  begins  because  of  the 
uniting  of  the  wound  edges  over  the  wire,  thus  enclosing  it,  true  wood  cells 
and  vessels  again  appear  but  the  arrangement  of  these  elements  for  some 
time  is  horizontal,  or  spiral,  diagonally  ascending,  caused  by  the  strong 
pressure  of  the  wire  at  the  time  when  the  cambial  zone  still  lay  back  of  it. 

The  extreme  twisting  of  the  wood  fibres,  which  can  be  confirmed  also, 
to  a  slighter  extent  normally,  in  a  great  many  trees,  and  manifests  itself  in 
different  degrees  in  individuals  of  the  same  species,  is  physiologically  inter- 
esting. The  twisted  groivth  is  more  noticeable  in  dry  places.  The  greater 
twisting  of  the  wood  fibres,  probably  caused  by  the  bark  of  specimens  grown 
in  dry  places  which  becomes  inelastic  sooner,  is  less  easily  split  and,  there- 
fore, exercises  a  higher  pressure. 

The  practical  purpose  of  constriction  is  the  same  as  that  of  girdling  but 
without  tlie  danger  entailed  by  a  complete  removal  of  considerable  parts  of 
the  bark. 

Branch  Cuttings. 

The  term  cutting  is  applied  to  any  part  cut  from  the  parent  plant,  which 
by  its  reserve  food  materials  incites  various  cell  groups,  chiefly  those  near 
the  cut  surface,  to  renewed  vegetative  increase  so  that  a  cicatrization  tissue 
is  formed.  The  separated  part  by  forming  new  roots  develops  into  an  inde- 
pendent plant.  A  work  by  Simon^  throws  light  on  the  anatomical  conditions 
and  the  dependence  of  tissue  differention  on  external  factors,  which  appear 
during  the  pressure  and  can  not  longer  be  taken  into  consideration. 

It  may  be  asserted  that  an  asexual  propagation  of  this  kind  may  be 
found  in  all  classes  of  the  vegetable  kingdom  and  may  take  place  from  very 
different  organs.  We  recall  here  the  continued  growth  of  torn  off  mycelial 
threads,  of  cut  sclerotia,  of  isolated  fruiting  stems  of  the  frondiferous 
mosses  and  of  leaf  and  blossom  parts  of  phanerogams.  Beside  the  fre- 
quently occurring  root  cuttings,  cases  have  also  been  known  of  the  formation 
of  roots  from  fruits. 

We  are  concerned  here  for  the  present  with  cuttings  from  branches, 
the  cut  surfaces  of  which  react  to  the  wound  stimulus  by  the  formation  of 
callus.  In  connection  with  this,  we  will  then  discuss  propagation  by  root 
cuttings,  the  cicatrization  of  which  also  begins  with  the  formation  of  callus. 
The  transformation  of  the  callus  into  an  actual  overgrowth  edge  by  the 
formation  of  a  peripheral  cork  zone  bears  very  great  resemblance  to  the 
formation  of  the  overgrowth  edges  on  girdled,  or  transversely  cut,  woody 

1  Simon,  S.,  Experimentelle  Untersuchung-en  uber  die  Differenzierungsvorgange 
im  Callusgewebe  von  Holzgewachsen.     Leipzig  1908,  Gebr.  Borntrager. 


822 

l^ranclies.  But  in  cuttings  the  moist  medium,  in  which  the  cut  surface  is 
placed,  acts  as  a  modifier.  A  difference  should  also  be  determined  accord- 
ing to  whether  the  branch  furnishing  the  cutting  was  already  in  a  woody 
condition,  or  was  still  herbaceous.  Instead  of  extensive  analyses,  we  will 
give  here  illustrations  of  an  herbaceous  Fuchsia  cutting  and  a  woody  rose 
cutting. 

The  basal  part  of  the  Fuchsia  cutting  (Fig.  197)  is  shown  in  longi- 
tudinal section ;  j  to  j  indicates  the  original  cut  surface ;  the  elements  appear- 
ing below  this  line  were  formed  after  the  cutting  was  made;  above  it  {s  to  s) 
lie  the  original  tissues,  only  one-half  of  which  have  been  shown,     m  is  the 


lip         /f'0^ 


Fi«-.  197.     Fuchsia  cutting-. 


pith  ;  //,  the  wood,  r,  the  bark,  in  which  extend  the  phloem  fibres  {b).  These 
as  well  as  a  part  of  the  wood  cells  {h')  have  browned  on  the  cut  surface  and 
died.  The  outer  bark  (r)  also  has  dried  up  in  the  region  of  the  cut  surface. 
The  younger,  inner  bark  layers,  on  the  contrary,  and  especially  the  pith, 
have  healed  over  the  wound  surface  by  an  abundant  cell  increase.  The 
outer  part  of  this  cicatrization  tissue  is  turned  to  cork  and  this  cork  layer 
{k)  has  grown  to  a  considerable  size  through  the  activity  of  the  cork  cam- 
bium {kc),  which  forms  the  protection  for  the  more  tender,  inner  bark 
tissue.  In  the  callus  bark  we  find  the  broadened  pouch  cells  (0),  with 
calcium  oxalate  in  raphides.  Near  these  are  isolated  cell  'groups,  with 
thicker  walls    (//),   which   represent   the  phloem  of  the  vascular  bundles 


823 

already  formed  in  the  callus,  their  wood  being  suggested  by  strands  of  short, 
reticulated  vessels  (g").  These  adjoin  the  vessels  in  the  wood  of  the  cut- 
ting, the  thin-walled  wood  cells  of  which,  rich  in  starch  and  bounding  the 
pith,  have  participated  in  the  formation  of  callus.  The  old  wood  of  the 
cutting  was  torn  when  cut.  The  torn  place  (d)  is  filled  with  callus  and  the 
cambial  zone  (c  to  c)  may  be  traced  even  into  this  torn  place;  it  passes 
through  the  callus  in  a  connected  curve.  The  normal  cambium  of  the  cut- 
ting lay  on  the  outer  side  of  the  wood  (h).  By  cutting  off  the  branch  in 
making  the  cutting  exactly  tlie  same  change  has  taken  place  as  in  the  ringed 


caf 


Fig.  198.     Rose  cutting'. 


branch.  At  first  uniform  parenchymatous  tissue  was  formed  from  the 
cambium,  in  which  short,  reticulated  vessels  (g)  gradually  appear.  Toward 
the  cut  surface  these  tissue  parts  have  become  bounded  by  a  heavy  cork 
layer  {k'),  but  in  the  outermost  bark  cells  increase  has  also  taken  place  and 
in  the  new  tissue  a  formation  of  short  vascular  cells  ((/')  on  the  outer  side 
of  which  is  recognizable  a  meristematic  layer  (c'). 

In  the  present  example  the  pith,  as  well  as  the  cambium,  has  been  the 
chief  centre  of  callus  formation. 

On  the  other  hand,  the  pith  has  remained  quite  inactive  in  the  case  of 
the  rose  cutting  (Fig.  198). 


824 

Here  too  j  to  j  indicates  the  line  .of  the  cut ;  all  below  this  is  callus 
formation,  which  has  pushed  out  the  thick  rolls  from  the  original  cambium 
and  spread  over  the  cut  surface  from  its  outer  edge  inward.  In  the  longi- 
tudinal section  shown  in  the  figure,  we  distinguish  a  roll  (ca)  cut  through 
radially  and  a  callus  (ca'-),  projecting  outward  from  the  back  edge  and  then 
cut  across,  the  bark  of  which  has  already  united  with  the  laterally  incurving 
ca.  Thus,  in  this  older  rose  cutting  at  any  rate  the  pith  is  covered  but  this 
takes  place  by  the  union  of  edges,  curving  in  from  the  periphery  toward  the 
centre,  while  in  the  Fuchsia  cutting  illustrated  above  the  main  mass  of  callus 
is  formed  by  the  pith  itself. 

The  indication  of  the  various  elements  agrees  in  general  with  that  of 
the  preceding  drawing,  m  is  the  pith,  which  was  here  torn  when  cut.  The 
cut  (ii)  has  been  filled  with  callus  projecting  out  from  the  back  edge;  h  is 
the  old  wood,  formed  before  the  branch  was  cut  ofif ;  nh,  the  new  wood 
formed  during  the  period  of  propagation,  exactly  corresponding  in  character 
to  the  new  wood  of  the  callus  in  the  grapevine.  This  begins  with  short, 
wide,  porous,  thick-walled  cell  masses,  rich  in  starch,  in  which  occur  like- 
wise short  reticulated  vessels.  Their  elements  become  narrower  and  nar- 
rower toward  the  outside  and  more  elongated,  more  and  more  resembling 
the  normal  ones  the  later  they  are  formed  after  the  cut  is  made,  i.  e.  the 
closer  they  lie  to  the  cambial  zone  cc.  This  cambial  zone  extends  around 
the  cut  surface  of  the  old  wood  in  broad  curves  and  is  covered  on  the  optside 
by  the  newly  formed  bark  (nr)  w^hich  is  not  completely  reproduced  in  the 
drawing.  We  notice  on  the  outermost  edge  of  the  bark  the  corked  and 
(lying  first  stages  of  callus  (a),  extending  at  first  over  the  cut  surface  and 
formed  of  broad,  spherical  to  pear-shaped  cells,  arranged  in  rows,  the  end 
cells  of  which  are  rounded.  These  cell  rows  are  increased  at  first  at  the 
ends,  since  the  outermost  cells  have  enlarged  and  been  divided  by  cross  walls, 
and  the  small  end  cells  thus  reduced  in  size  repeat  the  process  when  growing 
further. 

In  the  callus  roll  {ca"),  which  extends  from  the  back  outward,  and  has 
been  cut  transversely,  g  indicates  the  short  reticulated  vessels,  which  rcprc- 
sert  the  beginnings  of  the  new  wood.  Around  this  extends  the  cambial  zone 
(c').  b  is  the  old  phloem  strand,  formed  before  the  cutting  was  made.  It 
has  been  pressed  far  away  from  the  old  wood  at  the  cut  surface  by  the 
abnormal  new  wood  formation,  and  has  died  at  its  free  end.  The  cells  lying 
against  both  sides  of  the  phloem  fibre  groups  have  been  released  from  the 
sap  pressure  by  the  cut  and  have  stretched  transversely  (/),  while  in  a 
normal  condition  they  would  be  elongated.  The  remaining  outer  part  of 
the  old  bark  (r)  has  not  changed  and  has  closed  the  wound  with  cork,  o 
indicates  the  rhomboid,  isolated  crystals  and  stellate  druses  of  calcium 
oxalate. 

The  new  roots  grow  sometimes  from  the  callus  itself,  sometimes  from 
the  basal  regions  of  the  cutting  above  the  callus,  according  to  the  plant 
species. 


825 

The  Utilization  of  the  Various  Axial  Organs  for  Cuttings. 

Callus  formation  itself  as  we  see  is,  therefore,  the  simple  process  of 
healing  a  transverse  wound.  The  formation  of  the  cicatrization  tissue  at 
the  base  of  the  cutting  is  aided  by  especially  favorable  conditions.  Except 
in  healing  the  upper  edge  of  the  wound,  the  reserve  substances  in  the  cutting 
momentarily  find  no  other  use  than  in  the  cicatrization  of  the  lower  wound 
surface,  since  the  usually  shady  place  of  propagation  does  not  favor  the 
bursting  of  the  buds.  Where  the  growing  conditions  given  the  cuttings 
through  ignorance  cause  a  rapid  development  of  the  buds,  the  formation  of 
callus  and  roots  is  reduced  or  fails  entirely.  In  the  second  place,  the  moist 
place  of  growth  and  the  usually  increased  temperature  of  the  soil  act  in 
such  a  way  that  cell  increase  is  favored  on  the  lower  cut  surface,  i.  e.  the 
cicatrization  tissue  assumes  a  very  luxuriant  character.  The  formation  of 
callus  is  not  absolutely  necessary  for  the  cutting.  Plants,  which  very  easily 
produce  adventitious  buds,  reduce  their  callus  tissues  to  very  small  amounts. 
They  cover  their  cut  surface  by  a  formation  of  cork  and  utilize  their  reserve 
substances  at  once  for  the  formation  and  further  development  of  new  root 
primordia.  Here  an  abundant  cell  increase  occurs  only  in  the  cambial  zone, 
lying  immediately  in  the  cut  surface,  whereby  the  base  of  the  cutting 
enlarges  considerably  (Begonia).  The  formation  of  callus  can  become  very 
injurious  in  trees  which  form,  adventitious  roots  with  difficulty,  since  by  its 
especially  abundant  development  it  consumes  the  material  provided  for  the 
formation  of  new  roots.  We  find,  at  times,  enormous  knotty  callus  swell- 
ings without  any  formation  of  roots  (conifers). 

The  kind  and  age  of  the  cutting  and  the  vegetative  conditions  given  it 
determine  which  tissue  shall  participate  in  the  callus  formation.  The 
cambium  always  takes  part  in  this.  Where  it  does  not  assume  exclusively 
the  process  of  healing,  it  is  assisted  by  the  parenchyma  of  the  inner  bark,  or 
also  by  a  part  of  all  of  the  parenchyma  of  the  pith.  Further,  even  the 
parenchyma  of  the  wood  and  that  of  the  older  bark  can  participate  in  this. 
In  herbaceous,  rapidly  growing  plants,  even  in  their  thick-walled  elements, 
a  cell  increase  occurs  near  the  cut  surface  because  of  the  formation  of 
tyloses  in  the  vessels  and  of  a  new  formation  of  cross  walls  in  the  collen- 
chyma  of  the  older  bark.  It  has  been  observed  here  ^  that  the  thickened 
walls  of  the  collenchyma  cells  and  the  vessels  in  the  immediate  proximity 
of  the  tyloses  swell  up,  become  porous,  and  are,  in  part,  re-absorbed. 

The  more  living  parenchyma  therein  present,  the  more  rapid  and 
abundant  is  the  callus  formation.  The  cuttings  are  generally  made  at  a 
node  directly  beneath  a  bud.  In  a  cross  section  through  a  bud-cushion  it  is 
found  that  the  parenchyma  mass  is  greatly  developed  here  by  the  passing 
over  of  the  medullary   connections   into  the  bud.     At  the  node  the  pith 


1  H.  Criiger  on  Trinidad;  Westindische  Fragmente,  XII.  Einig-es  iiber  die 
Ge'webesveranderung'en  bei  der  Fortpflanzung'  durch  Stecklinge  bei  Portulaca  oler- 
acaea.     Bot.  Zeit.  1S60,  p.  371. 


826 

parenchyma,  as  a  whole,  is  usually  living  and  capable  of  dividing,  while  it 
has  died  in  the  remaining  part  of  the  branch  and  is  partially  torn. 

It  should  be  remarked,  however,  that  no  constant  rules  may  be  given 
for  the  kind  of  callus  formation.  Often,  especially  in  herbaceous  plants, 
the  cuttings  form  only  very  little  if  any  callus  on  the  wound  surface,  swell- 
ing out  and  being  cut  ofif  by  cork,  but  in  another  case  the  plants  furnish 
considerable  masses  of  callus.  The  perfectly  herbaceous  summer  cuttings 
of  V'itis,  especially  the  American  varieties,  usually  develop  but  little  callus ; 
sometimes,  however,  great  masses  of  it.  The  same  is  true  for  rose  cuttings, 
if  they  are  cut  in  the  early  spring  in  a  vegetative  soft  condition,  from  forced 
plants  and  stuck  in  a  warm  sand  bed.  A  large  supply  of  food  and  its  slow 
utilization  awaken  a  tendency  to  callus  excrescence. 

A  work  by  J.  Hanstein\  provided  with  a  detailed  bibliography,  takes  up 
girdled  cuttings.  He  found  that  such  cuttings,  with  isolated  wood  and  bark, 
which  had  been  girdled  near  the  base,  developed  roots  above  the  girdled 
surface  and  not  on  the  under  cut  surface.  If  cuttings,  which  had  already 
formed  roots,  were  girdled,  the  further  development  of  these  roots  ceased 
and  a  new  formation  began  directly  above  the  girdled  surface.  An  excep- 
tion to  this  rule  is  found  in  all  those  plants  in  which  fully  developed  vascular 
bundles  are  found  or,  at  least,  a  fully  developed,  sieve  tube  system  in  the 
pith.  In  them  despite  the  girdling  roots  are  found  on  the  under  cut  surface 
of  the  cutting.  When  stating  these  results,  we  need  only  add  that  the  oper- 
ation must  be  carried  out  with  ripe,  or  nearly  ripened  axes  in  order  to  obtain 
these  results.  If  very  young  herbaceous  tips  of  woody  plants  are  used,  in 
which  also  the  girdling  can  be  done  cleanly  only  with  difficulty,  the  new  root 
system  is  produced  on  the  cut  surface,  or  in  its  immediate  vicinity.  In  this 
all  the  tissues  with  the  exception  of  the  old  prosenchyma  elements  participate 
in  the  callus  formation.  The  part  above  the  girdled  surface  then  frequently 
dries  up.  The  same  phenomenon  may  be  observed  if  cuttings  are  placed 
upside  down  in  the  earth.  Only  infrequently  do  such  cuttings  grow  further. 
After  they  have  formed  callus  and  even  roots  on  the  end  standing  in  the  soil, 
which  is  organically  the  upper  end,  they  usually  die  back  from  above  down- 
ward to  a  small  basal  part  and  then  develop  new  shoots  from  this. 

The  results  are  of  practical  importance  inasmuch  as  they  clearly  illus- 
trate the  transference  of  the  plastic  material,  necessary  for  all  new  structure 
formation.  We  see  that  the  main  paths  for  the  building  materials  should 
be  sought  in  the  sieve  tube  system  in  the  bark.  If  such  paths  exist  also  in 
the  pith,  a  transference  of  the  plastic  substance  likewise  takes  place  there. 
Besides  these  main  paths  there  are  also  in  cases  of  necessity  side  paths,  which 
become  of  importance.  The  parenchyma  cells  of  the  bark  and  pith  will  also 
conduct  the  plastic  materials  upward  and  downward  and  likewise,  as  we  see 
in  the  new  formation  of  bark  on  bark  wounds,  the  medullary  ray  cells  in  the 
axis  can  radially  transport  dissolved,  reserve  substances ;  but  the  quantity 

1  Hanstein,   Johannes,    tjber   die   Leitung-  des   Saftes   durch    die   Rinde,     Pring-- 
sheini's  Jahrbiicher  fur  wissensch.  Botanik,  Vol.  II,  1860,  p.  392-467. 


827 

transported  in  this  way  is  small  and,  therefore,  insufficient  for  any  new- 
structures  worth  mentioning.  The  plastic  substances  are  carried  much 
more  poorly  organically  upward,  i.  e.  toward  the  tip,  than  organically 
downward. 

As  we  see  from  cuttings  set  upsidedown  and  can  perceive  also  from 
intentionally  reversed  grafts,  under  favorable  conditions  a  transference  of 
all  fluid  materials  in  the  plants,  the  raw  soil  solutions  as  well  as  the  plastic, 
organized  constructive  substances,  is  possible  in  all  directions.  The  most 
easily  passable  paths  are  naturally  used  first;  when  any  hindrance  occurs 
there  the  side  paths  become  of  increased  importance.  In  cuttings  callus  can 
be  formed  on  every  wounded  place  and  this  callus  can  produce  axes  con- 
taining chlorophyll  and  roots.  Whether  such  a  case  will  actually  occur 
depends  on  external  conditions  and  the  typical  developmental  law  peculiar 
to  each  plant,  changed  only  with  difficulty.  Many  plants  form  adventitious 
roots  from  the  internode  so  rapidly  that  the  callus  formation  on  the  cut 
surface  has  not  sufficient  time  to  make  any  development  worth  mentioning. 

Contradictions  in  the  results  of  the  various  observers  are  explained  by 
the  diversity  of  the  external  influences.  Thus  Stoll^  states  that  no  callus 
became  visible  with  Pogostemon  Patchouli,  while  Hansen^  observed  it.  The 
former  found  no  new  vegetative  points  were  developed  from  the  callus 
tissue,  while  the  latter  could  prove  them,  etc. 

In  practice  it  is  advisable  in  propagating  bushes  not  to  make  cuttings 
from  ripened,  old  wood  but  from  succulent  shoots,  which  when  possible  are 
taken  from  plants  forced  in  the  winter  in  greenhouses.  Under  certain  con- 
ditions it  is  advisable  to  make  cuttings  also  from  plants,  which  as  a  rule  are 
propagated  from  seeds.  It  is  a  well  known  fact  that  cucumber  and  melon 
plants  from  seed  of  the  previous  year  make  very  luxuriant  foliage  growth 
but  set  fruit  less  abundantly.  Old  seed  with  contents  poor  in  water,  how- 
ever, like  wilted  seed  potatoes  and  the  Hke,  behaves  more  favorably  since 
the  vegetative  activity  of  the  plant  appears  to  be  modified.  Cuttings  from 
the  tips  of  vigorous  shoots  of  cucumber  and  melon  plants,  forced  in  the  hot 
bed  and  bearing  the  first  fruit  possibly  in  May,  give  within  a  few  days  and 
about  this  time  well  rooted  plants  with  greater  fertility  than  plants  from  seed. 

Here,  at  the  end  of  the  chapter,  it  is  necessary  to  call  attention  to  the 
fact,  that  propagation  by  cuttings  is  often  used  for  the  development  of  new 
varieties.  Many  teratological  and  pathological  conditions,  which  appear 
temporary  in  dififerent  parts  of  the  plant,  become  fixed  in  the  cutting.  A 
great  many  plants  with  highly  variegated  foliage,  varieties  with  double 
blossoms,  etc.,  which  originally  appeared  on  isolated  shoots,  have  been  made 
permanent  by  cuttings.  Temporary  juvenile  stages  in  Conifers  varying 
with  the  place  of  growth  are  propagated  further  by  cuttings  and  offered  for 
sale  as  new  forms  or  varieties.     A  few  striking  examples  of  this  kind  form 


1  Tiber  die  Bildung-  des  Callus  bei  Stecklingen.     Bot.  Zeit.  1874,  Nos.  46  and  47. 

2  Hansen,  Ad.,  tJber  Adventivbildungen.     Sitzung-sber.  d.  phys.-med.     Sozietat 
zu  Erlangen  June  14,  1880. 


828 

valuable  suggestions  for  further  experiments  along  this  line.  According  to 
Beissner^  in  order  to  obtain  Chamaecyparis  squarrosa  from  cuttings  of 
Biota  orientalis  only  the  small  branch  axes  with  decussate  leaves  should  be 
used,  which  are  found  close  above  the  cotyledons.  The  majority  of  these 
little  branches  always  give  Biota  meldensis,  but  with  an  evident  scale-like 
position  of  the  leaves,  Biota  orientalis.  Likewise,  cuttings  of  the  first  shoots 
of  Callitris  qiiadrivalvis  give  a  new  form.  The  fixed  juvenile  stage  of 
Cupressus  sempervirens  may  be  seen  in  C.  Bregeoni;  the  first  shoots  of 
C.  Lawsoni  give  a  form  with  squarrous  leaves.  Retinospora  ericoidcs,, 
Zucc.  was  obtained  from  Chamaecyparis  sphaeroidea  var.  Andalyensis. 

The  diversity  of  plants  obtained  from  the  ivy  according  to  whether  the 
cutting  is  taken  from  blind  or  blossoming  wood  is  well  known. 

Aside  from  the  often  simpler  leaf  form  of  blossoming  wood,  which  is 
easily  transmitted  to  plants  from  cuttings,  we  often  find  their  habit  of 
growth  to  be  more  dwarfy  and  bushy.  The  subject  of  the  retention  of 
juvenile  forms  has  recently  been  treated  thoroughly  by  Diels". 

Propagation  by  root  cuttings  is  still  but  little  used,  although  very  advan- 
tageously in  many  woody  plants.  Paulownia,  Ailanthus,  Syringa,  Aralia, 
Mespilus,  Rosa,  Malus  may  be  propagated  by  removing  larger  root  branches 
before  the  first  growth  in  the  spring,  or  before  the  second  growth  in  July. 
These  are  cut  into  pieces  possibly  5  cm.  long  and  laid  flat  in  rows  in  the  soil. 
New  plants  rapidly  becoming  independent  by  their  own  root  formation  are 
produced  at  dififerent  places  in  the  piece  of  root  by  adventitious  bud  forma- 
tion. Among  the  conifers,  Araucaria,  Podocarpus  and  Gingko  are  said  to 
be  advantageously  propagated  by  root  cuttings  especially  if  these  are  set  in 
a  warm  bed.  Large  root  stocks  survive  splitting  lengthwise;  each  half  then 
develops  adventitious  buds. 

Some  plants  may  also  be  propagated  by  bud  cuttings  (Yitis,  Paconia 
arhorea).  The  buds  are  cut  from  the  old  wood  in  the  spring  just  as  if  one 
were  cutting  long  buds  with  some  wood  for  grafting  and  these  hud  cuttings 
are  laid  flat  on  the  surface  of  the  soil  in  pots.  It  is  advisable,  however,  to 
excite  rapid  growth  by  warming  the  soil. 

We  can  also  speak  of  tuber  cuttings,  since  there  exists  a  method  of 
propagating  plants  by  boring  the  eyes  out  of  the  fleshy  tubers  with  a  part 
of  the  tuber  tissue  containing  reserve  substances  (potatoes,  caladiums). 
Usually  the  part  of  the  tuber,  which  has  been  cut  out,  forms  cork  on  its 
exposed  wound  surface  at  the  expense  of  the  starch  and  retains  the  remain- 
ing reserve  substances  for  the  first  nutrition  of  the  eyes,  which  become 
independent  quickly  by  the  development  of  adventitious  roots.  The  cutting 
of  seed  potatoes  should  be  discussed  in  this  connection.  In  practice  the 
precaution  is  observed,  as  a  rule,  of  not  placing  the  pieces  of  tubers  in  the 
soil  immediately  after  cutting.     This  precaution  is  perfectly  justified,  since, 

1  Beissner,  t)ber  Formveranderung-  von  Koniferensamling-en.  Kegel's  Garten - 
flora  1879.  p.  172,  cit.  Bot.  Jahresber.  1879,  11,  p.  2. 

-  Diols,  L.,  Jug-endformcn  und  Bliitenreife  im  Pflanzenreich.  Berlin  1906,  Gebr. 
Borntragrer. 


829 

in  planting  freshly  cut  pieces,  a  decay  easily  occurs  among  them  as  soon  as 
even  a  little  moisture  is  present  in  heavy  soils.  If  on  the  contrary  the  cut 
pieces  are  left  a  few  days  in  the  air,  cork  layers  are  formed  under  the  cut 
surface,  which  protect  the  pieces  of  tuber.  If  the  tubers  are  cut  too  early 
before  sprouting,  it  may  happen  in  some  varieties  that  the  pieces  remain  for 
some  time  in  the  soil  apparently  unchanged  without  any  sprouting  of  the 
eyes.  It  is,  therefore,  advisable  with  tender  varieties  to  spread  the  tubers 
before  planting  in  a  light,  warm,  place  until  the  eyes  begin  to  enlarge  and 
then  to  undertake  the  cutting. 

The  importance  of  the  cork  formation  on  the  cut  surface  is  shown  by 
an  experiment  made  by  AppeF,  who  supplemented  the  results  of  studies  by 
Kny^  and  Olufsen^.  While  the  two  last  named  investigators  perceived  the 
tuber's  chief  protection  against  infection  by  parasites  to  be  the  wound 
periderm  forming  beneath  the  cut  surface  after  a  short  time,  Appel  proves 
that  the  potato  is  able  to  protect  itself  before  the  wound  cork  is  produced. 
He  finds  that  in  the  most  favorable  cases  the  periderm  formation  sets  in 
only  on  the  third  day  after  the  injury  and  ends  after  two  days  more.  There- 
fore, the  wounded  place  would  lie  unprotected  for  that  length  of  time 
against  the  demonstrably  rapidly  penetrating  bacteria  of  decay  if  the  walls 
of  the  undestroyed  cells  lying  directly  beneath  the  wound  surface  did  not 
turn  to  cork  immediately  on  the  side  toward  that  surface.  In  fact,  this  cork 
deposition  completed  after  twelve  hours  was  found  in  a  part  of  the  cell  wall 
of  the  first  and  second  cell  layers  beneath  the  wound  surface  to  be  entirely 
sufficient  to  prevent  infection  from  Bacillus  phytophthorus.  The  process 
of  suberization  develops  less  well  if  the  pieces  of  tuber  dry  at  once  and  are 
kept  warm  (for  example,  within  doors).  The  outermost  cell  layers  of  the 
cut  surface  then  dry  up  so  quickly  that  the  two  factors  necessary  for  the 
turning  to  cork,  viz :  oxygen  and  moisture,  have  only  insufficient  access  to 
the  tissue  layers  under  consideration. 

The  closing  of  wounds  in  all  fleshy  parts  of  plants  takes  place  in  the 
same,  or  a  similar  manner*. 

Grafting. 

Improving  the  stock  by  grafting  consists  in  the  artificial  removal  of  one 
or  more  buds  and  their  insertion  in  a  living  part  of  a  plant  for  the  sake  of 
further  nutrition  and  development.  The  inserted  parts  are  usually  held 
fast  by  a  bandage  and  protected  by  grafting  wax  from  the  injurious  effects 
of  the  atmospheric  conditions.  The  inserted  part  can  in  general  be  called 
the  "scion,"  while  the  nourishing  trunk  is  called  the  "stock."  The  newly 
produced  tissue  furnished  in  part  by  the  stock  and  in  part  by  the  scion. 


1  Appel,  otto,  Zur  Kenntnis  des  Wundverschlusses  bei  den  Kartoffeln.     Ber.  d. 
Deutsch.     Bot.  Ges.  1906,  p.  118. 

2  Kny,  L..,  tJber  die  Bildung  des  "Wundperiderms  am  Knollen  in  ihrer  Abhan- 
g-igkeit  von  ausseren  Einfllissen.     Ber.  d.  Deutsch.     Bot.  Ges.  1899,  p.  1S4. 

3  Olufsen,    Untersuchung-en    iiber    Wundperidermbildung-    an    Kartoffelknollen. 
Bot.  Centralbl.     Supplement,  Vol.  XV,  1903,  p.  269. 

*  Kiister,  Ernst,  Patholog-ische  Pflanzenanatomie.     Jena  1903,  G.  Fisher,  p.  1S5  ff. 


830 

which  unites  the  two  artifically  connected  members,  is  called  the  "connecting 
layer/'  or,  according  to  Goppert,  "intermediary  tissue."  The  scion  is  either 
a  single  bud,  which  has  been  separated,  together  with  a  part  of  the  adjacent 
bark,  or  a  piece  of  a  twig  with  several  buds.  According  to  the  cultural 
purpose  the  scion  can  be  inserted  at  the  place  of  its  removal,  or  at  some 
other  place  in  the  same  individual  or  (most  frequently)  on  some  other  indi- 
vidual. In  the  first  phase,  only  the  effect  of  the  injury;  in  the  latter,  in 
addition  the  influence  of  the  difference  in  character  of  the  scion  and  the 
stock  will  have  to  be  considered. 

This  process  of  improving  the  "stock"  will  have  to  be  considered  first 
of  all  as  a  process  of  wound  healing;  the  favoring,  or  arresting  influence, 
will  have  to  be  taken  into  account  secondarily,  due  possibly  to  the  mutual 
interaction  of  the  two  artificially  connected  plant  parts. 

Among  the  authors  treating  this  subject  thoroughly,  Goppert^  should 
be  named  first  of  all.  He  took  up  the  subject  especially  through  anatomical 
studies.  A  year  after  the  publication  of  Goppert's  well  illustrated  work  I 
published  a  supplementary^  article,  in  part  confirming  it  and  in  part  correct- 
ing it".  Among  the  earlier  physiologists,  the  statements  of  Hanstein^,  of 
de  Candolle*,  of  Treviranus^  are  especially  worthy  of  consideration. 
Thouin®  made  a  systematic  compilation  of  all  the  possible  variations  in  the 
process  of  grafting.  He  based  his  work  on  Duhame^,  La  Ouintinye^, 
"Rozier®,  Cabanis^"  and  the  other  horticultural  writers  and  by  means  of 
abundant  bibliographical  citations  facilitated  tremendously  the  study  of  the 
history  of  the  art  of  grafting. 

Of  the  various  forms  of  grafting  w^hich  Thouin  describes  in  his  book 
under  separate  names  and  usually  illustrated,  only  a  very  few  have  found  a 
general  acceptance.  All  the  forms  in  use  at  present  will  from  a  pathological 
point  of  view  be  best  arranged  in  their  respective  values,  according  to  the 
degrees  of  injury  w^hich  the  stock  suffers  and  according  to  the  greater  or 
lesser  degree  of  ease  with  which  the  wounds  can  be  healed.  Under  other- 
wise similar  circumstances,  the  success  of  the  manipulation  will  be  the  more 
certain  the  more  rapidly  the  tissue  of  the  scion  forms  a  firm  connection  with 
the  stock  and,  since  this  connection  is  brought  about  by  means  of  the  newly 
produced  cicatrization  tissue  of  the  wound,  the  rapidity  with  which  the 
wound  is  closed  becomes  the  standard,  chiefly,  if  not  exclusively,  for  judging 
the  value  of  the  form  of  grafting. 


1  Goppert,  iiher  innere  Vorg-ange  bei  dem  Veredeln  der  BJiume  und  Strilucher. 
Kassel  1874. 

2  Sorauer,  Vorlaufige  Notiz  iiber  Veredlung-.     Bot.  Zeit.  1875,  p.  201. 

3  Hanstein,  Dr.  J.,  Das  Reproduktionsvermog-en  der  Pflanzen  in  Bezug  auf 
ihre  Vermehrung  und  Veredlung.  Wiegandt's  Volks-und  Gartenkalendar  1865, 
p.  190. 

4  De  Candolle,  Physiologie  v6getale  II. 

5  Treviranus,  Physiologie  der  Gewachse  1838,  11,  p.  647. 

6  Thouin,  Monographic  des  Pfropfens.     Berg's  translation,  1824. 

7  Duhamcl,  Physique  des  arbres  1758,  II,  p.  75. 

8  De  la  Quintinye,  Le  parfait  jardinier.     Paris  1695. 

9  Rozier,  Cours  complet  d' Agriculture,  Vol.  V,  p.  346. 
10  Cabanis,  Principes  de  la  Greffe,  p.  105. 


831 

The  phenomena  of  union  possible  in  grafting  may  be  traced  to  the 
heaUng  processes  of  three  classes  of  wounds  which  I  have  called  bark 
wounds,  surface  wounds  and  cleft  wounds. 

The  injuries  termed  bark  wounds  (as  evident  from  the  earlier  chapters) 
are  those  produced  by  a  complete  removal  of  the  bark,  so  that  the  wood  is 
exposed  without,  however,  losing  any  of  its  parts.  The  form  of  grafting 
in  which  this  peeling  process  forms  the  main  part  of  the  injury  belongs  to 
the  type  of  budding.  Here,  at  the  time  of  the  greatest  cambial  activity,  the 
bark  is  raised  for  a  certain  distance  from  the  wood  of  the  stock  and  the 
scion  (bud)  is  inserted  into  the  exposed  place.  This  scion  consists  of  a 
single  eye  with  a  small  bark  shield  {budding  with  bark),  or  of  an  eye  which 
has  been  cut  out  with  some  wood  from  the  parent  branch  {budding  with 
ivood)  or  of  a  piece  of  an  entire  twig  which  can  be  inserted  in  different 
ways  and  is  shoved  under  the  bark  of  the  stock  with  its  cut  surface  against 
the  wood  cylinder  {bark  grafting). 

Under  the  term  "surface  wound"  are  included  all  the  injuries  in  which 
a  piece  of  the  wood  is  taken  away  together  with  a  complete  removal  of  a 
part  of  the  bark.  The  surface  wound  looks  and  behaves  differently,  accord- 
ing to  whether  this  wound  surface  is  produced  by  a  longitudinal  or  a  cross- 
cut. If  the  piece  is  cut  from  the  axis  longitudinally,  the  elements  of  the 
bark  and  wood  are  exposed  lengthwise.  The  rain  water  runs  off  easily 
from  this  surface  wound,  while  in  a  cut  across  the  trunk  it  collects  in  little 
troughs  and  can  much  more  easily  cause  the  decay  of  the  wood.  A  hori- 
zontal surface  wound  is  always  much  more  dangerous  for  the  axis  than  one 
running  vertically.  On  this  account  in  general  practice  diagonal  cuts  are 
usually  made,  instead  of  horizontal  ones. 

The  kinds  of  grafting,  in  which  surface  wounds  come  into  play  chiefly, 
or  exclusively,  belong  to  the  type  of  "Copulation."  The  simplest  form  of 
this  consists  in  the  setting  of  a  scion  in  a  diagonally  cut  surface,  produced 
by  the  cutting  off  of  the  tip  from  the  stock  where  it  is  of  the  same  thickness 
as  the  scion.  Most  nearly  related  to  this  is  the  single  and  double  saddle 
graft.  The  scion  and  stock  can  be  united  also  by  actual  longitudinal  surface 
wounds,  if  the  stock  is  cut  at  the  side  in  only  one  place  without  loosening  its 
tip.  The  scion  either  remains  attached  to  the  parent  plant  and,  likewise,  is 
cut  only  at  the  side  (ablactation),  or  cut  off  from  the  branch,  as  in  other 
forms  of  grafting,  it  is  fitted  to  the  stock  by  lateral  paring.  In  order  that 
the  scion  may  fit  more  closely  in  a  lateral  position,  its  lower  end  is  cut  to  a 
wedge  and  this  end  is  forced  into  a  cleft  at  the  base  of  the  surface  wound 
of  the  stock.  In  many  plants  (Camelias)  the  scion  is  not  infrequently  cut 
to  a  short  wedge  and  this  wedge  is  forced  into  a  lateral  cleft  in  the  stock, 
produced  by  a  short  diagonal  downward  cut  into  the  wood  (insertion). 
When  the  grafting  fails,  stock  thus  cut  suffers  least  of  all  and  after  a  short 
time  can  be  used  again. 

The  injury  from  which  the  trunk  suffers  most  is  the  cleft  wound.  The 
form  of  grafting  with  such  wounds  is  cleft  grafting.     This  was  at  first  used 


832 


833 

generally  in  Germany  but  now  only  for  isolated,  special  cases  to  rejuvenate 
older  trunks.  Cleft  grafting  consists  of  pushing  a  scion,  cut  wedge  shaped 
on  two  sides,  into  a  cleft  in  the  stock  which  has  been  cut  off  square.  This 
cleft  is  produced  by  splitting  or  by  cutting  out  a  wedge  from  the  wood. 

In  considering  the  processes  of  healing,  i.  e.  processes  of  union  in  the 
different  forms  of  grafting,  we  must  distinguish  first  of  all  whether  this  has 
been  carried  out  on  soft  w^ood,  or  on  branches  of  mature,  strong  wood.  In 
the  first  case  more  tissues  participate  in  the  formation  of  the  "layer  of 
union"  than  in  the  latter  case  in  which  a  mass  of  tissue  is  chiefly  involved, 
formed  from  the  cambial  zone  (at  times  also  from  the  pith  zone).  This 
tissue  forces  itself  into  the  space  between  the  scion  and  the  stock,  or  figur- 
atively speaking  must  pour  in  between  the  two  adjacent  parts. 

OCULATION   OR   BUDDING. 

The  most  interesting  processes  of  union  are  found  in  oculation.  In  the 
plate  here  given,  a  budded  rose  is  pictured.  In  one-half  of  this  drawing 
(from  I  to  ^),  the  tissue  structures  are  shown  after  six  days;  in  the  other 
half  (from  2  to  5)  after  about  four  weeks.  The  section  through  the  place 
of  budding  clearly  shows  the  inserted  bud  at  E,  the  stock  at  w.  In  the 
stock,  hh  is  the  old  wood  of  the  previous  year,  sh,  the  wood  of  the  current 
year,  formed  at  the  time  of  oculation.  R  L  are  the  bark  strips,  raised  by  the 
T-cut;  in  them,  h  should  indicate  the  phloem  fibres,  t  the  dead  tissue  of  the 
cut  edge. 

At  the  time  the  bark  strips  were  spread  out  from  one  another  by  the 
inpushing  of  the  bud  (£),  the  cambium  was  very  active.  The  raising  of 
the  bark  takes  place  here  in  the  sapwood  in  such  a  way  that  the  youngest 
vascular  primordia  {g)  and  the  cambial  layers  (c)  lying  in  front  of  them 
remained  attached  to  the  bark  strips. 

Often  only  the  bark  is  raised.  In  fact,  under  some  conditions,  pieces 
of  the  entire  cambial  region  with  the  youngest  bark  cells  remain  attached  to 
the  wood.  No  evidence  of  any  fixed  law  has  been  recognized  in  this  con- 
nection. It  seems  that  the  momentarily  tenderest  part  is  torn  when  the 
bark  is  raised  and  that  individual  homologous  tissues  can  behave  differently 
at  the  same  time  in  the  same  varieties ;  in  fact,  that  even  the  bark  on  the 
different  sides  of  the  trunk  has  a  different  loosening  quality.  Therefore, 
the  processes  of  healing  are  unlike  in  the  same  species  and  variety  even  in 
the  same  grafted  individual  at  different  heights. 

Even  after  12  hours  a  change  in  the  peripheral  cell  layers  may  be  recog- 
nized on  the  edges  of  the  wound  in  the  bark  as  well  as  in  the  wood ;  the 
walls  of  these  cells  have  thickened  and  turned  yellow,  either  on  the  exposed 
side  alone,  or  on  all  sides  of  the  cell ;  the  cell  contents  have  increased.  It 
cannot  be  determined  whether  this  has  taken  place  only  because  of  swelling, 
as  in  the  wall,  or  by  the  transference  of  material  from  the  inner  part  of  the 


834 

wood  toward  the  periphery.  The  first  developmental  stages  differ  according 
to  the  life  activity  of  the  exposed  cells.  As  a  rule,  all  places  on  the  exposed 
wood  are  not  covered  with  sapwood  capable  of  increase.  If  the  tissue  of 
the  sapwood  does  not  begin  to  increase,  the  cell  walls  on  the  edges  of  the 
wound  swell  and  turn  brown,  together  with  their  contents ;  they  also  collapse 
somewhat  and  form  an  irregular  thick  yellow  stripe.  The  walls  in  the  cell 
groups,  which  are  adjusting  themselves  for  increase,  usually  turn  brown 
only  slightly  and  frequently  after  a  short  time  begin  to  form  wound  callus. 
The  thin-walled  tissue,  gradually  growing  out  in  parallel  rows  (ok),  is  the 
wound  tissue,  the  growth  conditions  of  which  were  described  under  wounds 
due  to  barking.  In  Fraxinus,  for  example,  this  could  be  observed  to  be  i6 
cells  thick  after  two  days.  The  arrangement  of  the  callus  is  comparatively 
rarely  as  regular  as  it  is  shown  in  the  drawing.  Because  some  parts  of  the 
wood  do  not  form  wound  callus,  the  adjacent  cell  rows  radiate  from  one 
another  and  cover  over  the  places  remaining  inactive.  This  callus  forma- 
tion is  so  rapid  that  the  covering  of  the  inactive  places  and  the  close  union 
of  the  elements  coming  from  the  different  sides  is  a  matter  of  course. 

The  bark  strips  on  an  average  proceed  less  rapidly  to  the  formation  of 
wound  callus.  The  products  of  the  new  formation  are  also  different.  To 
be  sure,  the  peripheral  cells,  rich  in  cyptoplasm,  project  somewhat  (k)  soon 
after  the  operation,  but  cell  increase  does  not  always  occur  or,  in  case  it 
does  begin,  its  product  is  only  cork  which  can  protect  the  wound  surface. 
The  formation  of  new  structures  is  more  energetic  and  increases  until  an 
abundant  wound  callus  tissue  is  formed  usually  first  toward  the  inner  angle, 
where  the  bark  strip  is  firmly  attached  to  the  wood  (ok). 

The  rapidly  formed  wound  callus  masses  of  the  bark  and  wood,  as  well 
as  ultimately  those  of  the  scion,  unite  and  in  the  shortest  possible  time  form 
a  temporary  protection  for  the  graft  wound.  We  say  "a  temporary  protec- 
tion" for,  actually,  the  tissue  as  yet  reproduced  is  only  short-lived.  As  soon 
as  the  the  callus  tissue  has  acquired  a  considerable  extent  and  seems  exposed 
to  increasing  pressure,  a  meristem  zone  is  formed  in  it  at  a  certain  distance 
from  the  periphery,  which  at  times  is  strengthened  by  cork  cells.  The 
maturing  of  this  meristem  zone  depends  upon  the  distance  between  the  stock 
and  scion.  At  times,  at  a  very  short  distance,  only  a  few  lateral,  isolated 
aggregations  may  be  recognized  but  when  the  intermediate  space  is  great 
and  the  wound  callus  formation  luxuriant,  continuous  zones  may  be  discov- 
ered, which  often  after  having  a  looped  course  are  connected  with  the 
sharply  protruding  cambial  zone  of  the  older  overgrowth  tissue  formed  on 
the  bark  strips  (cCjCc). 

The  meristem  zone  is  not  drawn  in  the  young  wood  callus  because  it 
does  not  appear  until  later. 

In  common  with  the  cambial  zone  of  the  bark  strips  (cc),  this  callus 
meristem   furnishes  first  of  all  the  actual  connecting  tissue  consisting  of 


835 

wood  parenchyma  in  the  form  of  thick-walled,  isodiametric  cells,  or  cells 
somewhat  stretched  radially,  irregularly  quadrangular,  which  appear  not 
infrequently  with  somewhat  bent  walls  {kg).  These  represent  the  begin- 
nings of  a  wood  body,  which  is  being  formed  under  slight  pressure.  By 
their  increase  they  gradually  compress  all  the  thin-walled,  first-formed 
tissue,  retaining  the  character  of  phloem  parenchyma  {ok)  and  representing 
the  first  closing  of  the  wound.  When  the  meristematic  zone  is  formed  in 
loops,  round  masses  of  wood  parenchyma  are  produced,  enclosing  the  brown 
dead  cell  complexes  of  the  original  tissue.  Gradually  the  whole  tissue  {ok) 
is  pressed  back  between  i  and  2  by  cells  similar  in  character  to  those  marked 
{kg),  which  store  up  starch. 

Under  favorable  conditions,  the  scion  also  participates  in  closing  the 
wound.  In  the  present  drawing,  a  bud  is  shown  with  the  bark  shield,  but 
without  any  wood.  The  cut  £  is  a  cross  section  only  through  the  bark 
shield.  The  bud  belonging  to  this,  which  must  be  imagined  in  the  direction 
(0),  lies  above  the  plane  of  the  section;  in  this  section  only  the  large  central, 
vascular  bundle  {gh),  which  extends  to  the  bud,  and  a  smaller  one  adjacent 
to  it  have  been  drawn.  The  third,  smaller  bundle,  present  in  every  unin- 
jured bud  cushion  and  likewise  traversing  slantingly  the  axis  of  the  branch 
on  the  other  side  of  the  central  bundle,  has  been  cut  away  here  in  removing 
the  bark  shield;  this  does  not  affect  the  outgrowth  of  the  bud.  On  the 
other  hand,  the  absence  of  the  central  vascular  bundle  will  always  signify  a 
failure  in  budding.  The  bark  shield  with  the  rapidly  drying  bud  bracts  can 
grow  further  without  the  vascular  body  but  in  my  experience  it  has  never 
happened  that  an  excessively  luxuriant  overgrowth  tissue  from  the  bud  had 
formed  adventitious  buds  and  in  this  way  compensated  for  the  dead  bud. 

To  be  sure,  the  formation  of  adventitious  buds  takes  place  in  many 
bud  grafts,  as  is  shown  in  the  following  Fig.  200  of  an  herbaceous  bark 
graft  of  Aesculus  rubicunda  on  Aesculus  Hippocastanum,  but  up  to  the 
present  I  have  found  this  bud  formation  only  on  luxuriant  overgrowth 
edges  of  the  stock.  The  bark  strips  {ne)  have  produced  such  strong  new 
structures  that  they  have  thereby  been  pushed  out  from  the  scion  like  wings. 
Numerous  adventitious  buds  (a)  stand  on  the  edge. 

In  the  budded  rose  (Fig.  199),  the  whole  inner  surface  of  the  bark 
shield  {E)  has  already  produced  new  wound  tissue,  sometimes  more,  some- 
times less,  according  to  the  age  of  the  mother  cells.  The  cambial  zone  of 
the  bundle,  lying  below  the  phloem  fibre  groups  {b),  has  formed  the  new 
cells  very  abundantly,  as  is  shown  by  the  protruding  tip  {z).  The  new 
structure  on  the  inner  side  of  the  shield  bears  the  character  of  bark  tissue 
and  is  already  distinguished  by  numerous  crystals  of  calcium  oxalate,  while 
the  cambial  zone  {c),  which  begins  to  form  new  wood  elements,  appears  in 
later  stages  of  the  coalescence  in  connection  with  the  cambial  zone  {cc)  of 
the  bark  strips.  As  soon  as  this  union  takes  place  a  continuous  cambial  ring 
is  formed  again  about  the  whole  circumference  of  the  tree.     The  cambial 


836 

zone  of  the  bud  represents  an  integral  part  of  this.  The  zone  (cc),  if  traced 
backward,  is  found  to  be  a  direct  prolongation  of  the  cambial  ring  of  the 
uninjured  axial  part. 

If  the  wound  is  closed  by  the  coalescence  of  the  different  wound  tissues 
and  the  union  of  their  cambial  zones,  the  thin-walled  tissue  of  the  wound 
callus  (ok)  has  almost  disappeared  and  has  been  replaced  by  actual  uniting 
tissue  in  which  groups  of  porous  cells  may  be  often  distinguished  from  less 
porous  ones,  as  mentioned  above.  As  indicated  by  the  bark  tip  (-?-j)  the 
wood  parenchyma,  which  takes  over  the  formation  of  a  permanent  union,  is 
also  produced  directly  and  in  fact  in  the  angles  where  the  bark  strip  and 
wood  body  join,  i.  e.  where  the  indicating  line  from  kg  ends.  When  it  is 
perceived  that  the  bark  strips  {3  R  L)  have  been  so  raised  by  the  budding 
knife,  that  not  only  the  whole  cambial  zone  but  also  the  young  sap  wood 
elements  already  differentiated  remain  attached  to  them,  then  it  is  evident 
that  this  connecting  tissue  is  a  product  of  sapwood  cells  already  somewhat 
older  (not  those  most  recently  formed).  This  tissue  is  not  produced  from 
the  wound  callus  (which  is  never  formed  in  the  inner  angles)  but  from  the 
division  of  cells  already  destined  to  be  wood  cells  and  vessels. 

We  have,  therefore,  three  different  factors  which  furnish  a  similar 
product,  the  wood  parenchyma,  already  described  as  the  uniting  tissue, 
which  takes  over  the  process  of  uniting  scion  aiid  stock.  The  first  factor  is 
the  bark  strip  from  the  stock,  the  second  the  callus  of  the  exposed  wood 
body,  the  third  the  scion.  The  momentary  strength  of  the  different  factors 
determines  which  one  of  these  three  actually  produces  the  union  in  a  grow- 
ing graft  or  bud.  The  variations  w^hich  may  be  observed  are  extraordi- 
narily great.  The  quickest  possible  formation  of  wound  callus,  which  takes 
over  the  temporary  closing  of  the  wound,  is  essential  for  the  success  of  the 
graft.  However,  the  union  becomes  permanent  only  if  the  cambial  zone 
{cc)  of  the  strips  (R  L)  which  forms  the  new  wood  and  which  I  have 
occasionally  called  "the  mobile  wound-wall"  occurs  in  permanent  union  with 
the  cambial  zone  (c)  of  the  scion  (or  bud)  and  forms  wood  elements 
remaining  in  a  connected  layer.  The  mobile  wound-wall  shows  the  charac- 
ter of  the  usual  overgrowth  edge  by  its  cambial  zone  which  is  spirally 
twisted  on  the  free  side,  and  distinguished  from  this  overgrowth  edge,  the 
"fixed  wound-wall,"  by  the  large,  inpushed  zone  of  wood  parenchyma  (kg), 
which  passes  out  from  the  fixed  wound-wall.  The  point  of  union  of  the 
cambial  zones  of  stock  and  scion  (or  bud)  is  recognizable  not  only  in  the 
year  of  the  union  but  remains  so  for  many  years,  by  the  course  of  the  wood 
elements.  In  the  line  of  union,  which  extends  from  c  to  cc,  the  elements 
are  more  or  less  strongly  elongated  tangentially,  while  in  the  interior  of  the 
wound-wall  they  have  already  assumed  the  normal  vertical  arrangement 
and,  therefore,  in  cross  section  appear  actually  cut  across  (hh'),  thus  resem- 
bling the  normal  wood  (hh).  If,  in  the  production  of  this  uniting  tissue, 
the  cambial  zone  (c)  of  the  scion  (or  bud)  unites  with  that  of  the  stock  (cc) 
to  form  a  continuous  ring,  it  is  evident  that  this  ring  is  not  everywhere 


837 


equally  distant  from  the  centre  as  in  an  ungrafted  or  unbudded  trunk,  but  at 
z  and  cc  shows  a  deep  depression,  an  S-like  curvature.  This  curved  line  of 
union,  G  dp  pert' s  "line  of  demarcation,"  is  visible  to  the  naked  eye  and  is 
noticeable  even  in  the  bark  covering\ 

In  the  second,  usual  method  of  budding  "with  a  heel,"  the  bud  is  cwf/rom 
the  branch  with  a  little  piece  of  wood  attached  and  is  shoved  into  the  stock. 
In  this  the  processes  of  healing  vary  somewhat  from  those  described  above. 
The  disadvantage  in  this  method  is  a  retarding  of  the  union;  the  advantage, 
however,  lies  in  the  increased  certainty  of  preserving  the  bud.  In  separating 
the  bark  shield  from  the  wood  body, 
for  the  purpose  of  bark  budding,  the 
actual  bud  cone  is  not  infrequently  left 
on  the  branch  if  its  vascular  bundle 
cylinder  has  been  too  greatly  lignified. 
The  bud  on  the  bark  shield  then  has  a 
hole  on  its  underside  and  does  not 
sprout.  Untrained  workers  overlook 
this  little  hole  and  bud  in  vain. 

The  same  process  of  healing,  as  in 
budding  with  a  heel,  is  found  in  hark 
grafting.  Only  in  this  case  the  stock  is 
more  injured  since  it  must  first  be  cut 
square  off,  then  the  bark  on  one  side  is 
split  and  somewhat  raised  for  the  in- 
sertion of  the  scion  as  is  done  in  bud- 
ding. Instead  of  the  single  eye  a  diag- 
onally cut  branch  is  used,  bearing 
several  buds.  The  slanting  cut  surface 
forms  simple  overgrowth  edges,  i.  e. 
fixed  wound-walls,  which  unite  with 
the  mobile  wound-walls  of  the  bark 
strips  of  the  stock  and  the  uniting  tis- 
sue of  its  exposed  wood  surface.  In 
bark  grafting  {"whip  grafting"), how- 
ever, the   stock  has  more  to  do  and 

stores  up  less  reserve  plastic  material,  since  the  part  of  the  cross  section  on 
the  end  surface  of  the  stock  not  covered  by  the  scion  must  also  be  overgrown. 

The  luxuriance,  to  which  the  process  of  coalescence  can  attain  in  bark 
grafting  on  strong  stock,  is  shown  by  the  accompanying  drawing  (Fig.  200), 


nl- 


Fig-.  200. 


Bark  graft  of  Aesculus,  with 
adventitious  buds. 


1  The  difference  between  the  pre.sent  experiments  and  previous  worlt  lies  in  the 
proof  of  the  different  origin  of  the  tissue  of  union  or,  according  to  Goppert,  the  "inter- 
mediary cell  tissue."  He  thinks  that  tlie  production  of  the  tissue  which,  in  common 
with  the  cambium,  takes  over  the  coalescence,  must  come  from  the  medullary  rays, 
while  Hanstein  considers  the  whole  tissue  of  union  to  be  produced  by  the  cambium 
alone.  Actually,  all  elements,  still  capable  of  new  formation,  can  take  part  in  the 
formation  of  the  wound  callus  and  tissue  of  union.  In  many  ti'ees,  for  example, 
good  instances  of  wound  callus  may  be  obtained  which  is  formed  from  the  pith 
body,  particularly  the  pith  crown.      (Tilia.) 


838 

of  the  grafting  of  Aesculus  rubicunda  on  Acsculus  Hippocastanum,  taken 
from  nature.  A  few  weeks  after  the  grafting  the  new  structures  on  the 
inner  side  of  the  bark  strips  («/)  of  the  stock  had  become  so  extensive  that 
they  stood  out  Uke  wings  from  the  scion  and  produced  adventitious  buds  (a) 
on  the  cut  surface. 

Copulation  and  Grafting. 

In  copulation,  the  lower  end  of  the  scion  and  the  upper  end  of  the  stock 
are  cut  slanting,  and,  when  possible,  both  are  of  the  same  size.  The  two 
cut  surfaces  are  so  fitted  to  one  another  that  the  respective  tissues  of  both 
coincide.  Thus  we  have  here  simply  two  surface  wounds.  These  form 
complete  overgrowth  edges  which  push  in  between  the  scion  and  stock. 
When  the  manipulation  is  well  carried  out  and  the  space  between  the  wound 
surfaces  very  small,  the  closing  of  the  wound  is  so  perfect  that  even  the 
microscope  can  show  no  spaces  between  the  old  wood  of  the  cut  surfaces 
and  the  compressed  connecting  tissue.  Goppert  finds  that,  in  copulation,  this 
connecting  tissue  dies  in  a  young  condition  without  disappearing,  while  in 
grafting,  when  the  union  is  complete,  it  remains  for  a  long  time  organically 
active.  In  my  experience,  no  such  difference  dependent  upon  the  method 
used  has  appeared  in  the  length  of  life  of  the  connecting  tissue.  In  older 
cases,  holes  may  indeed  be  noticed,  or  brown,  decayed  masses  of  dead  tissue. 
It  seems  to  me,  however,  that  this  would  occur  in  all  grafting  without  any 
distinction  as  to  method  used,  if  the  wound  by  very  careful  adjustment  of 
stock  and  scion  has  been  closed  by  the  wound  callus  first  produced  without 
any  subsequent  formation  of  woody  parenchymatous  connective  tissue  in 
the  union.  Copulation  may,  therefore,  retain  the  value  and  the  universal 
application  which  it  has  had  up  to  the  present.  However,  I  consider  the 
simplest  form  to  be  the  best  and  the  so-called  English  grafting,  as  well  as 
Thouin's  methods  (Miller,  Kiififner,  Ferrari,  etc.)  disadvantageous  or  even 
injurious  and  trifling. 

Cleft  grafting  may  be  considered  as  the  most  dangerous  operation.  The 
stock  is  usually  cut  off  square  and  split  once,  or  several  times,  deep  into  the 
wood.  The  scion  is  cut  wedge  shape  and  so  clamped  in  the  cleft  that  its 
cambial  zone  forms  the  connection  between  the  two  parts  of  the  cambial  ring 
of  the  stock  separated  by  the  cleft.  In  case  the  wedge-shaped  scion  is  not 
herbaceous,  it  will  on  both  sides  produce  wound  walls  from  the  remaining 
part  of  its  cambium  alone.  This  occurs  also  on  the  split  edges  of  the  stock. 
The  united  connecting  masses  will  endeavor  to  fill  out  the  space  in  the  old 
wood.  On  an  average,  this  succeeds  very  rarely;  in  spite  of  the  grafting 
wax,  moisture  penetrates  into  the  split  from  the  square  cut  surface  of  the 
stock  and  easily  causes  decay  or  allows  some  fungus  to  enter. 

The  process  of  grafting  naturally  does  not  depend  upon  the  existence 
of  a  definite  cambial  zone  but  will  be  possible  also  in  monocotyledons. 
DanieP  gives  an  example  of  this ;  he  carried  out  grafting  experiments  suc- 
cessfully with  Vanilla  and  Philodendron. 

1  Daniel,  L,.,  Greffe  de  quelques  Monocotyledones  sur  elle-s-memes.  Conipt.  rend. 
1S99,  II,  p.  654. 


839 

In  concluding  this  consideration  of  the  healing  processes  of  wounds,  it 
should  be  emphasized  once  more  that  the  decision  as  to  the  relative  value  of 
the  grafting  method  used  refers  here  only  to  axes  at  least  one  year  old  and 
already  provided  with  well  developed  wood.  In  grafting  the  soft  wood  of 
woody  plants,  or  herbaceous  plants,  the  choice  of  method  may  be  governed 
by  purely  practical  considerations.  In  the  coalescence  usually  so  many 
elements  of  the  cut  surfaces  (older  bark  and  wood  elements  in  pith)  partici- 
pate in  the  formation  of  wound  callus  that  a  close  union  takes  place  under 
all  circumstances  favorable  for  the  plant  body,  provided,  of  course,  that  a 
sufficient  relationship  exists  between  scion  and  stock. 

The  Longevity  of  Grafted  or  Budded  Individuals. 

It  cannot  be  denied  that,  aside  from  the  possible  action  of  different 
peculiarities  of  the  two  grafted  parts  on  one  another,  grafting  influences  the 
development  of  the  individual.  As  Duhamel  has  already  emphasized,  the 
tissue  changes  at  the  place  grafted  will  at  any  rate  cause  a  change  in  the 
conductive  capacity.  The  connecting  layer  will  produce  retardation  of  the 
water  conduction  and  an  easier  storing  up  of  the  descending,  plastic  ma- 
terials in  the  part  which  consists  of  wood  parenchyma,  rich  in  starch,  as  also 
later  when  the  connecting  layer  is  formed  from  interwoven  prosenchyma 
elements.     The  results  of  these  changes  have  already  been  discussed. 

The  limit,  up  to  which  different  individuals  can  be  united  with  one 
another  to  form  a  persistent,  normally  functioning  organism,  as  yet  little 
understood,  may  be  determined  by  the  fact  that,  in  general,  only  plants  of 
the  same  natural  families  can  be  grafted  (or  budded)  upon  one  another  with 
any  prospect  of  success.  According  to  all  previous  experience,  this  would, 
however,  represent  the  extreme  limit.  A  sufficient  number  of  examples  are 
known  of  cases  where  members  of  the  same  family  cannot  be  united  perma- 
nently. In  fact,  varieties  of  the  same  family  can  remain  united  for  a  few 
years  and  then  in  the  end  break  the  union,  in  which  case,  as  a  rule,  one  part 
dies.  It  is  probable  that,  aside  from  the  material  relationship,  a  similar 
biological  development  is  absolutely  necessary  in  the  two  individuals  which 
are  to  unite.  I,  therefore,  believe  that  the  different  beginning  and  end  of 
the  vegetative  phases  (leaf  formation,  setting  of  fruit,  etc.)  and  the  different 
amounts  of  water  needed  by  the  individuals  is  very  decisive  for  the  perma- 
nence of  even  those  unions  which  were  successful  in  the  beginning.  Often 
such  cases  of  grafting  remain  fresh  for  many  months  without  any  firm 
union.  In  herbaceous  grafting  of  heterogeneous  varieties,  or  organs,  it  is 
found  that  the  scion  often  continues  growth  and  develops  a  sickly  inflor- 
escence but  finally  dies.  So  far  as  I  have  had  insight  into  this  matter,  no 
union  had  taken  place.  Both  parts  may  have  done  their  best;  all  their 
tissues,  capable  of  developing  further,  can  produce  new  structures  and 
even,  in  places,  a  nominal  wound  callus  but  a  brown  stripe  extends 
between  the  tissue  masses  of  both  parts,  which  shows  at  once  to  which 
individual  the  tissue  in  question  belongs.     The  brown  stripe  is  either  formed 


840 

of  the  swollen  walls  of  the  outermost  cells,  or  caused  by  the  collapse  of  all 
the  cells  of  the  wound  edges.  Usually  on  the  boundary  a  cork  layer  has 
been  formed  by  the  suberization  of  the  walls  of  the  peripheral  parenchyma 
cells  or,  besides  this,  by  the  appearance  of  actual  cork  cells. 

In  genera  which  finally  unite,  as,  for  example,  Iresine  on  Alternanthera, 
it  is  found  that  for  whole  stretches  of  the  grafted  surfaces,  the  connecting 
tissues  grow  side  by  side,  cut  off  from  each  other  by  a  cork  layer. 

Similar  cases  may  be  proved  in  root  grafts  (Bignonia)  and  it  could  be 
observed  in  cleft  grafts  of  Paeonia  arhorea  on  fleshy  roots  of  Paeonia  offici- 
nalis that  the  root,  as  stock,  had  served  only  as  a  receptacle  for  the  scion. 
This  latter  had  formed  roots  without  any  union  with  the  stock. 

Root  grafting  is  in  general  a  very  good  method.  Even  for  our  fruit 
trees  it  had  been  used  by  Sickler  at  the  end  of  the  seventeenth  ( ?)  century 
and  later  Seigerschmidt  in  Mako  recommended  it  very  highly \  Root 
l)ieces,  varying  in  thickness  from  the  size  of  a  quill  to  that  of  one's  thumb, 
seemed  suitable,  if  provided  with  fine  roots.  They  were  cut  in  pieces  eight 
to  twelve  cm.  long,  were  grafted  by  copulation  or  cleft  grafted  and  the  place 
of  union  covered  with  earth  until  only  two  or  three  eyes  extended  above  the 
soil.  Trunks  of  old  seed-  or  stone-fruits  give  an  abundant  material  for 
stock,  when  they  have  to  be  removed.  Of  course,  the  roots  must  be  very 
healthy.  The  method  of  grafting  roses  on  pieces  of  roots  in  January  or 
February  has  been  adopted  already.  For  Clematis  and  other  woody  plants, 
this  method  of  grafting  is  becoming  more  and  more  of  a  favorite. 

It  may  be  presumed  from  the  very  beginning  that  under  certain  cir- 
cumstances which  condition  a  scanty  coalescence,  the  life  period  of  a  graft 
will  be  very  short.  The  question,  whether  the  process  of  grafting  in  itself 
limits  the  life  period,  as  Thouin  and  Goppert  have  stated,  must  be  laid 
aside.  .  It  cannot  be  denied  that  grafted  fruit  trees,  on  an  average,  are 
shorter  lived  than  those  grown-  on  their  own  roots.  It  may  even  be  granted 
that  a  dying  of  the  trees,  as  Goppert  has  observed,  is  initiated  in  the  line  of 
demarcation  by  a  gradual  rotting  of  the  place  of  union  but  it  is  not  credible 
that  this  process  of  rotting  may  be  the  cause  of  actual  death,  or  even  of 
disease,  in  grafted  trees.  It  is  found,  on  the  contrary,  that  even  badly  united 
copulants,  which  at  first  may  have  been  simply  stuck  together  on  one  side, 
can  in  the  end  give  perfectly  healthy  permanent  trunks.  The  old  places  of 
union  have  the  firmest  wood.  A  storm  may  twist  the  trees  off  more  easily 
at  any  other  place  than  at  that  of  the  union.  Goppert's  observations  may 
possibly  hold  as  the  rule  only  in  old  trunks  which  have  been  regrafted  later. 
I  would  explain  the  comparatively  earlier  death  of  grafted  trunks  by  the 
fact  that  not  only  better  but  also  more  tender  cultural  varieties  are  used  for 
grafting.  These,  aside  from  the  disturbances  which  they  undergo  in  the 
cutting,  are  in  themselves  more  susceptible  to  disturbances  in  growth  and 
to  unfavorable  weather  than  the  specimens  grown  from  the  seed,  which 
approach  more  or  less  the  hardier  nature  of  the  stock. 
1  Weiner  Obst-  und  Gartcnzcitung:  1876,  p.  587. 


841 

Mutual  Influence  of  Scion  and  Stock. 

In  regard  to  the  influence  of  the  stock  on  the  scion,  the  experience  of 
practical  growers  has  shown  for  some  time  that  apples  set  on  Paradise 
stock  retain  a  lower  habit  of  growth  and  at  times  bear  fruit  even  in  the  first 
year  after  grafting.  In  the  Doucin  the  forms  become  larger  and  fertility- 
begins  after  a  few  years,  while  the  scion,  on  a  stock  of  Pints  Malus,  attains 
the  usual  tree  form  and  bears  fruit  only  after  a  considerable  number  of 
years.  For  pears,  the  quince  and  Crataegus,  which  love  moist  soils, 
form  the  best  dwarf  stock.  For  exposed  or  dry  positions,  Pirus  Malus 
prunifolia  major,  together  with  P.  M.  baccata  cerasiformis,  the  cherry  apple, 
have  been  recommended  from  several  localities  as  stock  for  apples^  P.  M. 
prunifolia,  originating  in  Siberia,  is  hardy  and  may  be  used  as  a  street  tree. 
It  differs  from  the  variety  of  P.  M.  baccata  by  its  conspicuous,  retained 
calyx.  With  the  variety  of  P.  M.  baccata  belongs  also  P.  M.  cerasiformis, 
which  drops  its  calyx  at  the  time  of  ripening. 

Lindemuth  states,  in  regard  to  the  life  period  of  tree  trunks,  that  varie- 
ties grafted  on  Paradise  stock  seldom  live  more  than  15  to  20  years,  while 
specimens  grafted  on  seedlings  of  true  tree  varieties  of  Malus  can  become 
150  to  200  years  old.  Of  the  remaining  literature,  we  will  mention  the 
following  examples : 

Sour  cherries  grafted  on  sweet  cherries  thrive  less  well  than  sweet 
varieties  on  sour  ones-.  Oberdieck  found  that  sweet  cherries  bore  abun- 
dantly on  sour  cherries. 

Treviranus^  quotes  that  walnut  and  chestnut  trees  of  the  late  sprouting 
varieties  are  said  never  to  succeed  on  early  sprouting  varieties  (according 
to  Cabanis,  Traite  de  la  greffe).  On  the  other  hand,  in  seed  fruits,  this 
method  of  grafting  later  varieties  on  early  ones  is  said  to  have  good  results 
and  to  bring  about  an  earlier  ripening  of  the  fruit*.  In  peaches,  grafting 
in  itself,  whether  of  early  varieties  on  late  varieties,  or  conversely,  seems 
to  give  good  results.  Gauthier  reported  to  the  Parisian  Societe  cent,  d' 
Horticulture^  that  he  had  grafted  peaches  in  August  or  September  on  typical 
fruit  spurs  {coiirsonnes) ,  as  well  as  on  those  which  have  elongated,  both 
late  varieties  on  early  varieties,  and  conversely.  The  fruits  are  said  to 
become  larger  because,  in  the  tree  which  is  grafted  with  a  late  ripening 
variety,  the  fruit  of  the  stock  can  be  harvested  first  and  then  the  tree  can 
use  its  remaining  strength  to  mature  the  fruit  on  the  branches  of  the  grafted, 
late  variety.  In  the  opposite  cases,  of  grafting  on  late  varieties,  the  whole 
tree  becomes  stronger  because  late  varieties  in  general  have  a  more  luxuriant 
habit  of  growth. 


1  Lieb,  Pyrus  Malus  prunifolia  major.     Pomolog-.  Monatshefte  1S79,  p.  130. 

2  Lindemuth,     Veg-etative     Bastarderzeugung     durch     Impfung-.       Landwirtsch. 
.Tahrbiicher  1S78,  Part  6. 

3  Treviranus,  Physiologie  der  Gewachse  II,  1838,  p.  648  ff. 

4  V.  Ehrenfels,  tJber  die  Krankheiten  und  Verletzungen  der  Friicht-   und  Gar- 
.tenbaume.     Breslau  1795,  p.  108. 

5  Ortgies,   Vorteilhaftes   Pfropfen   von    Pfirsichbaumen.     Pomolog.    INIonatsliefte 
V.  Lucas  1879,  p.  61. 


842 

An  older  example  from  Duhamel^  should  be  mentioned  in  this  connec- 
tion. Almonds  grafted  on  plums  and,  conversely,  plums  on  almonds,  at 
first  grow  very  well  but  usually  retrogress  after  one  or  several  years.  The 
almond  has  a  much  more  luxuriant  habit  of  growth,  sprouts  earlier  in  the 
year  and,  as  scion,  forms  a  strong  roll  at  the  place  of  grafting.  It  is 
probable,  therefore,  that  such  a  scion,  requiring  more  water  earlier  and 
constantly,  will  thrive  on  a  less  luxuriant  stock  as  long  as  this  is  able  to 
satisfy  the  young  twigs  from  its  reserve  store  in  the  trunk.  If  the  grafted 
branch  becomes  several  years  old,  its  needs  become  greater  and,  if  it  cannot 
accommodate  itself  to  the  stock,  as  frequently  occurs  (dwarf  trees  of  seed 
fruits),  it  gradually  degenerates  from  a  lack  of  nutriment.  The  results  vary 
greatly,  according  to  soil,  amount  of  water  and  variety.  Conversely,  a 
stock  which  blossoms  too  early  and  grows  too  luxuriantly  will  supply  more 
to  a  scion,  requiring  a  lesser  amount,  than  this  can  take  up.  The  super- 
fluous material  from  the  stock  is  quickly  worked  over  into  new  structures. 
If  many  groups  of  buds  are  present,  this  excess  manifests  itself  in  the  pro- 
duction of  long  shoots.  If,  however,  as  in  grafting,  most  of  the  lateral 
buds,  or  eyes,  are  suppressed,  the  material  remains  at  the  disposal  of  the 
thickening  ring  of  the  trunk.  Thus,  instead  of  prosenchymatous  elements, 
aggregations  of  wood  parenchyma  are  formed,  which,  in  the  Amygdalaceae, 
easily  become  gum  centres  as  I  also  have  observed.  Among  the  older 
observers,  Duhamel  reports  that  almond  stock,  grafted  with  plum  scions, 
will  die  from  gummosis  at  the  place  of  grafting. 

Experience  has  also  taught,  in  the  very  general  practice  of  grafting 
pears  on  quince  or  apples  on  Paradise  stock,  that  death  sets  in  the  more 
quickly  for  rapid  growing  scions,  the  drier  the  soil  and  the  fewer  the  roots 
which  the  stock  has  developed  in  it.  The  scions  fail  much  the  more  rapidly. 
Duhamel  also  cites  cases  when,  under  such  disproportionate  need  of  water 
in  scion  and  stock,  even  simple  transplanting  has  led  to  death  through  failure 
of  union  (almonds  on  plum  stock),  while  the  little  trees  of  the  same  series, 
left  standing  in  the  nurseries,  remain  healthy.  The  pruning  of  the  roots 
in  transplanting  has  decreased  too  greatly  the  momentary  capacity  of  water 
absorption  in  the  stock.  Peaches  on  prune  stock  are  also  said  to  give  no 
especially  permanent  union-.  The  wood  of  the  scion  is  said  to  turn  red  and 
soon  degenerate.  I  would  add  here  an  experiment  with  the  grafting  of 
raspberries  on  Rosa  canina^.  Among  rubus  scions  grafted  by  copulation, 
I  found  two  branches  developing  on  one  specimen,  one  of  which  bore  four 
normal  raspberries.  In  the  autumn,  however,  the  scion  died  and,  upon  inves- 
tigation, the  coalescence  was  found  to  have  been  very  slight.  On  the  upper 
part  of  the  surface  of  copulation,  only  the  stock  had  developed  cicatrization 
tissue.  On  the  other  hand,  on  the  lower  part  of  Rosa,  as  on  Rubus,  abundant 
wound  callus  had  been  formed,  showing  normal  processes  of  coalescence. 


1  Duhamel  du  Monceau,  La  physique  des  arbres  1758,  II,  p.  89. 

2  Pomolog.  Monatshefte  1879,  p.  370. 

3  Sorauer,  P.   Rubus  auf  Rosa.     Zeitschr.  f.  Pflanzenkrankh.  1S9S,  p.  227. 


843 

Evergreen  foliage  seems  to  be  no  hindrance  to  growth  on  deciduous 
stock.  Scions  of  Prunus  laurocerasus  on  Pr.  Padus,  of  Quercus  Ilex  and 
Q.  Subcr  on  Q.  sessiliflora,  of  Cedrus  Libani  on  Larix  curopaea  are  said  to 
thrive  but  there  is  no  report  as  yet  as  to  a  favorable  growth  of  deciduous 
wood  on  evergreen  stock.     Thouin  contradicts  the  former  statement\ 

Of  the  noteworthy  results  of  Duhaniel's  experiments,  it  should  be  men- 
tioned here  that,  for  example,  the  fruit  of  the  winter  Christ  pear  on  quince 
had  a  more  delicate,  juicier  flesh  and  a  finer,  deeper  colored  skin,  as  con- 
trasted with  scions  grafted  on  wild  stock.  Leclerc  du  Sablon^  observed 
that  pears  grafted  on  pears  store  up  less  reserve  substances  in  their  aerial 
parts  than  when  grafted  on  quince  stock,  while  the  roots  are  poorer  in 
reserve  substances.  This  latter  fact  might  be  explained  by  the  greater  fer- 
tility after  grafting  on  quince  stock. 

It  is  remarkable  that  pears  and  apples,  which  form  so  perfect  a  union 
with  remotely  related  stock,  can  never,  or  rarely  ever,  be  brought  to  form  a 
permanent  union  with  each  other.  Numerous  experiments  have  been  made 
in  this  connection.  Thus  Knight"  reports  a  case  of  apple  on  pear  stock, 
which  for  one  year  yielded  an  abundant  harvest  but  died  the  following 
winter.  The  fruit  is  said  to  have  had  blackened  cores,  not  containing  a 
single  seed.  Recent  observers  have  affirmed  this  fact  in  general,  but  em- 
phasize the  fact  that  exceptions  may  occur.  Thus  Stoll*  reports  that  apple 
scions  took  well  on  pear  trees  and  bore  very  soon  but  the  fruit  was  small  and 
the  graft  usually  died  in  the  fourth  year.  The  head  gardener,  Seifert,  in 
Segeberg  (Holstein)  describes  a  five  year  old  apple  graft  on  pear  stock 
which  in  the  fourth  year  had  borne  six  well  developed  apples  (Ribston 
Pippin).  The  apples  had  a  good  flavor  but  the  crown  of  the  tree  had  a 
weak  growth.  I  have  known  of  some  favorable  results  from  pear  grafts  on 
apples.  In  Czerwentzitz,  near  Ratibor,  many  examples  were  found  of  pears 
which  had  been  grafted  on  apples.  The  method  was  in  use  at  least  ten  years 
ago.  In  the  first  experiment  (Geisshirten  pear  on  apple)  it  was  found  that 
after  the  second  year  the  fruit  from  pears  on  apple  stock  ripened  two  weeks 
earlier  than  on  the  main  trunk.  The  scion  lived  eight  years.  Less  vigorous 
stock  gave  no  good  results.  Most  varieties,  to  be  sure,  remained  alive  but 
made  no  growth.  When  the  same  grafting  was  repeated  on  the  middle 
branches  of  the  crown,  a  number  of  specimens  died  after  two  or  three  years. 
The  others  lived  in  a  weak  condition  for  some  time  without  setting  fruit.  A 
note  by  Gillemot''  originates  from,  this  period.  He  had  two-year-old  pear 
grafts  on  apple  stock  and  also  had  grafted  cherry  scions  (Royal  Amarelle) 
in  the  bark  of  a  plum  (Prunia  institita).     The  scions  developed  very  long 

1  Thouin,  Monographie  des  Pfropfens.     Berg-'s  translation,  1S24,  p.  114. 

2  Leclerc  du  Sablon,  Sur  I'influence  du  sujet  sur  le  greffon.     Compt.  rend.  1903, 
CXXXV.  p.  623. 

3  Hort.  Transact.  II,  p.  201. 

4  Stoll,   Das  Veredeln  von  Birnen   auf  Apfeln.     Wiener   Obst-    und  Gartenzeit. 
1876,  p.  10. 

5  Gillemot,    Beitrag-    ziir   Veredlung-   verschiedenartig-er    Gewachse    aufeinander. 
Wiener  Obst-  u.  Gartenzeit.  1S76,  p.  121. 


844 

fchoots  and  bore  comparatively  many  and  handsome  fruits  in  the  second  year 
but  died  after  bearing. 

Up  to  the  present,  such  experiments  have  been  repeated  on  all  sides  but 
as  yet  no  further  desirable  results  have  been  attained  than  those  known  for 
a  long  time  in  regard  to  the  use  of  dwarf  stock.  In  some  cases  it  was 
evident  that  the  manner  of  grafting  decided  the  success.  Thus,  for  example, 
Carriere^  reports  that  the  varieties  of  pears  Bon  chretien  Rans,  Doyenne  de 
Juillet,  Beurrc  Gifford,  Beurre  Box.  did  not  grow,  or  died  soon  after  pro- 
ducing weak  shoots,  if  they  were  budded  on  quince  {greffe  en  ecusson).  On 
the  other  hand,  the  results  are  considerably  more  favorable,  if  cleft-grafting 
is  adopted  and  branch  tips  used  as  scions.  The  fertility  is  unusually  great. 
Ligustrum  ovalifolium  as  stock  is  also  said  to  behave  differently  with  differ- 
ent varieties  of  lilac.  Only  Syringa  Josikea  is  said  to  succeed  when  budded 
(greffe  en  ecussion)  while  Syringa  Emadi  persica  and  others  develop  well 
only  when  cleft  grafted  (greffe  en  fente). 

Recently  special  attention  has  been  given  this  question  in  the  grafting  of 
grapes  because  of  the  struggle  against  the  grape  louse.  The  number  of 
works  on  this  subject  is  very  great,  so  that  we  call  attention  only  to  a  few 
important  ones.  First  of  all  Couderc-  determined,  by  questioning  about  450 
French  grape  growers,  that  even  the  power  of  resistance  of  an  American 
stock  to  the  attack  of  the  grape  louse  is  usually  somewhat  reduced  by  graft- 
ing and  also  that  the  different  varieties  used  as  scions  exercise  an  influence 
varying  in  intensity. 

Cases  occur,  however,  in  which  a  very  vigorous  scion  can  increase  the 
power  of  resistance.  Ravaz'',  among  others,'  lays  especial  emphasis  on  the 
fact  that  the  stock  influences  the  growth  of  the  scion  and  also  its  fertility. 
We  owe  to  Hotter*  precise  figures  on  the  changes  in  grapes,  due  to  the  influ- 
ence of  the  stock.  He  investigated  different  varieties  of  grapes  grown  on 
vines  grafted  on  Riparia  and  on  self  roots  of  vines  of  the  same  varieties. 
Among  9  varieties,  yy  per  cent,  of  the  juice  from  the  grafted  vines  contained 
more  acid  than  that  from  the  non-grafted  vines,  of  which  65  per  cent,  con- 
tained more  sugar  than  those  grafted  on  American  stock.  These  statements 
are  directly  opposite  to  those  of  CurteP,  who  found  the  fruit  of  grafted 
vines  larger,  the  skin  thinner  and  the  seeds  less  numerous  but  larger.  The 
juice  was  richer  in  sugar  than  acid,  poorer  in  ash  elements,  especially  phos- 
phates, richer  in  nitrogenous  elements  but  poorer  in  tannin.  We  have 
purposely  cited  both  observations  in  order  to  show  how  differently  the  stock 


1  Carri^re,  Quelques  observations  a,  propos  de  la  greffe.  Revue  hort.  1876,  II, 
p.  208. 

2  From  the  Weinbau-Kong-ress  of  the  16th  to  19th  of  August,  1894  in  Lyon;  cit. 
Zeitschr.  f.  Pflanzenkrankh.  1895,  p.  118. 

3  Ravaz,  L.,  Choix  des  porte-greffes.  Revue  de  viticulture  1895,  Nos.  100, 
105,  106. 

■1  Hotter,  E.,  Der  Einfluss  der  amerikanischen  Unterlagsreben  auf  die  Qualitat 
des  Weines;  cit.  Centralbl.  f.  Ag-rikulturchemie  1905,  p.  625. 

5  Curtel,  G.,  De  I'influence  de  la  greffe  sur  la  composition  du  raisin.  Compt. 
rend.  1904.    Vol.  CXXXIX,  p.  491. 


,845 

can  act.     We  find  further  experiences  reported  in  the  Memoirs  of  the  Im- 
perial Department  of  Health  in  Berlin. 

Thus,  for  example,  the  twenty-fifth  Memoir  confirms  the  above  men- 
tioned observation  that  the  American  vine,  when  grafted,  loses  in  power  of 
resistance  to  the  grape  louse,  jaundice,  etc^. 

In  regard  to  the  technic  which  has  come  into  use  in  grafting  grapes,  we 
will  follow  Schmitthenner's-  statements.  He  emphasizes  the  fact  that,  at 
present,  the  so-called  English  tongue  grafting  is  almost  universally  used. 
This  is  a  form  of  splice  grafting  in  which  the  diagonal  cut  is  not  long  but  the 
cut  surface  of  graft  and  stock  have  also  an  axial  incision.  The  scion  is  split 
and  shoved  into  the  cleft  of  the  stock  so  that  scion  and  stock  dovetail.  Ana- 
tomical investigation  shows  that  in  grafting  grapes  the  activity  of  the 
cambium  is  more  reduced  than  in  any  other  form  of  grafting;  the  annual  ring 
formed  after  grafting  is  much  weaker  than  the  normal  one.  The  influence 
of  the  wound  is  much  more  considerable  than  in  grafting  other  woody  plants 
and  extends  even  to  the  next  node,  since  all  the  ducts  are  filled  with  corky 
tyloses  containing  wound  gum. 

Tompa^  had  already  given  detailed  anatomical  data  on  grafting  grapes 
in  a  herbaceous  condition.  However,  the  grafting  of  grapes  will  be  com- 
pletely efifective  only  if  one  uses  as  stock,  not  the  American  varieties,  but 
hybrids  of  those  which  are  adapted  to  the  various  localities'*. 

Since  the  end  of  the  last  century,  the  formation  of  hybrids  by  grafting 
has  been  better  understood.  The  best  known  example  is  Cytisus  Adami 
which  is  said  to  have  come  from  the  grafting  of  Cytisus  purpureus  on  Labur- 
num vulgar e  and,  at  times  sirice  1826,  has  produced  on  different  branches 
sometimes  the  blossoms  of  one  variety,  sometimes  those  of  the  other. 
According  to  A.  Braun°  the  retrogression  did  not  appear  until  sixteen  years 
after  the  grafting.  Laubert"  found  that  retrogressive  formation  should  be 
ascribed  to  a  bud  variation,  in  which  the  branch  form,  representing  Cytisus 
purpureus,  also  completely  resembles  anatomically  the  true  variety.  Bei- 
jerinck''^  found  that  this  bud  variation  could  be  incited  often  by  wound 
stimulus. 

The  description  of  a  different  example  was  published  in  1875^.  In  an 
English  grape  house,  a  vine  which  had  been  grafted  with  Black  Alicante  was 
re-grafted  some  time  later  with  three  varieties  on  the  Black  Alicante  as 


1  Funfundzwanzigste  Denkschrift  betreffend  die  Bekampfung-  der  Relilaiis- 
krankheit.     Bearbeitet  im  Kaiserl.  Gesundheitsamte  bis  October  1,  1903. 

2  Schmitthenner,  F.,  Verwachsungsersclieinung-en  an  Ampelopsis-  und  Vitis- 
Veredlung-en.  Internat.  pliytopath.     Dienst.  1908,  No.  1. 

3  Tompa,  A.,  Soudure  de  la  greffe  herbacee  de  la  vig-ne.  Annal  Instit.  ampelo- 
logique  hongrois  1900,  Vol.  I,  No.  1. 

4  Teleki,  Andor,  Die  Rekonstruktion  der  Weingarten  usw.  Wien  und  Leipzig, 
Hartlebens  Verlag,  1907. 

5  Bot.  Jahresber.  1873,  p.  537. 

6  Laubert,  R.,  Anatomische  und  morphologische  Studien  am  Bastard  Labur- 
num Adami.  Poir.     Bot.  Centralbl.     Supplementary  Volume  X,  Part  3. 

"^  Beijerinck,  M.  W.,  Beobachtungen  iiber  die  Entstehung-  von  Cytisus  purpureus 
aus  Cystisus  Adami.     Ber.  d.  Deutsch.  Bot.  Ges.  1908,  Part  2,  p.  137. 

8  Grieve,  Culford,  Bury  St.  Edmunds,  Singular  Sport  of  a  Grape  Vine.  Gard. 
Chron.  1875,  p.  21. 


846 

stock.  One  of  these  three  varieties,  together  with  a  small  piece  of  its  stock, 
was  cut  ofif  later.  Immediately  a  sprout,  standing  near  the  centre  of  the 
branch  of  the  second  inserted  variety  (Trebbiano)  showed  a  spur  with 
grapes  which  resembled  absolutely  the  variety  (Golden  Champion)  which 
had  been  removed.  On  either  side  of  this  abnormal  spur,  the  Trebbiano 
stock  bore  its  characteristic  fruit.  Therefore,  no  other  hypothesis  remains 
possible  than  that  the  Champion  variety,  which  had  been  removed,  had 
exercised  an  influence  backward  into  the  stock  (Black  Alicante)  and 
through  this  to  the  laterally  grafted  Trebbiano  variety. 

Lackner  has  cited  another  remarkable  and  older  case\  He  found  in 
the  garden  Palavicini  near  Genoa,  under  the  name  Maravilla  di  Spana,  an 
orange  (Bigardia  hisarro  Riss.)  which,  on  parts  of  its  outer  surface,  showed 
callus  excrescences  and  corresponding  ones  in  the  flesh,  resembling  in  places 
a  lemon,  in  others  an  orange  and  sometimes  candied  lemon  peel.  It  has  been 
proved  that  this  form  originated  about  1640  when  a  gardener  in  Florence 
grafted  some  stock  but  the  scion  did  not  take.  Directly  beneath  the  place 
grafted,  however,  a  branch  appeared  which  bore  this  very  remarkable  fruit. 
The  blossoms  are  likewise  different,  some  being  white,  others  red. 

In  1873  the  "Revue  horticole"  published  a  case  in  which  a  Mr.  Zen  had 
bred  new  rose  varieties  by  grafting.     These  varieties  remained  true. 

Focke-  mentions  a  white  moss  rose  which  had  been  grafted  on  a  red 
Centifolia.  Such  a  plant  developed  bottom  shoots  which  bore  some  white 
moss  roses,  some  Centifolia  and  also  moss  roses  with  partly  red  petals. 
Besides  the  roses  here  described,  Pirus,  Begonia,  Oxyria  and  Abies  have  also 
been  named  as  genera  in  which  graft  hybrids  can  occur. 

Daniels  found  a  backward  action  of  the  scion  on  the  stock  in  one  in- 
stance in  which  old  pears,  grafted  on  quince,  had  been  sawed  off  2  m.  above 
the  surface  of  the  soil.  Branches  developed  from  these  naked  stumps,  some 
bearing  normal  quince  leaves,  others  mixed  forms,  between  quince  and  pear''. 
This  same  author,  in  collaboration  with  Jurie,  cites  similar  instances  in 
grafted  grapes.  Of  these,  however,  Ravaz*  has  proved  that  such  variations 
also  occur  in  non-grafted  vines.  Such  cases  of  interchange  occur  often ; 
there  is  always  a  tendency  to  trace  formal  differences  back  to  the  special 
influence  of  the  grafting,  which,  in  fact,  are  only  variations  in  luxuriant 
branches.  Such  variations  appear  also  after  severe  pruning  of  the  older 
axes.  We  need  recall  only  the  manifold  leaf  forms  on  the  bottom  shoots  of 
Morus,  Populus,  etc.,  after  the  trunks  have  been  sawed  off. 

The  majority  of  errors  occur  in  grafting  experiments  on  herbaceous 
plants.     For  this  we  have  also  examples  by  Daniel^  who  grafted  turnip 

1  Lackner,  Einfluss  des  Edelreises  auf  die  Unterlage  bei  Orangen.  Monatsschrift 
d.  Ver.  z.  Bef.  des  Gartenbaues  v.  Wittmark  1878,  p.  54. 

2  Focke,  Die  Pflanzen-Mischling-e.  Ein  Beitrag-  zu  Biologie  der  Gewachse.  Bot. 
Centralbl.  1880,  p.  1428. 

3  Daniel  L.  Un  nouvel  de  la  greffe.    Compt.  rend,  1903,  Vol.  XXXVII. 

4  Ravaz,  L.,  Sur  les  variations  de  la  vigne  grefCee;  response  a,  M.  L.  Daniel. 
Montpellier  1904. 

5  Daniel  L.,  Creation  des  variet#s  nouvelles  au  moyen  de  la  greffe.  Compt.  rend. 
1894,  I,  p.  992. 


847 

rooted  cabbages  on  Alliaria  and  this  on  the  green  cabbage.  He  found  mor- 
phological and  anatomical  differences  in  the  plants  produced  from  the  seed 
of  the  grafted  specimens.  Under  this  head  belong  also  potato  grafting 
experiments  and  the  grafting  of  Solanum  Lycopersicum  on  potatoes.  In 
regard  to  the  grafting  of  various  Solanaceae  on  each  other  there  exist  very 
many  experiments  which  we  have  described  more  fully  in  the  second  edition 
of  this  manual  (cf.,  p.  692  ff).  The  most  thorough  experiments,  continued 
up  to  the  present  time,  are  those  by  Lindemuth,  whose  investigations  have 
been  considered  under  the  section  on  Albinism  (cf.,  p.  677  ff).  Molisch^ 
has  repeated  earlier  experiments  and,  agreeing  with  Strasburger  and 
Vochting,  has  arrived  at  the  conclusion  that  the  production  of  graft  hybrids 
may  well  be  explained  theoretically  but  has  not  actually  been  satisfactorily 
proven  since,  as  he  says,  he  and  the  others  had  found  that  scion  and  stock 
always  retain  their  morphological  character. 

We  are  not  able  to  share  this  point  of  view  since  Lindemuth's-  latest 
experiments,  as  well  as  those  of  E.  Baur,  sufficiently  demonstrate  the  influ- 
ence of  the  scion  on  the  stock.  Nevertheless,  bud  variations  in  many  cases 
are  also  found  which  have  nothing  to  do  with  the  material  influence  of  the 
scion  on  the  stock  but  are  probably  traceable  to  wound  stimulus.  Arrest- 
ment phenomena  of  very  dift"erent  kinds,  as,  for  example,  increased  pressure 
in  the  bud,  can  initiate  a  different  development  of  the  young  axis. 

The  influence  of  the  stock  on  the  scion  is  a  well  known  fact  in  horticul- 
ture. We  will  recall  only  the  different  effect  of  the  stock  on  one  and  the 
same  apple  variety.  Grafted  on  Doucin,  a  stronger  wood  growth  and  a 
later  fertility  was  produced,  on  Paradise  stock  a  lesser  wood  growth  and  an 
earlier  setting  of  fruit.  No  general  rule  may  be  laid  down.  The  result 
depends  not  only  on  the  plant  variety  but  also  on  the  accessory  conditions 
(age,  habitat,  form  of  nutrition,  etc.). 

The  Natural  Processes  of  Coalescence. 

Very  frequently  we  find  in  hedges  the  union  of  two  branches,  which 
oftentimes  have  grown  toward  each  other  from  opposite  directions*.  The 
same  phenomenon  may  be  observed  in  roots  in  dense  tracts  of  trees. 

The  root  fusions  can  take  place  in  a  young  stage  of  the  organ  at  a  time 
when  the  epidermis  is  still  capable  of  division.  According  to  Franke^  this 
process  appears  in  the  ivy  {Hedera  Helix)  and  the  wax  flower  {Hoy a  car- 
nosa),  in  both  of  which  plants  the  epidermal  cells  of  two  adjacent  roots 
grow  toward  each  other  like  papillae  and  unite.  These  cells  then  divide  and 
thereby  produce  a  few  layers  of  connecting  tissue.  This,  however,  does  not 
have  the  firmness  of  the  connecting  tissue  produced  from  the  cambial  zone 


1  Molisch,  H.,  tJber  Pfropfung-en.     Lotos  1896;  cit.  Bot.  Jahresber.  1S97,  I,  p.  155, 

2  Lindemuth,  H.,  Kitaibelia  vitifolia  Willd.  mit  g-oldg-elb  marmorierten  Blattern! 
Gartenflora  1889,  p.  431.    tJber  Veredlung-sversuche  mit  Malvaceen.     Ibid.  1901,  No.  1. 

3  Franke,  Beitrage  z.  Kenntnis  der  Wurzelverwachsung-en.  Beitrage  z.  Biologie 
der  Pflanzen  von  F.  Cohn,  VoL  III,  Part  3;  cit.  Bot.  Centralbl  1SS2.  Vol  X  No  11 
p.  401.  '         ■       ' 


848 

in  two  bark-covered  roots  of  older,  woody  plants.  The  same  process  sets  in 
here  as  in  the  union  of  aerial  organs.  The  bark  on  the  surfaces  of  contact 
is  sometimes  pushed  toward  the  outside,  sometimes  enclosed  like  little 
islands ;  the  cambium  no  longer  increases  where  the  pressure  makes  itself 
felt  on  the  places  of  contact,  but  unites  from  a  common  layer,  enclosing  both 
roots.     Each  year,  when  properly  nourished,  this  layer  forms  new  wood 

layers  above  the  place  of  union. 
In  regard  to  the  anatomical 
conditions  in  the  coalescence  of 
tree  trunks,  we  will  refer  to 
Kiister's  different  works^  and 
will  mention  here  only  one  rare 
case  which  we  have  observed 
personally.  This  was  found  in 
the  Ellguther  forest,  near  Pros- 
kau,  in  a  pine ;  at  several  places 
(ju  its  trunk  a  second,  thinner 
trunk  had  grown  fast  by  natural 
in-arching. 

The  base  of  the  weaker 
tree  had  been  cut  off  many  years 
before  so  that  the  trunk  was 
obliged  to  draw  its  nourishment 
entirely  from  the  older  pine.  At 
the  time  observed,  they  were 
perfectly  healthy,  and  formed  a 
common  crown;  only  it  seemed 
to  me  that  the  in-arched,  root- 
less trunk  bore  somewhat 
shorter  needles. 

I  possess  a  piece  of  the 
trunk  of  another  pine  in  which 
the  tip  of  a  branch,  possibly  five 
cm.  in  diameter,  had  bored  into 
the  main  axis  and  there  disap- 
peared entirely.  This  is  an 
example  of  so-called  "handled 
trees." 

All  processes  of  this  kind 
arise  from  the  ability  of  the  cambial  tissue  to  form  connecting  layers  between 
different  axes.  The  processes  differ  from  grafting  only  in  the  previous 
separation  of  the  cambial  layers  by  the  bark  of  the  plant  parts;  these  layers 


FiS-    -01.     Pine    iruin    tlie    Ellguther    I'oie.st    in 

which   one  trunk  has  continued  to   nourish  a 

second,    rootless    one    connected    by    natural 

grafting-. 


1  Kiister,  E.,  tjber  Stammverwachsungen.  Jahrb.  f.  wiss.  Bot.  Vol.  XXXIII, 
Part  3. — Pathologische  Pflanzenanatomie.  Jena  1903,  Gustav  Fischer,  p.  173,  Section 
Wound  Wood. 


849 

unite  later.  The  bark  must  have  been  removed  by  gradual  rubbing.  If  the 
union  of  the  axes  takes  place  of  itself,  a  connected  wood  covering  is  depos- 
ited each  year  over  the  place  of  union.  Often  rather  larger  brown  pieces  of 
dead  bark  are  incorporated  in  the  surface  of  the  union.  This  may  be 
explained  by  the  uneven  formation  of  the  two  axes  which  have  come  in 
contact.  If  two  trunks,  covered  with  bark  scales,  touch  each  other,-  the 
most  prominent  places  are  rubbed  down  first  and  unite,  while  more  deeply 
lying  hollows  do  not  participate  in  the  union  but  are  enclosed  by  the  new 
tissue. 

In  forests  and  especially  spruce  and  pine  tracts,  tzvin  trunks  are  fre- 
quently met  with,  which,  beginning  at  the  base,  had  united  for  different 
distances.  Less  frequent  are  the  cases  in  which  the  upper  parts  of  the  main 
axes  of  separate  origin  have  grown  together. 

A  cross  section  of  the  base  of  a  twin  trunk  often  shows  three  centres. 
In  conifers,  the  middle,  third  stem  has,  as  a  rule,  become  very  resinous.  At 
any  rate,  the  top  of  the  main  axis  was  broken  oi^  when  young  and  two 
lateral  eyes  have  taken  over  the  growth.  Instead  of  forming  horizontal 
branches,  these  have  developed  into  two  top  shoots  which,  after  a  consider- 
able number  of  years,  have  suppressed  the  dying  main  axis  and  finally  over- 
grown it.  Their  overgrowth  edges  have  gradually  united  so  that,  finally, 
one  single,  united  cylinder  has  come  from  the  three  axes. 

According  to  the  experiments  mentioned  under  grafting,  it  may  be 
assumed  as  a  definite  fact  that  a  union  can  take  place  between  parts  of  indi- 
viduals of  different  kinds.  Spruces  and  firs,  apples  and  pears,  with  each 
other  and  on  quinces,  or  almonds  and  plums,  and  the  like,  may  serve  as 
examples  well  known  to  all.  Nevertheless,  a  limit  in  the  relationship  of  the 
plants  certainly  exists  here,  beyond  which  actual  coalescence  cannot  take 
place  in  spite  of  the  closest  contact  and  vigorous  rubbing.  To  be  sure,  a 
whole  list  of  reports  on  the  union  of  very  heterogeneous  plants  may  be  found 
in  the  literature  on  this  subject  but  a  part  of  these  statements  is  based  cer- 
tainly upon  erroneous  observations^  in  which  union  was  assumed  where  only 
overgrowth  took  place. 

Having  so  fully  described  the  processes  of  wound  healing,  we  may  here, 
without  being  misunderstood,  express  the  opinion  that  the  apparently  rigid 
wood  body  of  a  tree  may  be  caused  to  take  on  all  imaginable  forms  if  the 
tissue  produced  from  the  cambium  is  confined  in  some  way.  It  can  be  said 
figuratively  that  the  wood  trunk  flows  about  any  ob j  ect  standing  permanently 
in  the  way  of  its  growth  in  thickness ;  it  grows  over  it  and  can  enclose  it 
entirely.  Examples  of  so-called  encysted  stones,  fir  cones  and  even  animal 
mummies  have  frequently  been  observed. 

We  can  here  omit  the  enumeration  of  special  cases,  since  we  now 
possess  a  number  of  most  interesting  books  about  remarkable  trees  and  all 


1  Moquin    Tandon,    Pflanzen-Teratologie,    Schauer's    translation,    1S42,    p.    274. 
Masters,  Vegetable  Teratology  1869,  p.  55. 


850 

kinds  of  botanical  nature  curiosities.  The  one  by  Ludwig  Klein^  may  be 
the  most  instructive  at  present.  This  seems  especially  fitted  to  arouse  and 
increase  a  love  of  trees  by  its  more  than  200  illustrations,  made  from  photo- 
graphic exposures. 

Wound  Protection. 

^^'e  have  already  partially  discussed  natural  wound  protection  in  so  far 
as  it  is  produced  by  cork  formation.  In  the  wood  body  of  trees,  however, 
no  cork  deposit  is  found  rapidly  covering  the  surface  of  the  wound,  but  the 
vessels  in  all  such  places  are  filled  with  tyloses  or  a  gummy  substance 
(zvoiind  gum)  usually  easily  soluble  in  boiling  nitric  acid  (dissolved  with 
difficulty  in  the  Correae).  This  is  found  when  healthy  wood  adjoins  the 
dead  wood.  As  a  rule,  the  tyloses  are  accompanied  by  some  gum  formation. 
Both  kinds  of  filling  make  the  wood  of  the  branch  stump  absolutely  imper- 
vious to  water  and  air  and  quickly  close  the  wound  within  the  period  of 
growth.  It  is  evident  from  this  observation  that  we  would  do  well  to  thin 
our  trees  in  winter  shortly  before  cambial  activity  begins". 

In  a  great  number  of  woody  plants,  the  vessels  and  frequently  many 
of  the  other  wood  elements  are  filled  with  calcium  carbonate''.  This  is 
found,  as  a  rule,  in  the  heart  wood  and  those  tissues  of  which  the  cells  have 
a  chemical  and  physical  constitution  resembling  heart  wood,  such  as  the  pith 
enclosed  by  the  heart  wood  and  the  dead,  discolored  wood  of  knots  and 
wounds.  This  filling  is  usually  so  complete  that,  after  such  pieces  of  wood 
have  been  burned,  solid  calcium  casts  of  the  cells  are  found  which  had  con- 
tained the  carbonate.  The  process  may  be  explained  as  follows :  whenever 
opportunity  is  afforded,  the  soil  water,  containing  the  calcium  in  the  form  of 
bi-carbonate,  quickly  passes  through  the  wood  cells  and  vessels,  and  gives 
off  carbon  dioxid ;  it  also  deposits  the  calcium,  which  is  no  longer  soluble, 
as  a  precipitate  on  the  inner  side  of  the  vessels.  In  living  heart  wood  which, 
unlike  the  growing  sapwood,  cannot  quickly  work  over  the  calcium  salt,  each 
increase  in  temperature  will  cause  the  giving  off  of  carbon  dioxid  and  induce 
the  precipitation  of  calcium.  In  wounds,  the  carbon  dioxid  will  likewise 
disappear  because  of  the  exposure  of  the  tissue.  While  the  sapwood,  which 
deposits  no  lime,  protects  itself  from  the  entrance  of  air  by  the  formation  of 
tyloses  or  gum  (probably  as  the  result  of  the  entrance  of  air  into  vessels 
previously  filled  with  sap)  we  find  in  heart  wood  a  deposition  of  lime  as  a 
means  of  protection. 

In  the  normal  trunk,  the  formation  of  heart  wood  occurs  first  in  the 
advance  stages ;  after  injury,  however,  it  sets  in  at  once  and  gives  rise  to  the 


1  Klein,  Ludwig,  Bemerlvonswcrte  Baiime  im  Grossherzogtum  Baden.  Heidel- 
berg 1908.     Winter's  Univcrsitatsbuchhandlung-. 

2  Bohm,  Uber  die  Funktion  der  veg-etabilischen  Gefasse.  Bot.  Zeit.  1879,  p.  229. 
The  most  abundant  literature  on  the  formation  of  Tyloses  may  be  found  in  Kiister, 
E.,  Patholog-ische  Pflanzenanatomie,  1903,  p.  98. 

y  Molisch,  ijber  die  Ablagerung  von  kohlensaurem  Kalk  im  Starame  dicotyler 
Holzgewachse.  Sitzungsber.  d.  mathemat.-naturwissenschaftl.  Klasse  d.  k.  Akad. 
d.  Wissensch.  zu  Wien.,  Vol.  LXXXIII,  No.  13  (1881). 


EDGAR  TULU; 

851 


false  heart  wood  formation^  which,  through  the  action  of  fungi  and  bac- 
teria, can  be  transformed  to  heart  rot-. 

This  attack  by  micro-organisms  has  led  to  the  establishment  of  a  num- 
ber of  parasitic  diseases,  which,  however,  essentially  arise  from  disturbances 
in  the  process  of  wound  healing.     As  first  in  importance,  we  will  name 

Wound  Gum. 

Prillieux  describes  this  disease  as  "Gommose  hacillaire,"  and  Viala  as 
"Roncet."  The  leaves  remain  green  but  become  irregularly  cleft  and  de- 
formed. In  cross  section,  the  wood  shows  black  points  and  specks  which 
enlarge  and  loosen  its  structure.  Later  the  phloem  separates  from  the 
xylem.  On  the  cut  surfaces  from  which  the  disease  spreads,  clefts  arise 
which  are  infected  by  saprophytes.  Prillieux  found  that  the  plant  died 
after  three  to  five  years. 

The  black  points  in  the  wood  arise  from  a  brown,  gummy  deposit,  which 
fills  the  vessels  and  cells  of  the  wood  parenchyma  and  swarms  with  bacteria 
(motile  rods).  Prillieux  found  in  an  infection  experiment,  made  in  May 
in  the  laboratory,  the  characteristics  of  the  disease,  which  bear  great  resem- 
blance to  those  of  Baccarini's  "Malnaro." 

Viala  and  Foex,  as  well  as  Mangin,  disagree  with  Prillieux,  in  that  they 
hold  that  the  described  phenomena  of  disease  can  be  produced  by  very  dif- 
ferent causes  and  are  not  absent  even  in  healthy  plants. 

This  difference  in  opinion  was  settled  by  Rathay^,  who  proved  first  of 
all  that  gum  can  occur  in  perfectly  healthy  vines.  He  found  gelatinous 
threads  in  healthy,  one-year-old  shoots  of  Vitis  riparia,  extending  from  the 
ducts  and  composed  of  gum.  The  vessels  filled  with  gum  {"gum  cells") 
may  be  seen  in  Fig.  202,  /.  This  gave  the  color  reactions  of  the  pentoses. 
In  Vitis  vinifcra,  V.  Labrnsca,  V.  Solonis,  V.  ariaonica,  etc.,  the  reaction  is 
found  only  in  wood  two  or  more  years  old.  If  this  process  occurred  in  young 
vines,  it  could  not  be  observed  until  July,  when  the  gum  is  pressed  out.  In 
the  root,  gum  formation  is  less  abundant. 

As  Rathay  reports,  even  in  the  grapevine,  a  normal  heart  wood  forma- 
tion may  set  in  finally  in  plants  twenty  years  old  but  takes  place  irregularly 
since  scattered  places  of  the  inner  sapwood  are  involved  in  the  change  and 
produce  the  brown  spots,  which  Prillieux  has  described  as  the  symptoms  of 
Gummose  hacillaire.    When  such  a  brown  place,  extending  backward  like  a 


1  Tuzson,  J.,  Anatomische  und  mykologisclie  Untersuchung-en  iiber  die  Zer- 
setzung-  und  Konservierung-  des  Rotbuchenholzes.  Berlin  1905,  cit,  Centralbl.  fiir 
Bakt.  1905,  II,  Vol.  XV,  p.  482. 

2  Herrmann,  tJber  die  Kernbildung  bei  der  Buche.  Naturf.  Ges.  Danzig-;  cit. 
Bot.  Centralbl.  1905,  Vol.  XCIX. 

3  Rathay,  E.,  tJber  das  Auftreten  von  Gummi  in  der  Rebe  und  iiber  die  "Gom- 
mose bacillaire."  Kremla,  H.,  tJber  Verschiedenheiten  im  Aschen-Kalk-  und 
Magnesiagehalte  von  Splint-,  Wund-  und  Wundkernholz  der  Rebe.  Jahresber.  d.  k. 
k.  onolg.  u.  pomolog.  Lehranstalt  in  Klosterneuburg.     Wien.  1896. 


852 

thread  in  the  sapwood  (Fig.  202,  j)  is  examined,  it  is  found  that  the  broad 
vessels  are  filled  with  a  brown  gummy  mass  in  which  are  crystalline  precipi- 
tates of  calcium  carbonate  (^)  ;  the  contents  of  the  wood  parenchyma  and 
medullary  ray  cells  surrounding  the  vessel  are  deep  brown  and  the  adjoining, 
narrower  vessels  (e)  are  filled  with  tyloses.  Starch  is  found  only  in  the 
sapwood ;  in  the  heart  wood,  instead  of  the  starch,  brown  grains  are  found 
which  turn  to  bluish  black  with  ferric  chlorid.  Stoppages  of  the  vessels  r.re 
not  found  in  the  sapwood  but  only  in  the  heart  wood.  They  are  caused 
primarily  by  tyloses,  which  occur  exclusively  in  the  inner  heart  wood,  while, 
in  the  outer  heart  wood  ring,  stoppage  by  gum  or  calcium  predominates. 
Often  whole  row^s  of  vessels  in  summer  wood  are  filled  with  calcium,  usually 
in  the  carbonate  but  at  times  in  the  oxalate  form  (Fig.  202,  4).  The  calcium 
carbonate,  deposited  in  the  youngest  parts  of  the  heart  wood,  is  dissolved 
later.  In  the  same  way,  the  great  amount  of  gum  in  the  sapwood  disappears 
with  the  change  to  heart  wood. 

The  tissue  next  to  the  wound  surface  in  a  horizontal  wound  dies  back, 
more  or  less.  In  the  living  tissue  immediately  underlying  this,  the  vessels 
are  stopped  up  by  means  of  gum,  farther  back  by  the  formation  of  tyloses. 
The  fact  that  the  vessels  have  drops  and  layers  of  gum  only  on  the  parts 
adjoining  the  wood  parenchyma  cells,  while  the  gum  is  lacking  when  they 
adjoin  neighboring  vessels,  proves  that  it  is  the  wood  parenchyma  cells 
which  excrete  the  gum.  The  changes  which  characterize  the  heart  wood 
begin  much  earlier  on  wound  surfaces  than  on  normal  uninjured  trunks, 
extending  backward,  however,  only  so  far  as  the  wound  stimulus  was  effec- 
tive. On  this  account,  it  is  termed  "wound  heart  wood,"  by  some  observers 
"false  heart  wood"  in  order  to  distinguish  it  from  true  heart  wood.  Many 
bacteria  are  found  near  the  cut  surface  but  not  in  the  deeper  part  of  the 
various  centres  of  heart  wood  formation,  beginning  at  the  wood  surface  and 
extending  as  light  brown  tissue  stripes  through  the  sapwood.  Since  the 
disease  agrees  in  appearance  with  Gummose  hacillaire,  it  is  understood  to  be 
an  immediate  result  of  injury  in  older  parts  of  the  trunk.  This  wound 
stimulus  may  act  chiefly  on  the  protoplasm  of  the  wood  parenchyma  cells 
surrounding  the  vessels ;  ^t  may  be  continued  further  because  of  the  con- 
tinuity of  the  protoplasm  of  adjoining  cells  and  may  incite  the  wood  paren- 
chyma cells  to  a  premature  formation  of  tyloses.  These  cells,  therefore, 
grow  old  and  die  prematurely.  The  normal  secretion  of  gum,  at  first  very 
abundant,  ceases  with  the  formation  of  tyloses.  The  process  described  is 
made  clearer  by  an  examination  of  the  accompanying  figures. 

In  Fig.  202,  ^  (an  alcohol  preparation  from  a  ten-year  branch  of  Vitis 
riparia),  j  indicates  the  boundary  between  two  annual  rings;  m,m  medullary 
rays,  g,  gum  cells,  g'  vessels  with  strongly  contracted  gum  contents.  At  the 
right  (Fig.  i),  are  reproduced  two  gum  cells  from  a  one-year-old  shoot  of 
Vitis  vinifera  (blue  ToUinger)  ;  their  contracted  gum  contents  are  seen  in 
the  centre.     Only  the  inner  outline  of  the  cell  walls  is  drawn.     Fig.  j  is  the 


85: 


fflHigpiffiii 


Fig.  202.     Stoppage  of  the  ducts  in  a  grapevine  suffering  from  wound  decay 
(After  Rathay.) 


854 

cross  section  of  a  brown  wood  thread  from  the  sap  wood  of  a  very  old  vine ; 
j,j,j,j,  the  boundaries  of  the  annual  rings;  k,  a  radial,  fibrous  crystalline 
aggregation  of  calcium  carbonate  imbedded  in  the  brown  gum  mass  of  a 
broad  vessel;  the  contents  of  the  adjoining  wood  parenchyma,  of  the  libri- 
form  fibres  and  medullary  ray  cells  are  much  browned  and  those  lying 
nearest  the  vessels  tt,  are  filled  with  tyloses. 

Fig.  202,  4,  shows  a  vessel  in  cross  section,  the  adjoining  wood  paren- 
chyma cells  from  a  dead  piece  of  wood  lying  under  the  terminal  wound  of  a 
one-year-old  shoot.  Besides  colorless  gum,  it  contains  radially  arranged, 
stem-like  aggregations  of  calcium  oxalate.  The  lower  figure  is  that  of  a 
vessel  with  the  surrounding  wood  parenchyma  from  the  heart  wood  of  a 
very  old  grapevine.  The  vessel  is  filled  with  tyloses  in  which  are  contained 
crystalline  aggregations  of  calcium  carbonate  (after  Rathay). 

We  have  cited  this  case  here  because,  as  typical  of  many  other  cases,  it 
proves  clearly  that  the  gum  formation  is  the  result  of  wound  stimulus  and 
at  tlie  same  time  shows  how  easily  diseases  may  be  listed  as  parasitic,  in 
which  is  concerned  only  a  subsequent  infection  by  parasites  which  infest 
wounds. 

This  concerns  especially  herbaceous,  fleshy  and  juicy  organs.  In  this 
connection,  attention  should  be  called  to  a  work  by  Spieckermann^  who 
points  out  especially  the  resistance  of  a  cork  membrane  to  bacteria  and  the 
necessity  of  a  definite  high  amount  of  moisture  in  the  surrounding  air  as 
well  as  the  water  content  of  the  tissue  itself,  aside  from  its  specific  sensitive- 
ness, in  order  to  make  p()ssil)le  bacterial  decomposition  even  on  a  wound 
surface. 

The  Slimy  Exudations  of  Trees. 

In  connection  with  the  relation  of  parasitic  infection  to  wound  surfaces, 
already  mentioned  under  "Gummose  hacillaire,"  we  will  mention  here  the 
phenomenon  where  a  usually  slimy,  or  gelatinous,  and  at  time  clayey  looking 
exudation  is  noticeable  very  frequently  in  different  kinds  of  trees,  and  even 
in  summer  remains  moist  and  variously  colored. 

According  to  our  conception  of  the  matter,  an  excessive  bleeding  of  the 
trunk  is  involved  here  from  wounds  which  cannot  heal,  Molisch-  has 
proved  that  a  local  bleeding  pressure  makes  itself  felt  in  every  wound  which 
begins  to  be  overgrown.  In  consequence  of  the  injury,  the  cambium,  as 
well  as  the  parenchymatous  elements  of  the  wood  and  bark,  is  incited  to 
increased  activity  and  cell  division.  With  this  is  connected  such  an  increase 
of  turgor  that  water  is  pressed  out  of  the  wound  often  under  enormous 
pressure  (at  times,  9  atmospheres). 


1  Spieckermann,   A.,   Beitraf?   ziir  bakteriollen   Wundfilulnis    cler    Kulturflanzen. 
Landwirtsch.  Jahrbiicher  1902,  p.  155. 

2  Molisch,  H.,  tJber  lokalen  Blutungsdruck  und  seine  Ursachen.     Bot.  Zeit.  LX; 
cit.  Just's  Jahresber  1902,  II,  p.  618. 


855 

If  the  analyses  of  the  sap  from  bleeding  grapevines  are  studied  closely^, 
it  is  found  that  besides  small  quantities  of  organic  substances,  nitrogen, 
phosphoric  acid  and  calcium  are  also  present,  i.  e.  it  may  be  considered  as  a 
nutrient  solution  very  well  suited  for  infection  by  micro-organisms  and  for 
their  increase.  Ludwig  has  studied  this  thoroughly".  In  a  number  of  pub- 
lications he  describes  a  white  slimy  exudation  in  the  oak,  birch,  Saliceae,  etc., 
due  to  Leuconostoc  Lagerheimii  Ludw.  with  which  are  associated  various 
fermenting  fungi  {Saccharomyces  Ludwigii  Hans,  etc.).  A  "hrotvn  slimy 
exudation,"  found  in  apples,  birches,  poplars,  horsechestnuts  and  other  fruit 
and  street  trees,  showed  Micro-coccus  dendroporthos  Ludw.,  with  which  is 
associated  Trula  monilioides  Cord.  Ludwig  found  a  "red  slime"  in  the  late 
summer  on  the  stumps  of  old,  healthy  beeches  and  observed  in  it  a  filament 
bacterium  (Leptothrix?)  and  Fusarium  moschatum.  He  met  with  the  same 
bacterium  in  a  yellowish  white  bleeding  sap  with  a  gelatinous,  granular  con- 
sistency in  lindens  and  sometimes  in  birches.  He  also  found  toward  the 
middle  of  April  on  fresh  branch  wounds  of  a  hornbeam  a  milky  looking  slime 
which  contained  Endomyces  vernatis  Ludw.  together  with  alcohol  producing 
yeast.  In  one  of  his  later  works^  we  find  mention  of  mites  (Hericia)  and 
eelworms  (Rhabditis)  as  animal  companions  of  such  bacteria  and  fungi.  In 
the  Zeitschrift  fiir  Pflanzenkrankheiten  1899,  p.  13,  we  find  a  Hst  of  all  the 
infesters  of  slimy  exudations  which  have  been  confirmed  not  only  for 
Germany  but  also  for  the  tropics.  Of  course  this  list  will  be  constantly 
increased  according  to  whether  the  micro-organisms,  belonging  to  specific 
localities,  have  had  opportunity  to  infect  the  bleeding  wounds  of  trees. 

The  organisms  here  named  may  be  considered  to  be  injurious  to  trees 
only  in  so  far  as  their  infection  delays  or  prevents  the  closing  of  the  wound. 
Wounds  which  have  been  made  by  frost,  lightning,  animals,  etc.,  and  intro- 
duce periodic  bleeding,  form  the  primary  cause  of  the  slimy  exudations.  If 
it  is  found  necessary  agriculturally  to  remove  such  weakening  causes,  the 
only  method  possible  would  be  to  cut  out  carefully  the  diseased  places  and 
paint  the  fresh  edges  of  the  wound  with  coal  tar. 


1  Ravizza,  F.,  tJber  das  Thranen  der  Weinrebe  usw.  Staz.  sperimentali  1888; 
cit.  Biedemiann's  Centralbl.  f.  Agrik.  18S8,  p.  541.  According-  to  investigations  by 
Neubauer  and  v.  Canstein  (Annalen  der  Oenologie,  Vol.  IV,  1874,  Part  4,  p.  499)  the 
sap  of  the  grapevine  (gathered  in  the  dry  year  1874)  which,  in  its  fresh  condition, 
is  as  clear  as  water,  and  neutral,  but  easily  becomes  clouded  by  bacterial  growth  and 
then  reacts  as  an  alkali,  contained  at  the  time  of  experiment  2.1204  g.  of  solid  matter 
per  liter,  of  which  0.7408  g.  were  mineral  elements  and  1.3796  g.  organic  substance. 
An  analysis  of  the  ash  gave  10.494  percent,  potassium;  1.437  percent,  sulfuric  acid; 
0.188  percent,  ferric  oxid;  2.822  percent,  phosphoric  acid;  41.293  percent,  calcium; 
5.534  percent,  magnesia;  34.791  percent,  carbon  dioxid;  2.857  percent,  chlorid;  0.810 
percent,  silicic  acid  in  the  raw  ash.  Besides  these  acids,  an  organic  magnesia  salt, 
gum,  sugar,  and  calcium  tartarate,  inosit,  succinic  acid,  oxalic  acid  and  unknown 
extractive  substances,  were  found.  Rotondi  and  Ghizzoni  (Biedermann's  Centralbl. 
1879,  p.  527)  also  mention  besides  starch,  sugar  which  the  Neubauer  investigations 
had  not  found  in  the  fresh  sap.  Only  the  volatilized  sap  which,  with  the  giving  off 
of  carbon  dioxid  and  the  elimination  of  calcium  phosphate,  together  with  a  yellow 
coloration,  had  a  weakly  acid  reaction,  showed  all  the  sugar  reactions. 

2  Ludwig,  F.,  Der  Milch-  und  Rotfluss  der  Baume  und  ihrer  Urheber. — ^tJber  das 
Vorkommen  des  Moschuspilzes  im  Saftfluss  der  Baume;  cit.  Zeitschr.  f.  Pflanzen- 
krankheiten 1892,  p.  159,  160. 

3  Ludwig,  P.,  tJber  die  Milben  der  Baumfliisse  und  das  Vorkommen  des  Hericia 
Robin!  Canestrini  in  Deutschland.     Zeitsch.  f.  Pflanzenkrankh.  1906,  p.  137. 


856 


Root  Injuries. 

Having  thoroughly  discussed  the  overgrowth  processes  of  the  aerial 
axis  after  all  kinds  of  injury,  we  can  quickly  summarize  the  healing  of  root 
wounds.  They  correspond  with  those  of  the  aerial  axis  and  undergo  modi- 
fications only  inasmuch  as  the  surrounding  medium  often  interferes  with  the 
process  of  overgrowth.  For  example,  if  the  soil  is  very  moist,  the  stage  of 
callus  formation  is  prolonged,  the  transformation  of  the  callus  tissue  to  the 

liniuT   overgrowth    edge   is   slower   and  

the  possibility  of  infection  by  wood  de- 
stroying fungi  greater.  These  factors, 
however,  become  less  significant  if  the 
root  wound  surface  is  exposed  to  the  air. 
The  influence  of  light,  warmth  and  dry- 
ness promotes  the  closing  of  the  wound 
and  removes  any  far-reaching  influence, 
from  even  large  wound  surfaces,  on  the 
condition  of  health  of  the  whole  root. 
The  best  proof  is  found  in  much  fre- 
quented forests  in  the  \icinity  of  large 
cities  where  the  superficial  roots  are 
constantly  rubbed  bare  by  pedestrians 
and,  nevertheless,  find  opportunity  to 
cover  the  edges  of  the  wound  with  over- 
growth walls.  The  adjoining  figure  illus- 
trates such  a  root  so  worn  that  only  the 
first  formed  annual  rings  are  found  to  be 
still  intact  on  the  upper  side.  A  cross 
section  shows  that  no  {)arasitic  wound 
decay  has  occurred  at  the  wounded 
place;  the  wood  of  the  lower  side  is 
sound. 

The  wounds  produced  in  transplant- 
ing deserve  the  most  consideration. 
Transplanting  is  a  necessary  process, 
which  cannot  be  omitted  in  any  nursery, 

for  trade  rec|uires  the  delivery  to  the  purchaser  of  trees  which,  after  trans- 
portation to  a  permanent  place,  exhibit  the  greatest  possible  capacity  for 
vigorous  growth  and  development. 

In  transplanting  older  trees  with  well  developed  tops  and  extensive  root 
systems,  a  cutting  ofiF  of  the  larger  root-branches  cannot  be  avoided ;  hence 
the  great  danger  of  attack  by  parasitic  root  decay,  which  gradually  advances 
into  the  trunk.  But  even  if  this  danger  has  been  prevented  by  the  painting 
of  the  cut  places  with  tar,  the  transplanting  of  old  trees  is  always  a  danger- 
ous operation  because  the  activity  of  the  root  system  is  retarded  until  new 


Fig.    203.     A   llat-lyinff   root   of   the 
alder  harked  by  the  tread  of  feet. 


857 

root  fibres  may  be  formed  and  the  top,  during  this  time,  must  draw  water 
from  the  reserves  stored  up  in  the  wood  body.  Because  of  the  mutual 
dependence  of  the  subterranean  and  aerial  axes^  it  is  necessary  to  cut  back 
the  top  of  the  transplanted  tree,  corresponding  to  the  change  in  the  root 
system.  The  further  advanced  the  foliage  of  the  tree,  the  more  necessary 
is  this  pruning.  In  practice,  other  means  for  reducing,  as  far  as  possible,  the 
evaporation  of  the  aerial  parts  are  used,  such  as,  for  example,  the  wrapping 
of  the  trunk,  frequent  sprinkling  of  the  top,  artificial  shade,  etc. 

Trees  are  usually  sold  from  nurseries  in  a  leafless  condition  but  even 
here  the  quickly  developing  foliage  requires  a  sufficient  supply  of  water. 
This  can  be  made  possible  only  by  newly  formed  roots.  It  is,  therefore,  of 
the  greatest  importance  to  deliver  the  trees  in  such  a  condition  that  they  will 
form  new  roots  as  quickly  and  abundantly  as  possible.  This  depends  upon 
the  method  of  growing  the  trees  and  the  way  in  which  the  roots  have  been 
cut.  The  older  the  root  is,  the  scantier  the  development  of  new  fibrous 
roots  on  the  cut  surface ;  the  larger  the  cut  surface,  the  more  slowly  it  is 
overgrown  and  the  greater  the  danger  of  root  decay.  R.  Hartig-  has  thor- 
oughly described  this  for  conifers  and  deciduous  trees. 

On  this  account,  the  first  rule  is  to  grow  the  trees  so  as  to  avoid  as  far 
as  possible  wide  spreading,  large  roots,  such  as  trees  usually  form  when 
developing  undisturbed  in  one  place  and  to  produce  a  root  system  in  the 
form  of  a  ball  of  close  standing,  short  but  well  branched  roots.  This  is  done 
best  by  repeated  cutting  of  the  roots  in  the  first  years  of  growth. 

Twisting  the  long  tap  root  is  often  recommended  instead  of  cutting  it,  as 
this  would  avoid  decay.  The  widely  experienced  Goppert^  holds  to  this 
view.  As  a  fact,  twisted  roots  develop  lateral  roots  quickly  on  their  convex 
side"^.  In  the  water  cultures  of  fruit  trees,  which  I  made  in  Proskau,  some 
seedlings  of  the  apple,  pear,  pine,  maple,  etc.,  had  curved  tap  roots  because 
they  had  reached  the  bottom  of  the  small  receptacles  and  remained  there  for 
some  time.  The  root  tips  of  other  plants  were  injured  when  taken  from  the 
sand.  The  majority  of  both  kinds  of  seedlings  developed  lateral  roots 
much  sooner  than  the  uninjured  experimental  plants,  set  earlier  in  larger 
receptacles.  This  circumstance  seems  practical,  as  a  confirmation  of  the 
view  of  those  who  recommend  striving  for  early  root  branching  in  trans- 
planting by  bending  the  tap  root  and  not  injuring  it.  We  cannot,  however, 
approve  of  this  method ;  in  heavy  soils,  especially,  where  we  had  experi- 
mentally planted  apple  seedlings  with  cut  back  tap  roots  and  others  with 
uninjured  but  spirally  twisted  ones,  the  removal  from  the  soil  for  the  second 


1  Kny,  L.,  On  correlation  in  the  growth  of  roots  and  shoots.  (Second  paper.) 
Annals  of  Botany,  Vol.  XV,  No.  60,  Dec,  1901. 

2  Hartig-,  R.,  Die  Zersetzungserscheinuhgen  des  Holzes  der  Nadelbaume  und 
der  Eiche.  Berlin  1S7S. — Lehrbuch  d.  Pflanzenkrank.  3rd.  ed.  Berlin  1900.  Springer, 
p.  263. 

3  Goppert,  Innere  Zustande  d.  Baume  nach  ausseren  Verletzungen.  Breslau 
1873. 

4  Noll,  Fr.,  trber  den  bestimmenden  Einfiuss  von  Wurzelkr-iimmungen  auf 
Entstehung  und  Anordnung  der  Seitenwurzeln.  Landwirtsch.  Jahrbiicher  1900;  cit. 
Zeitschr.  f.  Pflanzenkrankh.  1902,  p.  55. 


autumn  transplanting  was  attended  with  much  greater  danger  for  the  twisted 
specimens.  To  aid  in  the  removal,  the  plants  were  pulled  slightly  and,  in 
doing  so,  it  became  evident  that  the  twisted  specimens  broke  very  easily  at 
the  first  bend  in  the  root. 

It  is,  therefore,  advisable  to  cut  the  seedling  tap  roots  at  once  at  the  first 
transplanting,  so  that  several  root  branches  are  formed  at  the  root  neck; 
those  near  the  cut  surface  develop  new  lateral  axes  in  the  second  year. 

This  makes  possible  not  only  an  increase  of  the  organs  of  absorption  but 
also  causes  the  production  of  a  root  ball  in  which  the  earth  is  held  between 
the  numerous  roots. 

PrantF  first  studied  thoroughly  the  anatomical  changes  which  occur 
when  younger  roots,  especially  the  germinating  ones,  are  injured.  He  found 
in  vegetables  (peas,  horse  beans,  etc.)  that  the  loss  of  the  tender  root  tip 
was  completely  made  good  by  the  development  of  a  new  one  in  which  all  the 
tissue  systems  participated  if  the  injury  took  place  close  to  the  tip  of  the 
root.  If  he  cut  off  the  germinating  root  somewhat  further  back  from  the 
apical  cell  regeneration  took  place  but  all  the  tissues  did  not  participate  in 
this,  only  the  juvenile  vascular  strands.  The  method  of  cutting,  used  almost 
exclusively  in  general  practice,  viz:  the  one  injuring  the  mature  tissues, 
does  not  bring  about  a  regeneration  of  the  root  tip ;  instead  of  this,  callus 
formation  by  the  bark  body  sets  in,  thereby  covering  the  cut  surface. 

Nemec's"  work  is  even  more  thorough  and  comprehensive. 

In  contrast  to  the  assunTption  that  true  regenerations,  in  w^hich  the  part 
removed  from  the  individual  is  directly  formed  anew  in  its  original  shape 
and  with  its  original  physiological  peculiarities,  rarely  occur  in  the  vegetable 
kingdom,  experiments  show  just  the  opposite  for  roots. 

It  is  here  only  a  question  of  injurying  the  youngest  possible  organs.  In 
roots,  restitution  remains  limited  really  to  the  zone  where  the  cells  on  the 
whole  wound  surface  (possibly  with  the  exception  of  the  epidermis  and  the 
outermost  bark  layers)  are  still  meristematic.  As  soon  as  the  cells  of  the 
outermost  bark  layers,  together  with  the  central  rows  of  the  sclerome, 
approach  maturity,  the  meristematic  cell  layers  alone,  adjoining  the  pcri- 
cambium,  participate  in  the  regeneration.  It  is  found  further  that  the  vege- 
tative point  of  a  root,  of  which  the  meristematic  cells  externally  appear  uni- 
form, still  possesses  a  certain  specialization.  The  cells  are  not  equipotential 
and  can  not  produce  different  tissues  under  arbitrarily  changed  conditions. 
Such  specific  differences  are  present  in  the  "Statocytes."  The  mobility  of 
starch  grains  in  these  presupposes  specific  peculiarities  of  the  protoplasm, 
since  in  different  callus-like  hypertrophied  cells  starch  grains  are  also  formed 
which  at  times  can  be  still  greater  than  those  of  the  statocytes  and  yet,  under 
the  influence  of  gravity,  cannot  be  moved  easily.  The  fact  that,  under  the 
influence  of  a  sufficiently  strong  centrifugal   force,  they  can  move  cen- 


1  Prantl,   Untersuchunfren  iiber  die   Regeneration   des  Veg-etations-punktes   an 
ang-iospermen  Wurzeln.     Wurzburg  1S73. 

2  Nemec,  B.,  Studien  iiber  die  Regeneration.     Berlin  1905,  Gebr.  Borntrager. 


859 

trifugally,  proves  that  they  are,  nevertheless,  specifically  heavier  than  the 
cytoplasm.  Therefore,  the  cytoplasm  of  the  statocytes  must  have  less  specific 
weight  and  must  be  very  fluid,  i.  e.  it  must  contain  very  few  elements  of 
considerable  consistency.  Nemec  also  discovered  peculiar  cytoplasmic 
accumulations  in  the  statocytes  of  the  root  cap,  which  certainly  represent 
an  especial  reaction. 

If  a  young  root  is  cut  ofif  above  its  zone  of  growth  and  not  within  it,  no 
regeneration  but  substitution  takes  place,  for  new  lateral  roots  are  produced, 
of  which  those  nearest  the  wound  surface  are  caused  by  their  geotropic 
sensitiveness  to  grow  down  more  perpendicularly  than  if  they  had  developed 
from  an  uninjured  main  root.  This  makes  possible  the  utilization  of  the 
soil  layers  for  nutrition,  which  the  perpetidicular,  downward  growing  main 
root  would  have  traversed^  A  fasciation  of  the  lateral  roots  takes  place  at 
times  after  injury,  or  removal  of  the  main  root.  Lopriore-  was  able  to 
produce  this  fasciation  artifically. 

Gnarly  Overgrowth  Edges. 

One  universal  characteristic  in  the  overgrowth  of  wounds  is  that  the 
wood  fibres  do  not  always  parallel  throughout  the  new  structure  but  are 
often  bent  and  twisted  until  at  times  they  are  looped.  These  variations  in 
the  course  of  the  fibres  form  what  is  termed  "gnarly  wood."  The  adjoining 
figure  of  the  overgrowth  cap  of  an  oak  branch,  from  which  the  bark  has  been 
removed,  gives  the  best  insight  into  this.  The  oak  furnishes  especially  good 
examples  of  a  complete  closing  of  large  wound  surfaces  by  overgrowth  and 
the  luxuriance  of  the  uniting  wound  edge  not  infrequently  brings  about  the 
condition  where,  for  example,  in  sawed  off,  larger  branches,  the  newly 
formed  tissue  does  not  have  a  flat  surface  but  one  more  or  less  strongly 
convex,  becoming  hemispherical  to  spherical  in  form.  In  such  overgrowth 
caps  small  centres  are  often  found,  the  so-called  gnarl  eyes  (Fig.  203,  a), 
around  which  variously  twisted  wood  fibres  {p)  are  deposited.  By  the  term 
"gnarl  eyes,"  however,  actual  buds  are  not  understood  but  rather  depressed 
tissue  centres,  around  which  are  deposited  the  wood  fibres  in  the  form  of  a 
bowl  and  later  serpentinely  twisted ;  in  this  way  representing  the  "curly 
grain"  in  wood.  While  a  spear-like,  woody  excrescence  appears  where 
actual  eyes  are  produced,  in  gnarl  eyes  a  deep  depression  is  found  formed  of 
parenchymatous  tissue,  often  increased  by  the  rounding  up  and  separation 
of  the  cells.  Wood  is  deposited  around  this  depression,  normally  composed 
of  wood  cells,  medullary  ray  cells  and  vessels.  The  abnormality  lies  only  in 
the  bowl-like  arrangement,  recalling  the  gnarl  tuber,  and  the  frequent 
occurrence  of  medullary  ray  structures  greatly  broadeited  and«  resembling 
medullary  spots,  which  at  times  can  develop  into  secondary  centres. 

1  Bruck,  W.  F.,  Untersuchung-en  iiber  den  Einfluss  von  Aussenbedingnng-en  auf 
die  Orientierung  von  Seitenwurzeln.  Zeitsch.  f.  allgem.  Physiolog-ie  Vol.,  Ill,  1904, 
Part  4. 

2  Lopriore,  G.,  I  caratteri  anatomici  delle  radioi  nastriformi.  Roma  1902.  Note 
sulla  biologia  dei  processi  di  rigenerazione  delle  cormofite,  etc.  Atti  Acad.  Gioenia. 
Catania  1906,  Vol.  XXI. 


86o 


We  consider  the  curly  or  gnarly  wood  only  as  an  extreme  case  of  per- 
fectly normal  processes,  in  the  variation  of  the  wood  fibres  when  obstacles 
occur  which  prevent  their  longitudinal  arrangement  in  the  part  of  the  plant. 
Such  obstacles  can  differ  greatly.  Each  normal  branch  insertion  becomes 
the  cause  of  a  change  in  the  course  of  the  wood  fibres  surrounding  it.  The 
new  formation  of  wood  bodies  within  the  bark,  described  under  bark  tubers, 
represents  a  further  cause.  Finally,  however,  we  find  the  most  varied 
phenomena  of  arrestment  in  the  formation  of  an  annual  ring,  produced  by 
differences  in  tension  in  the  growing  axis.  Such  differences  in  tension  are 
constantly  present  and  are  often  strengthened  by  external  influences.  Frost 
action,  for  example,  which  causes  the  formation  of  parenchyma  bands,  is 


Fig-.   204.     Gnarlly  wood  sliucture  of  the  ovGrgrowth   cap  of 

branch. 


of  especial  significance.  Another  external  cause  is  the  contact' of  one 
branch  with  another.  Besides  mechanical  pressure,  conditions  of  light  are 
also  of  influence ;  they  cause  variations  in  the  nutrition  of  the  different  sides 
of  the  cambial  ring.  Internal  processes  of  growth,  as,  for  example,  the 
rapid  outpushing  of  a  suddenly  broadened  medullary  ray,  are  also  of  impor- 
tance. These  can  tiistend  the  bark  into  knobs,  causing  a  repression  in  the 
growth  of  the  adjoining  wood  layers  and  the  like.  All  such  disturbances 
must  change  the  pressure  conditions  which  the  bark  girdle  in  its  entirety 
exercises  on  the  cambium  and  will,  therefore,  influence  the  development  of 
the  wood  formed  from  it.  We  find  in  the  spiral  twisting  of  the  wood  body 
in  every  trunk,  hew  greatly  the  course  of  the  fibres  is  influenced  by  the 


86i 

pressure  conditions,  even  in  the  normal  trunk.  Our  experiments  in  binding 
a  wire  ring  around  a  growing  axis  prove  how  much  the  wood  fibres  can  be 
forced  from  a  longitudinal  into  an  approximately  horizontal  position  by 
pressure. 

It  is,  therefore,  the  different  pressure  constantly  endured  and  exercised 
by  the  bark  girdle,  which  conditions  the  development  and  course  of  the  wood 
fibres.  Therefore,  to  explain  gnarly  wound  wood,  it  is  necessary  to  assume 
a  theory  of  the  polarity  of  the  cells  and  the  displacement  of  like  poles  as 
represented  by  Voechting  and  Mauled 

Bark  Tubers. 

In  concluding  the  chapter  on  the  processes  of  wound  healing,  we  have 
still  to  consider  the  production  of  spherical  woody  swellings,  or  tuberous 
outgrowths  of  the  bark  of  trees  and  (more  rarely)  herbaceous  plants.  These 
structures  are  generally  called  "wood  tubers"  or  "gnarl  tubers."  Their 
structure  and  production  differ,  thus  necessitating  a  subdivision  into  separate 
groups.  Their  character  as  correlative  hyperplasias  is  their  common  quality. 
They  are  to  be  considered  as  the  counteraction  of  the  organism  to  previous 
phenomena  of  arrestment.  The  arrestment  can  consist  in  the  cessation  of 
the  development  of  a  bud  or,  independent  of  any'  bud,  can  be  produced  by 
the  death  of  scattered  tissue  groups  in  the  bark.  The  dying  of  different  cell 
groups  in  the  bark  body  of  the  woody  axes  occurs  extensively.  Frost  and 
heat,  local  increase  in  pressure  and  the  like,  can  caiise  the  death  of  cell 
groups  without  any  injury  to  the  whole  organism,  which  responds,  not  infre- 
quently, by  an  increased  new  formation  near  the  centre  of  arrestment.  The 
dead  tissue  groups  are  sometimes  only  encysted  by  cork  layers,  sometimes 
also  accompanied  by  cell  layers,  increasing  for  some  time,  or  permanently, 
according  to  the  time  and  kind  of  disturbance  and  the  amount  of  the  nutri- 
tive supply  in  the  surrounding  tissue.  The  cell  layers  either  produce  only 
parenchymatous  protuberances  or  cause  the  formation  of  new  wood  bodies, 
spherical  in  arrangement,  with  gnarled  fibres.  The  latter  process  can 
increase  to  the  production  of  independent  tuberous  wood  bodies  within 
the  bark. 

I  have  made  no  personal  study  of  the  first  group  of  bark  tubers,  the 
production  of  which  is  traced  back  to  bud  primordia  retarded  in  develop- 
ment, and  in  consequence  will  quote  the  descriptions  of  earlier  authors. 
Trecul-  should  be  named  first  among  these.  He  describes  in  detail  some 
cases  of  tuber  formation  (in  the  oak  and  hornbeam)  and  comes  to  the  con- 
clusion that  the  tubers  always  owe  their  production  to  a  bud  which  originally 
is  directly  connected  vascularly  with  the  wood  body  of  the  branch  or  trunk. 
Such  a  bud  may  lie  dormant  a  number  of  years  without  projecting  more 


1  Maule,  C,  Der  Faserverlauf  im  Wundholz.  Bibliotlieca  botanica  Part  33. 
Erwin  Naeg-ele.     Stuttgart  1S96. 

2  Trecul,  Memoire  sur  le  developement  des  loupes  et  des  broussins,  en\asasres  au 
point  de  vue  de  I'accroissement  en  diametre  des  arbres  dicotyledones.  Annales  des 
scienc.  nat.  3  serie.    Botanique  t.  XX,  1S53,  p.  65. 


862 

than  2  mm.  (at  least  in  the  hornbeam)  above  the  surface  of  the  bark.  After 
a  few  years  of  such  lethargy,  the  fibro-vascular  body  can  renew  its  activity 
and  develop  into  a  spherical,  oval  or  even  ellipical  wood  tuber. 

The  death  of  dormant  buds  occurs  of  itself  after  a  considerable  number 
of  years,  if  not  hastened  by  external  circumstances,  since  the  connection  is 
broken  between  the  part  of  the  bud  lying  in  the  bark  and  that  in  the  wood 
body  by  the  interposition  of  the  wood  mantle  of  the  branch  which  bears  the 
bud.  The  outer  part  of  the  bud,  covered  with  scales  and  lying  on  top  of 
the  bark,  remains  in  place  for  some  time;  it  dries  up  very  slowly  and  finally 
is  thrown  ofT. 

This  bud,  originally  attached  to  the  wood  body,  can  also  be  loosened  by 
the  splitting  ofif  of  its  fibro-vascular  bundle  from  the  wood  of  the  trunk.  As 
a  rule,  the  portions  of  the  bud  which  project  above  the  bark  surface  die, 
while  its  fibro-vascular  body,  thus  isolated  in  the  bark  continues  to  form  new 
wood  layers  and  its  own  bark  without  the  aid  of  foliage ;  it  must,  therefore, 
draw  its  plastic  material  from  the  surrounding  green  bark  of  the  trunk. 
This  growth  may  continue  for  years ;  the  outer  side  of  the  wood  tubers  may 
die  from  the  destruction  of  external  agents  and,  nevertheless,  the  tubers  can 
continue  to  form  new  wood  on  the  inner  side.  In  the  red  beech,  as  in  the 
hornbeam,  these  tubers  are  produced  from  adventitious  buds. 

Th.  Hartig^  describes  the  production  of  tubers  in  the  red  beech  from 
preventitious  buds.  The  weak  basal  buds  in  the  red  beech  die  after  possibly 
twenty  years  inasmuch  as  the  bud  stem,  lying  in  the  bark,  is  separated  from 
the  part  of  the  bud  in  the  wood  by  the  interposition  of  a  completely  uniform, 
connected  wood  layer  of  the  branch  bearing  the  bud.  The  part  of  the  pre- 
ventitious bud  lying  in  the  bark,  however,  can  remain  alive  for  some  time 
and  leading,  as  it  were,  a  parasitic  life,  grow  by  continued,  concentric  wood 
formation,  into  those  wood  tubers  which,  as  large  as  peas  or  hazelnuts, 
project  above  the  bark  and  are  peculiar  to  the  luxuriantly  growing  beech 
trunk  in  middle  age. 

Dutrochet-,  whose  personal  view  is  related  to  the  then  prevailing  bud 
root  theory,  describes  the  tuberous  outgrowths  as  bud  embryos  (meri- 
thalles).  Unlike  the  normal  buds  of  the  axis,  these  are  not  inserted  on  top 
of  and  between  each  other  but  remain  without  any  connection  with  the  other 
bud  embr}'os  and  their  vascular  strands  and,  therefore,  do  not  form  a  part 
of  the  axial  cylinder.  So  long  as  such  an  embryo,  the  primordium  of  an 
adventitious  bud,  remains  isolated  in  the  other  tissues,  it  develops  no  leaf  and 
no  bud  but  retains  its  spherical  form  and  grows  by  constantly  developing 
new  wood  layers,  covered  with  their  own  bark.  If  this  isolated  wood  body, 
the  primordium  of  an  adventitious  bud,  finally  comes  in  contact  with  the 
axial  body,  its  own  bark  disappears  because  of  the  pressure  and  the  wood 

1  Hartigr,  Th.,  VoUstandige  Naturg-eschichte  der  forstlichen  Kulturpflanzen 
Deutschlands,  p.  176.     Berlin  1852. 

2  Observations  sur  la  forme  primitive  des  embrvons  gemmalres  des  arbres 
dicotyledon^s,  1837.     (Nouv.  M6m.  du  Mus.  d'Hlst.  nat.  IV). 


863 

knot  forms  a  real  bud,  which  develops  leaves.  It  now  represents  a  gnarl 
tuber  (loupe)  ;  the  coalescence  of  several  such  tubers  forms  a  wen 
(broussin). 

This  theory  differs  from  those  developed  earlier,  inasmuch  as  in  it  the 
bud  is  considered  the  final  product  of  the  tuber  formation,  while  in  the 
others  it  is  held  to  be  the  initial  one.  Lindley^  who  describes  the  tubers 
mentioned  by  Dutrochet  in  the  beech,  cedar  and  poplar  and  who  found  in 
one  poplar-  that  branches  could  develop  from  them,  considers  them  to  be 
produced  from  adventitious  buds  and  cites  a  further  case  in  old  olive  trees, 
mentioned  by  Manetti.  He  says  that  the  tubers  (gnaurs)  in  these  trees 
were  cut  out,  together  with  a  part  of  the  bark,  and  planted  and  that  these 
tubers,  which  Manetti  called  Uovoli,  gave  young  plants.  Treviranus,  to 
whom  Morren  sent  some  cedar  tubers,  confirms  in  general  the  structure  of 
the  tubers  described  by  Dutrochet.  He  places  in  the  same  category  the 
phenomena  of  the  isolated  vascular  bundles  (leaf  trace  strands)  in  climbing 
Sapindaceae,  Calycanthus  floridus  and  C.  praecox,  some  Bignoniaceae,  etc. 

Schacht'*  explains  the  tubers  in  the  bark  of  poplars,  lindens,  beeches, 
etc.,  as  dwarfed  branches  which  have  grown  in  circumference  but  not  in 
length.  While  Hartig  points  to  the  first  beginnings  of  the  tubers  in  dormant 
buds,  Ratzeburg*  lays  stress  upon  the  bark  as  the  productive  centre  of  the 
same  beech  tubers  and  says  explicitly  that  they  do  not  extend  to  the  wood 
body.  Similarly  Rossmassler'  declares  that  the  tubers  of  the  mountain  ash 
(Sorbus  aucuparia) ,  which  he  investigated,  lie  only  in  the  bark  and  have  no 
connection  with  the  wood  body;  Kotschy'',  on  the  other  hand,  describes 
bark  tubers  lo  to  15  cm.  large  on  the  old  trunks  of  the  Lebanon  cedar,  as 
gnarly,  woody  excrescences,  firmly  fixed  in  the  bark,  which  are  connected 
with  the  mother  trunk  by  a  few  vascular  bundles.  Masters^  also  suspects 
that  some  of  the  tubers  (gnaurs  or  burrs)  in  the  elm,  etc.,  as  also  in  many 
apple  varieties,  are  only  aggregations  of  adventitious  buds. 

A  work  by  Krick**  reconciles  the  apparently  contradictory  theories.  He 
has  determined  that  the  bark  tubers  (Sphaeroplasts)  of  the  red  beech  de- 
velop in  connection  with  preventitious  buds,  either  separating  from  the  wood 
axis  of  the  trunk,  or  developing  independently  in  the  bark.  In  the  latter 
case  the  tubers  have  a  woody,  cork,  or  phloem  core  but  never  real  pith. 

The  latter  kind  of  tuber  formation  which  takes  place  in  the  bark  paren- 
chyma, outside  of  the  primary  group  of  phloem  fibres,  carries  us  over  to  the' 
second  group  of  bark  tubers  in  which  certainly  no  bud  primordia  participate. 


1  Lindley,  Theory  of  Horticulture  198.     Translated  by  Treviranus  1S50,  p.  37. 
-  Loc.  cit.,  p.  224. 

3  Schacht,  Der  Baum,  1853,  p.  134. 

4  Ratzetaurg-,    Die   /Standortsgewachse    und    Unkrauter    Deutschlands    und    der 
Schweiz.     Berlin  1859,  p.  243,  Note  1. 

5  Rossmassler,    Versuch    einer    anatomischen    Charakteristik    des    Holzkorpers 
der  deutschen  Waldbaume.     Tharandt.  Jahrb.  1847,  Vol.  IV,  p.  208. 

c  Kotschy,  Reise  in  den  cilicischen  Taurus.     Gotha  1858,  p.  267. 
7   Masters,  Veg-etable  Teratolog-y  1869,  p.  247. 

s  Krick,  Fr.,  tJber  die  RindenknoUen  der  Rotbuche.     Bibliotheca  botanica  1891, 
Part  25;  cit.  Bot.  Zeit.  1892,  p.  401. 


864 

In  this  we  have  to  mention  first  Gemet's^  investigations  of  tuber  formation 
in  Sorhus  aucuparia.  He  found  the  dead  tubers  so  loosely  attached  to  the 
bark  that  they  could  easily  be  lifted  out  v^ith  the  finger  nail  while  the  living 
ones  were  apparently  firmly  fixed  in  the  sapwood.  Nevertheless,  they 
proved  to  be  "completely  separated  from  it  and  appeared  as  bodies  possibly 
belonging  in  some  way  to  the  phloem  because  the  very  reddish  color  of  their 
smooth  under  end  corresponds  to  that  of  the  phloem."  Most  tubers,  when 
cut  through,  show  several  centres  about  which  complete  wood  layers  have 
developed  in  13  to  15  annual  layers,  provided  with  vessels  and  medullary 
rays  and  agreeing  in  their  cell  structure  with  the  wood  of  the  trunk.  The 
course  of  the  wood  layers  was  gnarly.  The  annual  rings  were  almost  always 
broader  in  the  under  half  of  the  tubers  toward  the  trunk  than  in  the  upper 
one,  projecting  from  the  trunk.  It  was  not  possible  to  prove  any  connection 
with  a  bud.  Even  when  a  tuber  lay  near  a  wen,  no  connection  could  be 
found  with  any  of  the  many  bud  cones  of  the  wen. 

Unfortunately,  Gernet  had  no  opportunity  to  study  the  initial  stages  of 
tuber  development ;  the  youngest  stages  in  his  material  were  tubercles  0.5 
mm.  in  size,  still  completely  enclosed  in  the  bark,  without  having  caused  any 
external  protuberance.  They  lay  outside  the  phloem  fibre  and  were  spher- 
ical or  ellipsoid  and  showed  several  centres  about  which  the  wood  body  had 
already  been  deposited.  This  consisted  of  parenchymatously  formed  cells 
in  which  a  differentiation  of  medullary  ray  cells  became  recognizable  in 
longitudinal  sections.  The  first  indications  of  vessels  may  be  considered  to 
be  represented  by  a  few  cells  with  large  lumina  but  still  lying  above  each 
other  with  almost  horizontal,  unbroken  walls  and  containing  less  starch,  or 
none  at  all.  The  farther  all  these  cells  lay  from  the  centre,  the  more  clearly 
noticeable  became  the  lessening  of  their  radii  and  the  lengthening  of  their 
tangential  axes ;  their  cross  section  approximated  that  of  summer  wood.  In 
older  tubercles  are  found  at  first  sharply  differentiated  a  few  pitted  vessels 
and  a  clearly  recognizable  central  parenchymatous  centre,  rich  in  starch. 
The  wood  body  was  surrounded  by  a  cambial  zone  and  its  own  bark.  In 
the  upper  half  of  the  tubers,  cork  formation  took  place  at  times  in  the  inner 
bark.  The  outer  side  of  this  newly  produced  cork  zone  was  united,  not 
infrequently,  with  the  cork  zone  of  the  trunk.  The  part  of  the  bark  isolated 
by  such  a  cork  zone  (Gernet's  "cork  dam")  loses  its  starch  grains,  becomes 
filled  with  air  and  dies  gradually  so  that  the  outer  side  of  the  tuber  body 
contains  dead  tissue.  As  a  rule,  the  appearance  of  these  cork  layers  also 
introduces  the  death  of  the  tuber,  which  occurs  within  the  next  few  years. 
The  under  half  of  such  diseased  tubers,  as  well  as  that  of  perfectly  healthy 
ones,  retains  its  living  bark  tissue  and  the  formation  of  the  bark  body  pro- 
gresses with  that  of  the  wood  body.  From  this  we  may  conclude  that  the 
tuber  grows  downward  and  thus  its  upper  part  gradually  projects  above  the 
surface  of  the  bark  of  the  trunk  by  rupturing  it. 


1  Gernet,  C.  v.,  tJber  die  Rindenknollon  von  Sorbus  aucuparia.     Moskau  1860. 


865 

Judging  by  this,  Gernet  arrives  at  the  conclusion  that,  even  if  he  did 
not  know  the  initial  stages  of  the  tubers,  he  must  still  deny  any  connection 
between  them  and  the  wood  body  of  the  trunk  and  can  consider  the  tubers 
to  be  produced  neither  from  preventitious  nor  adventitious  buds. 

Having  investigated  the  tubers  of  apple  trees,  I  can  confirm  absolutely 
this  point  of  view.  For  my  investigation  I  had  at  my  disposal  tubers  vary- 
ing in  size  from  a  millet  grain  to  a  pea ;  they  came  from  the  base  of  the  trunk 
of  a  young  apple  tree,  possibly  eight  years  old.  The  tubers  lay  in  the  outer 
bark,  from  which  they  could  be  easily  separated.  The  tmder  side  was  either 
completely  covered  with  a  smooth  bark  (Fig.  205,  i  a)  or  showed  a 
"brownish,  dry  point,  without  any  bark  and  somewhat  depressed  {i-k)  which 
was  surrounded  by  a  green  circular  bark  wall. 

Fig.  205,  2  gives  the  median  cross  section  of  the  latter  kind  of  tuber. 
In  this  we  see  a  median  core  {2,h)  consisting  of  two  phloem  fibre 
groups  separated  by  a  little  parenchyma ;  other  tubers  have  only  one  phloem 
strand  in  the  core,  or  two  or  three  isolated  cores.  Around  the  bundle  are 
deposited  cells,  parenchymatous  in  form,  with  slightly  lignified  walls  and 
arranged  radially.  It  is  evident  that  they  are  formed  after  the  manner  of 
cork  cells.  At  times  only  a  group  of  thick- walled,  brown  parenchyma  cells, 
with  or  without  starch  or  phloem  fibres,  is  found  in  the  centre  of  the  tuber; 
yet  thisi  is  a  more  rare  case.  Finally,  tubers  are  formed  now  and  then 
with  a  small  central  cavity,  filled  with  the  brown  remains  of  cells. 

The  radially  arranged,  circular  zone  of  lignified,  parenchymatous  cells 
passes  over  gradually  into  narrow,  thick-walled,  somewhat  elongated  wood 
parenchyma  cells,  horizontal  or  diagonal  in  course,  between  which  lie  scat- 
tered, short,  broad  vessels  with  simple  pits  (Fig.  205,  2,g').  These  groups 
are  already  divided  into  numerous  circles  of  vascular  bundles  by  approxi- 
mately cubical  medullary  rays  deposited  in  one  to  three  rows.  The 
phenomenon ,  begins  here  which  continues  in  alternative  zones  out  to  the 
periphery  of  the  wood  body,  viz :  that  the  elements  of  the  one  part  of  the 
bundle,  which  lies  between  two  medullary  rays,  show  a  course  differing  from 
that  in  the  adjacent  bundle.  While  the  cells  and  vessels  of  the  one  part 
seem  cut  crosswise  {2  h"),  the  fibres  of  the  adjacent  part  are  cut  longitudin- 
ally. This  is  found  in  trunks  which  have  overgrown  some  constriction  and 
may  be  explained  only  by  the  theory  that  the  diiTerent  parts  of  the  cambium 
of  the  wood  body,  which  curves  about  the  core  like  a  shell,  are  exposed 
simultaneously  to  different  pressure  and  strain.  Since  the  young  tuber 
body  has  no  exact  spherical  form  but  is  only  approximately  round,  the  parts 
which  are  to  overgrow  the  corners  already  formed  elongate  more  in  the 
same  length  of  time. 

The  elements  become  narrowed,  longer  and  thicker-walled  toward  the 
outside  of  the  tuber  until  they  have  nearly  the  length,  form  and,  in  places, 
arrangement  of  the  normal  wood  body. 

Inside  the  tuber,  as  in  the  wood,  a  differentiation  of  the  annual  rings 
into  spring  and  summer  wood  is  found,  so  that  it  is  evident  that  the  tuber 


866 

is  a  wood  body,  provided  with  the  peculiarities  of  the  species  and  isolated  in 
the  bark ;  its  elements  grow  in  all  directions  around  one  or  more  elongated 
or  short  cores. 


\ "  ....'zhmmmmm^m^^ 


Fig.  20 j.     B;iik  tulx'is  Irom  an  apple  tiunl 


The  cambial  zone  {2  c),  surrounding  the  wood,  annually  produces  a 
new  bark  {2  rs)  and,  in  injuries,  heals  the  wounds  just  as  in  a  normal  trunk. 
Such  an  injury  has  taken  place  in  Fig.  204,2  since  the  bark  and  sap  wood 
have  been  removed  from  the  tip  of  the  tuber  by  some  external  influence.    In 


86; 

consequence  of  this  a  normal  overgrowth  edge  (2  u)  completely  covered 
with  bark  is  produced  which  forms  the  outwardly  noticeable  circular  wall 
about  the  tip  of  the  tuber  (Fig.  204,  ik). 

The  fact,  noticeable  at  first,  that  phloem  fibres  are  found  in  the  centre 
of  a  wood  body,  leads  to  the  conclusion  that  the  tissue  surrounding  the 
phloem  fibre  groups  is  the  place  where  the  formation  of  the  wood  begins. 
This  conclusion  is  still  more  strengthened  by  the  structures  near  the  tubers. 
Frequently  younger  phloem  bundles  are  found  here,  even  at  times  the  very 
youngest  ones  just  appearing  from  the  cambial  zone,  which  are  surrounded 
by  peculiar,  radially  arranged  cells  (Fig.  204,5).  In  some  cases  these 
plate-like  cells  of  the  "phloem  circumvallation"  turn  blue  with  iodine  and 
sulfuric  acid ;  in  most  cases,  however,  they  turn  yellow.  This  shows  that, 
as  a  fact,  the  tissue  surrounding  the  phloem  group  tends  easily  to  cell 
increase. 

The  overgrowth  of  the  phloem  by  cork  tissue  is  in  no  way  restricted  to 
the  tissues  surrounding  the  gnarl  tuber.  In  the  trees  I  have  investigated  it 
was  found  in  different  places  after  many  an  injury.  In  this,  however,  the 
cells  always  have  the  character  of  cork  cells  and  serve  excellently  to  cut  off 
a  diseased  phloem  bundle  from  the  healthy  wood.  Any  one  who  has  worked 
much  with  diseased  trees  knows  how  sensitive  the  bark  cells  are  which  have 
apparently  so  resistant  a  structure.  Their  brown  color  and  the  more  dis- 
tinct appearance  of  their  layers  make  it  possible  to  trace  the  disease  deeper 
into  the  healthy  tissue  than  can  be  done  in  the  surrounding  bark  parenchyma. 

The  overgrowth  of  the  phloem  begins,  as  a  rule,  in  the  cells  of  the 
phloem  sheath  and  remains  limited  at  times  to  one  side,  or  at  least  develops 
more  vigorously  on  the  outerside.  Similar  phenomena,  like  the  overgrowth 
of  the  phloem  bundles,  are  found  also  in  some  parts  of  the  parenchyma. 
Without  any  reason,  known  as  yet,  the  parenchyma  here  substitutes  for  the 
core  a  meristem  zone  in  the  bark  which  increases  by  growing  around  the 
centre  of  fibres,  thus  beginning  the  formation  of  bark  tubers.  Such  tubers 
have  usually  a  som.ewhat  regular  structure  since  the  course  of  the  tissue 
elements  in  several  annual  rings  keeps  to  the  same  direction.  In  a  median 
longitudinal  section  which  may  be  recognized  by  the  fact  that  the  medullary 
rays  lie  in  approximately  the  same  plane,  the  bent  vessels  are  cut  through 
their  whole  length  so  that  they  interrupt  the  dark,  parallel  wood  cell  zones 
as  clear,  concentric  rings. 

The  drawings  (Fig.  206)  made  from  the  bark  of  a  healthy  one-year-old 
pear  twig  give  an  interesting  contribution  to  the  explanation  of  tuber  forma- 
tion. We  see  in  Fig.  206,  i,  the  basal  part  of  a  very  strong  one-year-old  pear 
shoot  of  which  the  buds  (a)  are  set  in  the  normal  two-fifths  position  ;  h  is  the 
one-sided  swelling  in  the  centre  of  the  internode,  reproduced  again  in  cross 
section  in  Fig.  206,  5,  cut  through  in  the  deepest  part,  which  is  turned 
toward  the  base  of  the  twig,  in  Fig.  206,  5  in  the  median  region,  and  in  Fig. 
206,  4  in  the  highest  zone.  In  Fig.  206,  j,  4,  5,  the  same  letters  indicate  the 
same  parts;  r,  the  bark,  g  and  g-,  etc.,  the  bark  vascular  bundles  in  various 


868 

stages  of  development.  It  is  evident  that  those  first  formed  also  become 
smaller  at  first  after  entering  the  axis.-  m  is  the  pith;  w  b,  the  pith  bridge 
of  a  central  leaf  trace,  of  which  the  secondary  bundles  are  unequally  devel- 
oped; m  St,  medullary  rays;  hb  phloem  fibre  groups,  which  compose  the 
central  core  of  the  wood  cord  formed  in  the  bark.  In  Fig.  206,  4  rt  is  the 
bark  killed  by  pressure  and  pressed  into  the  trunk  by  the  xylem  strand 
formed  in  the  axis  of  the  branch.  Fig.  206,  5  g^  indicates  a  xylem  strand 
with  the  beginnings  of  overgrowth;  this  is  seen  to  be  more  strongly  devel- 
oped on  the  outer  side.  Fig.  206,  5  gr'  is  a  xylem  strand  which  has  not  closed 
completely  into  a  wood  cylinder.  Its  formation  took  place  as  follows :  cell 
increase  began  on  the  outer  side  of  the  phloem  fibre  group  in  the  phloem 
sheath  and  led  to  the  formation  of  vascular  elements  and  wood  cells.  The 
one-sided  wood  body  thus  produced  is  closed  by  the  gradual  union  of  the 
two  edges,  turned  to  the  centre  and  growing  toward  each  other.  Fig.  206, 
5  c'  is  the  cambial  zone  of  a  xylem  strand  already  closed  internally  but  still 
pressed  into  a  kidney  shape  at  the  place  of  union.  Fig.  206,^  gives  a  part 
of  Fig.  206, J  g'  somewhat  magnified. 

In  Fig.  206,-?  is  seen  the  complete  correspondence  with  the  centre  of 
the  gnarled  tuber  in  the  apple,  hb  is  the  phloem  fibre  group ;  p,  the  wood 
parenchyma ;  g,  the  vessels ;  x,  short,  cross-cut  wood  cells ;  x',  wood  cells, 
extending  horizontally  from  the  inner  convexity  of  the  wood  cord  at  the 
place  where  the  two  edges  have  united ;  m  represents  the  rows  of  medullary 
rays  spread  out  like  grasping  arms ;  c,  the  cambial  zone  surrounding  the 
strand;  r,  the  youngest  bark  parenchyma  of  the  specialized  zone  of  bark. 

The  xylem  strands  (Fig.  206,5)  ^^^>  therefore,  produced  at  the  base  of 
the  swelling  by  an  unusually  abundant  nutrition  of  the  phloem  sheath; 
theii-  primordia  lie  at  unequal  heights.  When  enlarging,  they  compress  at 
first  the  bark  tissue  (Fig.  206,5)  which  separates  them  from  each  other  and 
finally  also  the  tissue  lying  above  them,  which  separates  them  from  the  axial 
cylinder  and  is  found  later  as  a  brown  mass  in  the  centre  of  the  wood  body 
(Fig.  206,^  rt).  With  their  entrance  into  the  axial  cylinder,  the  form  of 
the  xylem  strands  in  the  bark  is  changed;  the  core  becomes  eccentric  and 
finally  pressed  back  to  the  tip  of  the  wedge-shaped  strand  as  shown  in  Fig. 
206,^  g',  g-,  g^.  The  change  of  form  is,  therefore,  exactly  the  reverse  of 
that  undergone  by  the  normal  vascular  bundle  which  enters  the  bark  from 
the  axial  cylinder. 

Farther  out  the  branch  becomes  normal^ . 

The  occurrence  of  bark-produced  wood  strands,  therefore,  explains  as 
follows  the  production  of  the  gnarl  tuber.  The  mature  tuber  is  a  wood 
sphere  isolated  in  the  bark,  of  which  the  upper  surface  is  composed  of  a 
cambial  and  bark  mantle,  receiving  its  nourishment  from  the  surrounding 
bark  tissue.     According  to  the  investigations  of  the  above-named  scientists, 

1  On  the  similarity  of  this  formation  of  the  secondary  wood  with  that  in  the 
Papindaceae  compare  Sorauer,  Die  Knollenmaser  der  Kernobstbaume.  Landwirtsch. 
Versuchsstationen  1-878. 


y 


Fig-.  206.     Production  of  isolated  wood  centres  in  the  bark  of  a  one  year  old  pear 

branch. 


870 

wliicli  need  repeating,  the  gnarl  tubers,  or  tuber  gnarls,  can  develop  from  a 
dormant  bud  and  are,  therefore,  originally  connected  with  the  wood  body 
of  the  branch.  In  many  cases,  however,  they  are  produced  as  bowl-like 
wood  deposits  around  a  group  of  phloem  fibres,  or  some  other  bark  tissue 
group  without  any  connection  with  the  wood  cylinder  or  a  bud  primordium. 
The  tuber  is  gradually  pushed  out  into  the  outermost  regions  of  the  bark, 
which  is  beginning  to  form  the  cortex ;  the  longitudinally  elongated  xylem 
strands  of  the  bark,  related  to  the  tuber  formation,  can  press  back  into  the 
axial  body  and  become  elements  of  the  normal  wood  cylinder  of  a  branch. 
External  wounds  in  the  tuber  body  are  healed  by  overgrowth,  just  as  in  the 
normal  branch  and  there  is  no  reason  to  doubt  that  adventitious  buds  can 
develop  from  the  overgrowth  edges  as  well  as  from  the  normal  bark  of  the 
tuber,  as  has  been  stated  for  the  olive. 

Mention  should  be  made  of  the  fact  that  the  large  spherical  swellings, 
produced  on  oak  branches  by  the  overgrowth  of  places  where  Loranthus 
curopacus  had  grown,  have  also  been  termed  gnarl  tubers  or  heads.  Accord- 
ing to  our  division  of  the  subject,  these  are  not  actual  "gnarls"  but  gnarly 
overgrowth  edges. 

Tine  Tammes^  describes  as  abnormal  overgrowths  the  peculiar  cone- 
like processes  on  Fagus  silvatica  which  usually  grow  broader  on  one  side 
and  overlap.  Investigation  shows  that  the  stump  of  a  branch  is  involved 
here,  which  has  been  closed  by  gnarly,  hypertrophied  wound  edges.  The 
hypertrophy  has  been  caused  by  the  severe  pruning,  of  the  trees  on  account 
of  which  a  superabundance  of  plastic  material  is  deposited  at  the  remaining 
centres  of  growth. 

Peters,  in  his  observations  on  Helianthus  annuus  and  Polygonum  cus- 
pidatum-  gives  an  example  of  bark  tubers  in  herbaceous  plants.  The  tubers 
produced  in  the  middle  bark  should  be  considered  as  the  reaction  of  the 
plant  to  wound  stimulus.  A  few  cell  groups  in  the  bark  die  and  dry  up; 
the  cavity  thus  produced  becomes  surrounded  by  a  cambial  zone  which 
forms  wood  on  the  inner  side  and  bark  tissue  on  the  outer. 

Th.  Hartig''  mentions  examples  of  tuber  formation  in  roots  when 
describing  the  fact  that  young  aspens  occur  in  great  numbers  on  cleared 
tracts  where  no  seed  bearing  trees  had  stood  for  some  time.  As  Th.  Hartig 
explains,  the  little  plants  owe  their  existence  to  the  continued  growth  of 
roots  left  from  long  dead  and  outwardly  vanished  trees. 

The  basis  of  root  growth  in  these  cases  is  always  a  tuber-like  woody 
thickening  of  a  weak  root  strand.  The  tubers  themselves  are  somewhat 
like  those  at  the  gnarly  base  of  old  oaks  or  lindens  and  those  in  the  bark  of 
the  red  beech ;  they  are  the  woody  trunk  of  a  dormant  eye  which,  completely 
individualized,  lives  a  parasitic  life  on  the  root  of  the  parent  plant  "like  the 
dormant  eyes  of  the  American  species  of  pine."     The  aspen  roots  are  kept 

1  Tine  Tarnmes,  tJber  eigentumlich  gebildete  Maserbildungen  an  Zweigen  von 
Fagus  silvatica  L.    Recueil  des  travaux  hot.  Ncerl.  No.  1.     Groningen  1904. 

2  Cit.  Zeitschr.  f.  Pflanzenkrankh.  1905,  p.  26. 

3  Loc.  cit.,  p.  429. 


871 

alive  by  these  tubers  without  any  growth  of  the  feeding  root.  As  a  rule, 
the  piece  of  root,  bearing  the  tuber,  is  found  to  be  dead  and  decaying  a  few 
centimeters  from  the  tuber.  Andreae^  describes  gnarled  tubers  on  the  roots 
of  Ailanthus  glandulosa;  they  are  produced  from  roots  and  from  branch 
primordia. 

In  connection  with  this,  a  structure  may  be  mentioned  here  which  is 
often  described  as  the  Club  root  of  beets~  but  has  not  yet  been  sufficiently 
explained.  Usually  in  dry  soil  there  appears  near  thd  crown,  or  a  little 
farther  down,  a  spherical  swelling  covered  with  cork,  resembling  the  root 
body  in  structure  but  differing  from  it  in  composition  because  of  a  greater 
water,  ash  and  protein  content.  The  vascular  body  shows  that  the  swelling 
should  be  considered  as  the  enlargement  of  a  vascular  ring  of  the  parent 
root  and  may,  therefore,  be  considered  an  offshoot  of  it  probably  caused  by 
an  excess  of  nitrogen  after  some  injury^.  The  swelling  is  not  parasitic  but, 
because  of  its  porous  bark  structure  and  its  inert  sugar  content,  is  easily 
infested  by  animal  and  vegetable  enemies. 

Leaf  Injuries. 

In  consideration  of  the  fact  that  the  results  of  injuries  appear  more 
clearly  in  leaves  and  other  fleshy  parts  of  plants,  we  will  call  attention  to 
the  conditions  which  w^e  call  wound  stimulus.  The  first  effect  of  the 
stimulus,  which  is  exercised  on  the  organ  by  every  injury,  may  well  consist 
in  a  traumatropic  deposition  of  protoplasm  in  the  tissue  immediately  adja- 
cent to  the  wound  surface.  According  to  Nestler's*  investigations,  the 
protoplasm  in  the  uninjured  cells  collects  on  the  side  toward  the  wound  and 
somewhat  later  the  nucleus  moves  toward  that  side.  This  action  of  the 
stimulus  extends  a  few  cell  rows  into  the  healthy  tissue  and  after  about  48 
hours  reaches  its  maximum.  After  this,  a  more  or  less  complete  return  to 
the  normal  condition  sets  in.  This  change  in  position  seems  to  take  place 
more  quickly  in  the  light  than  in  the  dark. 

In  the  same  way,  the  chlorophyll  apparatus  often- undergoes  a  consid- 
erable change  of  position-'^.  In  many  cases  an  increase  of  respiration  may 
be  noticed  at  the  same  time;  in  the  fleshy  parts  of  plants,  especially,  a  rise 
in  temperature  could  be  proved  which  has  been  called  fever  reaction".  The 
production  of  carbon  dioxid  in  wounded  leaves  is  said  to  be  especially  in- 
creased if  they  are  poor  in  carbon-hydrates'^.     The  reactions  set  in  earlier 

1  Andreae,  tJber  abnorme  Wurzelanschwellungen  bei  Ailanthus  glandulosa. 
Inaugural  dissertation.     Erlangen  1894. 

2  Briem,  H.,  Strolimer  und  Stift,  Die  Wurzelkropfbildung-  bei  der  Zuckerriibe. 
Osterr.  Ungar.  Z.  f.  Zuckerindustrie  1892,  Part  2. 

3  Geschwin,  Le  goitre  de  la  betterave.  La  sucrerie  indigene.  Cit.  Bot.  Centralbl. 
f.  Bakt.  II,  1905,  p.  486. 

4  Nestler,  A.,  tJber  die  durch  Wundreiz  bewirkten  Bewegungserscheinungen  des 
Zellkerns  und  des  Protoplasmas.     S.  Akad.    Wien  CVII,  I,  1898. 

5  Pfeffer,  W.,  Pflanzenphysiologie.  2nd  Ed.  1904,  Vol.  II,  p.  819.  Here  also 
literature  on  the  action  of  Wound  Stimulus. 

6  Richards,  Herbert  Maule,  The  evolution  of  heat  by  wounded  plants.  Annals 
of  Bot.  XI;  cit.  Bot.  Jahresber.  1897,  p.  99. 

7  Dorofejew,  N.,  Zur  Kenntnis  der  Atmung  verletzter  Blatter.  Ber.  d.  Deutsch. 
Bot.  Ges.  XX,  1902,  p.  396. 


872 

or  later  according  to  the  degree  of  injury.  According  to  Townsend*  the 
hastening  of  growth  becomes  evident  in  6  to  24  hours  after  slight  injuries, 
while  severe  injuries  at  first  cause  an  arrestment  before  the  increase  in  rate 
begins,  which,  according  to  the  plant,  reaches  its  maximum  in  12  to  96  hours 
and  then  gradually  returns  to  the  normal  condition.  Krassnosselsky=  traces 
the  increase  of  respiration  to  an  increase  of  the  respiratory  enzyme.  He 
carries  out  further  Kovchoff's  experiments  which  show  that  an  increase  in 
the  whole  amount  of  protein  and  especially  of  the  nucleo-proteids  takes 
place  after  an  injury  and  then  proves  (in  injured  bulbs)  that  the  sap  con- 
tains more  oxydases  than  does  that  from  uninjured  specimens.  The  same 
is  true  of  potatoes. 

The  subsequent  reactions  of  leaves  after  injury  vary  greatly  according 
to  the  species  of  the  plant,  the  age  of  the  leaf  and  the  time  of  injury.    We 


Fig.   207.     Injury   to  a   leaL"  of    Leucojum    vernum,   which   is   being  closed   l)y  callus 
I'ormation.     (Alter  Frank.) 

will  content  ourselves  with  discussing  the  two  extremes,  viz :  the  reaction  of 
a  tough  leathery  leaf  and  that  of  a  fleshy  one.  In  the  former,  Prunus 
Laurocerasus  represents  a  case  in  which  a  sloughing  process  of  the  injured 
cell  group  is  connected  with  the  injury  as  has  already  been  mentioned  under 
the  results  of  spraying  with  copper.  According  to  Blackman''  and  Matthaei* 
cither  the  injured  cells  alone  die,  or  those  immediately  adjoining  them, 
according  to  the  part  of  the  leaf  injured.  A  brown  zone  with  a  Hghter 
colored  centre  is  produced  around  the  wound.  The  epidermis  splits  in  this 
hyaline  region  and  colorless,  very  thin-walled,  cells  grow  out  of  the  adjoin- 

1  Townsend,  C.  D.,  The  correlation  of  growth  under  the  influence  of  injuries;  cit. 
Bot.  Jahresber.  1897,  I,  p.  98. 

-  Krassno.«selsky,  Bildiing  der  Atmungsenzyme  in  verletzten  Pflanzen.  Ber.  d. 
Deutsch.  Bot.  Ges.  1905,  Vol.  XXIIT,  p.  143. 

3  Ber.  d.  Deutsch.  Bot.  Ges.  1903,  p.  165. 

4  Blackman,  F.  F.,  and  Matthaei,  G.  L.,  On  the  reaction  of  leaves  to  traumatic 
stimulation.    Ann.  Bot.  XV;  cit.  Zeitschr.  f.  Pflanzenkrankh.  1902,  p.  61. 


873 

ing  mesophyll.  These  form  a  cuticle  and  thus  represent  a  complete  cover- 
ing of  the  wounded  leaf  surface.  When  this  covering  is  complete,  the  dead 
tissue  is  thrown  off.  In  this  the  pressure  of  moist  air  is  taken  for  granted. 
In  other  cases  a  normal  periderm  is  formed  from  several  cell  layers  which 
suffices  as  a  protection  for  the  healthy  leaf  tissue. 

The  second  case  of  the  healing  of  leaf  injuries,  viz :  by  callus  formation, 
is  explained  by  the  accompanying  figure.  It  is  the  cut  wound  from  a  cut 
on  Leucojum  vernum.  The  wound  lay  in  the  open  space  between  the  two 
tissues  of  lamellae  /  and  f  •,vv  vv  are  the  edges  of  the  wound  with  the  dead 
pieces  of  tissue.  The  wound  cavity  is  now  filled  by  the  callus  cells  devel- 
oping by  elongation  from  the  fresh  tissue,  which  lack  chlorophyll  and  have 
suberized  walls.  The  normal  condition  of  the  leaf  is  represented  at  the 
left  side  of  the  figure  where  i  i  indicates  a  large  air  chamber;  the  tissue  sur- 
rounding it  has  not  been  changed  by  wound  stimulus,  o  is  the  upper  and  u 
the  .under  side  of  the  leaf.  Many  fleshy  leaves  react  according  to  this 
scheme,  but  their  processes  of  healing  vary  greatly,  depending  on  the  subse- 
quent participation  of  the  process  of  cork  formation.  Complete  union  of 
the  edges  of  the  wound  can  also  take  place,  as  may  be  observed,  for  example, 
in  the  cut  surfaces  of  fleshy  roots  and  tubers^  The  union  is  sometimes  the 
result  of  organic  coalescence,  sometimes  only  a  cementing  of  the  surfaces 
since  the  cut  cells  are  changed  into  a  gum-like  mass  by  the  swelling  and 
disintegration  of  their  walls. 

The  leaf  can  under  certain  circumstances  reproduce  the  part  arti- 
ficially removed  (regeneration,  according  to  Kiister)  or  form  a  compen- 
sating organ  (restitution")  according  to  the  specific, character  of  the  leaf, 
its  youth  and  its  distance  from  the  reserve-substance  containers. 

Frequently  whole  leaves,  or  pieces  of  leaves,  removed  from  the  plant, 
can  form  new  roots  and  aerial  axes.     This  capacity  is  utilized  for 

Leaf  Cuttings. 

The  best  known  and  most  frequent  use  of  leaf  propagation  is  found 
in  begonia  culture.  According  to  Hansen^,  in  the  various  varieties  of 
Begonia  Rex  wounds  produced  by  slashing  the  nerves  of  the  leaf  lying  flat 
on  the  soil  are  closed  at  once  by  callus.  In  this  way  a  tuberous  tissue  is 
formed  on  the  mother  leaf  from  which  tissue,  or  that  immediately  sur- 
rounding it,  roots  develop ;  later,  sprouts  are  formed  from  the  same  tissue, 
which,  however,  do  not  develop  their  own  roots  but  are  nourished  by  the 
above-mentioned  roots  of  the  callus.  Sprouts  develop  there  from  one  or  a 
few  cells  of  the  epidermis  near  the  cut  rib,  sometimes  nearer,  sometimes 
farther  from  the  wound.     In  such  cells,  a  horizontal  partition  wall  is  pro- 

1  Fig-dor,  Wilhelm,  Studien  iiber  die  Erscheinung-  der  Verwachsung-  im  Planzen- 
reiche.     Sitzungsber.  d.  Akad.  d.  Wissensch.  Wien;  cit.  Bot.  Zeit.  1S91,  No.  23. 

2  Figdor,  "Wilhelm,  tjber  Regeneration  der  Blatt-spreite  von  Scolopendrium. 
Bericht  d.  Deutsch.  Bot.  Ges.  1906,  Vol.  XXIV,  Part  1.— Figdor,  Wilhelm,  tJber  Resti- 
tutionserscheinungen  an  Blattern  von  Gesneriaceen.  Jahrb.  f.  wiss.  Bot.  1907,  Vol. 
XLIV,  Part  1. 

3  Hansen,  Ad.,  Vorlauflge  Mitteilung.     Flora  1879,  p.  254. 


874 

duced  at  first  and  gradually  by  further  division  the  meristem  of  the  young 
sprout  from  which  a  roll  differentiates  as  the  first  leaf. 

The  roots  are"  formed  laterally  from  a  few  cells  lying  near  the  cambial 
zone  of  the  vascular  bundle.  These,  therefore,  "endogenously"  formed 
roots  soon  rupture  the  overlying  tissue.  As  l*"r.  RegeP  states,  the  roots  of 
begonia  branch  cuttings  can  aJso  arise  from  the  inter-fascicular  cambium. 
This  author,  who  has  investigated  several  other  begonias  beside  Begonia 
Rex  with  rhizome-like,  recumbent  petioles,  as,  for  example,  Begonia  im- 
perialis  and  B.  xanthina,  mentions  that  the  formation  of  buds  also  takes 
place  on  the  leaf  blade  near  the  incisions.  After  the  epidermal  cells  have 
divided,  the  underlying  collenchyma  and  the  ground  tissue  are  also  drawn 
into  the  new  formation  and  help  in  producing  the  mound  of  cicatrization 
tissue  at  the  place  cut.  This  tissue  differs  from  that  of  branch  cuttings 
only  in  the  fact  that  here  the  epidermis  participates  in  the  cell  increase. 

This  activity  of  the  epidermis  can  become  of  very  especial  physiological 
imi)ortance  immediately  after  the  cut  is  made  since  a  few  of  the  upper  epi- 
dermal cells  near  the  wound  elongate  like  hairs  (pseudo-root  hairs)  and, 
without  doubt,  develop  a  root-like  activity  until  the  true  roots  are  formed.  . 

In  the  adjoining  Fig.  208  are  shown  the  new  structures  on  the  cut  sur- 
face of  a  larger  leaf  rib  in  a  hybrid  Rex  begonia.  A  indicates  the  old  part 
of  the  leaf,  B  the  new  structures.  At  first  an  abundant  callus  tissue  {c) 
develops  from  the  cut  and  soon  shows  an  apical  growth  of  its  cell  rows  but 
indicates  by  the  parallel  edges  of  the  cork  cells  that  it  is  in  the  process  of 
transition  to  overgrowth  edges.  The  endogenously  formed  new  root  (w) 
breaks  out  on  the  under  side  of  the  boundary  between  the  callus  and  the  old 
leaf  tissue,  while  on  the  upper  side,  two  new  bud  primordia  have  already 
been  formed.  The  younger  one  of  these  shows  at  d  the  meristematic  tissue 
of  the  young  bud  with  the  epidermis  {e).  This  meristematic  tissue  is  pro- 
duced by  the  division  of  the  original  epidermal  cells  and  the  sub-epidermal 
tissue.  The  second  bud  has  been  formed  earlier  at  a  point  lying  farther 
away  from  the  cut  and  already  is  further  developed.  The  real  bud  cone  {d) 
is  already  overgrown  by  a  more  convex  leaf  primordium  {hi)  into  which 
extend  young  spiral  vessels  (/).  The  vascular  bundle  ring  of  the  older 
part  of  the  leaf  is  indicated  at  g,  while  t  indicates  the  vascular  bundles 
extending  into  the  new  root. 

Kny-  noted  that  the  vascular  bundles  had  become  larger  on  the  petioles 
of  Begonia  Rex,  on  which  adventitious  sprouts  had  been  produced.  The 
cambium,  like  the  adjacent  ground  tissue,  had  continued  its  cell  division, 
whereby  the  new  walls  between  the  adjacent  bundles  were  predominantly 
parallel  to  the  outer  surface  of  the  petioles.     Kny  regarded  this  as  the 


1  Reg-el.  Fr.,  Die  Vermehrunfr  der  Begoniaceen  aus  ihren  Blattern  usw. 
Jena'ische  Zeitschr.  f.  Naturwiss.  1876,  p.  477;  cit.  Bot.  Jahresber.  1876,  p.  423,  439, 
452,  etc. 

2  Kny,  L,.,  t)ber  die  Ein-schaltunj;:  des  Blattes  in  das  Verzweig-ungssystem  der 
Pflanze.  From  "Naturw.  Woclienschrift"  1904;  cit.  in  Bot.  Centralbl.  (Lotsy)  1904, 
No.  50,  p.  612. 


875 

beginning  of  an  inter-fascicular  cambium  which,  developing  further,  would 
have  closed  the  peripheral  bundles  into  a  circle. 

From  the  many  observations  already  made  on  leaf  cuttings,  the  assump- 
tion is  justifiable  that  the  processes  described  above  for  begonia  may  occur 
also  in  many  other  leaf  cuttings.  The  foliage  shoots  develop  from  more  or 
less  superficial  cells ;  the  root  primordia  are  produced  from  the  cells  border- 
ing the  cambial  zone  and  either  break  through  the  old  tissue  of  the  cuttings 
or  arise  from  the  cicatrization  tissue  of  the  wound.  Variations  in  the 
different  genera  are  usually  unimportant  and  differences  of  opinion  among 


yCi'^-iJjlinsu^^ 


^n> 


'CT' 


_^j^m-^ 


Fis.  208.     Leaf  cutting:  from  a  hybrid  form  of  Begonia   Rex. 


the  various  authors  are  often  explained  by  the  fact  that  individuals  of  the 
same  plant  species  under  different  conditions  and  of  different  age  do  not 
always  show  exactly  the  same  processes.  Beinling's^  investigations,  for 
example,  prove  that  the  genus  Peperomia  does  not  form  any  callus  but 
covers  the  cut  surface  with  wound  cork.  He  also  found  buds  produced 
from  the  ground  parenchyma  of  the  petiole,  or  the  blade,  but  not  from  the 
epidermis  and  always  independent  of  the  vascular  bundle.     On  the  other 


1  Beinling-,  E.,  Untersuchimgen  liber  die  Entstehung-  der  adventiven  Wurzeln 
und  Laubknospen  an  Blattstecklingen  von  I'eperomia.  Inauguraldissertation. 
Breslau  1878,  p.  23. 


876 

hand,  Hansen'  describes  in  detail  the  processes  of  root  and  sprout  formation 
in  Achimenes  and  Peperomia  from  the  callus.  In  this  only  the  first  adven- 
titious roots  are  produced  from  the  already  existing  tissue  elements.  After 
the  callus  tissue  had  increased  for  some  time  numerous  pro-cambial  strands 
showed  themselves  in  the  callus,  extending  in  all  directions  toward  the 
surface.  Their  cells  soon  changed  into  tracheae ;  so  that  "callus"-  is  pro- 
vided with  a  branched  system  of  vascular  bundles.  Soon  the  peripheral 
cells  of  this  tissue  appear  to  be  abundantly  filled  with  protoplasm;  they 
divide  and  produce  a  meristem  which  differentiates,  as  do  the  normal  vege- 
tative points,  and  soon  an  epidermis  becomes  very  distinct. 

In  the  leaf  cuttings  of  the  monocotyledons,  the  processes  of  bud  forma- 
tion are  the  same  as  those  in  dicotyledons.  Magnus''  describes  bulb  cuttings 
of  hyacinths.  Numerous  adventitious  buds  are  formed  on  the  ventral  side 
of  the  cut  surface  which,  in  case  the  bulb  scale  was  still  young,  are  produced 
from  an  epidermal  cell  or  in  older  scale  pieces  from  the  underlying  paren- 
chyma. At  first  tender  knobs  of  tissue  are  formed  from  the  dividing  tissue 
cells  which  continue  growth  at  the  apex  in  diverging  cell  rows;  dividing 
dichotomously.  It  is,  therefore,  actual  callus.  On  further  developed  knobs, 
a  circular  wall  appears,  developing  into  the  first  sheath-like  scale  of  the 
adventitious  bud,  while  the  enclosed  apical  cell  shows  growth  in  diverging 
cell  rows.  On  the  bulb  scales  of  Lilium  Tigrinum  and  L.  Auratum  the  buds 
are  also  formed  on  the  outer  edge  of  the  inner  side.  The  rootlets,  arising 
on  the  outer  side  from  the  phloem  region  of  the  vascular  bundles,  live  only 
a  short  time  since  the  young  plant  at  once  forms  independent  roots. 

The  processes  of  bud  formation  in  leaf  cuttings  do  not  differ  essentially 
from  the  voluntary  production  of  the  buds  on  uninjured  leaves  on  the  plant. 
Numerous  examples  of  these  are  well  known*.  They  have  been  observed , 
in  mosses  and  ferns"',  in  lilies  and  other  monocotyledons,  most  numerously 
in  dicotyledons.  Beijerinck  formed  as  a  law  for  the  latter,  that  the  vascular 
bundles  of  the  leaf  have  an  influence  on  the  primordia  of  the  adventitious 


1  Hansen,  Ad.,  Uber  Adventivbildung'en.  Sitzungsber.  d.  phys.-med.  Soc.  zu 
Erlang-en  vom  14  Juni,  1880;  cit.  Bot.  Centralbl.  ISSO,  p.  1001. 

2  Opportunity  is  here  griven  to  call  attention  to  the  fact  that  the  authors  include 
two  different  conditions  under  the  name  "Callus." 

They  call  tissue  callus  which  is  produced  from  the  first  cell  divisions,  and  has 
for  some  time  an  arrang-ement  in  rows;  it  continues  growth,  especially  at  the  apex 
of  the  cell  rows,  and  lacks  all  differentiation. 

In  the  second  place,  however,  the  authors,  in  accordance  with  general  usage, 
understand  by  callus  the  structure  differentiated  from  the  callus  by  the  production 
of  a  cork  zone,  the  formation  of  an  inner  meristem  centre  and  the  separation  of  a 
ground  tissue.  This  structure  has  already  become  similar  to  the  tissue  from  the 
wound  in  which  it  is  produced.  However,  the  juvenile  conditions,  distinguished  by 
apical  growth,  should  be  distinguished  from  these  mature  conditions  and  I  propose, 
on  this  account,  to  apply  the  term  "callus"  only  to  the  first  structures,  while  the 
later  stages  can  be  known  as  "cicatrization  tissue." 

3  Magnus,  Hyacinthenblatter  als  Stecklinge.  Sitzungsber.  d.  Ges.  naturforsch. 
Freunde  vom  16  Juli,  187S;   cit.  Bot.  Zeit.  1878,  p.  765. 

4  Beijerinck,  M.  W.,  Over  het  onstaan  van  Knoppen  en  wortels  uit  bladen. 
Nederl.  Kruidkund.  Archief.  Serie  II,  Deel  III,  p.  438-493;  cit.  Bot.  Centralbl.  1883, 
No.  17,  p.  112. 

5  Farlow,  Bot.  Zeit.  1874,  p.  ISO. — Cramer,  Geschlechtslose  Vermehrung  des 
Farnprothalliums,  namentlich  durch  Gemmen  resp.  Konidien.  Denkschr.  d.  Schweiz. 
Naturforsch.  Ges.  XXVIII.  1880. 


877 

organs.  The  adventitious  buds  are  always  found  on  the  upper  surface 
where  the  woody  part  of  the  vascular  bundles  is  turned  toward  the  upper 
side  of  the  leaf;  they  are  produced  in  the  axes  of  the  ribs  and  are  usually 
more  strongly  developed  the  thicker  the  vascular  bundles.  The  roots  are 
produced  from  the  phloem  side  of  the  vascular  bundles. 

RegeP  enumerates  the  plants  on  which  buds  of  leaf  origin  have  been 
observed.  A  few  examples  may  be  named  here  since  the  buds  develop 
their  own  roots  after  having  been  carefully  removed  from  the  leaf  and, 
therefore,  are  of  importance  in  propagation.  Besides  the  well  known 
Bryophyllum  calycinum,  which  Berge-  studied  and  on  which  incisions 
between  two  serrations  of  the  leaf  develop  a  meristematic  tissue  in  an  early 
stage  and  from  this  meristem  buds,  the  following  species  are  noteworthy: 
Hyacinthus  Pauzolsii,  Fritillaria  impcrialis,  Omit  hog  alum  thyrsodies, 
Drimia,  Malaxis,  Cardamine,  Nasturtium,  Brassica  oleracea,  Ranunculus 
bulbosus,  Chelidonium  majus,  Levisticum  offic,  Ultricularia,  Begonia  quad- 
ri-color,  B.  phyllomaniaca'-^.  Hansen*  mentions  also  Hippuris,  Elodea 
canadensis  and  other  water  marsh  plants.  Caspary"  mentions  Nymphaea 
micrantha  and  its  hybrids.  He  also  cites  examples  in  which  an  inflorescence 
developed  instead  of  a  leaf.  In  this  way  the  upper  side  of  the  petiole  of  a 
cucumber  (Cucuniis  sativus)  was  covered  with  more  than  120  staminate 
blossoms  without  a  single  vegetable  leaf. 

The  success  of  propagation  by  leaf  cuttings  depends  upon  the  indi- 
viduality of  the  leaf  as  well  as  upon  the  plant  species.  Very  young  leaves 
must  be  excluded  because  of  the  immaturity  of  their  tissue  systems ;  very 
old  ones  because  of  their  scanty  life  energy  and  the  ripeness  of  their  chloro- 
phyll apparatus. 

According  to  Lindemuth's'^  observations,  in  genera  where  the  leaves  can 
be  used  as  cuttings,  the  plants  thus  produced  are  on  an  average  stronger 
than  those  from  wood  cuttings.  As  soon  ^  as  a  leaf  has  developed  a  few 
roots,  it  may  be  considered  a  new  individual,  even  when  it  is  not  able  to 
produce  shoots.  This  arises  from  the  capacity  of  such  leaves  to  live  longer 
than  unrooted  ones  and  GoebeF  could  also  prove  an  increased  growth  in 
thickness  (in  Bryophyllum).  Lindemuth  also  observed,  in  a  begonia,  that 
a  flower  shoot  can  be  formed  instead  of  foliage  shoots  in  leaf  cuttings.  This 
circumstance  might  indicate  that  the  leaves  furnish  different  products  of 
assimilation  at  different  ages  and  places  on  the  axis.  Usually  the  assimilates 
capacitate  the  bud,  produced  on  the  leaf  cutting,  to  form  only  foliage  shoots. 


1  L.OC.  cit,  p.  452. 

2  Beitrag-e  zur  Entwicklungsg-eschichte  von  Bryophyllum  calycinum.  Zurich 
1877;  cit.  Bot.  Jahresber.  rv,  p.  423. 

^-  Mohl,  t^ber  die  Cambiumschicht  des  Stammes  der  Phanerogamen  und  ihr 
Verhaltnis  zum  Dickenwachstum  desselben.     Bot.  Zeit.  1858,  p.  196. 

4  Log.  cit.,  p.  1002. 

■'■'  Casparv,  Bliitensprosse  auf  Blattern.  Schriften  d.  phys.-okonom.  Gesellsch. 
XV,  1874,  p.  99. 

6  Lindemuth,  H.,  Weitere  Mitteilungen  iiber  regenerative  Wurzel-  und  Spross- 
bildung  auf  Laubblattern  (Blattstecklinge).     Gartenflora  1903,  p.  619. 

7  Flora  1903,  p.  133. 


878 

Often,  however,  they  are  of  a  concentration  which  makes  possible  the 
formation  of  flower  buds. 

In  general  practice  at  times  the  petiole  is  used  for  jiropagation  instead 
of  the  leaf,  in  case  the  leaf  itself  is  too  tender.  A  recent  example  is  the 
propagation  of  the  cultivated  forms  of  Begonia  scmperflorens,  which  is  sold 
under  the  name  of  Gloire  de  Lorraine  and  greatly  prized  as  a  winter 
bloomer'.  In  February  the  most  vigorous  leaves  are  cut  ofif  close  to  the 
stem  and  the  petiole  set  i  to  2  cm.  deep  in  sand  and  peat  mold.  At  a  tem- 
perature of  18  to  22  degrees  C.  these  petioles  form  root  balls  as  large  as 
walnuts.  Other  begonias  as,  for  example,  the  Rex  forms  set  roots  from 
their  petioles  but  almost  never  develop  strong  buds.  The  petioles  of  cab- 
bage, celery  and  other  fleshy  plants  behave  similarly. 

The  flower  stems  of  Primula  sinensis  may  be  used  successfully  as  cut- 
tings. Cramer'-  used  flowers  with  the  leaf-like  perianth  of  this  plant,  in 
which  buds  were  produced  in  the  axes  of  the  reproductive  leaves.  A  case, 
which  Baillon  observed,  showed  that  the  fruit  could  also  be  used  as  cuttings ; 
in  this,  roots  developed  from  the  fruit  of  a  cactus^.  The  same  author  also 
cut  in  two  just  above  the  base  the  ovary  of  Jussieus  salicifolia.  This  bore 
two  leaflets  near  the  centre,  and  was  cut  during  and  after  blossoming  in 
such  a  way  that  the  ovules  could  be  seen ;  these  cuttings  were  set  in  a  pot. 
Three  weeks  later  the  well-rooted  cuttings  w^ere  transplanted.  A  small 
branch  with  scales  appeared  in  the  angle  of  the  carpels.  The  upper  part  of 
the  blossom  died  and  a  circular  scar  was  formed*.  Irmisch  describes  root 
formation  on  the  cotyledons  of  Biinium  crcticum  and  Carnm  Bulhocasta- 
niinv'.  I  have  seen  root  formation  in  the  broken-ofif  cotyledons  of  beans 
(Phaseolus  vulgaris).  Carriere  found  roots  on  the  fruits  of  Lilium  lanci- 
foliiini.  Reinling"  found  flower  stems  of  Echevcria  which,  in  moist  sand, 
had  grown  roots. 

Hildebrand"  describes  a  fruit  of  Opuntia  Ficus  indica  out  of  w^hich  a 
second  had  sprouted ;  both  fruits  after  separation  from  the  iplant  developed 
leaf  sprouts.  The  same  thing  happened  with  blossom  buds  of  Opuntia 
Raffinesquiana.  Therefore,  each  plant  organ  may  be  capable  of  developing 
leaf  sprouts  b}  the  formation  of  adventitious  buds,  provided  first  that  it 
contains  enough  resen-e  substances  to  live  for  some  time  separated  from  the 
parent  plant,  and  secondly  that  the  external  conditions  are  favorable.  A 
summary  by  Magnus"*  gives  further  details  together  with  the  theories  of 
Klcbs,  Goebel  and  others. 


1    Kir.st,   Vermeil  runs'   fler   Begonie   "C51()ire   dc    Lorraine."      I'rakt.    Katgeber   im 
OJ:)st-  u.  Gartenbau  1906,  No.  5. 

-  Bildungsabweichungen,  p.  37. 

3  Vegetable  Teratologie,  p.  160. 

*  Bot.  Zeit.  1S6.5.  p.  527,  from  Adansonia,  Vol.  I,  p.  181. 

s  Flora  1S5S,  p.  32,  42. 

6  Beinling,  Unler.suchungen  iiber  die  Entstehung  der  adventiven  Wurzeln  und 
Laubknospen  an  Blattstecklingen  von  Peperomia.'    Inaug.-Diss.     Breslau   1878. 

7  Hildebrand,    F.,    tjber    Bildung    A'on    Laubspro.ssen    aus    BlUtensprossen    von 
Opuntia.     Ber.  d.  Deutsch.  Bot.  Ges.  1888,  Vol.  VI,  p.  109. 

*<  Magnus,  Weiner,  Regenerationserscheinungen  bei  Pflanzen.     Naturwissensch. 
AVochenschrift  1906,  No.  40. 


879 

Injury  to  the  Foliage. 

The  results  of  partial  or  entire  defoliation  must  naturally  become 
apparent  in  the  amount  of  dry  substance  produced.  The  effect  varies 
according  to  the  amount  and  age  of  the  leaves  removed  and  also  the  possi- 
bility of  compensation  for  the  lack  of  foliage  by  the  existing  buds  and  the 
amount  of  reserve  substances  necessary  for  their  unfolding  stored  in  the 
axis. 

The  annual  reports  on  forestry  give  sufficient  examples  for  forest 
trees.  It  is  not  necessary  to  go  further  into  this  subject  he;-e  since  each 
separate  case  must  be  judged  for  itself.  In  the  numerous  injuries  due  to 
caterpillars,  for  example,  the  amount  of  injury  depends  upon  the  time  and 
duration  of  the  eating.  Reference  should  be  made,  in  this  connection,  to 
Ratzeburg\  He  describes,  in  detail,  the  influence  of  defoliation  on  the 
annual  ring  formation  of  spruces  and  pines  and  treats  later  of  deciduous 
trees".  Cieslar's''  experiments  show  that  the  anatomical  structure  of  a 
wood  ring,  produced  after  extensive  defoliation,  was  changed  (it  became 
much  more  tender).  Under  certain  circumstances  the  vessels  can  be  entirely 
lacking*  in  wood  produced  after  defoliation.  Hartig^'  had  already  proved 
that  a  decrease  in  number  of  the  vessels  goes  hand  injiand  with  the  decrease 
of  foliage.  Kny"  had  already  touched  on  the  subject  that  under  certain  cir- 
cumstances double  annual  rings  can  be  produced.  Wieler'  showed  by 
experiments  that  the  boundaries  between  spring  and  summer  wood  can  be 
entirely  efifaced  by  changes  in  nourishment. 

Such  effects  can  also  occur  in  fruit  trees  and  often  manifest  themselves 
in  the  yield.  In  only  a  few  cases  can  a  partial  defoliation  prove  to  be  advis- 
able agriculturally  as,  for  example,  in  grapevines,  if  they  constantly  produce 
new  foliage  shoots  which  use  up  the  supply  of  nutrition  necessary  for  the 
maturing  of  the  grapes. 

Among  annual  and  biennial  cultivated  plants,  beets  come  especially 
under  consideration  because,  in  years  when  fodder  is  scarce,  the  older  leaves 
are  broken  off  in  the  course  of  the  summer  and  used  to  feed  the  cattle.  An 
example  from  Bohemia-  proves  that  the  root  body  is  thereby  forced  to  form 
more  new  foliage  than  it  would  otherwise  and  that  the  storage  of  reserve 
substances  suffers  from  this.  It  was  found  here  that,  after  defoliation,  not 
only  did  the  beet  root  remain  smaller  but  the  sugar  content  was  about  lO 


1  Ratzeburg,  Waldverderbni.s,  I,  p.  160,  234,  etc. 

2  Loc.  cit.  II,  p.  154,  190,  233. 

3  Cieslar,  A.,  tjber  den  Einfluss  verschiedenartig-er  Entnadelung-  auf  Grnsse  und 
Form  des  Zuwachses  der  Schwarzfohre.     Cit.  Just's  Jahresber.  1900,  II,  p.  278. 

4  Lutz,  K.  G.,  Beitrage  zur  Physiologie  der  Holzgewachse.  Ber.  D.  Bot.  Ges. 
1S95,  p.  185. 

c  Hartig,  R.,  tJber  Dickenwachstum  und  Jahrringbildung.  Cit.  Zeitschr.  f. 
Pflanzenkr.  1892,  p.  292. 

«  Verhandl.  d.  Bot.  V.  d.  Prov.  Brandenburg  1879. 

7  Wieler,  A.,  Tiber  Beziehungen  zwisclien  dem  sekundaren  Diclvenwachstum  und 
den  Ernahrungsverhaltni.ssen  der  Baume.     Tliarander  forstl.  Jalirb.  1892,  V.  42. 

s   Blatter  f.  Zuckerrubenbau.     1905,  No.  20. 


88o 

per  cent,  less  than  in  the  undisturbed  beets.  Aderhold's^  experiments  with 
roots  and  grain  gave  similar  results.  It  was  found  in  grain  that  the  length 
of  the  heads  was  strongly  affected,  irrespective  of  the  reduction  of  the  whole 
harvest. 

Nevertheless,  one's  fears  should  not  carry  one  too  far,  nor  should  slight 
losses  of  leaf  substances  be  considered  of  too  great  importance  as  has 
recently  been  estimated  by  many  pathologists  in  judging  the  injury  due  to 
fungi.  It  must  not  be  forgotten  that  the  parts  of  still  vigorously  growing 
leaves,  which  have  lost  some  of  their  lamina,  are  excited  to  increased  effort, 
as  I  have  proved  experimentally*.  Boirivant''  found,  in  fact,  that  after  the 
removal  of  leaf  blades  the  petioles  and  stems  participate  to  a  greater  degree 
than  usual  in  the  assimilation  and  that  their  parenchymatous  tissue  can 
begin  to  elongate  and  increase. 


1  Aderhold,  R.,  Ul)pr  die  duich  teilweise  Zerstorung-  de.s  Blattvverkes  der  Pflanze 
zugrefiiglen  Schaden.  Prakt.  Blatter  f.  Pflanzenbau  u.  Pflanzenschutz.  Ill  Jahrg-. 
1905,  Part  2. 

2  Sorauer,  P.  Studien  iiber  Verdunstung.  Forsch.  a.  d.  Gebiete  der  Agrrikultur- 
physik.     Vol.  Ill,  Part  4-5,  p.  109. 

3  Boirivant,  A.,  Sur  les  tissu  assimilateur  des  tiges  privees  de  feuilles.  Just's 
Bot.  Jahresb.  1898,  II,  p.  231. 


SUPPLEMENT. 


Page  307.  New  investigations  on  Chlorosis  have  been  published  by 
Molz  (Die  Chlorose  der  Reben,  Jena  1907,  G.  Fischer).  In  confirmation  of 
the  theory,  w^hich  we  have  expressed,  a  lack  of  oxygen  for  the  roots  may 
actually  be  considered  as  the  cause.  On  this  account  low  positions,  where 
water  flowing  from  higher  ground  can  collect,  are  the  most  dangerous.  In 
heavy  soils  the  development  of  the  root  system  suffers  from  this.  Lime 
itself  cannot  produce  chlorosis  but  soils  rich  in  lime  cause  especially  the 
death  of  the  roots,  since  they  are  often  very  fine  grained  and  can  produce  an 
alkaline  reaction.  Therefore,  we  may  speak  of  a  calcium  chlorosis.  Con- 
tinued drought,  as  well  as  cold,  can  also  produce  chlorosis.  Worth  consid- 
eration is  Molz's  theory  that  the  weak  constitution  of  a  chlorotic  plant  can 
be  carried  over  by  the  wood  used  for  propagation.  The  disease  can  either 
be  inherent  in  the  cuttings  from  the  beginning,  or  "certain  disadvantageous 
circumstances  from  outside,  resulting  from  an  inherited,  strong  predisposi- 
tion, can  cause  the  production  of  the  icteric  phenomenon  and  its  results." 
A  permanent  cure  cannot  be  brought  about  by  iron  sulfate.  At  best  only 
the  symptoms  will  be  removed  and  it  is  probable  that  the  greening  of  the 
leaves  is  not  caused  by  the  iron  but  by  the  sulfuric  acid. 

Page  335.  Molz  studied  dropsy  in  grape  cuttings  (Bericht  der  Kgl. 
Lehranstalt  zu  Geisenheim  a.  Rhein,  1906).  The  cuttings  had  stood  for 
some  time  in  damp  soil.  They  were  swollen  up  like'clubs  in  different  places, 
thus  splitting  lengthwise  the  outermost  tissue  layers.  A  white,  spongy  tissue 
became  visible  in  the  gaping  wound,  which  consisted  of  hypertrophied  bark 
cells.  Molz  considers  the  disease,  which  is  not  uncommon  in  moist  vine- 
yards, to  be  identical  with  that  in  Ribes  aureum  described  by  Sorauer. 

Page  345.  Black  specks  are  found  in  the  one-year-old  shoots  of  T'itis 
vinifera  and, appear  somewhat  raised.  Molz  (Centralblatt  f.  Bakt.  II,  Vol. 
XX,  1908,  Nos.  8  und  9)  describes  these  as  small,  round  knobs  of  a  blunt, 
conical  form  ("bark  warts"),  which  may  be  considered  as  a  compensation 
for  the  lenticles  not  found  in  Vitis  vinifera.  Each  one  has  a  stoma  on  its ' 
tip  which  dries  up  rather  early.  This  drying  extends  to  the  neighboring  cell 
groups  and  advances  until  halted  by  the  formation  of  a  protecting  cork 
layer.    The  stronger  and  better  nourished  the  tissue  is  the  more  quickly  the 


882 

protecting  cork  is  produced.  Poorly  nourished  shoots  produce  no  protect- 
ing cork  and  on  this  account  bear  especially  large  and  numerous  bark  warts. 
These  black  specks,  therefore,  furnish  a  standard  for  judging  the  degree  of 
maturity  of  the  wood  and  the  health  of  the  vine.  The  more  numerous  and 
the  larger  they  are,  the  less  mature  in  general  is  the  wood. 

Page  378.  In  Geisenheim,  Julie  Jiiger  observed  a  wen  formation  of 
the  apple  tree  (Zeitschr.  f.  Pflanzenkrankh.  1908).  The  cause  has  not  been 
sufficiently  determined,  but  is  probably  to  be  found  in  some  disturbance  of 
nutrition,  which  manifests  itself  in  the  widening  of  the  medullary  rays. 
Some  medullary  rays  in  their  primordia  show  a  greater  cell  increase  and 
widening  of  the  individual  cells.  The  process  is  connected  with  the  forma- 
tion of  gnarl  spikes  from  the  medullary  excrescences  in  Ribcs  mijrum  and 
Pints  mains  chinensis,  which  we  have  described. 

Pages  391  and  395.  The  iron  spotted  condition  of  potatoes  was  unusu- 
ally wide-spread  in  the  wet  year  of  1907  and  connected  with  it  appeared  a 
yellow  to  brown  discoloration  in  the  vascular  bundle  ring.  This  discolor- 
ation, in  common  with  a  frecjuent  diseasing  of  the  stem  end,  in  which  at 
times  a  Fusarium  was  concerned,  has  influenced  Appel  to  explain  the 
so-called  leaf  roll  disease,  a  form  of  the  curling  disease,  as  a  fungus  epi- 
demic. Appel  maintains  that  the  Fusarium,  found  at  the  stem  end,  grew 
during  the  winter  through  the  vascular  bundle  ring  into  the  eyes  of  the 
tuber  and  caused  the  following  year  an  increased  occurrence  of  the  disease 
and  a  gradual  destruction  of  the  potatoes.  The  same  theory  has  been 
advanced  by  Reinke  and  Hallier,  only  they  have  made  another  fungus 
responsible  for  it.  Sorauer  proves  (Internationaler  phytopathol.  Dienst, 
Stiick  2,  1908)  that  the  Fusarium,  to  be  sure,  may  be  found  frequently  but 
that  other  slime  fungi  appear  just  as  often;  that  all  fungi  could  never  be 
observed  to  be  growing  in  the  vascular  bundle  ring  of  the  tuber  up  to  the 
eyes.  It  is  not  a  question  of  a  fungous  disease  and  its  continuance  through 
the  tubers  into  the  following  year.  The  phenomena  of  discoloration  in  the 
tuber  may  rather  be  explained  by  the  increase  of  the  enzymes  which  Prof. 
Gruss  has  proved  to  have  accumulated  especially  about  the  stem  end.  Con- 
sequently, a  relatively  larger  amount  of  sugar  w^ould  be  present,  which 
would  form  an  especially  favorable  substratum  for  numerous  micro- 
organisms. 

Page  496.  The  influence  of  electricity  on  plant  growth  was  tested  at 
the  Hatch  Experiment  Station  of  the  Massachusetts  Agricultural  College 
(cit.  Z.  f.  Pflanzenkrankh.  1908).  Raphanus  sativus  was  used  ^s  the  experi- 
mental plant.  It  showed  a  hastening  of  the  rate  of  growth  and  an  increase 
in  weight  of  foliage  and  roots;  the  leaves,  however,  were  a  lighter  green  and 
•  were  inclined  to  leaf  blight.  The  electric  stimulus  seems  to  act  on  the 
organs  in  the  same  way  as  does  a  lack  of  light. 

Gassner  (Berichte  d.  D.  Bot.  Ges.,  1907,  Part  i)  can  confirm  the  results 
of  Lowenherz's  experiments  mentioned  in  the  text.    The  curvature  produced 


883 

by  the  action  of  the  current,  which  could  be  observed  in  all  plants,  did  not 
always  remain  the  same.  At  times  if  was  toward  the  negative  pole ;  in 
other  cases,  toward  the  positive  pole. 

In  opposition  to  the  cultural  experiments  with  barley,  published  earlier 
by  Lowenherz  and  confirmed  later  by  Gassner,  which  prove  an  injurious 
effect  of  the  electric  current,  the  first  named  author  now  reports  favorable 
results  (Z.  f.  Pflanzenkrankh.  1908,  Part  i).  With  a  weaker  current  he 
found  a  hastening  of  the  growth  of  a  seedling;  the  injurious  action  began 
only  with  an  increase  of  the  current. 

Page  524.  In  the  reports  of  the  Hatch  Experiment  Station  of  the 
Massachusetts  Agricultural  College  (cit.  Z.  f.  Pflanzenkrankh.  1908)  may 
be  found  observations  on  the  leaf  blight  of  conifers  and  other  evergreen 
trees  as  the  result  of  winter  and  spring  frosts.  The  trees  show  the  blight 
usually  only  On  one  side,  which  corresponds  to  the  prevailing  direction  of 
the  wind.  If  dry  winds  blow  with  a  high  temperature  at  a  time  when  the 
soil  is  still  frozen,  the  plants  cannot  find  sufficient  compensation  in  the 
frozen  soil  for  the  increased  transpiration  and  the  leaves  dry  up.  This  is 
the  same  theory  which  found  expression  earlier  as  explanation  for  the  drop- 
ping of  pine  needles.  The  native  conifers  suffered  less,  in  case  they  did  not 
stand  on  unfavorable  soil,  when  compared  with  the  imported  varieties  of 
Picea,  Abies,  Juniperus,  Taxus,  Buxus,  etc. 

Page  675.  According  to  Stocklasa's  investigations,  Ueber  die  glykoly- 
tischen  Enzyme  in  Pflanzenorganismus,  Z.  f.  physiol.  Chemie,  Vols.  50  and 
51,  1907,  the  anaerobic  respiration  is  an  alcoholic  fermentation  in  which  a 
certain  amount  of  lactic  acid  has  formed  together  with  alcohol  and  carbon 
dioxid.  This  holds  good  also  for  frozen  organs  (beets,  potatoes,  etc.). 
Zymases  and  lactacidases  are,  therefore,  not  destroyed  by  the  freezing. 
Lactic  acid,  alcohol,  carbon  dioxid,  acetic  and  formic  acid  are  also  formed 
by  enzymes  in  living  plant  and  animal  cells.  The  decomposition  of  the 
hexoses  by  glycolytic  enzymes  is  normally  completed  without  the  cooper- 
ation of  bacteria.  In  the  precipitates  procured  from  pure  plant  juices  by 
absolute  alcohol  and  ether,  the  author  found  fermentation  enzymes  which 
produced  a  lactic  acid  and  alcohol  fermentation  in  the  glycose  solution ;  in 
this  process  with  easy  access  of  oxygen  definite  amounts  of  acetic  and 
formic  acid  are  always  formed. 

Page  677.  Fallada's  investigations  (Oesterr.  Ungar.  Zeitschr.  f. 
Zucherindustrie  u.  Landw.  Part  V,  1907)  on  the  white  leaf  conditions  of 
beets  favor  the  theory  that  the  white  parts  of  the  leaf  remain  in  a  younger 
developmental  stage  and  with  a  scantier  cell  content  and  are  more  suscep- 
tible to  the  influence  of  light  and  heat  than  are  the  green  organs.  The 
etiolated  leaves  had  a  greater  water  content ;  the  smaller  amount  of  organic 
substances  gave  a  relative  increase  of  protein  especially  of  the  non-albu- 
minous nitrogen  compounds.  The  potassium  and  phosphoric  content  was 
greater;  the  calcium  and  silicic  acid  content  was  smaller. 


Page  717.  For  the  diseases  of  the  horseradish,  we  have  referred  to 
our  detailed  article  in  the  Zeitschrift  fiir  Pflanzenkrankheiten,  1899,  p.  132. 
It  is  stated  there,  "The  forms  of  disease  mentioned  appear  to  me  on  this 
account  only  as  a  great  increase  of  a  wide-spread  tendency  to  gummy 
degeneration  .  .  .  because  in  the  production  of  the  masses  filling  the 
vessels  the  liquification  of  the  secondary  membranes  cooperates  in  certain 
cases."  This  theory  has  been  shared  recently  by  A.  Schleyer  (Der  Anbau 
des  Merrettichs  usw.  cit.  Biedermanns  Zentralbl.  f.  Agrik.,  Part  8,  1908). 
He  says,  "In  my  opinion,  the  turning  black  is  conditioned  by  the  fact  that 
the  Pentosane  and  the  sugar  in  the  horseradish  degenerates  into  gum." 
Experiments  also  confirm  the  theory  that  lime  should  be  used  as  a  remedy 
(since  humic  acid  is  often  present  in  the  soil).  When  the  plants  v/ere 
cultivated  in  nutrient  solutions,  some  of  which  were  made  up  with  calcium, 
others  without  it,  the  gummy  degeneration  of  "the  sugar"  could  be  proved 
very  soon  in  the  plants  which  did  not  have  calcium. 

Page  718.  The  subject  of  the  injuries  due  to  the  gases  of  smoke  and 
other  industrial  waste  substances  is  beginning  to  be  separated  as  a  special 
branch  of  general  pathology  and  is  represented  by  a  special  publication. 
Since  1908,  there  has  existed  the  "Sammlung  von  Abhandlungen  iiber 
Abgase  und  Rauchschaden"  edited  by  Prof.  Dr.  Wislicenus,  who  has  already 
given  in  the  first  part  a  comprehensive  description  "Ueber  die  Grundlagen 
technischer  und  gesetzlicher  Massnahmen  gegen  Rauchschaden." 

Recent  investigations  by  Haselhofif  (Z.  f.  Pflanzenkrankh.  1908)  treat 
of  the  action  of  sulfurous  acid  on  soil.  The  experiments  show  that  vege- 
tation is  not  injured  if  the  soil  contains  such  amounts  of  decomposable 
bases  (especially  calcium)  that  the  sulfuric  acid,  formed  from  the  supplied 
acid,  is  combined.  The  case  described  by  Wieler  of  soil  impoverishment  in 
the  presence  of  free  acids  in  the  soil  may  be  found  very  rarely  (perhaps  in 
forest  soils).  If,  on  the  other  hand,  sulfurous  acid  is  introduced  into  the 
soil  during  the  growth  of  the  plants  so  that  it  shows  an  acid  condition,  dis- 
turbances in  growth  become  clearly  noticeable.  In  soils  continuing  copper, 
the  copper  is  carried  over  into  easily  soluble  compounds  of  the  sulfurous 
acid  and  this  dissolved  copper  can  then  become  injurious  to  vegetation.  But 
even  here  calcium  carbonate  helps  since  it  arrests  the  dissolving  action  of 
the  acid. 

Page  761.  The  occurrence  of  a  disadvantageous  effect  of  Bordeaux 
solution  on  the  yield,  which  we  first  observed,  has  been  confirmed  by  recent 
experiments  of  v.  Kirchner  (Z.  f.  Pflankrank.,  Part  II,  1908).  The  author 
takes  the  older  literature  also  into  consideration.  Probably  the  shading 
action  of  the  solution  should  be  made  responsible  for  the  lessened  yield. 
This  would  explain  also  the  rapid  turning  green  of  leaves  with  strong 
illumination.  The  greater  amount  of  starch  is  not  to  be  ascribed  to 
increased  assimulation  but  to  a  decreased  removal  of  the  assimilates. 


885 

Page  765.  Kelhofer  (Internat.  phytopath.  Dinest,  1908,  Part  3)  has 
reported  some  points  in  regard  to  the  making  of  Bordeaux  Mixture.  The 
effectiveness  of  the  mixture  depends  not  only  on  the  quality  of  the  materials 
used  but  also  on  the  proportionate  amounts  of  the  two  elements  and  on  the 
method  of  preparation. 

In  regard  to  the  proportionate  amounts,  it  should  be  emphasized  that 
the  copper  precipitate  loses  its  physical  properties  the  more  quickly  and  the 
danger  of  washing  away  by  rain  is  the  greater  the  more  calcium  is  used  in 
preparing  the  solution.  According  to  Kelhofer's  experiments,  it  is  further 
desirable  that  the  copper  vitriol  solution  and  the  lime  milk  are  mixed  when 
cool  and  in  the  most  dilute  condition  possible  and,  on  this  account,  the 
copper  solution  must  be  poured  slowly  into  the  lime  milk;  otherwise  the 
precipitate  assumes  a  powdery  form  which  conglobates.  Although  the 
addition  of  sugar  is  to  be  recommended  in  general,  care  must  be  taken  not 
to  use  too  large  amounts  since  the  copper  solution  thereby  may  be  more 
easily  washed  away.  At  any  rate  the  amount  of  sugar  necessary  to  make 
the  mixture  keep  depends  upon  the  amount  of  calcium,  inasmuch  as  solu- 
tions prepared  with  a  good  deal  of  calcium  need  more  sugar.  Thus,  for 
example,  when  using  i,  2  and  3  kg.  calcium,  to  2  kg.  vitriol  to  each  100  liters 
of  water,  20,  30  or  40  gr.  of  sugar  have  been  found  necessary  in  order  to 
protect  the  copper  precipitate  permanently  from  decomposition,  i.  e.  for  at 
least  a  year.  In  common  usage,  where,  as  a  rule,  plenty  of  calcium  is  used, 
it  is  advisable  to  take  on  an  average  50  gr.  sugar  for  each  hektoliter.  With 
this  addition  the  whole  amount  of  Bordeaux  mixture  needed  can  be  pre- 
pared at  the  same  time  in  the  spring  at  the  beginning  of  the  season;  the 
mixture  will  then  keep  through  the  summer. 

Page  /"/'2.  The  investigations  of  Rudolph  Friedrich  (Ueber  die  Stoff- 
wechselvorgange  der  Verletzung  von  Pflanzen.  Centralbl.  f.  Bakteriologie, 
etc.  II,  Vol.  XXI,  p.  330)  have  confirmed  the  observations  of  Zaleski  and 
Hettinger  that  an  increase  of  protein  takes  place  at  the  wounded  place. 
Besides  this,  however,  Friedrich  found  that  in  the  storage  organs  beneath 
the  soil,  as  well  as  in  the  fruits  and  leaves,  a  decrease  of  carbo-hydrates 
and  an  increase  of  acidity  (with  the  exception  of  bulbs)  sets  in  as  a  com- 
mon, secondary  phenomenon  of  the  injury.  If,  with  Ad.  Mayer,  the  acids 
are  considered  as  the  products  of  oxidation  of  the  sugars,  then  the  increased 
acidity  is  explained  by  the  more  active  respiratory  need  of  the  injured 
organ.  The  decrease  of  carbo-hydrates  will  be  explained  partially  by  the 
fact  that  they  are  used  for  protein  synthesis.  A  corresponding  decrease  of 
amids  or  the  amido  acids  may  be  considered  as  further  reactions  to  trau- 
matic stimulus.  These  substances  are  used  in  the  construction  of  the  protein 
molecule.  In  the  potato  the  smallest  starch  grains  are  used  up  and  intro- 
duce the  formation  of  sugar. 

Page  787.  Hedrick,  Taylor  and  Wellington  made  girdling  experi- 
ments on  tomatoes  and  chrysanthemums   (Bulletin  288  of  the  Agriculture 


886 

Experiment  Station  at  Geneva).  No  beneficial  effects  could  be  determined. 
On  the  contrary,  the  plants  were  very  evidently  injured.  Knobby  dwellings 
were  formed  on  the  axes;  the  leaves  became  sickly  and  the  root  system 
less  developed. 

A  confirmation  of  my  personal  studies  on  the  processes  after  girdling 
may  be  found  in  Krieg's  contributions  on  callus  and  wound  wood  formation 
in  girdled  branches  and  their  histological  changes  (Beitriige  zur  Kallus-  und 
Wundholzbildung  gcringelter  Zweige  und  deren  histologische  Veriinderun- 
gen.  Wiirzburg  1908,  Nubers  Verb).  The  observations  on  Vitis  are  new 
in  that  the  formation  of  new  structures  as  a  result  of  girdling  were  proved 
in  the  pith,  although  the  pith  had  not  been  injured  at  all.  This  fact  is 
important  because  it  shows  that  the  wound  stimulus,  or  the  changes  in  tissue 
tension  setting  in  after  each  injury,  manifests  itself  in  regions  far  distant 
from  the  wound  surface  and  separated  from  it  by  firm  wood  zones.  This 
makes  better  understandable  the  changes  in  the  pith  body  due  to  frost 
injuries  in  which  the  wood  ring  shows  no  disturbances  of  any  kind. 

The  formation  of  wound  wood  in  the  pith  of  Vitis  was  observed  by 
Krieg,  who  ascribes  it  to  the  action  of  the  products  of  decomposition  of  the 
woody  part  killed  by  the  girdling.  This  wound  wood  consisted  of  parenchy- 
matous aggregations  resembling  pith  spots.  These  were  enclosed  by  a  ring 
of  cambium.  The  ring  lying  within  the  pith  bark  developed  wood  with 
numerous  vessels  toward  the  inside  and  sieve  tubes  toward  the  outside.  The 
other  pith  spot,  adjacent  to  the  pith  crown,  formed  the  sieve  tubes  from  its 
cambial  ring  tdward  the  inside  and  wood  toward  the  outside.  The  corre- 
sponding parts  of  both  new  structures  united  later  with  the  respective  parts 
of  the  overgrowth  edge.  In  the  meantime,  the  plant  had  replaced  the  wood 
already  killed  in  girdling  by  the  formation  of  new  wood  and  sieve  tissue 
in  the  pith. 

Page  825.  W'e  owe  varied  and  careful  experiments  to  Elsie  Kupfer 
(Studies  in  Plant  Regeneration.  Dissertation  of  Columbia  University,  New 
York,  1907).  Of  these,  we  will  emphasize  first  the  experiments  on  root 
cuttings  of  Roripa  Armoracia.  Pieces  of  the  root  laid  flat  in  the  soil  formed 
new  shoots  from  the  cambium  of  both  the  upper  and  under  cut  surfaces.  If 
bark  and  cambium  had  been  cut  away,  sprouts  developed  after  a  preliminary 
callus  formation  at  different  places  near  the  vascular  bundle  and  more 
abundantly  at  the  upper  than  on  the  under  end.  The  capacity  to  form 
sprouts,  which  otherwise  is  peculiar  to  the  cambium,  therefore,  extends  in 
this  case  to  the  callus  tissue  newly  produced  as  a  reaction  to  wound  stimulus. 
Longitudinal  sections  of  roots  of  Pastinoca  sativa,  which  were  laid  hori- 
zontal in.  sand,  developed  new  sprouts  on  both  cut  surfaces  near  the  cam- 
bium. In  isolated  pieces  of  bark,  sprouts  were  produced  on  the  inner  side 
and  roots  on  the  outer  side.  The  isolated  central  cylinder  formed  only 
roots. 

The  experiments  with  potatoes  are  very  instructive.  If  any  eye  at  all 
was  left  uninjured  on  some  aerial  shoot,  this  developed  an  aerial  tuber.     If 


all  the  eyes  were  removed,  only  root  formation  took  place.  Pieces  of 
potato  tubers,  from  which  the  eyes  had  been  cut  out  together  with  the 
adjoining  tuber  parenchyma,  formed  new  eyes  on  these  cut  surfaces.  In 
the  potato  leaves,  either  a  simple  formation  of  roots  appears  at  the  under 
end  of  the  petiole  or  a  tuber  swelling,  containing  starch,  or  a  combination 
of  the  two,  or  a  regular  small  tuber  with  eyes. 

As  a  total  result  of  all  the  experiments  for  which  blossom  and  fruit 
stems  were  also  used  with  success,  we  may  recognize  that  for  regeneration 
the  presence  of  an  abundant  reserve  material  is  necessary.  Pure  white 
sprouts  of  different  plants  formed  no  roots.  Darkening,  or  removal  of  the 
carbon  dioxid,  prevented  regeneration.  Since  certain  parts  of  the  plant  are 
not  capable  of  regenerating  one  or  another  organ,  even  when  all  conditions 
are  favorable,  one  is  led  to  the  point  of  view  that  different  substances  must 
be  present  which  determine  the  formation  of  any  certain  organ.  Such  sub- 
stances should  be  thought  of  in  the  form  of  enzymes,  which  are  not  present 
in  all  cells  but  are  localized  in  definite  parts  of  the  plant  body. 

Page  833.  In  regard  to  callus  formation,  which  takes  place  between 
tlie  bark  shield  and  stock,  Ohlmann  expresses  himself  in  his  detailed  work 
(Ueber  die  Art  und  das  Zustandekommen  der  Verwachsung  zweier 
Pfropfsymbionten.  Centralbl.  f.  Bakteriol.  usw.  II,  Vol.  XXI  1908)  as 
follows :  "It  seems,  therefore,  that  callus  formation  may  begin  only  at 
the  bark  shield.  Sorauer  states  in  regard  to  this  c^uestion  that  no  law  for 
the  tearing  away  of  the  bark  may  be  determined.  According  to  Schmitt- 
henner,  the  trunk  splits  in  the  youngest  sapwood.  I  have  investigated  a 
great  number  of  plants  of  widely  different  species  in  regard  to  this  ques- 
tion. It  was  evident  that  the  cambium  remained  intact  on  the  bark.  In 
more  scattered  cases,  I  noticed  that  a  few  cambial  cells  had  remained 
hanging  to  the  youngest  wood.  Nevertheless,  I  have  noticed  this  so  rarely 
that  I  cannot  ascribe  any  significance  to  it."  It  should  be  remarked  here 
that  the  author  did  the  budding  at  a  time  "when  the  cambial  activity  was  in 
full  progress."  In  this  case,  the  author  was  correct.  If  the  budding  is 
done  later,  however,  then  the  cases  observed  by  Sorauer  become  more 
numerous. 

Page  854.  Blankinship  describes  a  bleeding  disease  occurring  fre- 
quently in  Montana  (North  America)  in  Populus  augustif olia ,  P.  bal- 
saniifera,  P.  dcltoides,  etc.  (Zeitschr.  f.  Pflanzenkh.,  Part  i,  1908).  The 
trees  bled  extremely  from  wounds  and  this  was  accompanied  by  the  bleach- 
ing or  yellowing  of  the  foliage.  At  times  the  wounds  on  different  axes 
developed  into  cavities  filled  with  a  gummy,  half  fluid  mass.  The  exuding 
sap,  laden  with  bacteria,  had  a  sweetish  taste  and  had  often  attracted  large 
brown  ants. 

A  "Jaundice"  of  the  poplar  is  connected  with  this  bleeding  disease,  in 
which  bleeding  may  also  appear  but  more  frequently  does  not.  The  foliage 
of  the  whole  tree  is  bleached  and  dries  up  in  the  intercostal  fields.     Death 


follows  after  3  to  5  years.  The  diseased  trees  stand  generally  in  low  places 
and  the  author  is  of  the  opinion  that  the  increase  of  the  alkali  content  in 
the  ground  water  is  to  blame.  This  trouble  is  found  in  Montana  not  simply 
on  poplars  but  also  on  other  trees  where  irrigation  is  used.  Drainage  is 
advisable. 

Page  856.  Minora  Shiga  (On  the  effect  of  a  partial  removal  of  roots 
and  leaves  upon  the  development  of  flowers.  Journ.  College  of  Science, 
Tokyo,  1907,  Vol.  XXIII,  Art.  4),  reports  on  the  promotion  of  blossom 
development  by  the  removal  of  the  part  of  the  roots.  Different  species  of 
very  different  plants  experimented  on  acted  differently  under  the  same 
manipulation.  In  IMiarbitis.  Pisum  arvense  and  ]'kia  Paha  the  removal  of 
the  main  root  and  small  lateral  roots  cause  an  unusually  early  and  luxuriant 
development  of  the  blossoms.  This  was  not  the  case  in  Fagopyrum. 
Cutting  off  of  the  side  roots  promoted  the  formation  of  blossoms  in  Vicia 
Paba  and  Pisum  sativum  var.  arz'ensc,  but  did  not  do  so  in  Pisum  Arvense. 

End  of  Vol.  I. 


INDEX,  Etc. 


MANUAL 


OF 


Plant  Diseases 


PROF.  DR.  PAUL  SORAUER 


Third  Edition— Prof.  Dr.  Sorauer 

In  Collaboration  with 

Prof.  Dr.  G.  Lindau      And      Dr.  L.  Reh 

Private  Docent  at  the  University  Assistant  in  the  Museum  of  Natural 

of  Berlin  History  in  Hamburg 


TRANSLATED  BY  FRANCES  DORRANCE 


Volume  I 
NON-PARASITIC  DISEASES 

BY 

PROF.  DR.  PAUL  SORAUER 

BERLIN 


WITH  208  ILLUSTRATIONS  IN  THE  TEXT 


889 


INDEX  TO  VOLUME  I.* 


Of  the  numerous  plant  names  cited  in  this  volume,  only  those  are  included  in  the 
index  of  which  detailed  accounts  have  been  given.  To  have  named  all  the  plants  used 
as  examples  for  certain  cases  of  disease  would  have  uselessly  encumbered  the  index. 


Abcission  of  twigs • -357-60 

Abies     105 

Ablactation  in  grafting    831 

Acacia.     Exudation  of   gum 707-8 

Acacia   longifolia,  with   intumescence. .  .437 

—  Microbotrya,  with  intumescence. .  .437 

—  pendtda,  with   intumescence 443 

Acclimatization    40 

Acer    94 

Acer.     Defoliation  due  to  heat 411 

Acer  caiiipcstre.     Goitre  gnarl  378 

—  italiiJii     160 

—  NcgiDido.     Discoloration    280 

—  obtusatuiii    160 

—  paliiiatmn.     Nanism     1^4 

—  plantanoides.      Discoloration 280 

—  Pscudoplantanus,    var.    Schwedleri. 

Discoloration    280 

Acetylene   744-47,  769 

Acetylene    poisoning    -46 

Acid  content.     Changes  due  to   lack  of 

light 668 

Acids  in  soil  240-41 

—  of  plant  roots.     Effect  of  neutrali- 
zation     402 

Acremonium     204 

Acremonium   in   sterile-head   condition .  .5^4 

Acrocylindrium    204 

Acrospermum     54 

Aeration  of  the  soil    241 

Aesculus    154 

Aesculus  macrostachya   105 

Agaricum     53 

Agaricus   campestris    99 

Agathosma    134 

Ageratum    147 

Agrogyrum  repots,  P.  B go 

Agrosiemma   Githago    74 

Ailanthus     102 

Air,  Dilute.     Effect   314 

—  IMoist.     Effect  on  plants  injured  by 

drought     425 

—  Too  dry.     Effect   408-22 

Akrolein,  Injury  due  to 757 

Albication    308 

Albinism  36,  677-84,  698,  847 

Alder  bogs.     Discoloration  of  water 251 

Alders.     Death    153 

Algae,  Green,  as  nitrogen  collectors. ..  .273 

Alinit     270 

Alkali  grass    195 

—  soils     267 

Alkalinitv  of  the  soil    367 


AHeiitospora  radicicola,  Wakker   227 

Allium  Cepa  30 

Alnus   glntiiwsa    98 

Fasciation    333 

Amanita  initscaria   288 

Ammonia     730-32 

Ammonia,  Free.     Combination    272 

Ammonium  salts.     Use  as  top  dressing. 268 

Use   on   meadows 363 

—  sulfate     769 

Ampelopsis  hedcracea.     Emergences.  ..  .440 

Aniygdahis  Pcrsica.     Xanism    144 

Amylocarbol     760 

Anabaena     11 

Anaesthetica     765-66 

Anasfatica  hicrochttutica   176 

Andropogon    nutans    696 

—  Sclioenanthns    (Jav.   Sereh)    693 

—  Sorghum.     Alafuta   disease 415 

Animals,  Wild,  Injury  due  to 781-83 

Annual-rings.      Production    774 

Radial  division    589 

Annual-rings,   False    615-17 

Anti-ferments     676 

Antibiosis     11 

Antinonnin    760 

Apcra  spica  vcnti   10 

Aphelandra.     Intumescence   448 

.Aphids    392 

Apogamy    342 

Apostasis    of    the    blossom 373 

Apostrophe    673 

Apple.     Bitter  pit    168-70 

—  Canker    586-92 

—  Tan  disease   210-13 

— ■  Varieties   for  dry  soils 175 

—  Water-core    .  .  .  ." 286-87 

—  Wen  formation    882 

—  Woolly  streaks  in  the  cores.  ..  .324-26 

Apples.  Winter.     Storage    32^ 

Apricots.      Mombacker   disease    479 

Aprocrenic    acid    240 

Araban     705 

Arabii:    699,    705 

Arabinose    167 

Arachis    hypogaea    690 

Araucaria    94 

Arrabbiaticcio    202 

Arsenic    compounds.      Injurious    effects 

741,  752,  761 

Artindo  arenaria,  L , 90,  150 

—  baltica    150 

Ascophora      54 


*It  has  seemed  advisable  to  use  the  German  index,  adapting  it  where  ever  neces- 
sary for  the  translation,  rather  than  to  change  the  form  entirely.     (Translator's  note). 


890 


/Iscoplwra    Beijcrinckii    556 

Ashes.      Showers    75 1 

Aspergillus    13.    53 

Ast'ergiUus   nicjer 17,   99 

Starvation  condition   288 

Asphalt   fumes   732-35 

Asphalting  of   streets    106 

Aster  alpinns   84 

Asteroma    radiosum 734 

Atmospheric  influences,   Injurious..  .408-674 
Atmospheric   moisture.     See   Humidity. 

Atoiiiaria  linearis  Stephn    221 

Aurigo    434-35.  460 

Autumn  coloration   1 27,  500-4 

Autumn  wood    774 

Avalanches    634 

.Axial  organs.     Wounds    772-8i 

Axillary  proliferation    375 

Axis.     Effect  of  constriction 817-21 

Azaleas.     Leaf-fall    352 

A::oUa   caroliniana    11 

Azotobacter    270,    273 

Azotobacter  chroococcnin    270 

Azurine    765 

Bacillus    albuiiiiiiiis    273 

—  antliracis    674 

—  Bcrestiieu'i    17 

—  betae    28 

—  biityriciis    273 

—  Cobb   (Pseitdoinonas  vascii!ariiiii)..'o')-; 

—  coli 273 

—  coli  coiiimunis    28 

—  fluorescens   liquejacicns    223 

—  foetidus    273 

—  liquefaciens    223,    273 

—  liqnidus    273 

•    —  iiiasciilicola     690 

—  niegatcriioii     273 

—  Mescntcricns  I'ldgalits   223,  273 

—  mycoides  223,  273 

—  nubilis     273 

—  phytophthorus    829 

—  prodigiosus  273,  674 

—  protcus  vulgaris    273 

—  pseud o-arabi nil s  696 

—  pyocyaiictis    674 

—  radicicola     273 

—  radicicola    Bcijeriiickii    ir 

—  ruber    ballicus    17 

—  sacchari  6<)4,  696 

—  subtilis   14,  22Ti,  273 

—  typlwsus  674 

—  ureae     273 

—  vascular  urn    696 

—  vulgaris    273 

—  vulgatus    14 

Bactcriorhiza    11,  223,  271 

Bacterium  copropliilum    273 

—  fuscum     273 

—  Hartlebi    272 

—  nitrobactcr    273 

—  pseudoarabinus    696 

—  sacchari    696 

"Baking"  of  the  soil    405 

Bamboo.     Nanism    144 


liarium   chlorid   in   waste   water 752 

r.ark.      Casting    258 

—  Injuries     797-810 

—  Injuries  from  sunl)urn   647 

—  Shedding    259,   328-3 1 

—  Springing Z^T-^'^ 

—  Wounds  due  to  hail  468 

Bark,   Rotten    258-59 

Bark   excrescences    329 

—  grafts    831,  837 

—  scurvy    2i7- 

—  tatters    575-76 

—  tubers    861-71 

—  warts    881 

Barrenness  of  hops   342-44 

Bassorin    699 

Batata.  See  Sweet  potato. 

"Baumschutz"    760 

Bead  cells   8 

Beans.     Intumescences    446 

Beech,  Red.     Black  blight   558 

Girdling  disease    219 

Beets.     Bacterial  gummosis  697 

—  Bactcriorhiza    223 

—  Club  root   871 

—  Dry  rot    415-16 

—  Fertilization  with  nitrate  of  soda.. 223 

—  Frost  action    531-32 

—  Heart   rot    415-16 

—  Lightning   effect    495 

—  Over- fertilization    389 

—  Running  to  seed,  due  to  frost..  .516-18 

—  Sterilization  of  seed   225 

—  Tail   rot    69" 

—  Unripeness     390 

—  White-leaf   condition    883 

—  Working  of  the  soil 226 

—  See   also    Fodder   beets ;    Roots, 

Edible. 

Begonia  fuchsioides.     Leaf-fall    353 

Begonias,    Tuberous.      Dropping   of    the 

blossoms    417 

Bellis  perennis  126 

Bending  of  branches   810-15 

Berberis     105 

Beta  vulgaris.     Rupture  of  roots 321 

Betula   piibescens    249 

Biogen    -.32 

Biota    144 

Biota  meldensis   828 

—  orientalis  105.  828 

Bitter  pit  in  the  apple  168-70 

Black-leg  of  the  edible  chestnut   709-10 

Black-ring  condition  of  horse-radish   717,  884 

Blackberry.     Canker    606-7 

Blast    47 

Blasting  of  legumes   i6o-6r 

Blastomania  A.     Br 378 

Bleeding  disease  of  the  poplar   887 

Blight 41,  608-13 

—  Predisposition     52 

Blight,  Black,  of  the  red  beech.  . 558 

Blight  caused  by  premature  ripening. ...  156 

Blindness  of  the  hop  342 

Blisters  from   sunburn    642 

Blorokziekte  in  coffee   230 


Blossom  development  promoted  by  root 

removal    888 

—  formation   induced   by   starvation 

condition    289 

—  organs.     Changes  due  to  frost.  .518-23 
Blossoms.     Apostasis   2,73 

—  Doubling    375 

—  Dropping    353 

—  Faulty    development 416-19 

—  Sunburn     645-46 

Blossoms,   Sterile.     Production    289-92 

Boletus    53 

Eordeaux  mixture  761,  884 

Injury  due  to    884 

Preparation    , 885 

Boronia    134 

Borosma    134 

Bosses  in  ducts   570 

Eosuch  of  tobacco   685 

Botrytis   14.  27,  53 

Botryiis  cinerea  14,  23,  394,  433,  706 

Bouillie  Celeste   765 

Branch  blight  in  forest  trees  5S8-59 

—  cuttings    821-24 

—  rips,  Freezing  back  of  older 553-55 

Branches.     Bending   810-15 

—  Internal  splitting  581-83 

—  Twisting    815-16 

"Branderde"     243 

"Brausche"  hops   344,  466 

Bread  tree,   St.  John's.     Swellings.  .  .339-40 

Breeding,  Task  of   665 

Brcmia   Lactucae    24 

Brenz-catechin    503 

Brindle  of  tobacco   685 

Brizopyrum    195 

Bromin     735-36 

Bromus  moUis.     Nanism    145 

Broussin    863 

Brown-chains  due  to  diptera   larvae.  ..  .614 

Brusone  disease  of  rice   315 

Bud  cushions.     Injury  due  to  frost 577 

—  cuttings  in  Vitis   828 

—  disease    146 

—  formation  on  leaves   378 

—  variation    146-47 

Budding 831,  833-38 

Buds.     Injury  from  sunburn    645 

—  Injury  from  too  dry  air  408-11 

—  Pressure    378 

Buds,  Accessory   561 

—  Dormant.     Death    862 

Bulbs,    Blossoming.     Failure   in    forcing 

297.   651-52 

"Bunt"  of  tobacco    685 

Burning  of  seed 186 

Burning  out  of  grass   285 

Cabbage  plants.     Behavior  in  frost.  .531-32 
Cacti.     Cork  disease   428-30 

—  Classiness    453-57,  7'^7 

—  Internal   intumescences    430,   454 

Caeoma    59 

-Caeonia   cerealium    59 

•Caladiums.     Tuber  cuttings    828 

"Calcipenuria    304 


Calcium.     Excess    399-403 

Jaundice  due  to   310 

with   grapes    402-3 

Calcium.     Lack.    Cause  of  silver  leaf... 286 

Changes  due  to   301-5 

Cultural  experiments    303 

Calcium  arsenate,  Injury  from   761 

— •  carbid    769 

—  chlorid   in  waste  water 751-52 

—  chlorosis     881 

—  fertilization  with  smoke  poisoning. 772 

—  nitrid     769 

—  oxalate     792 

Contents  of  cells  792 

Production   by   solution   of   car- 
bohydrates     792 

—  sulfid     741 

Calda   fredda    202 

Calico  of  tobacco   685 

Calluna 256 

CalUina  vulgaris  146,  242 

Callus     790 

—  Girdling  roll    787-97,  808 

Callus   formation  in   graft   symbionts. .  .887 

—  on  stems  of  Malopc  graiidiflora ..  .44^ 

Calycanthus     105 

Cambium.     Browning  due  to  frost 612 

CauicUna  sativa,  sown  to  prevent  lodg- 
ing  665 

Camellias.      Yellow    foliage    due    to   ex- 
cess of  light   671 

Campanula    146 

Cancer    53 

Candying  of  seeds 226,  387,  389 

Canker    42,  47,  586-608 

Canker,   Closed    587 

— -  Crotch,  in  fruit  and  forest  trees. 593 -94 

—  Open    587 

Canker  from  frost 583-85 

—  in  apple  trees   586-92 

—  in  blackberries   606-7 

—  in  cherry  trees   594-96 

—  in  coffee    230 

—  in  grape  vines   596-98,  601 

—  in    roses 602-6 

—  in   Spirea   598-600 

—  wounds    776 

Cannabis     147 

Cannonading  against  hail 470 

Caragona    105 

Carbohydrates,    Production    of    calcium 

oxalate  in  solution  of   792 

Carbolic  acid    225,    760 

Carbolineum    757 

Carbon-dioxid.    Effect  740,  746 

—  Effect  on  germination   109 

—  Excess    109,  406-7 

—  Lack,  Changes  due  to   316-19 

Carbon-disulfid    269 

Carcinoma     586-608 

Carex    256 

Carex  arciiaria  L 150 

Caries  Fabr 49,  56 

Carnations.     Classiness 717 

Carotin    282 

Cassavas.     Favorable  soil  232 


892 


Cassia  toineiitosa.     Intumescence 436 

Castanea    1 1 

Casting  of  the   fruit  spurs 338 

Catalase    676 

Cattleya.     Specking 261 

Celery.      Over-fertilization 392 

Cell  membrane.     Processes  of  loosening 
due  to  frost 581 

—  passages    613 

Celosia   crislata    33 

Fasciation    334 

Ceutaurca  cyaiiiis    74 

Cephalosporium    240 

Cerasin    699 

Ceratonia  Sil'ujua.       Outgrowths  on 

branches     339 

Ceratoptcris   tlialictroides    288 

Cereus  flagellifonnis.     Cork  disease 428 

—  nycticalus.      Classiness 453 

Chagrinization  of  the  rose  stem 434 

Chamaccyfaris   Laii'soniaiia    i59 

—  sphaeroidia,  var.   .linlalyciisis 828 

—  squarrosa    828 

Changelings  in  grapes   34^ 

Check  of  plants 9 

Chemico-physical    processes.      Effect    on 

soil  absorption    264-68 

Chemotropism    13 

Cherries,    Sweet.      Sensitiveness 209 

Cherry.      Canker 594-96 

—  Death    1 54,  555 

—  Effect  of  drought 281 

—  Frost   boils    572 

—  Gummosis    699-707 

—  Susceptibility  induced  by  frost .  154,  555 

—  Tan  disease    213-17 

—  Varieties  for  dry  soils 175 

Cherry  trees   along   the   Rhine.       Death 

due  to   frost 555-58 

Chestnut,   Edible.     Black-leg 709-10 

Root   disease    219-20 

Chici  on  Gingko  Biloba 386 

Chile  saltpeter 223,  311,  767 

Effect  as  top  dressing 390 

Injurious  effect   767 

Use  with  woody  plants 391-92 

Sec  also  Nitrate  of  soda. 

Chilling.  Disturbances  due  to 513-14 

Cbimnevs,   Solid    substances   given    off 

i>y   ■■ 737-47 

Chioranthy     342 

Chlorin     724-29 

Chlorin.     Lack,   Changes  due  to 306-7 

Chlorophvllan     S02 

Chlorosis 308,  881 

—  Transmission   by   grafting 697 

Chlorosis  due  to  calcium   881 

—  of  grapes  402 

—  of  tobacco  685 

Chorisis  376 

Chorizema     134 

Circumvallation.     Phloem    867 

—  Sec  also  Overgrowth. 

Cladosporium   14,  438,  545 

Cladosporiniii  javanicuni.     Wakker 227 

—  penicillioides    204 


Clasterosporium    carpopliiluin    Lev. 

.^derh 706 

Clavus    50 

Clay   soils.     Cracking 189 

—  —  Disintegration     190 

Clefts  due  to  frost 566-69 

Clefts  due  to  Polyponis  siilfureus 568 

Climate,   Continental    131-34 

—  Marine 13: -34 

Climatic  relations   134 

Clivia  nobilis.     Sunburn    643 

Clostridiioii  gclatinosum    2'/2,  273 

—  Pasteuriamiiii    270,   273 

Clover.     Pleophylly    376 

Clover,  Four-leaved    376 

Club-root  o'f  beets 871 

Coalescence.     Natural  processes 847-50 

Coating  substances.  Injuries  due  to.. 756-65 

Cobalt  in  waste  water 755 

Cobb's  disease  of  sugar  cane 696-97 

Coccus  caricac.  Fab 710 

Cocoa.     Fhytophthora  decay   462 

—  Unfavoral)lc  soil    231 

—  Wind    action    472 

Coffee.     Black   rust 230 

—  Blorokziekte     230 

—  Canker    230 

—  Djamoer   oepas    230 

—  Root  rot 23 1 

—  Swarte    roest    230 

—  Unfavorable   soil    230 

Coffee  arabica    230 

—  liberica     230 

Coffee  plantations.     Use  of  shade  trees. 657 

Cold,  Icturus  from  309 

Colletotrichum    261 

Collitris  quadrk'alz'is  828 

Coloration,  .\utumnal   127,  500-4 

in  trees   280-81 

—  Red,  due  to  excess  of  light 673 

in   grain    281-82 

Coloring   matter.   Red 127 

Colors,   Warming   up 127 

Commensalism    11 

Common  salt.     Sec  Sodium  chlorid. 
Compositae.     Doubling  of  the  blossoms. 375 

Cone  disease  of  conifers 372 

Conifers.     Blight  of  tops 487-89 

—  Cone   disease    372 

—  Differences   between    lightning   and 

frost   wounds    489-93 

—  Leaf   blight    from    frost 883 

—  Rcsirosis  • 711-16 

—  Ring  barking    615 

Conservatories,  Sunburn  in   643-44 

Coixsitution  of  soil.  Unfavorable. 

Chemical     264-407 

Physical    138-263 

Constriction,    Spiral    twisting   of    wood 

fibers  due  to  817 

Constriction  of  the  axis.     Effect 817-21 

Contagium  vivum  fluidum  of  the  mosiac 

disease    688 

Control  plants.     Cultivation    744 

Convallaria    iiiajalis    136 

Copper,  Injuries  due  to 740,  761 


893 


Copper  nitrate  in  waste  water 754-55 

—  rust  of  hops   283 

—  solutions,   Injuries  due   to 761 

Sec  also  Bordeaux  mixture. 

—  sprays.     Intumescences  after  use 

on  grapes    4-|0,   762 

—  sulfate  in  waste  water 754-55 

Copulation    831,   838-39 

Cork  disease  of  cacti 428-30 

—  formation   on   fruits 432-34 

—  holes    575-76 

—  outgrowths     426-28 

—  warts  on  grape  stems 432 

Conins  alba    105 

—  inascula    ■ 105 

—  sanguinea     105 

—  sibirica    105 

Correa    134 

Corylus    11,   105 

Coryiieum  Beijeriiickii,  Oud 556,  706 

—  giimmiparmn,   Oud 708 

Cotton.     Effect  of  fog 458 

—  Stem  browning    228 

—  Unfavorable  soils   229 

—  Wilt  disease   229 

Cow  bushes   Ij6 

Cramp  due  to  drought 281 

Crataegus    107,    127 

— •  Twisting    177 

Crenates     240 

Crenic  acid    240 

Creoline     760 

Crippling  phenomena,  due  to   frost 508 

Crops,   Preceding.     Influence    275 

Crotch   blight    594 

—  canker  in  fruit  and  forest  trees. 593-94 

Crust  formation  on  soils   no 

Cryptogams.     Sexual   organs    289 

—  Starvation    condition    287-89 

—  Tendency   to   dioecia 289 

Crystal-azurine    Mylius    765 

Cucumbers.     Splitting    462 

Cultivation.     Alethods.     Injurious 

effect    756-71 

Cultivation   of   moor   soil.   Changes   due 

to    256-58 

Cultures,  Feeding,  for  soil 142 

Cupressus    144 

Ciipressns   Brcgeoni    828 

—  Lawsoui    828 

—  seiiipervirens     828 

Currant,   Black.     Gnarl   formation 382 

Cuticula.     Rupture    623-24 

Cuttings.     Production   of  new  varieties. 827 

—  Utilization   of   various   organs.  .825-29 

Cuttings,   Leaf    873-78 

Cyathus    54 

Cycadeae     11 

Cydonia  lulgaris.     Gnarl   formation  ...  .385 

Cyiiibidium  Loivi.     Intumescence 444 

Cvstisus    105 

Cystospora  Icncostoiua    706 

—  nibesccns    556,   558 

Damping  off  of  shoots   134 

Dasyscypha    (Peziza)    JVitlkoiiitiiii 83 


Decay    196,  205 

Decomposition    196,   205 

Decomposition   of   proteins   due   to   lack 

of    light    669 

—  of  soil   196,  205 

Decorative    plants.      Drying    of    the    in- 
florescences     296-97 

Excessive    nitrogen     fertiliza- 
tion      393-95 

Dedoublement     376 

Defoliation,   Autumnal    527 

—  Summer   347,  411,  661 

Defoliation  due  to  frost   347,  527-31 

—  due  to  growth    347 

—  due  to  heat  347,  411,  644-45 

—  due  to  turgor   351 

Deforestration.      Bad    effects 89 

Degeneration     34-40 

Deiiiatopliora    nccatrix    710 

T>endrin     760 

Dendrobium.     Specking    261 

Denitrification    269 

Dew,  Capacity  of  sandy  soil  for  becom- 
ing wet  with 149 

Dew  fall,  Heavy  133 

Diaphysis    374 

Diaphysis  of  grain  heads   466 

—  of  potatoes   163-64 

Dicotyledons.     Resin   formation    716-17 

Didyinosphaeria   popidina    559 

Pidyiiiosporiuin  saliciintin    559 

Die-back  of  the  orange  392 

Digitellus    53 

I>ioecia.     Tendency  in   crytogams ..289 

—  Tendency   in   ferns 289 

Dioscorea     232 

Piospyros  Kaki.     Nanism 144 

Diptera  larvae,  producing  brown  chains. 614 
Discoloration  of  Fagns  sUz'atica 280 

—  of   trunks  and  branches 576-79 

—  of   woody   plants 279-81 

Disease.     Definition    9 

—  Excitor    27 

—  Inheritance     31-34 

— •  Limitation   of   concept 5-7 

—  Nature     5-40 

—  Predisposition    due    to    lack    of 

light    666-70 

—  Production     8-10 

—  Special  cases,  due  to  elevation 

above  sea-level    81-86 

Disease,  Absolute   7 

—  caused  by  smoke 49,  459 

—  Eelty     179 

—  Relative     7 

—  Shrivelling,  of  the  mulberry 690-92 

Diseases,  Constitutional    10 

—  Enzymatic    675,   717 

—  General     10 

—  Leaf -casting    349-5- 

—  Local,  of  plants  10 

—  Parasitic     13-19 

Diseases  due  to  location  of  the  soil.. 72,  137 

—  due  to  unfavorable  soil  condi- 

tions      72-408 

I   Djauwey  oepas  of  coffee   230 


894 


Dongkcllanziekte  of  sugar  cane 228 

Dormancy    353 

Dormant   eyes    785 

Dormant   period    125 

Dothiora  s/yliaeroidcs  Fr 559 

Double-rings    615-17 

Doubling   375,  376 

Dracaena.     Yellow  spots   435 

Drain  mats   ' 3^9 

Drain   tile.     Clogging    3^9 

Drainage I97,  -^S^,  233,  267 

Draining  of  moor  soil 257,  258 

Dropping  of  the  flowering  organs...  .353-57 

—  of  the  fruit   296 

—  See  also  Casting:  Shedding;  Shell- 

ing. 

Dropsy 335-39 

Dropsy  in   grape  cuttings 881 

—  in  pomes   338-39 

—  in  Ribes  aureitiii 336 

—  in  small  fruits   335-.38 

—  in  stone  fruits 338-39 

Drought    131 

—  Efl'cct  on  field  products 155-57 

—  Effect  on  germination I57-S8 

Drought,  Jaundice  due  to   311 

—  Physiological    245,  749 

Drought   cramp    281 

—  spots   in   grain 282 

—  tears    , 568 

—  with   the   cherry 281 

Dry-rot  due  to  waste  lime 195 

—  of  beets 4i5-'6 

Drying  of  foliage,  Premature 284-85 

Duct  bosses   57o 

Dunes    1 49 

Dwarf  growth    76,    142-47 

—  stock     105 

Dwarfing  due  to  scarcity  of  water 145 

Ecblastcsis 375 

Eel-worrns     855 

Electrical  discharges    480-97 

Electricity,  Effects  of  experimental. 488,  882 

Electricity  in   city  planting 403 

Electro-culture.       Disadvantages 496-97 

Electrolytes     193 

Elm.     Bark  refuse 259 

FJy))ius  aroiarius,  L 90.  150 

Embryonic  plasma    31 

Emergences 434 

—  in  Ampelopsis  liedcracca   440 

Encrustation  of  the  soil 134 

Endemics    19 

Endomyccs  veniatis  Ludw 855 

Enzymatic  diseases    675-71 7 

—  functions.      Displacement 675-717 

Enzymes 887 

Enzymes  in  plants 883 

Epidemics    19-23 

Epilobhun   liirstitiiin.     Adaptation  capa- 
city      ;;^22 

Epistrophe 673 

Equisetum  palustre,  L.,  Formation  of 

drain  mats  due  to. ...... , 319 

Ergot    ...:...:. • 50 


Ericaceae.     Root-ball   dryness 181-82 

Erineum    Pers    179 

Eriphorum     256 

Erysiphe  fabricii    49 

—  (jraiiii)iis    640 

Erysiphe   Th 53 

Ether-forcing    765 

Etiolation    308,  654-57 

Etiology    7 

Eucalyptus.     Intumescence    444 

Evaporation.     Increase   with   lack  of 

nutritive  substances   318 

Evoiiymiis  Japonica.     Nanism    144 

Excrescences  on  bark   329 

Exoascus    146 

Experiments,    Cultural,   with   lack   of 

calcium    303 

Exposure,   Southern    86 

Factors,    Vegetative.     Accumulation....  38 

Faille  of  tobacco 685 

Fagus    II 

Faqus  silvatica.      Discoloration 280 

Fallow  land   188-89,  273 

Fames    -^^ 

Familiola     53 

Fasciation    33,  3,?,y3-\ 

—  due  to  frost 559 

—  in  Picea  excelsa 332 

Felty   disease    179 

Fermentation,  Alcoholic   100 

Ferments.     Pectin    271 

Ferns.      Apogamy    342 

—  Tendency   to  dioecia 289 

Ferns,   Viviparous    342 

Ferric  sulfate.    See  Iron  sulfate. 

Fertilization.     Exhausting  effect    266 

Fertilization,  Salts  for 192 

Fertilization  of  moor  soil   257,  258 

—  with  green   manure 234,   267,   271 

—  with    iron    sulfate 402 

—  with  nitrate   of   soda 223 

—  with  potassium    129,   156 

Effect  on   growth 156 

—  with    sodium    chlorid 193 

—  with    straw    269 

Fertilizers.  Turning  to  peat 271 

—  Injurious  effects    767-71 

Fever   reaction   in   plants 871 

Field  Crops.     Effect  of  drought 155-57 

Over-fertilization     392-93 

Fields.     Spray  lightning  action 495-96 

Fig  trees.     Gummosis   7 10- 11 

Filositas     161-63 

Flaccidity.     Phenomena    8 

Flashes   of   lightning 480-87 

Flavor,  Frosty,  in  grapes 518 

—  Hard,  in  grapes,  due  to. hail 469 

Flax.     Jaundice  (le  jatinc)    283 

—  Reds   (Ic  rouge)    283 

—  Yellow  ( Ic  jaitiJe)    283 

Flocculency    193 

Flour.     Loss  of  baking  quality  due  to 

sprouted  grain   321 

Flower    clusters.      Shedding-   in    hya- 
cinths      365-67 


895 


Flower  pots.     Washing 205 

Flowering  organs,  Dropping 353 

]"lowers,  Green    342 

Flying  ashes    738,   741 

Fodder  beets.     Root  blight 220-26 

Fodder    peas.      Lodging 665 

Fog 458-60 

Fog.     Effect  on  cotton 458 

—  Protection   against   frost 511 

Foliage.     Injuries    879-80 

—  Perforation    .....427,  430-3^,  444.  449 

—  Premature  drying   284-85 

—  Yellowing  due  to   frost 554 

—  Yellowing  in  camellias  due  to  ex- 

cess  of   light 671 

Foliage,  Older.     Behavior  with  acute 

frost   action    524-26 

F"ood  concentration.     Increase 360-87 

Food  stuffs.    Relation  to  the  soil  struc- 
ture     264-74 

Fool's-head   formation   in   hops 342 

Forest  litter   186-87,  270 

Forest  trees.     Crotch  canker 593-Q4 

Isolation     2,2-j 

Forestration.     Advisability    8q 

Forests    ".  . . .  134-37.    187-88 

—  Use   as  protection 1 50 

"Forks"   of   grapes 345-46 

Fox  of  the  hop 282 

Freezing  back  of  older  branch  tops.. 553-55 

—  of  heavy   soil 235 

—  to   death    504-7 

Frenching  disease  of  toliacco   685 

Friability,  Dependence  of  tillage  on 194 

Frost.     Attack  on  immature  growth  ...  .554 

—  Behavior  of  beets   531-32 

—  Behavior  of  cabbage  plants 531-32 

Frost,  Acute.    Effect  on  foliage 524-26 

—  Black     537 

—  Experimental  production   of  par- 

enchyma wood  h\   617-20 

—  Late.     Damage   136,  432 

—  Protection  by  fog  against... 511 

—  Protective  measures  against ...  .624-30 

—  Susceptibility   of   moor   vegetation 

to     ..251-53 

—  Theory   of   the   mechanical   action 

of    620-23 

—  Varieties  hardy  to 500,  631 

Frost  action.     Effect  on  roots 562-66 

Special  cases    5 14-637 

• Theory  as  to   nature 507-13 

— •  blisters    524,  532-34,  5^9-74 

—  boils  of  cherries 572 

—  canker    583 

—  causing  cambial  browning 612 

cell  membrane  loosening, 581 

cell  passages 613 

changes  in  blossom  organs.  .518-23 

crippling  phenomena    508 

damage    136,  432 

deficient  greening  of  younger 

foliage     526-27 

defoliation    347,    527-31 

differences   in   tension 514 

drying  of  cherry  trees 555-58 


Frost  causing  dying  of  twigs 154 

excessive   chilling    508 

—  —  f  asciation    559 

—  —  heaving  of   seeds 536-37 

injury  to  bud  cushions 577 

injury   to    spring  growth 559 

internal   injuries  to   the   grain 

stalk 539-41 

internal  injuries  to  the  young 

grain 537-41 

internal  splitting  of  trunk  and 

branches    581-83 

• leaf  blight  of  conifers 883 

medullary    ray   displacement.  ..  .571 

movement   phenomena    547-53 

running  to  seed  of  beets 516-18 

rust  rings  in  fruit  523-24 

—  —  splitting  of  leaves   534-36 

stalk   lodging    542 

super-cooling    508 

■  wilting     549-51 

yellowing  of  foliage 504,  554 

—  clefts     566-69 

—  curve    630 

. —  danger  in  sandy  soil 149 

—  holes    197 

—  line     579-81 

—  plates 609 

—  prediction     630-31 

—  ridges    566 

—  tears.   Internal    569 

Open     583-85 

—  wounds    in    conifers 489-93 

—  wrinkles    574-75 

Frosting     504-7 

Fruchtkuchen    338,   339 

Fruit.     Cork   formation 432-34 

—  Dropping     296 

—  Hardy   varieties    631-33 

—  ]\Iealiness    166-68 

—  Ripening,   Premature    166 

—  Rust  rings  due  to  frost i-2)-2\ 

—  Rusting  of   the  peel 170 

—  Seedless    292-95 

—  Self-sterility 291 

—  Sprouting    .■ ■. 375 

—  Watery  taste   2,2:*, 

Fruit  cushio-ns.     See  Fniclifkitcheii. 

—  spurs.     Casting    338 

—  trees.     Crotch  canker 593-94 

Root   grafting    840 

—  varieties.     Advantages  of  pure 

planting    295 

for  dry  soils    174-75 

Fruits.      Double    376 

—  Sunburn     645-46 

Fiiligo    z'agans 56 

Fuiiiac/o  saliciiw,  Tul 710 

Functioning.     Maximum  degree    9 

—  Minimum  degree    9 

- —  Optimum  degree   9 

Fungus  marinus 53 

—  .panis  siiiiilis    53 

Furrowing  in   heavy,  soil 234 

Furrows,  Open 235,  511 

Fusarium     .' . 204 


896 


Fusariunt   iiioschatuiii    855 

Fusicladiuin    i/i 

ftisisporiuiii  candiduin  Lk 558 

Galactan    705 

Galactin     705 

Galactose  - 167 

Gallimaceus     5^ 

Gas,    IlL.niinating    744-47 

Gas  phosphate   768 

Gas-works,   Refuse    756 

Gases.     Exchange 314 

Gases,  Injurious.     Effects   718-71 

Gayhead  in  tobacco   229 

Geiivure  of  the  grape  vine 495 

Gemmules    31 

Generation,    Spontaneous    54 

Genista    150 

Geoponica    44 

Germ  plasm    31 

Germination.     Effect  of  carbon  dio.xid 

excess    109 

—  Effect  of  drought 157-58 

—  Xecessity  of  oxygen 109 

—  Tests    201 

Germination  of  seed  in   fruit 321 

in   ice   499 

Germination  power.     Higher 125 

Retention    107 

Gingko  Biloba.     CItici   386 

Cylindrical  gnarl    386 

A^,-/,/,/,,     386 

Girdling    : .  787-97,  885 

—  Effect  in  grape  culture 354,  788 

Girdling  disease  of  the  red  l)eech 219 

Gladiola.     Diseases    316 

Glassiness  of  cacti 453-57.  717 

—  of  carnations    ; 717 

—  of   grain    kernels 1^9-31 

—  of  orchids   651,  717 

Gloeosporium    261,   263 

Gloeosforium    nen'isequum    304 

Cnaplialiiiin    Lcoiifof>n(liuin    84 

Gnarl,   Cylindrical,  of  Gingko   Biloba.  .  .386 
Gnarl   formation  on  black  currant 382 

on   Cydonia  vulgaris    385 

on   Pirns  Mains  sinensis 381 

Gnarl  tuber    863 

Goitre  gnarl.  Herbaceous    378 

on  Acer  camf>estre  378 

on  Prunus  Padus   385 

on   trees    378-87 

Gold  of  pleasure,  sown  to  prevent  lodg- 
ing     665 

Gommose  Imcillairc    851 

Graft,  Bark   831.  837 

—  Cleft    831,  833,  838 

—  Root    840 

—  Saddle    831 

—  Whip     837 

Graft   symbionts.     Callus   formation.  ..  .887 

Grafting    829-47 

Grafting.  Dwarf  stock  in 105 

—  English   tongue    845 

—  Hybrid    formation   by    845 


Grafting.    ^^lutual  intlucnce  of  scion  and 

stock    in    841-47 

—  Transmission  of  chlorosis  in 697 

—  Yellowing  of  the  stalk  in 284 

Grafting  by  ablactation    831 

—  by  copulation    831,  838-39 

—  by   insertion    831 

—  of  grapes 844 

Grain.     Blackening   72 

—  Blasting 160-61,   282 

—  Delayed    ripening    365 

—  Diaphysis    466 

—  Drought  spots    282 

—  Effect  of  hail 464 

—  Eft'cct    of    harvesting    in    tiie    milk 

stage    295 

—  Excessive    straw    growth 365 

—  Glassy  kcrnals 129-31 

—  Internal  injury  due  to  frost 537-41 

—  Lodging   .365,  662 

—  Proliferated  heads  due  to  hail.... 466 

—  Red   coloration    28 1  -82 

—  Roots  from  seed  tips 1 16-20 

—  .Spotted   necrosis    372 

—  Sprouting    320-21 

Grain,  Winter.     Harrowing   236 

Granulation  of  the  rose  stem 434 

Grapes.     Bark  warts 881 

—  Canker   596-98,  601 

—  Changelings     346 

—  Chlorosis     402 

—  Corky  warts  on   stem 432 

—  Double  tips   345 

—  Dropping   of    blossoms    354 

—  Dropping  of   young   berries 788 

—  Effect  of  girdling 354,   788 

—  Effect  of  spray  lightning  493-95 

—  Excess   of   calcium 402-3 

—  Eorked  growth    345-46 

—  "Forks"    345 

—  Frosty  flavor    518 

—  Geiivure    405 

—  Grafting     844 

—  Hard  flavor  due  to  hail 469 

—  Hcrbaceousness    345 

—  Icterus    210,   402 

—  Injury  from  sunburn   646-47 

—  Intumescence     438 

after   copper    spraying 440 

—  Jaundice     402 

due  to  excess  of  calcium 310 

—  Leaf   scorch    283 

—  }faladie  f^cctiqiic    : 284 

—  Parching    283 

—  Pectin   disease    284 

—  Red  scorch    283 

—  Scab     596-98 

—  Shelling  of  the  blossoms 354 

—  See  also.  Vitis. 

Grapes,  Seedless   355 

Grapholitliia    Chernies    "^23 

—  pactolana     723 

Grass.     Burning  out    285 

—  Disappearance     362 

—  Effect  of  e.xcess  of  nitrogen 365 

—  Influence    276 


897 


Grasses.      Red    coloration 282 

Gray   sand 243 

Green-manure  fertilization   ....234,  267,  271 
Greening  of   inflorescences    341 

—  of  younger  foliage.     Deficient.   526-27 
Ground  water  level.    Depth  in  moor  soils. 257 

Lowering    106.    150-5-2 

—  Raising    183 

Growth.    Arrestment  due  to  radium  rays. 672 
due  to  Roentgen   rays    672 

—  Defoliation    347 

—  Effect  of  humidity   423-25 

of   potassium   fertilization 156 

Growth,   Double    156 

—  Immature.     Effect  of  frost   554 

—  Twisted    774,    821 

Guigiiardia  Bidwellii    26,  669 

Gum   cells    851 

Gum  exudation  in  Acacias   707-8 

in  bitter  oranges   708-9 

in   plants    707-17 

Gummosis.  Use  of  vinegar  made  from 
wine     707 

Gummosis  of  cherries   699-707 

—  of   fig  trees 710-11 

—  of   olives    711 

Gymnosporangium    53 

Gyiiinosporangium  Sabiiwc   62 

Gunnera    11 

Gypsum    195,  250,  402 

Habitat.  Effect  of  changes  on  herba- 
ceous plants    72-75 

Habits,  determining  peculiarities  in 
plants    39 

Hail    463-70 

—  Effect  on   grain 464 

—  Effect  on  hops   466 

—  Effect  on  potatoes   466 

—  Effect  on  rape 466 

—  Effect  on  tomatoes 467 

Hail,    cannonading   against 470 

—  causing  bark  wounds   468 

•  hard  flavor   in  grapes 469 

—  —  lodging  of  the  stalks  of  grain.. 542 
proliferated   grain    heads 466 

Handles  on   trees 848 

Hard-shells  of   seeds 115,  420 

Harp-trees    93 

Harrowing    236 

Harvest.     Decrease  due  to  tree  shade... 657 

Health.     Latitude    9 

Heart  rot   615.  851 

due  to  waste  lime 19; 

of   beets    415-16 

of  horse  radish   717 

Heart  wood.  False  851.  852 

Wound     852 

Heat.     Death   638 

—  Defoliation 347,  411-12,  644-45 

—  Excess 638-53 

Premature    ripening    640 

5"^^  also  Sunburn. 

—  Lack    498-637 

Heat   rigor    638 

Heath  soils.     Disadvantages    242 


Helianthus  annus.     Effect  of  defoliation. 341 

Helichrysum     I34 

Helotium 54 

Hemi-celluloses    705 

Hemi-parasites     i- 

Hemi-saprophytes    1-2 

Herbaceousness  in  grapes 345 

Hericia     855 

Hibiscus  vitif alius.     Intumescence 448 

Hieraciuiii    alpinum    84 

Hilling  of  heavy  soil 234 

Hippeastrum     127 

Hippophac  rhamnoides.     L 90,  150 

Hoar   frost    636 

Summer     637 

Hoeing  of  the  soil  184,  234 

Holoparasites     i- 

Holosaprophytes     12 

Homogamy     293 

Honey  dew   55,  412-15 

Hops.     Barrenness    34^-44 

—  Blindness    342 

—  Copper  rust   283 

—  Effect  of  hail 466 

—  Eft'ect  of  shading 283 

—  Eool's   head    formation 342 

—  Eox     282 

—  Heating    344 

—  Pole    red    283 

—  Red  tan    282 

—  Reds    282-83 

—  Summer   rust    282 

Hormodendrum  disease    742 

Horn  prosenchyma    707 

Horn  shavings.    Use  as  fertilizer.  .  .393,  395 
Horse  radish.      Black  ring  condition  .717,  884 

Heart  rot 717,  884 

Horticulture.     Use  of  sand 261 

—  Use  of  sphagnum  peat 260 

Hot  bed  plants.     Wilting 2-jj 

House  plants   419-20 

Leaf   fall    352 

Humea    I34 

Humic  acid   241,  722 

Humidity    123 

—  Effect  on  mode  of  growth 423-25 

Humidity,  Excessive.   Effect.  .75,  123,  423-57 

Humin    241 

Humus.  Raw 149.  190,  242,  271 

Humus   fermenting  organisms 272 

—  sandstone     243 

—  substances    15  r 

Hyacinths.    Ring  disease  of  bulbs. 326-27,  451 

—  Shedding   of    the    young   flower 

clusters    356-57 

—  Skin   diseases    451-53 

Hybrid  formation  by  grafting 845 

Hydrochloric  acid   724-29 

Hydrocyanic  acid    761 

Hydrofluoric  acid    729-30 

Hypochlorin    502 

Hypocrea  rufa   17 

—  Sacchari    227 

Hypoplasia    I77 

Hypoxylon     53 

Hvsterium     54 


898 


Ice,  Germination  of  seed  in 499 

Ice  coating   634-37 

—  formation.     Favorable   effect 510 

Icicles    634-37 

Icteriis     307-12 

—  due  to  cold 309 

—  of  grapes    310,  402 

Idioplasm    31 

Igniarius    53 

Immunity    128 

Immunity  and  predisposition 27-31 

Inmnmization,  Artificial    23-25 

1  nertia     39 

Inrtorescences.      Proliferation 374 

—  See  also  Blossoms ;   IHowering 
organs. 

Inflorescences  of  decorative  plants.     Dry- 
ing     2CX3-07 

Inheritance.     Nature   t,2 

Inheritance  of   disease 31-34 

Inscriptions,  Wounds  due  to 781 

Intra-molecular  respiration   99,  313 

Intumescence,  Internal    447 

Intumescence  after  copper  spraying. ..  .762 

—  due  to  spraying  injury 441 

—  on   Acacia   longi folia 437 

—  on  Acacia  microhotrya 437 

—  on  Acacia  pcndiila   443 

—  on   Aphelandra    448 

—  on  beans   446 

—  on  cacti.     Internal 430,  454 

—  on  Cassia  toiiientosa  436 

—  on  Cymbidium  Lou'i   444 

—  on    F.ucalyptus    444 

—  on  grapes    43cS 

—  on   Hibiscus  7'itifoliiis   448 

—  on  Mynnecodia  rchiuata   437 

—  on  peas    446 

—  on  Pelargonium  zotialc  438 

—  on   Ruellia  448 

Intumescences    432,  435-49 

Intumescentia    435 

I  nundations    195-96 

Iron.     Lack   307-12 

—  Occurrence  in  waste  water 753-54 

Iron    silicates    251 

—  sulfate     881 

Fertilization    402 

—  sulfid     250 

Iron-spottedness  of  potatoes 391,  882 

Irrigation  of  soil 182-83,   196 

Ishikubyo  of  the  mulberry   690 

Isolation  of  forest  trees 227 

Iso/yyniin  bifcrnatum   12 

Jadoo   fibre    263 

Jahresbericht,   Botanischer   60 

Jaundice    307-12 

—  caused  by  drought 311 

lack   of   iron 307-12 

lack  of  nitrogen .310 

lack  of  potassium 310 

Jaundice  (le  jatiiie)  of  flax    283 

—  of  grapes    402 

due  to  excess  of  calcium. .  .  .310 

—  of  poplars   887 


Le  jaune  of  flax  283 

Juglans    107 

Juniperus.     Rooting  of  branches 254 

Jitiiipenis  coiiiiiiunis  105 

—  plioc'iicca.     Bending  by  wind 475 

—  Sabina     105 

Juvenile  form,  Retrogcssion  to  the 377 

Kainit    404 

"Knick"    192 

Krados    42 

Lactic   acid,   Injury   from    factories   pro- 
ducing     761 

Laelia.     Specking   261 

Land.     Conversion   into   swami)s 196-99 

Land  plaster.     See  Gvpsum ;    Plaster, 
Land. 

Landslides.      Effect 90 

Larch.    Retrogression  in  its  cultivation. 81-84 

Latitude.     Greater   differences 120-31 

Latitude   of   health 9 

Latitude   of   life 9 

Laurus    133 

Layering.     Quinces    816 

Leaching.       Soil 243 

Lead.     Injuries  due  to 740 

Lead  nanism    753 

—  sand    243 

Leaf.      Aurigo 434 

Leaf  blight  of  conifers 883 

—  casting  diseases    349-52 

—  curl  of  potatoes 395-99,  882 

—  cuttings 378,  873-78 

—  edges,  dried  by  hydrochloric  acid.. 724 
- —  emergences    434 

—  fall  in  azaleas  352 

—  —  in    Begonia  fitclisioides 353 

in  house  plants 35^-53 

in  Libonia  floribunda  353 

See  also  Defoliation. 

—  injuries    871-73 

—  mould.     Use  with  orchids 262 

—  perforation    427,  430-32 

—  scorch   of  vines 283 

—  spot  diseases  of  sugar  cane 228 

—  wilting 365 

Leaves.     Bud    formation 378 

—  Cork  outgrowths   427 

—  Falling    346-49 

—  Injury  from  wind    477 

—  Splitting   from   frost 534-36 

—  Sunburn   in   nature 641-43 

—  See  also  Foliage. 

Leaves,    Bitten    430-32 

—  Perforated    430-32 

Legumes,    Blasting i6o-6r 

Leguminosae,   Advantages  to   soil   of 

growing    232 

Leguminosae  seeds.     Hard   shells 420-22 

Light   lines    420 

Lenticels    , 215 

—  in   potatoes    369 

Lepidiiiiu  sativum    74 

Leptosphaeria.     Lodging  of  grain  stalks    • 

clue  to  542 


899 


Leptothyrium  pomi  Mntg. 170 

Leuconostoc  Lagerhchnii  Ludw 855 

Libertella  faginca.     Desm 558 

Libonia  floribunda.     Leaf   fall 353 

Lichenism    11 

Lichens   on   trunks 331 

Life.     Latitude    9 

Light.      Excess 671-74 

Red  coloration    673 

Shadow  pictures   673 

Yellow  foliage  in  camellias 671 

—  Lack     654-70 

Changes   in  acid   content   in 

plants    668 

—  —  Protein   decomposition    669 

Sugar   blocking    667 

Lightning.     Effect   on   beets 495 

—  Effect   on   potatoes 495 

—  Flashes     480-87 

—  Internal  striking   486 

Lightning,   Spray    486 

Effect  on  fields  aii'l  meadows 

495-96 

Effect  on  grape  vines 493-95 

Lightning  wounds   in   conifers 489-93 

Lignification  of   roots    179-80 

Ligustrum    105 

Liliaceae.     Faulty  blossom  development. 417 

Lily-of-the-valley.      Failure 395 

Lime.     Scarcity  indicated  by  sorrel 22,7 

Lime  kilns.     Tar  vapor 72,7 

Liming   194.  238 

—  Periodic 268 

Lingua 53 

Linuin  usitatissiiintin    107 

Liquids,  Injurious.     Effect  718-71 

Lithiasis    1 70-74 

Litter.     Cautious  removal    149 

—  Excessive    use 194 

—  Layers    242 

—  Raking    196 

Loam,  Loose   191 

Lodging    131 

—  of   fodder  peas : 665 

—  of  grain       365,  662-66 

—  of  grain   stalks    542 

Longevity  due  to  grafting 839-40 

Lopas    43 

Loranthus    56 

Loranthits  sciicgalensis   708 

Loupe     863 

Loxas     43 

Lutidine     460 

Lychnis  diiinia    147 

—  vespertina    147 

Lyciuiii  barbaniiii,  L 150 

Lycogala 53 

Lycopus  curopaciis.     Adaptation   2)-^ 

Lysol 760 

Lythrum.     Adaptation   2-2 

Mafjita  disease   of   Andropogoti   sor- 

glutin    415 

Magic  ring,  Pomological    789 

Magnesium.      Excess 399-402 

. —  Lack.     Changes  due  to 305-6 


Magnesium  chlorid  in  waste  water 

750,  751-52 

Magnesium    compounds,    Concentrated. 

Poisonous  effect    361 

Magnolia  hypolcuca   159 

Maise.     Unfavorable   soil 231 

Mai  de  mosaico  of  tobacco 685 

Mai  della  bolla  of  tobacco 685 

Mai  della  gonima   708 

Mai  nero   219-20,  709 

Maladie  pcctique  of  grapes   284 

]\Ial  formations   57,  72 

Malope  grandiflora.     Stem  calluses 443 

Mains  sinensis.    See  Pirns  mains  sinensis. 

Maniinia  fimbria ta    559 

Manna.     Exudation    711 

Mannan    705 

Manniok     232 

Manure,  Green   234,  267,  271 

—  Stable.     Fresh    269 

Marciume  del  Fico 710 

Markasit    250 

Market  varieties    138 

Marb'ng    194,   238 

Marling,  Scurvy  from 370 

IMarshy  change   in   soil   causing   frost 

susceptibility    196 

Manche  of   tobacco 685 

Meadow  ore  192,  243-49,  251 

Meadows.     Effect   of   excess  of  potas- 
sium  405 

of   harrowing   236 

—  Improvement 362 

Meadows,  Changes  in   362-64 

—  Moor    260 

—  Mossy 364 

—  Rankly  growing  places  in 364 

—  Spray   lightning  on 495-96 

—  Use  of  ammonium  salts  on 363 

Mealiness   of   fruit 166-68 

Measures,   Protective,   against   frost.  .624-30 

Mechanics,   Developmental    66 

Medullary   rays.     Displacement   due   to 

splitting .■ 571 

Excrescences .  .380 

Mclacris    412 

Melligo 412 

Mercurialis   annna    147 

Metamorphosis,   Progressive    272-77 

—  Retrogressive    340-44 

Methods,    Preventative 22 

Micrococcus  dendroporthos..    Ludw 855 

Mildew    42 

—  See  also  Rubigo 

Milk  stage.  Effect  of  harvesting  grain 

in    295 

Millet,  Brush.     Unfavorable  soil 232 

—  Negro.     L^nfavorable  soil   222 

—  Sorghum.     Mafuta  disease   415 

Mimosa  pudica.     Drought  cramp   281 

Mimnlns    Tilingii    76 

Minimum,  Law  of  the 299 

Mites    855 

IMobilization  of  reserve  substances 106 

Moisture     319 

—  Fluctuations 273 


900 


Moisture.     Lack   275-87 

causing  clianges   in   produc- 
tion      278-79 

tip  blight    189 

in  the  soil 182 

Moisture,  Atmospheric.     Sec  Humidity. 

Mombacker  disease  of  apricots 479 

Mongrel  disease  of  tobacco 685 

Monilia  cinerea   706 

—  fructigena    706 

Monstra 57 

Monstrosities     57 

Moon-rings    613 

Moor  plants,   Horticultural 260 

Moor  soil.     Bacterial  flora 256 

Changes  through  cultivation. 256-58 

Depth  of  ground  water  level... 257 

Disadvantages    240-63 

Draining    257 

Fertilization     257-58 

Potassium   chlorid   treatment.  .  .257 

Sanding    256 

Moor   vegetation.      Susceptibility    to 

frost ." 251-53 

Morphaesthesia    139 

Mosaic  disease    229,  684-89 

Contagium   vivum   fluidum 688 

Effect  of  cultivation    687 

Predisposition    687 

Virus 687 

Mosaikbeiegsege  of  tobacco  685 

La  Mosaique  of  tobacco   685 

Movement  phenomena,  due  to  frost.  .547-53 

Mucor    53,  766 

Mucor  albus  e,s 

—  raceiiwsiis    lOi 

—  spiiwsus     99 

—  stoloiiifer    13,    lot 

Mulberry.     Ishil^ubyo    690 

—  Sliikuyobyo    690 

—  Shrivelling  disease .690-92 

Mulching   184-85,  235 

Mules  disease  of  potatoes 161-63 

Multicolor  of  potatoes 391 

Mycoplasm    34 

Mycorrhiza     11 

MyrDiccodia   cchiiiata.     Intumescence. .  .437 
Myrtus    133 

Nanism    142-47 

Necrobiosis     703 

Necrosis    56 

—  Spotted    372,   741 

Xccfria  ditissiiiia 46.  137,  588,  592 

Xcfytuii     760 

Nickel   in   waste   water 755 

Nicotine    460 

Xiellc  of  tobacco 685 

Nidularia    53 

Nit>flc  on  Gingko  Biloba   386 

Nitrate  of  soda  fertilization 193,  223 

_—  —  See  also  Chile  saltpeter. 

Nitric   acid    730 

Nitrogen    270 

—  Excess.    Effect  365,  387-99.  "09 

Effect   on    rhubarb 392 

Retarding  effect  on  ripening. .  .394 


Nitrogen.     Lack.     Clianges  in  produc- 
tion     287-98 

Nitrogen  fertilization.  Excessive.     Effect 

on  decorative  plants  393-95 

—  hunger    270 

Jaundice    310 

—  storage  by  bacteria 270 

Nutriment.     Increased  concentration. 360-87 

—  Lack   175.  275,  287-319 

—  Relation   to   plants 274-319 

Nyctomyces     56 

Xyctoiiiyces  candid  lis   614 

—  utilis    614 

Oculation.     See   Budding. 

Oecological    variations    j^ 

Oedema     335-39 

Oil  fumes.     Injury   757 

Olive.      Gummosis    711 

Olivile     711 

Ooze  coating.     Injury  to  sewage   dis- 
posal beds    366 

Ophiobolus    137 

—  causing  lodging  of  grain  stalks. ..  .542 

Optimum  degree  of  functioning 9 

Opuntia.     Cork  disease 429 

Orange.     Die-back   392 

Orange,  Bitter.     Gummy  exudation.  .  .708-9 
Orchids.     Classiness  651,  717 

—  Specking     26 1  -63 

—  Use  of  leaf  mould 262 

Organism.     Cultural  aim 6 

—  Developmental  mechanics    66 

—  Force   of   self-preservation 6 

—  Self-purpose     6 

Organs,  Axial.     Wounds   772-880 

Organs,  Sexual,  in  cryptogams 289 

Orobus  vcrnns  75 

"Orterde"     243 

Osinunda  regalis   288 

Outgrowths  on  roots   191 

Over-fertilization    of    celery 392 

—  of  field  plants   392-93 

—  of   rhubarb    392 

—  of   vegetables    392-93 

Overgrowth    edges.    Gnarly 859-61 

Overgrowth  of  wounds   776-81,  783 

Oxalate  of  calcium  792 

Oxalic  acid   22;^,  449 

content  of  edible  roots 22$ 

Oxalis  crenata   109 

Oxygen.     Excess.     Effect 315 

—  Lack.     Effect    313-16 

Suffocation    313 

—  Necessity   in    germination 109 

Oxygen   rigor    313 

Oxyphen  acid    503 

Paconia  arborea.     Bud  cuttings  828 

Pan-genesis    31 

Panachure.     See  Variegation. 

Paiidanus  javaiiicus.     Yellow  spots 434 

Pat'aver  somnifcrum.     Pistillody    372 

Parasites.     Energy  of  growth 15 

—  Nutritive    substrata    17 

Parasites,  Facultative    15 

—  Obligate    15 


90I 


Parasites.     Wound    15 

Parasites   of   weakness 15 

Parasitism    12 

Parching  of  grape  vines 283 

Parenchyma  wood.     Experimental  pro- 
duction by  frost  action 617-20 

Parenchyma   wood   aggregations 613-15 

Parenchymatosis   5.  33^ 

Parthenogenesis   178,  342 

Pathogeny    7 

Pathography    7 

Peach  buds.     Dropping 645 

—  rosette     6g8 

—  rot    763 

—  yellows    697-99 

Peanut  diseases   690 

Pears.     Lithiasis    170-74 

—  Stoniness    170-74 

—  Varieties  for  dry  soils 175 

Peas.     Intumescence    *. 446 

Peas,  Fodder.     Lodging   665 

Peat,  Sphagnum,  in  horticulture 261 

Peat  mulch 265 

Peatrification  of  the  fertilizer 271 

Peaty  earth    185 

Pectine    167 

—  disease  of  grapes 284 

—  fermenting  organisms    272 

—  ferments     271 

Peeling  of  bark  by  game 781 

Peli-sem   of  tobacco 685 

Pelargonium.      Bud   disease 146 

Pelargonium  coiialc   438 

Penicillium    14,  327,  766 

Penicilliiiiii  glaiicum    13,  204,  451 

Pennischini    spicatiiin.      Unfavorable 

soil    22,2 

Pentoses    167 

Perforation  of  the   foliage 

•  •  •  -427,  430-32,  444,  449 

Periodicity,   Corrective    3>i 

Peronospora  viciac    446 

Pestilences,    Chart    of . - 2t, 

Petalody    372 

Peziza    53 

Peziza   Willkoiiiinii    83 

Phalaenofsis   ainabilis.  var.   Riincnsfadi- 

ana.     Specking    , 261 

Phaseolus    30,    126 

—  Effect  of  lack  of  calcium 304 

Phenol    460 

Phenomena,    Life,    at   low    tempera- 
tures     498-50(J 

Phenyle,  Little's   Soluble   760 

Phillyrea.     Wind-bending    475 

Philodendron.     Grafting  experiments.  .  .838 

Phleom.     Circumvallation 867 

Phleum  pratense.     L 125 

Phoma    II,  261 

Plioina  Bctae,  Frank   222 

Phosphoric    acid.      Excess 405-6 

—  —  Lack    300,  312 

Phosphorus.     Lack.     Efifect 312 

Phragmidium    59 

Phyllachora  potiiigcna    (Schw.) 170 

Phyllerium   Fr 179 


Phyllocactus.     Cork   disease 4-9 

Phyllody    340-44 

Phyllomorphosis    34i 

Phyllosticta    261 

Phyllosficta  Sycophila.     Thiim 710 

Phytopathology    7 

—  Historical  survey   41-/1 

—  Periodical   literature    66 

Phytophthora     62 

Phytophthora  decay  of  cocoa   fruits 462 

Phytophthora  infestans  21 

Phytoptus    146 

Picea    105 

Picea  cxcclsa.     Fasciation   2i3- 

Picoline    460 

Pigment,   Red    127 

Pilobolus     54 

Pilosis    177-79 

Pimelea    134 

Pine.     Dropping  of  the   needles 349 

—  Shedding  of  the  bark 259 

—  See  also  Pinus. 

Pineapple.      Failure 650 

Pinosol    760 

Pinus     105 

—  Nanism     144 

Pinus  montana    '.  .247,  475 

—  sik'cstris    94,   107 

—  —  f.  turfosa   249 

—  See  also  Pine. 

Piricularia  Orysea   Br.   et   Cav 315 

Pints  coiniuunis    281 

—  IMlahis  sinensis.     Gnarl  formation .  .381 
Pissodcs  Hcrciniac    723 

—  scahricollis    723 

Pistillody    . 372 

—  in  Papavcr  soinnifcrnni    372 

Pisum    II 

Pisnin    satifuin    107 

Pith  bridges    577 

— ■  repetition     613 

—  spots    613 

Plant  coverings.     Effect    275-76 

Effect  on  soils 185-86 

— -diseases.     Classification    48 

— -diseases.   Constitutional    10 

General    10 

—  —  Local    10 

—  hygiene    71 

—  protection     59 

Plan  tag  0  alpina    84 

—  inaritiina     84 

Planting.     Depth    103 

Planting,  Autumnal.     Precautions    565 

—  Too  deep   98-120 

—  Too  shallow   105 

Plants.     Burning  in  moist  soil 199-200 

—  Check    9 

—  Cultural  position   55 

—  Dormant  period    125 

—  Etiolation    423 

—  Law  of  inertia 39 

—  Peculiarities  determined  by  habit..   39 

—  Power  of  resistance   18 

—  Protective   devices   against   para- 

sites        18 


go2 


Plants.     Relation  to  environment 10-13 

—  Relation   to   nutritive   sub- 

stances     274-319 

—  Rupture  of  fleshy  parts 3^ '-34 

—  Statistics  of  disease  71 

—  Stunting     175-/7 

Plants,   Herbacious.     Effect   of   changes 

in   habitat    72-75 

—  Tropical    190 

—  Woodv.     Adjustment  of  root 

body    78-81 

Development  of   axis 76-78 

Plants  injured  by  drought.     Effect  of 
moist    air    425-26 

Plasm,   Eml)ryonic    31 

—  Hereditary    31 

PlasiiioHiofyliora  Brassicac   364 

Plasjiiopara  viticola   280 

Plaster,  Land  195,  237-40,  250,  402 

Plaster   fertilization    237-40 

Plastidcn  theory   62 

Plastidules    31 

Platanus  orieiitalis.     Effect  of  lack  of 

calcium    304 

Plectridia.      Pectin   fermenting  organ- 
isms      272 

Pleophylly     376 

Pleospora  guuiinipara.     Oud 708 

Plowing,  as  inducing  soil  ripening" 277, 

Plowing,  Deep,  in  heavy  soil 234 

Plums.    Tan  disease  218 

—  Varieties  for  dry  soils I75 

Plums,  Rusty   166 

Poa  alpiiia    76 

Podocarpus.     Nanism    144 

Podosphaera  lencotricha.     Salm 640 

Poefih  of  tobacco  685 

Poisoning  due  to  lack  of  calcium 304 

—  of  soil    266 

Pole  red  of  hops  283 

Polycladia    146 

Polygonum  amphibiuvi    176 

—  vivipanun    76 

Poly  poms  snlfurcus   568 

Polysarchia    53 

Pomes.     Dropsy    338-39 

Pomological  magic  ring 789 

Poplar.     Bleeding  disease  887 

—  Jaundice    887 

Poplar,   Pyramidal.     Death    558 

Position,  Cultural,  of  plants 55 

—  Horizontal.    Effect  of  changes. ..  120-28 

Pot  cultures.     Soil 140 

Potassium.     Excess    403-5 

—  Lack.     Effect  on  production. .  .298-301 
in  Sfci-if/matocystis  nigra 300 

Potassium  chlorid  treatment  of  moor 

soil    257 

Potassium  fertilization  129,  156 

Potassium  hyperchlorate  767 

Potatoes.     Aerial  tubers   165 

—  Bacterial  ring  disease   398 

—  Black  dry  rot  391 

—  Brown  specks  on  foliage 397 

—  Cultural  varieties    209 

—  Diaphysis    163-64 


Potatoes.     Effect  of  hail 466 

—  Enlarging  of  the  parent  tuber 398 

—  Iron  spottedness  391,  882 

—  Leaf  curl  395-W,  882 

—  Lcnticels     369 

—  Lightning  eft'ect   495 

—  Mules    161-63 

—  Multi-colored   condition    391 

—  Over-fertilization     390-91 

—  Perforation  of  the  foliage 430 

—  Premature  ripening   161 

—  Prolepsis    163 

—  Running  out   208-209 

—  Rupturing  of  the  stem 321 

—  Scurvy,  Deep    430 

—  Secondary   tuber   formation 163 

—  Thread   formation    161-63 

—  Tuber   cuttings    828 

formation   without    foliage 164 

—  Turning  sweet    514-16 

—  Water  ends    163 

Potatoes,   Seed.     Method  of  cutting 828 

Pots,  Flower.    Washing  205 

Potted  plants.    Encrustation  of  the  soil. 205 

Souring    203-206 

Use  of  saucers  208 

Pox  of  tobacco   689-90 

Prateolus     53 

Predisposition   25-26,  27-34,  52,  62, 

83,  128,  223,  225,  301,  666-70. 
Predisposition.     Abnormal   26 

—  Hereditary     83 

—  Normal    26 

Predisposition  and   immunity    27-31 

—  to  blight    .' 52 

—  to   disease,    Inheritance 31-34 

due  to  lack  of  light 666-70 

due  to  lack  of  nutriment.  ..  .301 

in  beets  223,  225 

in  edible  roots   223,  225 

-^  to  the  mosaic  disease 687 

—  to  the  smoke  diseases  722 

—  See  also  Disposition. 

Pressure  of  the  buds 378 

Production.     Changes  due  to  lack  of 

nitrogen    287-98 

Prolepsis  of  the  potato 163 

Proliferation     374 

—  Axillary     375 

Proliferation  of  the  inflorescences 374 

Prophylaxis     7 

Prosenchyma,   Horn    707 

Protandry     293 

Proteins.     Decomposition  due  to  lack 

of  light   669 

Prothallia,  Ameristic  288 

Protogyny    293 

Prunulus    53 

Prunus    107 

—  Nanism    144 

Pniiius  avium.     Discoloration   280 

—  Cerasns.     Discoloration    281 

—  domcstica.     Discoloration   280 

—  Padus.     Goitre  gnarl  385 

—  pcrsica.     Discoloration    280 


903 


Pseudomonas   (Bacillus  Cobb)    vascu- 

larum    697 

—  camp  est  ris    223 

Pscndotieaiza  traclieipJiila   284 

Psychro-cHnic  blossoms    548 

Puccinia    . 53.    I37 

Puccinia  dispcrsa   128 

—  gluinantiii     128 

—  gram  ill  is    66,    128 

Pulteneae    134 

Pure-planting   of    fruit   varieties.      Ad- 
vantages     295 

Pyridine    460 

Pyrites    250 

Pynts  cydoiiia    51 

Pythium    227 

Pythium  de  Baryanuiii    222 

Oiiateniaria   Perscooiiii  Tul? 558 

Ouercus  pedunculata  So,  98 

Quinces.     Layering   816 

Races,  Biological   15,   128 

Radium  rays.  Arrestment  due  to 672 

Rain  storms   461-62 

Rape.     Effect  of  hail  466 

Raw-humus    241-43 

Red-rot    615 

Red-scorch  of  grapes 283 

Red-tan  of  hops 282 

Reds  (le  rouge)  of  flax  283 

—  of   hops    282-83 

Reductases    676 

Regeneration     887 

Relations,  Climatic   134 

Reseda  odoraia   126 

Reserve  substances.     Mobilization    106 

Resin   boils    712 

—  formation  in   Dicotyledons 716-17 

—  galls  on  stilt  roots 96 

—  gathering  causing  wounds 780 

Resinosis,  Acute   716 

—  Chronic     716 

Resinosis  of  conifers  711-16 

Resistance.     Plant  power   18 

Respiration,  Intra-molecular  99,  313 

Retiiwspora  ericoidcs  Zucc '..828 

Retrogression  to  juvenile  form   ^~~ 

Rhabditis    855 

Rhamnus    105 

Rha)iuuis  Frangnla    98 

—  piimila    76 

Rhi::obiiun  Beijerinckii   270 

—  Legumiiiosanim.     Frank    11 

—  radicicola     270 

Rhodanammonium    769 

Rhubarb.      Acid    retrogression    with 

nitrogen  excess   393 

—  Over-fertilization    392 

Ribes    105 

Ribes  aureum.     Dropsy  336 

—  nigrum.     Gnarl  formation   382 

Rice.     Brusone  disease   315-16 

Ricinus    100,   229 

Ricinus  communis   126 

Ring  barking  in  conifers 615 


Ring  disease  of  hyacinth  bulbs.  .326-27,  451 

Ringing.     See  Girdling. 

Ripening.     Retardation  due  to  excess  of 

nitrogen     394 

Ripening,  Premature   166 

cause  of  blight 156 

caused  by  excess  of  heat 640 

of   fruit    165-66 

of  potatoes   161 

Ripening  of  grain,   Delayed 365 

Robinia    1 54 

Robinia  Pseudacacia    107 

Roentgen  rays.     Arrestment  due  to 672 

Roesleria  hvpogaea   710 

Rolling    184 

Roncet    851 

Root  acids.    Effect  of  neutralization 402 

—  adjustment  of  woody  plants 78-81 

—  curvature    138-42 

—  cuttings   S28,  886 

—  decay    ig6 

—  decay  due  to  marshy  soil 196 

—  disease  of  the  true  chestnut 219-20 

—  grafts    .^ ....840 

—  growth    870 

—  injuries     856-59 

—  plants,  Wilting  of  the  foliage 365 

—  removal,   promoting  blossom   de- 

velopment     ' 888 

—  rot.     Coffee   23 1 

Sugar  cane    227-28 

—  tubercles 80 

Root-ball  dryness  of  the   Ericaceae.  .181-82 
Roots.     Freezing  562-66 

—  Lignification     179-80 

—  Outgrowths    191 

—  Scurvv,  Deep   367 

Girdle    368 

Knotted    367 

Surface    367 

—  Secretion   139,   151,  270 

Roots,  Edible.'    Black-leg  220-26 

Blight    220-26 

Oxalic  acid  content   223 

Predisposition  to  disease. .  .223,  225 

The   threads    220-26 

See  also  Beets. 

Roration     44 

Ros  mcllis  412 

Rosa    107 

Rosa  chiuensis.   Jaqu.   Green  blossoms. .  .342 

—  gallica    105 

Rose.     Canker    602-6 

—  Chagrination   of  the   stems 434 

—  Granulation   of   the   stems 434 

"Rose-kings"     373 

Rosette  growth    146 

—  shoots     2)77 

Rost  of  tobacco   685 

Rot,  Black,  drv,  of  potatoes 391 

—  Red    615 

—  Wet    22 

Le  rouge  of  flax  283 

Rouille  blanche  of  tobacco   685 

Rubber  plant.     Tubercle  disease 449-51 

Rubigo    44,  49,  53 


904 


Rubigo.    See  also  Mildew. 

Ruellia.     Intumescence    448 

Ritinex  acetosella   147 

Indication  of  a  scarcity  of  lime. 237 

Running  out  of  potatoes  2o8-2or) 

Rupture  of  fleshy  parts  of  plants 2>2i-24 

Rust     44 

Rust,  Black,  of  coffee  230 

—  White,  of  tobacco  690 

Rust  of  the  plum   166 

Rust  rings  in  fruit  due  to  frost 5-23-^4 

Rusting  of  the  peel  of  fruit 1 70 

Rusts  of  sugar  cane  696 

Sabre  growth    474 

Saccharogensis  diabetica    55 

Saccliaroiiiyces  Lndzvigii,  Hans 855 

Saccharomvcetes    100 

Saddle  grafts   831 

St.  Elmo's  fire   488 

St.  John's  bread  tree.     Swellings 339-40 

Salix  arenaria.     L 150 

—  ciiicrea    98 

—  herhacea    84 

—  reticulata    84 

—  ser/^yllifolia    76 

Saltpeter.     See   Nitrate  of  soda:   Chile 

saltpeter. 

Sak'iiiia   fiatans    11 

Sambucus    T05 

Sand,  Drifting  I49 

—  Ferruginous    251 

—  Shifting.     Efifect    470 

Sand  in  horticulture    . . .  r 261 

Sanding  of  moor  soil   256 

Sandstone,  Humus   243 

Sapocarbol     760 

.Saprophytism     12 

Satiircja  hortensis    74 

Saxifraga  cermia    76 

Scab  of  edible  roots  367-72 

—  of  grape-vines   596-98,  601 

Scarification   wounds    776-81 

Schizomycetes    62 

Sciadopytis.      Nanism    144 

Scion   in   grafting,    Mutual    infiuencc   of 

stock  and   841-47 

Sclcrotinia   Libcriinia    28 

Scoroglia     53 

Scurvy,  Bark   :i,72 

—  Deep,  of  potatoes  430 

—  Knotted    367 

—  Surface,  of  roots   t,6-j 

Scurvy  diseases   Z^l'l^ 

—  from  marling   370 

—  of  edible  roots  367-72 

—  spots  in  trees   461 

Sea  level.    Efifect  of  elevation  above.. 72-86 

Sea  water.     Inundation   192 

Secca    molle    202 

Secretions  of  the  root  body  139,  270 

Sedum  acre    75 

—  album    75 

—  hexangulare    75 

Seed.     Automatic  regulation  of  depth  of 

sowing    113 


Seed.    Burning 186 

—  Candying   226,  387 

—  Change  , 39 

' —  Coating.     See  Candying. 

—  Covering    109 

—  Cracking,  due  to  sunburn  647-48 

—  Depth  of  sowing  no,  113 

—  Germination  in  ice   499 

—  Germination  in  the  fruit    321 

—  Hard  shelled  condition    115,  420 

—  Heaving  due  to  frost   536-37 

—  Higher  germinating  power    125 

—  Injury   from  self-heating   652-53 

—  Mechanical    treatment    106-7 

—  Over-fertilization     387-89 

—  Quality  decisive  in  germination. ..  in 

—  Retention  of  germinating  power.. .107 

—  Soaking   106,   112,   157-58,  295 

—  Souring     201-203 

—  Sterilization  in  beets   225 

—  Swelling 106 

—  Too  deep  sowing 106-20 

—  Weakness  due  to  age T08 

Seed,  Dormant,   Germination    109 

Seed  time.     Efifect  of  postponement.  .639-41 
Seeding,  Delayed    200-201 

Susceptibility    to    parasitic 

attack 200-201 

—  Too  thick    147 

Seeds.     Specific  gravity   295 

Seeds,  Hard,  in  the  Leguminosae 420-22 

Soaking  in   sulphuric  acid 421 

—  Weak.     Behavior    295-96 

Selection,   Artificial    665 

Self-heating.     Injury  to  seed   652-53 

Self-preservation  in  the  organism 6 

Self-purpose  in  the  organism 6 

Self-sterility  in  fruit   291 

Senility.     Degeneration    34 

Sepedouiuiii    (chrysost'ennum?)    204 

Scrch  disease  of  sugar  cane  85,  692-96 

Serum  therapy    23 

Sewage 392 

Sewage  disposal  beds   364-67 

Attraction   to   crows 364 

Injury    from    coating    with 

ooze  and  mud    366 

Rats  as  pests   264 

Sodium   chlorid   content    ....750 

Sexual  organs  in  Cryptogams   289 

Shade.     Efifect  on  amount  of  harvest.. 657 

—  Effect  on  hops  283 

Shade  trees  in  cofifec  plantations 657 

Shading .411;   657-62 

Shadow  pictures  due  to  excessive  light. 673 

Sheath  growth    92 

Shelling  of  the  grape  blossom   354-56 

Shikuyobyo  of   the   mulberry 690 

Shoots.     Dropping   I34 

Shrivelling  disease  of  the  mulberry.  .690-92 

of  tea   692 

Silicates,   Ferric    251 

Silpha   atrata    364 

Silt.     Covering  of  soil 191 -94 

Silver-leaf     285-86 

Silver-leaf  due  to  lack  of  calcium 286 


905 


Skin  disease  of  hyacinths    451-53 

Slime     198 

Slime   cork    279 

—  exudation  of  trees 854-55 

Slope  of  the  soil  surface- 86-120 

Slopes,  Too  steep   89-91 

Small  fruits.     Dropsy   335-38 

Smelters.     Smoke    738.  740 

Smoke.      Chemical   composition 738-39 

—  Gases    718-36,  884 

—  Soil  poisoning   722 

Smoke  as  cause  of  disease 49,  459 

predisposition   to   disease 722 

Smoke  Commissions,  Federal   744 

Smoke   injuries.   Acute 721 

Chronic     721 

Invisible    721 

Smoke   injuries   with   calcium    fertiliz- 
ation      •/22 

—  production  in  smelting  furnaces. .  .738 

Smudges  as  protection  against  frost 628 

Snow  covering   76,  634 

as  protection  against  frost 624 

Snow  pressure    634-37 

Soaking  of  seed.     Advisability 295 

Soda  dust    743 

Sodium  chlorid    266 

content   of   sewage   disposal 

beds    750 

fertilization     193 

in  waste  water 748-51 

—  fumes    

—  nitrate.     See  Nitrate  of  soda. 

—  sulfid 

Soil.     Absorption   due  to   chemico- 

physical   processes    264-68 

—  Acid  content   240-41 

—  Aeration    241 

—  Alkalinity     367 

—  "Baking"    405 

—  Breaking  up    183 

—  Chemical   constitution.     Unfavor- 

able      264-407 

—  Covering  with   silt    I9I-94 

—  Crust   formation    no 

—  Cultivation    183-84,  226,  234,  245 

—  Feeding   Cultures    142 

—  Flocculency    193 

—  Harrowing    184 

—  Hoeing    184 

—  Impoverishment   91,  238,  266 

due  to  fertilization    266 

—  Increased  density  due  to  washing.. 748 

—  Irrigation    182-83 

—  Lack  of  moisture   182 

—  Leaching    243 

—  Mechanical  resistance    141 

—  Mulching    184-85 

—  Physical    constitution,   Unfavor- 

able      138-263 

—  Poisoning    266 

from   metallic   sulfur 250-51 

from  smoke    722 

—  Pulverization    191 

—  Reduction     190 

—  Removal  of  turf   184 


742 


741 


Soil.     Shading  due  to  weeds 658 

—  Slope  of  the  surface  72,  86-91 

—  Use  of  a  plant  cover 185-86 

Soil,  Alkali   195,  267 

—  Compact.     Improvement    194-95 

—  Dry.     Suitable  fruit  varieties.  ..  174-75 

—  Favorable  for  Cassava   232 

for  sweet  potatoes 22,2 

for  Taro    232 

for  yams   232 

—  Heavy.     Overcoming  dis- 

advantages  of    232-40 

—  Lean    1 52 

—  Light    148-89 

- —  Loamy     189-240 

—  Marshy,  causing  root  decay 196 

—  Moor.     See  Moor  soil. 

—  Peaty     185 

—  Sandy.     Capacity  for  becoming  wet 

with  dew    149 

Danger  from  frost  i-;9 

Disadvantages     148-50 

—  —  Leaching   149,  243 

—  Unfavorable    for    cocoa 230 

for  cofifee   230 

for  cotton    229 

for  maise    231 

for   millet    232 

for  Pennlsetum  spicatum 232 

for   Sorghum    231 

for  sugar   227 

for  tea    231 

for  tobacco    229-30 

• for  tropical  plants   22-],  232 

—  Unripe    272 

—  Virgin.     Mosaic  disease   less  pre- 
valent  on    687 

Soil  bacteria   256,  269 

—  conditions   causing   disease 72-407 

—  encrustation    134,   405 

—  exhaustion    265,   271 

—  heat.      Influence  of  excessive. 73, 648-50 

—  in   pot   cultures    140 

— ■  mass.   Limited    T38-47 

—  organisms.     Work    268-74 

—  ripening     2-7:^ 

—  solution.     Effect  of  too  high  con- 

centration      387 

—  structure.     Relation  of  food  sub- 

stances      264-74 

Unsuitable     148-240 

—  surface.      ]\Iulching    235 

—  —  Slope    86-120 

—  warmth.     See  Soil  heat. 

Solidago  virga  aurea  84 

Soot.     Composition    738 

—  Injuriousness    737 

Sorghum.     Unfavorable  soil   231 

Sorghum  millet.     Mafufa  disease 415 

Sorrel.     Indication  of  scarcity  of  lime.. 237 

Souring  of  seed   201-203 

South   wind.   Destructive    636 

Specific  gravity  in  seeds   295 

Specks.  Brown,  on  foliage  of  potatoes.  .297 

Sphacelus    608-13 

Sphaerocarpus     53 


900 


Sphagnum   187,  249,  256 

—  peat  in  horticulture   261 

Sphakelltinos    42 

SpHoceae  pouii  Fr 168 

Spinacla   olcracea    147 

Spiraca    105 

—  Canker    598-600 

Spirah'smus  Mor 334 

Splitting  of  cucumbers  462 

Sporodcsmium    710 

Spraying.     Intumescence  441,  762 

Spring  growth.     Freezing   559-62 

—  winds,  Raw.     Danger   479 

—  wood    774 

Sprouting  of  fruit   375 

—  of  the  stock 376,  378,  785 

Spruce.     Layering   253-54 

—  Sinker   formation    255 

—  Stilt   growth    92-94 

—  Top  blight    91 

—  Usefulness    253-56 

Stalks.     Lodging   542 

Staminody    342 

Starch    formation    299 

Statistics  of  plant  diseases   71 

Statocytes    858,  859 

Stem  browning  of  cotton  228 

Stercum   liirsufuin.     W'illd 614 

Siencjmntocystis    nujra.      Lack   of 

potassium     300 

Sterilc-hcad  condition  dwa  to  frost.  .542-47 

Sterility    289-92 

Sterility,   Hereditary    291 

Sterility  due  to  drought  290 

Stilbum     54 

Stilts.     Growth    92-98 

Stilts  on  pines   94 

Stimuli.   Traumatic    885 

Stock,  Grafting.     Dwarf    105 

Mutual    influence    of    scion 

and    841-47 

Sprouting   376.  378,  785 

Yellowing 284 

Stone  fruits.    See  Pomes. 

Stones  in  soil.     Significance   236 

Stoniness  of  pears   170-74 

Storage  of  winter  apples  323 

Strain  wood    553 

Stratification    159,   \o- 

Straw.     Fxcessivc  growth  in  grain 365 

—  Fertilization    269 

Street  planting    I53-5.t 

Streets.     .Asphalting   106 

Strcptothrix  species.     Humus   ferment- 
ing organisms    272 

Strophomania    334 

Stunting  of  plants   1/5-77 

—  of  trees,  due  to  wind  tictinn 474 

Substrata,  Xutritive.   for  parasites 17 

Suckers    331 

Suffocation  due  to  lack  of  oxygen 313 

Sugar.      Accumulation   due   to   lack   of 

light 668 

—  Blocking  due  to  lack  of  light 667 

Sugar  beets.     Root  blight 220-26 

Sugar  cane.     Cobb's  disease   696-97 

Diseases 227-28 


Sugar  Cane.     DongkcUancicktc   228 

Effect  of  lack  of  calcium 304 

Leaf  spot  disease   22S 

Powdery  disease   696 

Root  rot    227-28 

Rusts 696 

Sercli  disease    692-96 

Suillus    53 

Sulfarin.     Effect  of  use 372 

Sulfate  of  iron   192 

Sultkl,  Hydrogen   98,  741,  742 

—  Iron    250 

—  Sodium    741 

Sulfur.     Lack.     Changes  due  to 312 

Sulfur,   Metallic.     Poisoning  of  the 

soil    250-51 

Sulfuric  acid.  Free   250,  881 

Sulfuric  acid  for  soaking  hard  seeds... 421 

Sulfurous  acid    718-24,  884 

Summer  defoliation   347,  411,  -661 

—  drought.     Effect    501 

—  rust  of  hops  282 

Sun   cracks    647-48 

Sunburn.     Blisters    642 

—  Failure  of  seeds   643 

—  Injury  to  bark  647 

—  Injury  to  buds    645 

—  Injury  to  grapes   646-47 

—  Seed  cracking   647-48 

Sunburn  in  blossoms   645-46 

—  in   Cliz'ia   nobilis    643 

—  in    fruits    645-46 

—  of  leaves  in  nature 641-43 

—  spots  on   conservatory  plants. .  .643-^4 
Sunlight.     Effect  of  increased  intensity.  75 

Superphosphates     768 

.Surface  wounds    831 

Swamps.     Conversion  of  land  into.  ..  196-98 

Sweet   potatoes.     F'avorable  soil    232 

Symbionts.     Graft  callus  formation 887 

Symbiosis.   Antagonistic    11 

—  Mutualistic    11 

Symphoria    105 

Symptomatics    7 

Syringa.     Twisting   177 

Taaretes    147 

Tail-rot  of  beets  697 

Tainarix  gallica.     Wind   bending 474 

Tan   disease    209-19 

Apple    210-13 

Cherry     213-17 

Plum' 218 

Tannic  substances    151 

Taphrina.     Fr T46.  179 

Tar  coating.     Injury   756 

—  fumes    732-35 

—  vapor    737 

Taro.     Favorable  soil   232 

Taste,  Watery,  in  fruit 323 

Taxtis  haccata    254 

Tea.     Shrivelling  disease   692 

—  Unfavorable  soil   231 

Tears,  Frost,   Internal    569 

Tears  due  to  drought 568 

Tccoiiia  radicans.     Fasciation 334 

Temperature.     Fluctuations  88.  504.  506 


907 


Temperature,  Low.   Life  phenomena. 498-500 

Tension  differences  due  to  frost 514 

Teratology     7 

Tctvanychus  tclarius    412 

Thawing   506,   511 

—  Rapid   no,  511 

Therapy     7 

—  Internal     , 23-25 

—  Serum    23 

Thielai'iofsis  cfliaceficns    694 

Thiopene    460 

Thorn   formation    297-98 

Thread  formation  in  the  potato 161-63 

Thuja     144 

Thuja   (Biota)   orientalis   105 

—  obtusa.     Dwarf  growth   142 

—  Occidentalis    105 

—  plicata    105 

—  Warreana     105 

Thujopsis     . 144 

Tilia     94 

TiUa  parz'ifolia    616 

Tillage.      Dependence    on    friability    of 

the   soil    194 

Tip  blight   91,  154,  299 

from  lack  of  moisture 189 

Tips.  Double,  in  grapes. 345 

Tipula  suspecfa  Rtzb 614 

Tobacco.     Rosuch 685 

—  Brindle    685 

—  Bunt    685 

—  Calico    685 

—  Chlorosis     685 

—  Effect   of    covering   the    soil    with 

silt     194 

—  Effect  of  potassium  fertilization.  .  .405 

—  Fdulc    685 

—  Frenching  disease    685 

—  Gay  head  229 

—  Mai  de  mosaico  685 

—  Mai  delta  bolla   685 

—  Mauche    685 

—  Mosaic  disease  229,  684-89 

—  Mosaikbefegsege    685 

—  La  Mosaique    685 

—  Mongrel  disease    685 

—  Nielle    685 

—  Peh-sem    685 

—  Pocfih    685 

—  Pox    689-90 

—  Rost     685 

—  Romllc  blanche    _. 685 

—  Susceptibility  due  to  excessive  de- 

velopment     230 

—  Unfavorable  soil    229-30 

—  White   rust    690 

Tomatoes.     Effect  of  hail 467 

Top.     Drying   91 

Top  blight  of  conifers 487-89 

—  dressing.     Effect  of  anunonia  salts. 268 
Effect  of  Chile  saltpeter 390 

Torula  nionilioides  Cord 855 

Tracery,   Rusty    432 

Tradescantia    29 

Tradescantia  virginica.     Eft'ect   of  lack 

of  oxvgen    3^3 

Tramctr^  Pini  (Brot.) •..615 


Tree  of  life.     Chinese   142 

Japanese     142 

Tree  roots.     Elevation   92-98 

Influence    658 

Tree  seeds.    Treatment  158-60 

Tree  trunks  with  "handles"    848 

Trees.     Autumnal  coloration   280-81 

—  Goitre  gnarl    378-87 

—  Scurvy  spots    461 

—  Slimy  exudations   854-55 

—  Stunting  due  to  wind 474 

—  Swelling  of  wood   461 

—  Too  deep  planting   98-106 

Trees,  Fatty,  as  electrical  conductors. .  .483 

—  Forest.     Branch  blight   558-59 

—  Starchy,   as   electrical   conductors.  .483 
Trees  in  cities  and  towns.     Injuries  due 

to   electricity    493 

Trichia     " 53 

Trifolimn   pratense    107 

Triticum     126 

Tropical   plants    190 

Failure    84-86 

Soil  conditions   227,  232 

Tropics.      Effect    on    development    of 

vegetables    639 

Trunks.     Internal  splitting   581-83 

— ■  Lichen   covering    331 

Tuber 53 

Tuber,   Bark   861-71 

Tuber  cuttings  of  caladiums 828 

of  potatoes    828 

—  gnarls    863,  865 

Primordia     217 

Tubercle  disease  of  the  rubber  plant. 449-51 

Tubercularia    54 

Tubers,   Secondary,  in  potatoes 163 

Tulipa    109 

Tulips.     Falling 652 

Turf.     Burning   186 

—  Removal  from  soil   184 

Turgenia    latifolia    74 

Turgor,  causing  leaf  fall   351 

Turpentine   fumes,  causing   injury 757 

Tmz'   • '. 760 

Twig  abcission    357-6o 

—  disease    376 

Twigs.      Dying    134 

—  Susceptibility  induced  by  frost.... 154 
Twisting.   Compulsory 334 

—  Spiral    177.  334 

Twisting  of  the  branches  815-16 

Tylenchus  dcvastatrix    767 

—  hyacinthn   Pr. 32J 

—  sacchari  Solt\v 693 

ric.v  ruropacus  L 150 

Ulmin     241 

Union  of  parts.     See  Fasciation. 

Uredo     •  •  •   47 

Uredo  Ficus  Cast 710 

Ustilago     49 

Ustilaqo  Avcnac  C.  B 53 

—  Hordci  C.  B 53 

\'acciniuni 242 

Valeriana  Phu    75 


9o8 


Valsa  leucostoiiia   I54.  554 

—  oxysloma   153,   558 

—  prunastri  Fr 558 

Faiida  coenilea.     Spot  disease 263 

Vanilla.     Grafting  experiments   838 

Variegation    307,  677-84 

Varieties,  Oecological   73 

Vegetables.     Effect  of  tropical  climate 

on   growth    639 

—  Over-fertilization     39^-93 

—  Poor  development  in  tropics   639 

reltheiinia  (jlauca.     Dying  of  the  blos- 
soms     297 

Vermicularia    54 

Verticillium  riibcnimufu    204 

—  Sacchari    227 

I'ibiirmim   Opuliis   105 

/  'icia  Faba    80,   100 

Vinegar  made  from  wine.     Use  in  gum- 

mosis     707 

I  'iola  arvensis   74 

—  cucullata     75 

—  tricolor    76 

Virescence    341 

Virulence.     Theory    14 

Virus    684 

—  Mosaic   disease    687 

—  See  also  Enzymes. 

Vitis.     Bud  cuttings 828 

—  See  also  Grapes. 

litis  z'inifera.    Discoloration  280 

Viviparity    378 

Volcanoes,  Injuries  due  to   751 

Volutella    54 

Waste  lime  415 

causing  dry  rot   195 

heart   rot    195 

Waste  salts   401 

Waste  water    748-55 

containing  barium   chlorid 752 

calcium   chlorid    751-5^ 

cobalt    755 

iron    sulfate    755 

magnesium   chlorid    751-52 

nickel 755 

sodium   chlorid    748-51 

zinc  sulfate   75-2-53 

Water.     Discoloration  from  alder  bogs. 251 

—  Excess     319-360 

—  Scarcity.     Top  blight   189 

Cause  of  dwarfing   145 

—  Use  as  a  protection  against  frost.. 626 

Water,  Stagnant 197,  199 

Water  core  of  the  apple  286-87 

—  ends  in  the  potato  163 

—  lime    399 

—  shoots    331 

—  sprouts 331-3-2.  474 

Watering,  Injudicious   206-208 

W^eakness.     Parasites    15 

Weather.     Effect  21-22 

Wedge  cells    3^9 

Weeds.  Soil  shading  658 

W^en    863 

—  Formation  on  the  apple  882 

Whip  grafting  837 


White  lead.     Injury   756 

White-leaf  condition    307,  883 

Wilt  disease  of  cotton   229 

Wilting    276-77 

—  due  to  frost    548-51 

to  injudicious  watering   206 

—  of  foliage  of  root  plants  365 

Wind    471-79 

—  Effect   22,  462,  471-79 

on  cocoa   472 

—  Injury  to  leaves    477 

—  Pruning  action    474 

—  Stunting  of  trees   474 

Wind,  as  protection  against  frost 627 

—  Forest  protection  against   136 

W^ind-break    136,  471 

Wind-fall     471 

Winter  frost   637 

—  grain.     Harrowing    236 

—  lightning    486 

—  moisture    189 

—  seed.     Harrowing   236 

—  sunburn    648 

Witches  brooms   146,  376 

Use  of  Chile  saltpeter  391-92 

Wood.     Swelling  in  tree   461 

W^ood,   Curly    859 

—  Gnarlv     859 

—  Red    553 

Wood    fibers.      Spiral    twisting    due    to 

constriction     817 

Woody  plants.    Discoloration  279-81 

Woolly  streaks  in  apple  cores 324-26 

Wound   bark    792 

—  glim     851-54 

—  protection     850-51 

—  stimulus   871,  885,  886 

—  wall,  Mobile   836 

—  wood    772,   792 

Wounds    772-880 

—  Overgrowth     783-87 

Wounds,   Cleft    831 

—  Gnawed    782 

—  Rubbing    782 

Wounds  due  to  grafting   831 

—  due  to  resin  gathering   780 

—  to  the  axial  organs  772-80 

Xanthium     176 

Xanthoria  parictina  cushions   330 

Yams.     Favorable  soil   232 

Yellow-leaf  condition  192,  196 

due  to  excessive  light 671 

Yellow  sickness    307 

Yellow  spots    434-35 

in  Dracaena    435 

in  Pamianus  javanicus   434 

Yellowing  due  to  grafting  stock 284 

Zeoliths    265 

Zinc    740.   752 

—  blend    752 

—  oxid     752 

—  salts    752 

—  sulfate  in  waste  water 752-53 

Zinnia    I47 


® 


